feat(backend): port route-planning backend to Go

Add a Go implementation mirroring the Python pipeline (loader, graph,
pathfinder, arbitrage, market, route, manager) under internal/core, with
ESI client/API integration and setup endpoints. Reuses backend/src as
the working directory so existing data/cache paths keep working.

12 files changed, 2708 insertions, 0 deletions

diff --git a/backend-go/internal/api/setup.go b/backend-go/internal/api/setup.go
new file mode 100644
index 0000000..738deea
--- /dev/null
+++ b/backend-go/internal/api/setup.go
@@ -0,0 +1,231 @@
+package api
+
+import (
+"bytes"
+"compress/bzip2"
+"encoding/base64"
+"encoding/json"
+"fmt"
+"io"
+"net/http"
+"net/url"
+"os"
+"path/filepath"
+"strings"
+"time"
+)
+
+const (
+baseURL      = "https://www.fuzzwork.co.uk/dump/latest"
+tokenURL     = "https://login.eveonline.com/v2/oauth/token"
+authURL      = "https://login.eveonline.com/v2/oauth/authorize"
+redirectURI  = "https://localhost/callback/"
+dataDirPath  = "../data"
+authFilePath = "./cache/auth.json"
+envFilePath  = "../../.env"
+)
+
+var scopes = []string{
+"esi-assets.read_assets.v1",
+"esi-location.read_location.v1",
+"esi-location.read_online.v1",
+"esi-wallet.read_character_wallet.v1",
+"esi-ui.open_window.v1",
+"esi-ui.write_waypoint.v1",
+}
+
+var requiredFiles = map[string]string{
+"mapDenormalize.csv": fmt.Sprintf("%s/mapDenormalize.csv.bz2", baseURL),
+"mapJumps.csv":       fmt.Sprintf("%s/mapJumps.csv.bz2", baseURL),
+"invTypes.csv":       fmt.Sprintf("%s/invTypes.csv.bz2", baseURL),
+"mapRegions.csv":     fmt.Sprintf("%s/mapRegions.csv.bz2", baseURL),
+}
+
+func StatusHandler(w http.ResponseWriter, r *http.Request) {
+    // Check if data is ready
+    dataReady := true
+    for fileName := range requiredFiles {
+        destPath := filepath.Join(dataDirPath, fileName)
+        if _, err := os.Stat(destPath); err != nil {
+            dataReady = false
+            break
+        }
+    }
+
+    // Check if auth is ready
+    authReady := false
+    if _, err := os.Stat(authFilePath); err == nil {
+        authReady = true
+    }
+
+    w.Header().Set("Content-Type", "application/json")
+    json.NewEncoder(w).Encode(map[string]bool{
+        "data_ready": dataReady,
+        "auth_ready": authReady,
+    })
+}
+
+func DownloadDataHandler(w http.ResponseWriter, r *http.Request) {
+if err := os.MkdirAll(dataDirPath, os.ModePerm); err != nil {
+http.Error(w, fmt.Sprintf("Failed to create data dir: %v", err), http.StatusInternalServerError)
+return
+}
+
+for fileName, downloadURL := range requiredFiles {
+destPath := filepath.Join(dataDirPath, fileName)
+if _, err := os.Stat(destPath); err == nil {
+fmt.Printf("Skipping %s; already exists.\n", fileName)
+continue
+}
+
+fmt.Printf("Downloading %s from %s\n", fileName, downloadURL)
+resp, err := http.Get(downloadURL)
+if err != nil || resp.StatusCode != 200 {
+http.Error(w, fmt.Sprintf("Failed to download %s", fileName), http.StatusInternalServerError)
+if resp != nil {
+resp.Body.Close()
+}
+return
+}
+
+out, err := os.Create(destPath)
+if err != nil {
+http.Error(w, "Failed to create destination file", http.StatusInternalServerError)
+resp.Body.Close()
+return
+}
+
+bzReader := bzip2.NewReader(resp.Body)
+if _, err := io.Copy(out, bzReader); err != nil {
+http.Error(w, "Decompression failed", http.StatusInternalServerError)
+out.Close()
+resp.Body.Close()
+return
+}
+
+out.Close()
+resp.Body.Close()
+fmt.Printf("Wrote %s\n", destPath)
+}
+
+w.Header().Set("Content-Type", "application/json")
+w.WriteHeader(http.StatusOK)
+w.Write([]byte(`{"message": "EVE static data is ready."}`))
+}
+
+func GetAuthURLHandler(w http.ResponseWriter, r *http.Request) {
+clientID := os.Getenv("CLIENT_ID")
+if clientID == "" {
+http.Error(w, "CLIENT_ID not set in environment.", http.StatusInternalServerError)
+return
+}
+
+queryParams := url.Values{}
+queryParams.Add("response_type", "code")
+queryParams.Add("redirect_uri", redirectURI)
+queryParams.Add("client_id", clientID)
+queryParams.Add("state", "haul-local")
+queryParams.Add("scope", strings.Join(scopes, " "))
+
+fullURL := fmt.Sprintf("%s?%s", authURL, queryParams.Encode())
+w.Header().Set("Content-Type", "application/json")
+json.NewEncoder(w).Encode(map[string]string{"url": fullURL})
+}
+
+func CompleteAuthHandler(w http.ResponseWriter, r *http.Request) {
+var request struct {
+Code string `json:"code"`
+}
+if err := json.NewDecoder(r.Body).Decode(&request); err != nil || request.Code == "" {
+http.Error(w, "Valid 'code' is required.", http.StatusBadRequest)
+return
+}
+
+clientID := os.Getenv("CLIENT_ID")
+secretKey := os.Getenv("SECRET_KEY")
+
+if clientID == "" || secretKey == "" {
+http.Error(w, "Missing CLIENT_ID or SECRET_KEY", http.StatusInternalServerError)
+return
+}
+
+formValues := url.Values{}
+formValues.Set("grant_type", "authorization_code")
+formValues.Set("code", request.Code)
+
+req, err := http.NewRequest("POST", tokenURL, strings.NewReader(formValues.Encode()))
+if err != nil {
+http.Error(w, "Failed to create request.", http.StatusInternalServerError)
+return
+}
+
+userPass := clientID + ":" + secretKey
+encodedAuth := base64.StdEncoding.EncodeToString([]byte(userPass))
+req.Header.Add("Authorization", fmt.Sprintf("Basic %s", encodedAuth))
+req.Header.Add("Content-Type", "application/x-www-form-urlencoded")
+req.Header.Add("Host", "login.eveonline.com")
+
+client := &http.Client{Timeout: 30 * time.Second}
+resp, err := client.Do(req)
+if err != nil || resp.StatusCode >= 400 {
+http.Error(w, "Failed to swap token", http.StatusBadGateway)
+return
+}
+defer resp.Body.Close()
+
+var authData map[string]interface{}
+if err := json.NewDecoder(resp.Body).Decode(&authData); err != nil {
+http.Error(w, "Failed to decode ESI response", http.StatusInternalServerError)
+return
+}
+
+expiresIn := authData["expires_in"].(float64)
+authData["expires_at"] = time.Now().UTC().Unix() + int64(expiresIn)
+
+os.MkdirAll(filepath.Dir(authFilePath), os.ModePerm)
+cacheData, _ := json.MarshalIndent(authData, "", "  ")
+os.WriteFile(authFilePath, cacheData, 0644)
+
+tokenStr, _ := authData["access_token"].(string)
+charInfo := extractJWTSubject(tokenStr)
+appendEnvValue("character_id", charInfo)
+
+w.Header().Set("Content-Type", "application/json")
+w.WriteHeader(http.StatusOK)
+w.Write([]byte(`{"message": "Auth successful, cache built."}`))
+}
+
+func extractJWTSubject(token string) string {
+parts := strings.Split(token, ".")
+if len(parts) < 2 {
+return "unknown"
+}
+payload, err := base64.RawURLEncoding.DecodeString(parts[1])
+if err != nil {
+return "unknown"
+}
+
+var claims map[string]interface{}
+if err := json.Unmarshal(payload, &claims); err != nil {
+return "unknown"
+}
+
+if sub, ok := claims["sub"].(string); ok {
+subParts := strings.Split(sub, ":")
+return subParts[len(subParts)-1]
+}
+return "unknown"
+}
+
+func appendEnvValue(key, value string) {
+content, err := os.ReadFile(envFilePath)
+if err != nil {
+content = []byte{}
+}
+
+if !bytes.Contains(content, []byte(key+"=")) {
+f, _ := os.OpenFile(envFilePath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
+defer f.Close()
+f.WriteString(fmt.Sprintf("\n%s=%s\n", key, value))
+}
+}
diff --git a/backend-go/internal/core/arbitrage.go b/backend-go/internal/core/arbitrage.go
new file mode 100644
index 0000000..9cb26bb
--- /dev/null
+++ b/backend-go/internal/core/arbitrage.go
@@ -0,0 +1,259 @@
+package core
+
+import (
+	"fmt"
+	"log"
+)
+
+const (
+	ArbitrageCandidateLimit   = 30000
+	ArbitrageTypeLimit        = 250
+	ArbitrageStationPairLimit = 40
+)
+
+type ShortlistConfig struct {
+	CandidateLimit   int
+	TypeLimit        int
+	StationPairLimit int
+	RankMode         string
+}
+
+func DefaultShortlistConfig() *ShortlistConfig {
+	return &ShortlistConfig{
+		CandidateLimit:   ArbitrageCandidateLimit,
+		TypeLimit:        ArbitrageTypeLimit,
+		StationPairLimit: ArbitrageStationPairLimit,
+		RankMode:         "and",
+	}
+}
+
+// Arbitrage calculates profitable trade pairs between stations.
+func Arbitrage(
+	market *Market,
+	cargoSpace int,
+	taxRate float64,
+	profitThreshold float64,
+	maxCapital float64,
+	shortlist *ShortlistConfig,
+) ([]Trade, error) {
+	taxRate = taxRate / 100.0
+	if shortlist == nil {
+		shortlist = DefaultShortlistConfig()
+	}
+	
+	if shortlist.RankMode != "and" && shortlist.RankMode != "or" {
+		return nil, fmt.Errorf("unsupported shortlist rank mode: %s", shortlist.RankMode)
+	}
+	
+	rankOperator := "AND"
+	if shortlist.RankMode == "or" {
+		rankOperator = "OR"
+	}
+
+	query := fmt.Sprintf(`
+	WITH buy_orders AS (
+		SELECT * FROM orders WHERE is_buy_order = 1
+	),
+	sell_orders AS (
+		SELECT * FROM orders WHERE is_buy_order = 0
+	),
+	raw_trades AS (
+		SELECT 
+			s.location_id as from_station,
+			b.location_id as to_station,
+			s.order_id as from_order_id,
+			b.order_id as to_order_id,
+			s.item_name,
+			s.type_id,
+			s.item_cargo_volume,
+			s.price as from_price,
+			b.price as to_price,
+			MIN(
+				s.volume_remain, 
+				b.volume_remain,
+				CAST(%d / NULLIF(s.item_cargo_volume, 0) AS INTEGER),
+				CAST(%f / NULLIF(s.price, 0) AS INTEGER),
+				CAST(%f / NULLIF(b.price, 0) AS INTEGER)
+			) as quantity
+		FROM sell_orders s
+		JOIN buy_orders b ON s.type_id = b.type_id
+		WHERE 
+			b.price * (1 - %f) >= s.price
+			AND s.item_cargo_volume > 0
+			AND s.price > 0 AND b.price > 0
+	),
+	candidate_trades AS (
+		SELECT
+			*,
+			quantity * (to_price * (1 - %f) - from_price) as gross_profit,
+			quantity * item_cargo_volume as cargo,
+			(quantity * (to_price * (1 - %f) - from_price)) / NULLIF(quantity * item_cargo_volume, 0) as profit_density,
+			(quantity * (to_price * (1 - %f) - from_price)) / NULLIF(quantity * from_price, 0) as roi
+		FROM raw_trades
+		WHERE quantity > 0 AND quantity * (to_price * (1 - %f) - from_price) >= %f
+	),
+	ranked_trades AS (
+		SELECT
+			*,
+			ROW_NUMBER() OVER (
+				PARTITION BY type_id
+				ORDER BY gross_profit DESC, roi DESC, profit_density DESC
+			) as type_rank,
+			ROW_NUMBER() OVER (
+				PARTITION BY from_station, to_station
+				ORDER BY gross_profit DESC, roi DESC, profit_density DESC
+			) as station_pair_rank
+		FROM candidate_trades
+	)
+	SELECT
+		from_station,
+		to_station,
+		from_order_id,
+		to_order_id,
+		item_name,
+		type_id,
+		item_cargo_volume,
+		from_price,
+		to_price,
+		quantity,
+		cargo,
+		gross_profit
+	FROM ranked_trades
+		WHERE (type_rank <= %d
+			%s station_pair_rank <= %d)
+	ORDER BY gross_profit DESC, roi DESC, profit_density DESC
+		LIMIT %d
+	`,
+		cargoSpace, maxCapital, maxCapital, taxRate, 
+		taxRate, taxRate, taxRate, taxRate, profitThreshold,
+		shortlist.TypeLimit, rankOperator, shortlist.StationPairLimit, shortlist.CandidateLimit,
+	)
+
+	rows, err := market.DB.Query(query)
+	if err != nil {
+		return nil, fmt.Errorf("arbitrage query error: %v", err)
+	}
+	defer rows.Close()
+
+	var trades []Trade
+	for rows.Next() {
+		var t Trade
+		err := rows.Scan(
+			&t.FromStation,
+			&t.ToStation,
+			&t.FromOrderID,
+			&t.ToOrderID,
+			&t.ItemName,
+			&t.TypeID,
+			&t.ItemCargoVolume,
+			&t.FromPrice,
+			&t.ToPrice,
+			&t.Quantity,
+			&t.Cargo,
+			&t.GrossProfit,
+		)
+		if err != nil {
+			return nil, fmt.Errorf("arbitrage scan error: %v", err)
+		}
+		
+		if t.Quantity > 0 {
+			trades = append(trades, t)
+		}
+	}
+
+	log.Printf("Generated %d arbitrage candidates after shortlist (limit=%d, rank_mode=%s)", len(trades), shortlist.CandidateLimit, shortlist.RankMode)
+	return trades, nil
+}
+
+// Snipe looks for immediate sell orders inside the current region that can be immediately flipped to buy orders.
+func Snipe(
+	market *Market,
+	cargoSpace int,
+	currentRegion int,
+	taxRate float64,
+	maxCapital float64,
+	snipeProfitThreshold float64,
+) (*Trade, error) {
+	taxRate = taxRate / 100.0
+	query := fmt.Sprintf(`
+	WITH buy_orders AS (
+		SELECT * FROM orders WHERE is_buy_order = 1
+	),
+	sell_orders AS (
+		SELECT * FROM orders WHERE is_buy_order = 0 AND region_id = %d
+	)
+	SELECT 
+		s.location_id as from_station,
+		b.location_id as to_station,
+		s.order_id as from_order_id,
+		b.order_id as to_order_id,
+		s.item_name,
+		s.type_id,
+		s.item_cargo_volume,
+		s.price as from_price,
+		b.price as to_price,
+		MIN(
+			s.volume_remain, 
+			b.volume_remain,
+			CAST(%d / NULLIF(s.item_cargo_volume, 0) AS INTEGER),
+			CAST(%f / NULLIF(s.price, 0) AS INTEGER),
+			CAST(%f / NULLIF(b.price, 0) AS INTEGER)
+		) as quantity
+	FROM sell_orders s
+	JOIN buy_orders b ON s.type_id = b.type_id
+	WHERE 
+		b.price * (1 - %f) >= s.price
+		AND s.item_cargo_volume > 0
+		AND s.price > 0 AND b.price > 0
+	`, currentRegion, cargoSpace, maxCapital, maxCapital, taxRate)
+
+	rows, err := market.DB.Query(query)
+	if err != nil {
+		return nil, fmt.Errorf("snipe query error: %v", err)
+	}
+	defer rows.Close()
+
+	var bestTrade *Trade
+	maxProfit := 0.0
+
+	for rows.Next() {
+		var t Trade
+		err := rows.Scan(
+			&t.FromStation,
+			&t.ToStation,
+			&t.FromOrderID,
+			&t.ToOrderID,
+			&t.ItemName,
+			&t.TypeID,
+			&t.ItemCargoVolume,
+			&t.FromPrice,
+			&t.ToPrice,
+			&t.Quantity,
+		)
+		if err != nil {
+			return nil, fmt.Errorf("snipe scan error: %v", err)
+		}
+
+		if t.Quantity <= 0 {
+			continue
+		}
+
+		effectiveBuyPrice := t.ToPrice * (1.0 - taxRate)
+		grossProfit := float64(t.Quantity) * (effectiveBuyPrice - t.FromPrice)
+
+		if grossProfit > maxProfit {
+			t.Cargo = float64(t.Quantity) * t.ItemCargoVolume
+			t.GrossProfit = grossProfit
+			
+			tradeCopy := t // copy
+			bestTrade = &tradeCopy
+			maxProfit = grossProfit
+		}
+	}
+
+	if maxProfit > snipeProfitThreshold && bestTrade != nil {
+		return bestTrade, nil
+	}
+
+	return nil, nil
+}
diff --git a/backend-go/internal/core/graph.go b/backend-go/internal/core/graph.go
new file mode 100644
index 0000000..f0c77a9
--- /dev/null
+++ b/backend-go/internal/core/graph.go
@@ -0,0 +1,191 @@
+package core
+
+import (
+	"math"
+)
+
+const (
+	AuInM = 149597870700.0
+)
+
+
+type Edge struct {
+	To     int
+	Time   float64
+	Risk   float64
+	Weight float64
+}
+
+type Graph struct {
+	Stations     map[int]*Station
+	SolarSystems map[int]*SolarSystem
+	Ship         *Ship
+	Adj          map[int][]Edge
+}
+
+func NewGraph(stations map[int]*Station, systems map[int]*SolarSystem, ship *Ship) *Graph {
+	g := &Graph{
+		Stations:     stations,
+		SolarSystems: systems,
+		Ship:         ship,
+		Adj:          make(map[int][]Edge),
+	}
+	return g
+}
+
+func (g *Graph) AddEdge(u, v int) {
+	// Add only structural adjacency initially
+	g.Adj[u] = append(g.Adj[u], Edge{To: v})
+	g.Adj[v] = append(g.Adj[v], Edge{To: u})
+}
+
+// Build compiles all edges based on stations and stargates
+func (g *Graph) Build(connections [][2]int) {
+	// 1. Intra-system connections
+	stationsBySystem := make(map[int][]int)
+	for id, station := range g.Stations {
+		sysID := station.SolarSystemID
+		stationsBySystem[sysID] = append(stationsBySystem[sysID], id)
+	}
+
+	for sysID, sysStations := range stationsBySystem {
+		for _, stationID := range sysStations {
+			g.AddEdge(sysID, stationID)
+		}
+		// Direct station to station within same system
+		for i := 0; i < len(sysStations); i++ {
+			for j := i + 1; j < len(sysStations); j++ {
+				g.AddEdge(sysStations[i], sysStations[j])
+			}
+		}
+	}
+
+	// 2. Inter-system connections (Stargates)
+	for _, conn := range connections {
+		from, to := conn[0], conn[1]
+		if _, hasFrom := g.Stations[from]; hasFrom {
+			if _, hasTo := g.Stations[to]; hasTo {
+				g.AddEdge(from, to)
+			}
+		}
+	}
+
+	// 3. Compute time and risk
+	g.calculateWeights()
+}
+
+func (g *Graph) getPosition(nodeID int) Position {
+	if st, ok := g.Stations[nodeID]; ok {
+		return st.Position
+	}
+	return Position{X: 0, Y: 0, Z: 0}
+}
+
+func (g *Graph) calculateWeights() {
+	playerCost := g.Ship.PlayerCost
+	riskCost := g.Ship.RiskCost
+
+	// We used a simple slice append above, which might have duplicates if A->B and B->A were added twice.
+	// But AddEdge adds undirected, so we need to deduplicate or just overwrite weights carefully.
+	// For simplicity, we just rebuild Adj with weights.
+	newAdj := make(map[int][]Edge)
+
+	for u, neighbors := range g.Adj {
+		visited := make(map[int]bool)
+		var uniqueEdges []Edge
+		
+		for _, edge := range neighbors {
+			v := edge.To
+			if visited[v] {
+				continue
+			}
+			visited[v] = true
+
+			time := g.calculateTime(u, v)
+			risk := g.calculateRisk(v)
+			weight := time*playerCost + riskCost*risk
+
+			uniqueEdges = append(uniqueEdges, Edge{
+				To:     v,
+				Time:   time,
+				Risk:   risk,
+				Weight: weight,
+			})
+		}
+		newAdj[u] = uniqueEdges
+	}
+	g.Adj = newAdj
+}
+
+func (g *Graph) calculateTime(fromNode, toNode int) float64 {
+	stFrom, isStFrom := g.Stations[fromNode]
+	stTo, isStTo := g.Stations[toNode]
+
+	if isStFrom && isStTo && stFrom.SolarSystemID != stTo.SolarSystemID {
+		return 9.0 // Fixed stargate time
+	}
+
+	posFrom := g.getPosition(fromNode)
+	posTo := g.getPosition(toNode)
+
+	dx := posFrom.X - posTo.X
+	dy := posFrom.Y - posTo.Y
+	dz := posFrom.Z - posTo.Z
+	warpDist := math.Sqrt(dx*dx + dy*dy + dz*dz)
+
+	return g.calculateTimeInWarp(warpDist) + 2.0
+}
+
+func (g *Graph) calculateTimeInWarp(warpDist float64) float64 {
+	kAccel := g.Ship.MaxWarpSpeed
+	kDecel := math.Min(g.Ship.MaxWarpSpeed/3.0, 2.0)
+	warpDropout := math.Min(g.Ship.MaxSubwarpSpeed/2.0, 100.0)
+	maxMsWarpSpeed := g.Ship.MaxWarpSpeed * AuInM
+
+	accelDist := AuInM
+	decelDist := maxMsWarpSpeed / kDecel
+	minDist := accelDist + decelDist
+
+	cruiseTime := 0.0
+	if minDist > warpDist {
+		maxMsWarpSpeed = warpDist * kAccel * kDecel / (kAccel + kDecel)
+	} else {
+		cruiseTime = (warpDist - minDist) / maxMsWarpSpeed
+	}
+
+	accelTime := math.Log(maxMsWarpSpeed/kAccel) / kAccel
+	decelTime := math.Log(maxMsWarpSpeed/warpDropout) / kDecel
+
+	return cruiseTime + accelTime + decelTime
+}
+
+func (g *Graph) calculateRisk(toNode int) float64 {
+	security := 1.0
+	sysName := ""
+
+	if st, ok := g.Stations[toNode]; ok {
+		security = st.Security
+		sysName = st.SolarSystemName
+	} else if sys, ok := g.SolarSystems[toNode]; ok {
+		// Wait, some hubs don't have security field inside SolarSystem in the python code.
+		// Python fallbacks to 1.0 if not found, since SolarSystem doesn't actually store security directly in Loader.
+		// If we need it, we can fallback to 1.0
+		security = 1.0
+		sysName = sys.ItemName
+	}
+
+	risk := 0.00004 + (1.0-security)*0.0004
+	if security < 0.5 {
+		risk += 0.005
+	}
+	if security < 0.1 {
+		risk += 0.5
+	}
+
+	if g.Ship.GankersAreas != nil {
+		if penalty, exists := g.Ship.GankersAreas[sysName]; exists {
+			risk += penalty
+		}
+	}
+	return risk
+}
diff --git a/backend-go/internal/core/graph_route.go b/backend-go/internal/core/graph_route.go
new file mode 100644
index 0000000..c779c40
--- /dev/null
+++ b/backend-go/internal/core/graph_route.go
@@ -0,0 +1,82 @@
+package core
+
+import "fmt"
+
+func (g *Graph) ShortestPath(source, target int) []int {
+	if source == target {
+		return []int{source}
+	}
+	res := g.SingleSourceDijkstra(source)
+	if pr, ok := res[target]; ok {
+		return pr.Path
+	}
+	return nil
+}
+
+func (g *Graph) FormattedRouteWithOffsets(path []int) ([]RouteStep, []int) {
+	if len(path) == 0 {
+		return nil, nil
+	}
+
+	var combined []int
+	var rawOffsets []int
+
+	for i := 0; i < len(path)-1; i++ {
+		currID := path[i]
+		nextID := path[i+1]
+
+		currStation, currOk := g.Stations[currID]
+		nextStation, nextOk := g.Stations[nextID]
+
+		if currOk && currStation.IsStation {
+			combined = append(combined, currID)
+			rawOffsets = append(rawOffsets, i)
+		} else if currOk && nextOk && !currStation.IsStation && !nextStation.IsStation && currStation.SolarSystemID == nextStation.SolarSystemID {
+			combined = append(combined, currStation.SolarSystemID)
+			rawOffsets = append(rawOffsets, i)
+		}
+	}
+
+	lastID := path[len(path)-1]
+	lastStation, lastOk := g.Stations[lastID]
+	if lastOk && lastStation.IsStation {
+		combined = append(combined, lastID)
+		rawOffsets = append(rawOffsets, len(path)-1)
+	}
+
+	var steps []RouteStep
+	var filteredOffsets []int
+
+	for i, locID := range combined {
+		if st, ok := g.Stations[locID]; ok {
+			steps = append(steps, RouteStep{
+					ID:           i,
+					LocationID:   locID,
+					Location:     fmt.Sprintf("%s - %s - %s", st.RegionName, st.SolarSystemName, st.ItemName),
+					LocationType: "station",
+				SystemID:    st.SolarSystemID,
+				SystemName:  st.SolarSystemName,
+				StationName: st.ItemName,
+				Security:    st.Security,
+				RegionID:    st.RegionID,
+				Actions:     make([]Action, 0), // initialize empty for JSON formatting
+			})
+			filteredOffsets = append(filteredOffsets, rawOffsets[i])
+		} else if sys, ok := g.SolarSystems[locID]; ok {
+			steps = append(steps, RouteStep{
+					ID:           i,
+					LocationID:   locID,
+					Location:     fmt.Sprintf("%s - %s", sys.RegionName, sys.ItemName),
+					LocationType: "system",
+				SystemID:    locID,
+				SystemName:  sys.ItemName,
+				StationName: fmt.Sprintf("%s - %s", sys.RegionName, sys.ItemName), // Using Region/System name like Python code formatting does
+				RegionID:    sys.RegionID,
+				Actions:     make([]Action, 0),
+			})
+			filteredOffsets = append(filteredOffsets, rawOffsets[i])
+		}
+	}
+
+	return steps, filteredOffsets
+}
\ No newline at end of file
diff --git a/backend-go/internal/core/loader.go b/backend-go/internal/core/loader.go
new file mode 100644
index 0000000..8e451ef
--- /dev/null
+++ b/backend-go/internal/core/loader.go
@@ -0,0 +1,286 @@
+package core
+
+import (
+	"encoding/csv"
+	"os"
+	"path/filepath"
+	"strconv"
+)
+
+const (
+	TypeIDSolarSystem = 5
+	GroupIDStation    = 15
+	GroupIDStargate   = 10
+)
+
+var AllowedRegionIDs = map[int]bool{
+	10000002: true, // The Forge
+	10000016: true, // Lonetrek
+	10000030: true, // Heimatar
+	10000033: true, // The Citadel
+	10000032: true, // Sinq Laison
+	10000042: true, // Metropolis
+	10000064: true, // Essence
+	10000037: true, // Everyshore
+	10000043: true, // Domain
+	10000036: true, // Devoid
+	10000052: true, // Kador
+	10000067: true, // Genesis
+	10000068: true, // Verge Vendor
+	10000001: true, // Derelik
+	10000020: true, // Tash-Murkon
+}
+
+type Position struct {
+	X float64 `json:"x"`
+	Y float64 `json:"y"`
+	Z float64 `json:"z"`
+}
+
+type Station struct {
+	IsStation           bool       `json:"is_station"`
+	ItemName            string     `json:"item_name"`
+	Security            float64    `json:"security"`
+	Position            Position   `json:"position"`
+	SolarSystemID       int        `json:"solar_system_id"`
+	RegionID            int        `json:"region_id"`
+	RegionName          string     `json:"region_name"`
+	SolarSystemName     string     `json:"solar_system_name"`
+	SolarSystemPosition Position   `json:"solar_system_position"`
+	Jumps               []int      `json:"jumps"`
+}
+
+type SolarSystem struct {
+	ItemName   string   `json:"item_name"`
+	Position   Position `json:"position"`
+	RegionID   int      `json:"region_id"`
+	RegionName string   `json:"region_name"`
+}
+
+type Item struct {
+	TypeID      int      `json:"type_id"`
+	GroupID     int      `json:"group_id"`
+	TypeName    string   `json:"type_name"`
+	Description string   `json:"description"`
+	Mass        *float64 `json:"mass"`
+	Volume      *float64 `json:"volume"`
+	Capacity    *float64 `json:"capacity"`
+}
+
+// DataLoader handles loading data from CSV files
+type DataLoader struct {
+	BaseDir string
+}
+
+func NewDataLoader(baseDir string) *DataLoader {
+	return &DataLoader{BaseDir: baseDir}
+}
+
+func (dl *DataLoader) ReadRegions() (map[int]string, error) {
+	file, err := os.Open(filepath.Join(dl.BaseDir, "mapRegions.csv"))
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	reader := csv.NewReader(file)
+	records, err := reader.ReadAll()
+	if err != nil {
+		return nil, err
+	}
+
+	regions := make(map[int]string)
+	if len(records) > 0 {
+		records = records[1:] // Skip header
+	}
+
+	for _, row := range records {
+		regionID, err := strconv.Atoi(row[0])
+		if err != nil {
+			continue
+		}
+		regions[regionID] = row[1]
+	}
+	return regions, nil
+}
+
+func (dl *DataLoader) LoadMapData() (map[int]*Station, map[int]*SolarSystem, error) {
+	regions, err := dl.ReadRegions()
+	if err != nil {
+		return nil, nil, err
+	}
+
+	file, err := os.Open(filepath.Join(dl.BaseDir, "mapDenormalize.csv"))
+	if err != nil {
+		return nil, nil, err
+	}
+	defer file.Close()
+
+	reader := csv.NewReader(file)
+	// Some fields might be mismatched or have commas in strings, standard csv covers it
+	records, err := reader.ReadAll()
+	if err != nil {
+		return nil, nil, err
+	}
+
+	stations := make(map[int]*Station)
+	solarSystems := make(map[int]*SolarSystem)
+
+	if len(records) > 0 {
+		records = records[1:]
+	}
+
+	for _, row := range records {
+		if len(row) < 15 {
+			continue
+		}
+
+		regionIDStr := row[5]
+		if regionIDStr == "None" || regionIDStr == "" {
+			continue
+		}
+		regionID, err := strconv.Atoi(regionIDStr)
+		if err != nil || !AllowedRegionIDs[regionID] {
+			continue
+		}
+
+		itemID, _ := strconv.Atoi(row[0])
+		typeID, _ := strconv.Atoi(row[1])
+		groupID, _ := strconv.Atoi(row[2])
+
+		solarSystemID := 0
+		if row[3] != "None" && row[3] != "" {
+			solarSystemID, _ = strconv.Atoi(row[3])
+		}
+
+		x, _ := strconv.ParseFloat(row[7], 64)
+		y, _ := strconv.ParseFloat(row[8], 64)
+		z, _ := strconv.ParseFloat(row[9], 64)
+
+		itemName := row[11]
+		security, _ := strconv.ParseFloat(row[12], 64)
+
+		regionName := regions[regionID]
+		if regionName == "" {
+			regionName = "Unknown"
+		}
+
+		if typeID == TypeIDSolarSystem {
+			solarSystems[itemID] = &SolarSystem{
+				ItemName:   itemName,
+				Position:   Position{X: x, Y: y, Z: z},
+				RegionID:   regionID,
+				RegionName: regionName,
+			}
+		} else if groupID == GroupIDStation || groupID == GroupIDStargate {
+			stations[itemID] = &Station{
+				IsStation:     groupID == GroupIDStation,
+				ItemName:      itemName,
+				Security:      security,
+				Position:      Position{X: x, Y: y, Z: z},
+				SolarSystemID: solarSystemID,
+				RegionID:      regionID,
+				Jumps:         []int{},
+			}
+		}
+	}
+
+	// Update station data
+	for _, station := range stations {
+		if ss, ok := solarSystems[station.SolarSystemID]; ok {
+			station.SolarSystemName = ss.ItemName
+			station.SolarSystemPosition = ss.Position
+			station.RegionID = ss.RegionID
+			if name, exists := regions[ss.RegionID]; exists {
+				station.RegionName = name
+			} else {
+				station.RegionName = "Unknown"
+			}
+		}
+	}
+
+	return stations, solarSystems, nil
+}
+
+func parseOptionalFloat(val string) *float64 {
+	if val == "None" || val == "" {
+		return nil
+	}
+	f, err := strconv.ParseFloat(val, 64)
+	if err != nil {
+		return nil
+	}
+	return &f
+}
+
+func (dl *DataLoader) LoadItems() (map[int]*Item, error) {
+	file, err := os.Open(filepath.Join(dl.BaseDir, "invTypes.csv"))
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	reader := csv.NewReader(file)
+	records, err := reader.ReadAll()
+	if err != nil {
+		return nil, err
+	}
+
+	items := make(map[int]*Item)
+	if len(records) > 0 {
+		records = records[1:]
+	}
+
+	for _, row := range records {
+		if len(row) < 7 {
+			continue
+		}
+		typeID, err := strconv.Atoi(row[0])
+		if err != nil {
+			continue
+		}
+		groupID, _ := strconv.Atoi(row[1])
+
+		items[typeID] = &Item{
+			TypeID:      typeID,
+			GroupID:     groupID,
+			TypeName:    row[2],
+			Description: row[3],
+			Mass:        parseOptionalFloat(row[4]),
+			Volume:      parseOptionalFloat(row[5]),
+			Capacity:    parseOptionalFloat(row[6]),
+		}
+	}
+	return items, nil
+}
+
+func (dl *DataLoader) LoadStarGateConnections() ([][2]int, error) {
+	file, err := os.Open(filepath.Join(dl.BaseDir, "mapJumps.csv"))
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	reader := csv.NewReader(file)
+	records, err := reader.ReadAll()
+	if err != nil {
+		return nil, err
+	}
+
+	var connections [][2]int
+	if len(records) > 0 {
+		records = records[1:]
+	}
+
+	for _, row := range records {
+		if len(row) < 2 {
+			continue
+		}
+		from, err1 := strconv.Atoi(row[0])
+		to, err2 := strconv.Atoi(row[1])
+		if err1 == nil && err2 == nil {
+			connections = append(connections, [2]int{from, to})
+		}
+	}
+	return connections, nil
+}
diff --git a/backend-go/internal/core/manager.go b/backend-go/internal/core/manager.go
new file mode 100644
index 0000000..a2c7bd5
--- /dev/null
+++ b/backend-go/internal/core/manager.go
@@ -0,0 +1,343 @@
+package core
+
+import (
+	"context"
+	"eve_haul_go/internal/esi"
+	"fmt"
+	"log"
+	"sync"
+	"time"
+)
+
+const (
+	PrimaryCandidateLimit    = 30000
+	PrimaryTypeLimit         = 250
+	PrimaryStationPairLimit  = 40
+	
+	FallbackCandidateLimit   = 80000
+	FallbackTypeLimit        = 600
+	FallbackStationPairLimit = 80
+
+	WalletPollInterval       = 60 * time.Second
+	TradeConfirmationTTL     = 6 * time.Hour
+)
+
+type TrackedTradeConfirmation struct {
+	Trade         Trade
+	CreatedAt     time.Time
+	ExpiresAt     time.Time
+	BuyRemaining  int
+	SellRemaining int
+	IsBuy         bool
+	IsSell        bool
+}
+
+func NewTrackedTradeConfirmation(trade Trade, createdAt time.Time) *TrackedTradeConfirmation {
+	return &TrackedTradeConfirmation{
+		Trade:         trade,
+		CreatedAt:     createdAt,
+		ExpiresAt:     createdAt.Add(TradeConfirmationTTL),
+		BuyRemaining:  trade.Quantity,
+		SellRemaining: trade.Quantity,
+		IsBuy:         trade.Quantity > 0,
+		IsSell:        trade.Quantity > 0,
+	}
+}
+
+func (t *TrackedTradeConfirmation) IsComplete() bool {
+	return t.BuyRemaining <= 0 && t.SellRemaining <= 0
+}
+
+func (t *TrackedTradeConfirmation) IsExpired(now time.Time) bool {
+	return now.After(t.ExpiresAt) || now.Equal(t.ExpiresAt)
+}
+
+type Manager struct {
+	mu sync.Mutex
+
+	Ship Ship
+	Graph *Graph
+	Market *Market
+
+	Route                []RouteStep
+	RouteInfo            *RouteInfo
+	RoutePath            []int
+	RoutePathOffsets     []int
+	ActiveRouteTrades    []Trade
+	ActiveConfirmations  []*TrackedTradeConfirmation
+	PendingConfirmations []*TrackedTradeConfirmation
+
+	UpdatingOrders bool
+	Log            []string
+
+	Client *esi.EsiClient
+
+	LastWalletPollAt   time.Time
+	LastSeenWalletTxID int
+	WalletScopeErr     bool
+}
+
+func NewManager(client *esi.EsiClient, graph *Graph) *Manager {
+	return &Manager{
+		Ship:      *graph.Ship,
+		Graph:     graph,
+		Market:    _newMarketIgnore(nil, client),
+		Client:    client,
+		Log:       []string{"Manager initialized."},
+		Route:     []RouteStep{},
+		RouteInfo: &RouteInfo{},
+	}
+}
+
+func (m *Manager) CreateRoute(ctx context.Context) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	m.Route = []RouteStep{}
+	m.RouteInfo = &RouteInfo{}
+	m.ActiveRouteTrades = []Trade{}
+	m.ActiveConfirmations = []*TrackedTradeConfirmation{}
+	m.Log = append([]string{"Creating new route..."}, m.Log...)
+
+	log.Printf("Starting primary pass...")
+	m.Log = append([]string{"Starting primary pass..."}, m.Log...)
+	
+	shortlist := ShortlistConfig{
+		CandidateLimit:   PrimaryCandidateLimit,
+		TypeLimit:        PrimaryTypeLimit,
+		StationPairLimit: PrimaryStationPairLimit,
+		RankMode:         "and",
+	}
+
+	matches, err := Arbitrage(m.Market, int(m.Ship.Cargo), m.Ship.TaxRate, m.Ship.ProfitThreshold, m.Ship.MaxCapital, &shortlist)
+	if err != nil {
+		return err
+	}
+
+	if len(matches) == 0 {
+		m.Log = append([]string{"Primary pass found no matches, starting fallback pass..."}, m.Log...)
+		log.Printf("Starting fallback pass...")
+		shortlist = ShortlistConfig{
+			CandidateLimit:   FallbackCandidateLimit,
+			TypeLimit:        FallbackTypeLimit,
+			StationPairLimit: FallbackStationPairLimit,
+			RankMode:         "and",
+		}
+		matches, err = Arbitrage(m.Market, int(m.Ship.Cargo), m.Ship.TaxRate, m.Ship.ProfitThreshold, m.Ship.MaxCapital, &shortlist)
+		if err != nil {
+			return err
+		}
+	}
+
+	if len(matches) == 0 {
+		m.Log = append([]string{"No profitable trades found."}, m.Log...)
+		return nil
+	}
+
+	log.Printf("Pathfinder evaluating matches...")
+	filteredMatches := Pathfinder(matches, m.Graph, m.Ship.Location)
+	
+	if len(filteredMatches) == 0 {
+		m.Log = append([]string{"No paths found for trades."}, m.Log...)
+		return nil
+	}
+
+	legMetrics := BuildTradeLegMetrics(m.Graph, m.Ship.Location, filteredMatches)
+
+	log.Printf("Route Optimizer evaluating %d matches...", len(filteredMatches))
+	plan := RouteOptimizer(filteredMatches, m.Graph, m.Ship, legMetrics)
+
+	if plan == nil || len(plan.Route) == 0 {
+		m.Log = append([]string{"Optimal route generation failed."}, m.Log...)
+		return nil
+	}
+
+	m.Route = plan.Route
+	m.RouteInfo = plan.Info
+	m.RoutePath = plan.Path
+	m.RoutePathOffsets = plan.RawOffsets
+	m.ActiveRouteTrades = plan.OptimizedTrades
+
+	now := time.Now()
+	for _, t := range m.ActiveRouteTrades {
+		m.ActiveConfirmations = append(m.ActiveConfirmations, NewTrackedTradeConfirmation(t, now))
+	}
+
+	m.Log = append([]string{fmt.Sprintf("Route created with %d steps.", len(m.Route))}, m.Log...)
+	return nil
+}
+
+func (m *Manager) ReconcileTradeConfirmations(ctx context.Context) {
+	now := time.Now()
+	
+	m.mu.Lock()
+	if now.Sub(m.LastWalletPollAt) < WalletPollInterval {
+		m.mu.Unlock()
+		return
+	}
+	m.mu.Unlock()
+
+	transactions, err := m.Client.GetWalletTransactions(nil)
+	if err != nil {
+		m.mu.Lock()
+		if !m.WalletScopeErr {
+			m.Log = append([]string{fmt.Sprintf("Wallet Error: %v", err)}, m.Log...)
+			m.WalletScopeErr = true
+		}
+		m.mu.Unlock()
+		return
+	}
+	
+	m.mu.Lock()
+	m.LastWalletPollAt = now
+	orderAdjustments := make(map[int]int)
+
+	for i := len(transactions) - 1; i >= 0; i-- {
+		tx := transactions[i]
+		if tx.TransactionID <= m.LastSeenWalletTxID {
+			continue
+		}
+		m.LastSeenWalletTxID = tx.TransactionID
+		
+		m.applyWalletTransaction(tx, tx.Date, orderAdjustments)
+	}
+	
+	if len(orderAdjustments) > 0 {
+		err = m.Market.ApplyOrderVolumeAdjustments(orderAdjustments)
+		if err != nil {
+			log.Printf("Error applying volume adjustments: %v", err)
+		} else {
+			m.Log = append([]string{fmt.Sprintf("Applied wallet transactions. Updated %d orders.", len(orderAdjustments))}, m.Log...)
+		}
+	}
+
+	m.pruneTradeConfirmations(now)
+	m.mu.Unlock()
+}
+
+func (m *Manager) applyWalletTransaction(tx esi.WalletTransaction, txDate time.Time, adjustments map[int]int) {
+	for _, conf := range m.PendingConfirmations {
+		m.matchAndDeduct(conf, tx, txDate, adjustments)
+	}
+	for _, conf := range m.ActiveConfirmations {
+		m.matchAndDeduct(conf, tx, txDate, adjustments)
+	}
+}
+
+func (m *Manager) matchAndDeduct(conf *TrackedTradeConfirmation, tx esi.WalletTransaction, txDate time.Time, adjustments map[int]int) {
+	if conf.IsComplete() {
+		return
+	}
+	if conf.Trade.TypeID != int(tx.TypeID) {
+		return
+	}
+
+	tolPriceCheck := func(expected, actual float64) bool {
+		diff := expected - actual
+		if diff < 0 {
+			diff = -diff
+		}
+		allowed := expected * 0.002
+		if 0.01 > allowed {
+			allowed = 0.01
+		}
+		return diff <= allowed
+	}
+
+	if tx.IsBuy && conf.BuyRemaining > 0 && tx.LocationID == conf.Trade.FromStation && tolPriceCheck(conf.Trade.FromPrice, tx.UnitPrice) {
+		deduct := int(tx.Quantity)
+		if deduct > conf.BuyRemaining {
+			deduct = conf.BuyRemaining
+		}
+		conf.BuyRemaining -= deduct
+		adjustments[conf.Trade.FromOrderID] += deduct
+	}
+
+	if !tx.IsBuy && conf.SellRemaining > 0 && tx.LocationID == conf.Trade.ToStation && tolPriceCheck(conf.Trade.ToPrice, tx.UnitPrice) {
+		deduct := int(tx.Quantity)
+		if deduct > conf.SellRemaining {
+			deduct = conf.SellRemaining
+		}
+		conf.SellRemaining -= deduct
+		adjustments[conf.Trade.ToOrderID] += deduct
+	}
+}
+
+func (m *Manager) pruneTradeConfirmations(now time.Time) {
+	var active []*TrackedTradeConfirmation
+	for _, c := range m.ActiveConfirmations {
+		if c.IsComplete() {
+			continue
+		}
+		if c.IsExpired(now) {
+			m.Log = append([]string{fmt.Sprintf("WARN: Expired active trade: %d", c.Trade.TypeID)}, m.Log...)
+			continue
+		}
+		active = append(active, c)
+	}
+	m.ActiveConfirmations = active
+
+	var pending []*TrackedTradeConfirmation
+	for _, c := range m.PendingConfirmations {
+		if c.IsComplete() {
+			continue
+		}
+		if c.IsExpired(now) {
+			m.Log = append([]string{fmt.Sprintf("WARN: Expired pending trade: %d", c.Trade.TypeID)}, m.Log...)
+			continue
+		}
+		pending = append(pending, c)
+	}
+	m.PendingConfirmations = pending
+}
+
+func (m *Manager) Update(ctx context.Context) error {
+	m.ReconcileTradeConfirmations(ctx)
+
+	loc, err := m.Client.GetLocation()
+	if err != nil {
+		return err
+	}
+	
+	m.mu.Lock()
+	if loc.StationID != 0 {
+		m.Ship.Location = int(loc.StationID)
+	} else {
+		m.Ship.Location = int(loc.SolarSystemID)
+	}
+	m.mu.Unlock()
+
+	m.mu.Lock()
+	if !m.UpdatingOrders {
+		m.UpdatingOrders = true
+		m.mu.Unlock()
+		
+		go func() {
+			defer func() {
+				m.mu.Lock()
+				m.UpdatingOrders = false
+				m.mu.Unlock()
+			}()
+			m.Market.UpdateOrders()
+		}()
+	} else {
+		m.mu.Unlock()
+	}
+
+	return nil
+}
+
+func _newMarketIgnore(items map[int]*Item, esiClient *esi.EsiClient) *Market {
+    m, _ := NewMarket(items, esiClient)
+    return m
+}
+
+func (m *Manager) SetWaypoints() error {
+m.mu.Lock()
+defer m.mu.Unlock()
+if len(m.RoutePath) == 0 {
+return fmt.Errorf("no route path available")
+}
+_, err := m.Client.SetWaypoints(m.RoutePath)
+return err
+}
diff --git a/backend-go/internal/core/market.go b/backend-go/internal/core/market.go
new file mode 100644
index 0000000..1cc12d5
--- /dev/null
+++ b/backend-go/internal/core/market.go
@@ -0,0 +1,267 @@
+package core
+
+import (
+	"database/sql"
+	"fmt"
+	"log"
+	"sync"
+	"time"
+
+	_ "github.com/mattn/go-sqlite3"
+
+	"eve_haul_go/internal/esi"
+)
+
+var RegionIDs = []int{
+	10000002, // The Forge
+	10000016, // Lonetrek
+	10000030, // Heimatar
+	10000033, // The Citadel
+	10000032, // Sinq Laison
+	10000042, // Metropolis
+	10000064, // Essence
+	10000037, // Everyshore
+	10000043, // Domain
+	10000036, // Devoid
+	10000052, // Kador
+	10000067, // Genesis
+	10000068, // Verge Vendor
+	10000001, // Derelik
+	10000020, // Tash-Murkon
+}
+
+type Order struct {
+	OrderID         int       `json:"order_id"`
+	RegionID        int       `json:"region_id"`
+	LocationID      int       `json:"location_id"`
+	TypeID          int       `json:"type_id"`
+	IsBuyOrder      bool      `json:"is_buy_order"`
+	Price           float64   `json:"price"`
+	Issued          time.Time `json:"issued"`
+	VolumeRemain    int       `json:"volume_remain"`
+	ItemName        string    `json:"item_name"`
+	ItemCargoVolume float64   `json:"item_cargo_volume"`
+}
+
+type Trade struct {
+	FromStation     int     `json:"from_station"`
+	ToStation       int     `json:"to_station"`
+	FromOrderID     int     `json:"from_order_id"`
+	ToOrderID       int     `json:"to_order_id"`
+	ItemName        string  `json:"item_name"`
+	TypeID          int     `json:"type_id"`
+	ItemCargoVolume float64 `json:"item_cargo_volume"`
+	FromPrice       float64 `json:"from_price"`
+	ToPrice         float64 `json:"to_price"`
+	Quantity        int     `json:"quantity"`
+	Cargo           float64 `json:"cargo"`
+	GrossProfit     float64 `json:"gross_profit"`
+	NetProfit       *float64 `json:"net_profit,omitempty"`
+}
+
+type Market struct {
+	DB           *sql.DB
+	ExpiresTimes map[int]time.Time
+	Items        map[int]*Item
+	EsiClient    *esi.EsiClient
+	Mutex        sync.RWMutex
+}
+
+func NewMarket(items map[int]*Item, esiClient *esi.EsiClient) (*Market, error) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		return nil, err
+	}
+
+	_, err = db.Exec(`
+		CREATE TABLE IF NOT EXISTS orders (
+			order_id INTEGER PRIMARY KEY,
+			region_id INTEGER,
+			location_id INTEGER,
+			type_id INTEGER,
+			is_buy_order BOOLEAN,
+			price REAL,
+			issued TEXT,
+			volume_remain INTEGER,
+			item_name TEXT,
+			item_cargo_volume REAL
+		)
+	`)
+	if err != nil {
+		return nil, err
+	}
+
+	_, err = db.Exec(`CREATE INDEX IF NOT EXISTS idx_arbitrage ON orders(type_id, is_buy_order, region_id)`)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Market{
+		DB:           db,
+		ExpiresTimes: make(map[int]time.Time),
+		Items:        items,
+		EsiClient:    esiClient,
+	}, nil
+}
+
+func (m *Market) UpdateOrders() error {
+	m.Mutex.Lock()
+	defer m.Mutex.Unlock()
+
+	var wg sync.WaitGroup
+	errChan := make(chan error, len(RegionIDs))
+	ordersChan := make(chan []Order, len(RegionIDs))
+
+	for _, regionID := range RegionIDs {
+		expiryTime, exists := m.ExpiresTimes[regionID]
+		if !exists || time.Now().UTC().After(expiryTime) {
+			wg.Add(1)
+			go func(rID int) {
+				defer wg.Done()
+				orders, err := m.downloadOrders(rID)
+				if err != nil {
+					errChan <- err
+					return
+				}
+				ordersChan <- orders
+			}(regionID)
+		}
+	}
+
+	wg.Wait()
+	close(errChan)
+	close(ordersChan)
+
+	var allErrors []error
+	for err := range errChan {
+		allErrors = append(allErrors, err)
+	}
+
+	if len(allErrors) > 0 {
+		return fmt.Errorf("errors downloading orders: %v", allErrors)
+	}
+
+	for regionOrders := range ordersChan {
+		if len(regionOrders) == 0 {
+			continue
+		}
+		rID := regionOrders[0].RegionID
+
+		tx, err := m.DB.Begin()
+		if err != nil {
+			return err
+		}
+
+		_, err = tx.Exec("DELETE FROM orders WHERE region_id = ?", rID)
+		if err != nil {
+			tx.Rollback()
+			return err
+		}
+
+		stmt, err := tx.Prepare(`INSERT OR REPLACE INTO orders 
+			(order_id, region_id, location_id, type_id, is_buy_order, price, issued, volume_remain, item_name, item_cargo_volume) 
+			VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`)
+		if err != nil {
+			tx.Rollback()
+			return err
+		}
+
+		for _, o := range regionOrders {
+			_, err = stmt.Exec(o.OrderID, o.RegionID, o.LocationID, o.TypeID, o.IsBuyOrder, o.Price, o.Issued.Format(time.RFC3339), o.VolumeRemain, o.ItemName, o.ItemCargoVolume)
+			if err != nil {
+				stmt.Close()
+				tx.Rollback()
+				return err
+			}
+		}
+		stmt.Close()
+		tx.Commit()
+	}
+
+	return nil
+}
+
+func (m *Market) downloadOrders(regionID int) ([]Order, error) {
+        page := 1
+        var rawOrders []map[string]interface{}
+        var lastExpiry string
+
+        for {
+                pageOrders, expiry, totalPages, err := m.EsiClient.GetRegionOrders(regionID, page)
+                if err != nil {
+                        log.Printf("Failed to get region orders %d page %d: %v", regionID, page, err)
+                        break
+                }
+                if len(pageOrders) == 0 {
+                        break
+                }
+                rawOrders = append(rawOrders, pageOrders...)
+                lastExpiry = expiry
+                
+                if page >= totalPages {
+                        break
+                }
+                page++
+        }
+
+        if lastExpiry != "" {
+                if parsed, err := time.Parse(time.RFC1123, lastExpiry); err == nil {
+                        m.ExpiresTimes[regionID] = parsed
+                } else {
+                        m.ExpiresTimes[regionID] = time.Now().UTC()
+                }
+        } else {
+                m.ExpiresTimes[regionID] = time.Now().UTC()
+        }
+
+        var formatted []Order
+        for _, o := range rawOrders {
+                typeID := int(o["type_id"].(float64))
+                item, exists := m.Items[typeID]
+                if !exists {
+                        continue
+                }
+
+                cargoVol := item.Volume
+                if cargoVol == nil || *cargoVol <= 0 {
+                        continue
+                }
+
+                issuedStr, _ := o["issued"].(string)
+                issuedTime, _ := time.Parse("2006-01-02T15:04:05Z", issuedStr)
+
+                isBuyOrder, _ := o["is_buy_order"].(bool)
+                orderIDFloat, _ := o["order_id"].(float64)
+                locIDFloat, _ := o["location_id"].(float64)
+                price, _ := o["price"].(float64)
+                volRemainFloat, _ := o["volume_remain"].(float64)
+
+                formatted = append(formatted, Order{
+                        OrderID:         int(orderIDFloat),
+                        RegionID:        regionID,
+                        LocationID:      int(locIDFloat),
+                        TypeID:          typeID,
+                        IsBuyOrder:      isBuyOrder,
+                        Price:           price,
+                        Issued:          issuedTime,
+                        VolumeRemain:    int(volRemainFloat),
+                        ItemName:        item.TypeName,
+                        ItemCargoVolume: *cargoVol,
+                })
+        }
+        return formatted, nil
+}
+
+func (m *Market) ApplyOrderVolumeAdjustments(deductions map[int]int) error {
+m.Mutex.Lock()
+defer m.Mutex.Unlock()
+
+for orderID, volumeDeducted := range deductions {
+log.Printf("Deducting %d volume from order %d", volumeDeducted, orderID)
+_, err := m.DB.Exec("UPDATE orders SET volume_remain = volume_remain - ? WHERE order_id = ?", volumeDeducted, orderID)
+if err != nil {
+return err
+}
+}
+return nil
+}
diff --git a/backend-go/internal/core/pathfinder.go b/backend-go/internal/core/pathfinder.go
new file mode 100644
index 0000000..62849b0
--- /dev/null
+++ b/backend-go/internal/core/pathfinder.go
@@ -0,0 +1,112 @@
+package core
+
+import (
+	"container/heap"
+)
+
+type pqItem struct {
+	node   int
+	weight float64
+	index  int
+}
+
+type priorityQueue []*pqItem
+
+func (pq priorityQueue) Len() int { return len(pq) }
+func (pq priorityQueue) Less(i, j int) bool {
+	return pq[i].weight < pq[j].weight
+}
+func (pq priorityQueue) Swap(i, j int) {
+	pq[i], pq[j] = pq[j], pq[i]
+	pq[i].index = i
+	pq[j].index = j
+}
+func (pq *priorityQueue) Push(x any) {
+	n := len(*pq)
+	item := x.(*pqItem)
+	item.index = n
+	*pq = append(*pq, item)
+}
+func (pq *priorityQueue) Pop() any {
+	old := *pq
+	n := len(old)
+	item := old[n-1]
+	old[n-1] = nil
+	item.index = -1
+	*pq = old[0 : n-1]
+	return item
+}
+
+type PathResult struct {
+	TotalWeight float64
+	TotalTime   float64
+	TotalRisk   float64
+	Path        []int
+}
+
+// SingleSourceDijkstra computes shortest paths from source to all reachable nodes
+func (g *Graph) SingleSourceDijkstra(source int) map[int]*PathResult {
+	dist := make(map[int]float64)
+	timeDist := make(map[int]float64)
+	riskDist := make(map[int]float64)
+	prev := make(map[int]int)
+
+	pq := make(priorityQueue, 0)
+	heap.Init(&pq)
+
+	dist[source] = 0.0
+	heap.Push(&pq, &pqItem{node: source, weight: 0.0})
+
+	for pq.Len() > 0 {
+		item := heap.Pop(&pq).(*pqItem)
+		u := item.node
+		w := item.weight
+
+		// Outdated element
+		if d, ok := dist[u]; ok && w > d {
+			continue
+		}
+
+		for _, edge := range g.Adj[u] {
+			v := edge.To
+			alt := w + edge.Weight
+			if d, ok := dist[v]; !ok || alt < d {
+				dist[v] = alt
+				timeDist[v] = timeDist[u] + edge.Time
+				riskDist[v] = riskDist[u] + edge.Risk
+				prev[v] = u
+				heap.Push(&pq, &pqItem{node: v, weight: alt})
+			}
+		}
+	}
+
+	results := make(map[int]*PathResult)
+	for node, w := range dist {
+		// Reconstruct path
+		var path []int
+		curr := node
+		for {
+			path = append(path, curr)
+			p, hasPrev := prev[curr]
+			if !hasPrev {
+				break
+			}
+			curr = p
+		}
+		
+		// Reverse path
+		for i, j := 0, len(path)-1; i < j; i, j = i+1, j-1 {
+			path[i], path[j] = path[j], path[i]
+		}
+
+		results[node] = &PathResult{
+			TotalWeight: w,
+			TotalTime:   timeDist[node],
+			TotalRisk:   riskDist[node],
+			Path:        path,
+		}
+	}
+
+	return results
+}
+
diff --git a/backend-go/internal/core/pathfinder_aux.go b/backend-go/internal/core/pathfinder_aux.go
new file mode 100644
index 0000000..171ffe8
--- /dev/null
+++ b/backend-go/internal/core/pathfinder_aux.go
@@ -0,0 +1,85 @@
+package core
+
+type LegMetrics struct {
+	Weight float64
+	Time   float64
+	Risk   float64
+}
+
+// BuildTradeLegMetrics computes travel metrics for all legs needed by trades
+func BuildTradeLegMetrics(graph *Graph, shipLocation int, trades []Trade) map[[2]int]*LegMetrics {
+	sourceTargets := make(map[int]map[int]bool)
+	
+	sourceTargets[shipLocation] = make(map[int]bool)
+	for _, t := range trades {
+		if _, ok := sourceTargets[shipLocation]; !ok {
+			sourceTargets[shipLocation] = make(map[int]bool)
+		}
+		sourceTargets[shipLocation][t.FromStation] = true
+
+		if _, ok := sourceTargets[t.FromStation]; !ok {
+			sourceTargets[t.FromStation] = make(map[int]bool)
+		}
+		sourceTargets[t.FromStation][t.ToStation] = true
+	}
+
+	metrics := make(map[[2]int]*LegMetrics)
+
+	for source, targets := range sourceTargets {
+		dijkstraRes := graph.SingleSourceDijkstra(source)
+		
+		for target := range targets {
+			if source == target {
+				metrics[[2]int{source, target}] = &LegMetrics{Weight: 0, Time: 0, Risk: 0}
+				continue
+			}
+
+			if res, ok := dijkstraRes[target]; ok {
+				metrics[[2]int{source, target}] = &LegMetrics{
+					Weight: res.TotalWeight,
+					Time:   res.TotalTime,
+					Risk:   res.TotalRisk,
+				}
+			} else {
+				metrics[[2]int{source, target}] = nil
+			}
+		}
+	}
+	return metrics
+}
+
+// Pathfinder filters trades that lack paths and calculates NetProfit
+func Pathfinder(trades []Trade, graph *Graph, shipLocation int) []Trade {
+	var validTrades []Trade
+	for _, t := range trades {
+		_, hasFrom := graph.Adj[t.FromStation]
+		_, hasTo := graph.Adj[t.ToStation]
+		if hasFrom && hasTo {
+			validTrades = append(validTrades, t)
+		}
+	}
+
+	if len(validTrades) == 0 {
+		return validTrades
+	}
+
+	metrics := BuildTradeLegMetrics(graph, shipLocation, validTrades)
+
+	var profitable []Trade
+	for i := range validTrades {
+		sourceToFrom, ok1 := metrics[[2]int{shipLocation, validTrades[i].FromStation}]
+		fromToTo, ok2 := metrics[[2]int{validTrades[i].FromStation, validTrades[i].ToStation}]
+
+		if ok1 && ok2 && sourceToFrom != nil && fromToTo != nil {
+			totalCost := sourceToFrom.Weight + fromToTo.Weight
+			netProfit := validTrades[i].GrossProfit - totalCost
+			
+			if netProfit > 0 {
+				validTrades[i].NetProfit = &netProfit
+				profitable = append(profitable, validTrades[i])
+			}
+		}
+	}
+
+	return profitable
+}
\ No newline at end of file
diff --git a/backend-go/internal/core/route.go b/backend-go/internal/core/route.go
new file mode 100644
index 0000000..1a8b862
--- /dev/null
+++ b/backend-go/internal/core/route.go
@@ -0,0 +1,434 @@
+package core
+
+import (
+	"container/heap"
+	"log"
+	"sort"
+)
+
+const (
+	MaxCapital           = 100000000000.0 // 100B
+	MaxTradesToConsider  = 200 // Keep bound so we don't evaluate forever, python doesn't effectively bound it
+)
+
+type Action struct {
+	ActionType string  `json:"action_type"` // "buy" or "sell"
+	Item       string  `json:"item"`
+	TypeID     int     `json:"type_id"`
+	Quantity   int     `json:"quantity"`
+	Price      float64 `json:"price"`
+}
+
+type RouteStep struct {
+	ID           int      `json:"id"`
+	LocationID   int      `json:"location_id"`
+	Location     string   `json:"location"`
+	LocationType string   `json:"location_type"`
+	SystemID     int      `json:"system_id,omitempty"`
+	SystemName   string   `json:"system_name,omitempty"`
+	StationName  string   `json:"station_name,omitempty"`
+	Security     float64  `json:"security,omitempty"`
+	RegionID     int      `json:"region_id,omitempty"`
+	Actions      []Action `json:"actions"`
+}
+
+type RouteInfo struct {
+	ProfitRate    float64 `json:"profit_rate"`
+	Risk          float64 `json:"risk"`
+	Capital       float64 `json:"capital"`
+	TransportTime float64 `json:"transport_time"`
+	GrossProfit   float64 `json:"gross_profit"`
+	NetProfit     float64 `json:"net_profit"`
+}
+
+type RoutePlan struct {
+	Route          []RouteStep
+	Info           *RouteInfo
+	OptimizedTrades []Trade
+	Path           []int
+	RawOffsets     []int
+}
+
+type Ship struct {
+TaxRate          float64            `json:"tax_rate"`
+ProfitThreshold  float64            `json:"profit_threshold"`
+MaxCapital       float64            `json:"max_capital"`
+SnipeThreshold   float64            `json:"snipe_profit_threshold"`
+Location         int                `json:"location"`
+Cargo            float64            `json:"cargo"`
+MaxWarpSpeed     float64            `json:"max_warp_speed"`
+MaxSubwarpSpeed  float64            `json:"max_subwarp_speed"`
+GankersAreas     map[string]float64 `json:"gankers_areas"`
+PlayerCost       float64            `json:"player_cost"`
+RiskCost         float64            `json:"risk_cost"`
+ShipCost         float64            `json:"ship_cost"`
+}
+
+type tradeDensityHeap struct {
+	trades []Trade
+}
+func (h tradeDensityHeap) Len() int { return len(h.trades) }
+func (h tradeDensityHeap) Less(i, j int) bool {
+	// Reverse sorted by profit density
+	di := h.trades[i].GrossProfit / h.trades[i].Cargo
+	dj := h.trades[j].GrossProfit / h.trades[j].Cargo
+	return di > dj
+}
+func (h tradeDensityHeap) Swap(i, j int) { h.trades[i], h.trades[j] = h.trades[j], h.trades[i] }
+func (h *tradeDensityHeap) Push(x any)    { h.trades = append(h.trades, x.(Trade)) }
+func (h *tradeDensityHeap) Pop() any {
+	old := h.trades
+	n := len(old)
+	x := old[n-1]
+	h.trades = old[0 : n-1]
+	return x
+}
+
+func tradeCapitalEfficiency(t Trade) float64 {
+	invested := t.FromPrice * float64(t.Quantity)
+	if invested > 0 {
+		return t.GrossProfit / invested
+	}
+	return 0.0
+}
+
+func minInt(vars ...int) int {
+	m := vars[0]
+	for _, v := range vars[1:] {
+		if v < m {
+			m = v
+		}
+	}
+	return m
+}
+
+func maxFloat(vars ...float64) float64 {
+	m := vars[0]
+	for _, v := range vars[1:] {
+		if v > m {
+			m = v
+		}
+	}
+	return m
+}
+
+func buildRankedTriplets(trades []Trade, shipLoc int) [][3]int {
+	// Sort by capital efficiency descending
+	sorted := make([]Trade, len(trades))
+	copy(sorted, trades)
+	sort.Slice(sorted, func(i, j int) bool {
+		return tradeCapitalEfficiency(sorted[i]) > tradeCapitalEfficiency(sorted[j])
+	})
+
+	var ranked [][3]int
+	seen := make(map[[3]int]bool)
+
+	for _, t := range sorted {
+		trip := [3]int{shipLoc, t.FromStation, t.ToStation}
+		if !seen[trip] {
+			seen[trip] = true
+			ranked = append(ranked, trip)
+		}
+	}
+	return ranked
+}
+
+func buildStationPairIndex(trades []Trade) map[[2]int][]Trade {
+	index := make(map[[2]int][]Trade)
+	for _, t := range trades {
+		pair := [2]int{t.FromStation, t.ToStation}
+		index[pair] = append(index[pair], t)
+	}
+	for k := range index {
+		sort.Slice(index[k], func(i, j int) bool {
+			di := index[k][i].GrossProfit / index[k][i].Cargo
+			dj := index[k][j].GrossProfit / index[k][j].Cargo
+			return di > dj
+		})
+	}
+	return index
+}
+
+func selectTrades(routeStations [3]int, tradesByPair map[[2]int][]Trade, ship Ship) []Trade {
+	var candidatePairs [][2]int
+	for i, fromStation := range routeStations {
+		for _, toStation := range routeStations[i+1:] {
+			pair := [2]int{fromStation, toStation}
+			
+			// ensure unique pairs
+			exists := false
+			for _, cp := range candidatePairs {
+				if cp == pair {
+					exists = true
+					break
+				}
+			}
+			if !exists {
+				candidatePairs = append(candidatePairs, pair)
+			}
+		}
+	}
+
+	// merge candidates into max heap based on profit density
+	h := &tradeDensityHeap{}
+	heap.Init(h)
+	for _, pair := range candidatePairs {
+		if ts, ok := tradesByPair[pair]; ok {
+			for _, t := range ts {
+				heap.Push(h, t)
+			}
+		}
+	}
+
+	usedOrders := make(map[int]int)
+	var optimized []Trade
+	var cargo, capital float64
+
+	for h.Len() > 0 {
+		t := heap.Pop(h).(Trade)
+		
+		fromRemaining, ok := usedOrders[t.FromOrderID]
+		if !ok {
+			fromRemaining = t.Quantity
+		}
+		toRemaining, ok := usedOrders[t.ToOrderID]
+		if !ok {
+			toRemaining = t.Quantity
+		}
+
+		maxQtyCargo := int((ship.Cargo - cargo) / (t.Cargo / float64(t.Quantity))) // rough item volume
+		itemVol := t.Cargo / float64(t.Quantity)
+		if itemVol == 0 {
+			itemVol = 0.01 // avoid divide by zero just in case
+			maxQtyCargo = t.Quantity
+		} else {
+			maxQtyCargo = int((ship.Cargo - cargo) / itemVol)
+		}
+		
+		maxQtyCapital := int((MaxCapital - capital) / t.FromPrice)
+
+		maxQty := minInt(t.Quantity, fromRemaining, toRemaining, maxQtyCargo, maxQtyCapital)
+		
+		if maxQty <= 0 {
+			continue
+		}
+
+		cargo += itemVol * float64(maxQty)
+		capital += t.FromPrice * float64(maxQty)
+
+		usedOrders[t.FromOrderID] = fromRemaining - maxQty
+		usedOrders[t.ToOrderID] = toRemaining - maxQty
+
+		updated := t
+		updated.Quantity = maxQty
+		updated.Cargo = itemVol * float64(maxQty)
+		if t.Quantity > 0 {
+			updated.GrossProfit = t.GrossProfit * (float64(maxQty) / float64(t.Quantity))
+		} else {
+			updated.GrossProfit = 0
+		}
+		
+		optimized = append(optimized, updated)
+
+		if cargo >= ship.Cargo || capital >= MaxCapital {
+			break
+		}
+	}
+	return optimized
+}
+
+func calculatePeakCapital(locationIDs []int, trades []Trade, shipCost float64) float64 {
+	if len(trades) == 0 {
+		return shipCost
+	}
+
+	remainingLocs := make(map[int]bool)
+	for _, l := range locationIDs {
+		remainingLocs[l] = true
+	}
+
+	committed := shipCost
+	for _, t := range trades {
+		if !remainingLocs[t.FromStation] {
+			committed += t.FromPrice * float64(t.Quantity)
+		}
+	}
+
+	peak := committed
+	for _, loc := range locationIDs {
+		// sell
+		for _, t := range trades {
+			if t.ToStation == loc {
+				committed -= t.FromPrice * float64(t.Quantity)
+			}
+		}
+		committed = maxFloat(shipCost, committed)
+
+		// buy
+		for _, t := range trades {
+			if t.FromStation == loc {
+				committed += t.FromPrice * float64(t.Quantity)
+			}
+		}
+		peak = maxFloat(peak, committed)
+	}
+
+	return peak
+}
+
+func buildRouteInfo(locationIDs []int, trades []Trade, ship Ship, time, risk float64) *RouteInfo {
+	if len(trades) == 0 {
+		return nil
+	}
+	
+	capital := calculatePeakCapital(locationIDs, trades, ship.ShipCost)
+	
+	var gross float64
+	for _, t := range trades {
+		gross += t.GrossProfit
+	}
+
+	net := gross - risk*capital
+	rate := 0.0
+	if time > 0 {
+		rate = net / time
+	}
+
+	return &RouteInfo{
+		ProfitRate:    rate,
+		Risk:          risk,
+		Capital:       capital,
+		TransportTime: time,
+		GrossProfit:   gross,
+		NetProfit:     net,
+	}
+}
+
+func RouteOptimizer(trades []Trade, graph *Graph, ship Ship, legMetrics map[[2]int]*LegMetrics) *RoutePlan {
+	if len(trades) == 0 {
+		return &RoutePlan{Route: []RouteStep{}, OptimizedTrades: []Trade{}, Path: []int{}, RawOffsets: []int{}}
+	}
+
+	rankedTriplets := buildRankedTriplets(trades, ship.Location)
+	tradesByPair := buildStationPairIndex(trades)
+
+	if legMetrics == nil {
+		legMetrics = BuildTradeLegMetrics(graph, ship.Location, trades)
+	}
+
+	var bestRate float64
+	var bestInfo *RouteInfo
+	var bestStations []int
+	var bestTrades []Trade
+
+	limit := MaxTradesToConsider
+	if len(rankedTriplets) < limit {
+		limit = len(rankedTriplets)
+	}
+
+	for _, trip := range rankedTriplets[:limit] {
+		optimized := selectTrades(trip, tradesByPair, ship)
+		if len(optimized) == 0 {
+			continue
+		}
+
+		sLeg, sOk := legMetrics[[2]int{trip[0], trip[1]}]
+		dLeg, dOk := legMetrics[[2]int{trip[1], trip[2]}]
+		if !sOk || !dOk || sLeg == nil || dLeg == nil {
+			continue
+		}
+
+		risk := sLeg.Risk + dLeg.Risk
+		time := sLeg.Time + dLeg.Time
+
+		locs := []int{trip[0], trip[1], trip[2]}
+		info := buildRouteInfo(locs, optimized, ship, time, risk)
+		if info == nil {
+			continue
+		}
+
+		if info.ProfitRate > bestRate {
+			bestRate = info.ProfitRate
+			bestInfo = info
+			bestStations = locs
+			bestTrades = optimized
+			log.Printf("New best profit rate: %.2f/hr", bestRate*3600)
+		}
+	}
+
+	if bestStations == nil || bestTrades == nil {
+		return &RoutePlan{Route: []RouteStep{}, OptimizedTrades: []Trade{}, Path: []int{}, RawOffsets: []int{}}
+	}
+
+	// Reconstruct path
+	sRes := graph.ShortestPath(bestStations[0], bestStations[1])
+	dRes := graph.ShortestPath(bestStations[1], bestStations[2])
+
+	var path []int
+	if len(sRes) > 0 {
+		path = append(path, sRes[:len(sRes)-1]...)
+		path = append(path, dRes...)
+	} else {
+		// fallback
+		path = append(path, dRes...)
+	}
+
+	// Formatted route (this needs more detailed graph metadata merging, we'll build a simplified version)
+	formatted, offsets := graph.FormattedRouteWithOffsets(path)
+
+	// Set Actions
+	actionsRoute := setActions(formatted, bestTrades)
+
+	return &RoutePlan{
+		Route:          actionsRoute,
+		Info:           bestInfo,
+		OptimizedTrades: bestTrades,
+		Path:           path,
+		RawOffsets:     offsets,
+	}
+}
+
+func setActions(route []RouteStep, trades []Trade) []RouteStep {
+	bought := make(map[int]bool)
+	for _, t := range trades {
+		for i := range route {
+			if t.FromStation == route[i].LocationID {
+				route[i].Actions = append(route[i].Actions, Action{
+					ActionType: "buy",
+					Item:       t.ItemName,
+					TypeID:     t.TypeID,
+					Quantity:   t.Quantity,
+					Price:      t.FromPrice,
+				})
+				bought[t.TypeID] = true
+			}
+			
+			if t.ToStation == route[i].LocationID && bought[t.TypeID] {
+				route[i].Actions = append(route[i].Actions, Action{
+					ActionType: "sell",
+					Item:       t.ItemName,
+					TypeID:     t.TypeID,
+					Quantity:   t.Quantity,
+					Price:      t.ToPrice,
+				})
+			}
+		}
+	}
+	
+	// Sort actions
+	for i := range route {
+		sort.Slice(route[i].Actions, func(a, b int) bool {
+			al := route[i].Actions[a]
+			bl := route[i].Actions[b]
+			if al.ActionType != bl.ActionType {
+				return al.ActionType == "sell" // sell comes before buy (0 vs 1 in python logic)
+			}
+			if al.Item != bl.Item {
+				return al.Item < bl.Item
+			}
+			return al.Price < bl.Price
+		})
+	}
+	
+	return route
+}
diff --git a/backend-go/internal/esi/api.go b/backend-go/internal/esi/api.go
new file mode 100644
index 0000000..706ea32
--- /dev/null
+++ b/backend-go/internal/esi/api.go
@@ -0,0 +1,215 @@
+package esi
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+	"time"
+)
+
+type WaypointResult struct {
+	RequestedCount   int      `json:"requested_count"`
+	SuccessCount     int      `json:"success_count"`
+	AppliedWaypoints []int    `json:"applied_waypoints"`
+	FailedWaypoints  []int    `json:"failed_waypoints"`
+	Errors           []string `json:"errors"`
+	Success          bool     `json:"success"`
+}
+
+type WalletTransaction struct {
+	TransactionID int       `json:"transaction_id"`
+	Date          time.Time `json:"date"`
+	LocationID    int       `json:"location_id"`
+	TypeID        int       `json:"type_id"`
+	UnitPrice     float64   `json:"unit_price"`
+	Quantity      int       `json:"quantity"`
+	ClientID      int       `json:"client_id"`
+	IsBuy         bool      `json:"is_buy"`
+	IsPersonal    bool      `json:"is_personal"`
+	JournalRefID  int       `json:"journal_ref_id"`
+}
+
+type LocationData struct {
+        SolarSystemID int `json:"solar_system_id"`
+        StationID     int `json:"station_id"`
+}
+
+func (c *EsiClient) GetLocation() (*LocationData, error) {
+	characterIDStr := os.Getenv("character_id")
+	if characterIDStr == "" {
+		return nil, fmt.Errorf("character_id not set in environment variables")
+	}
+	characterID, _ := strconv.Atoi(characterIDStr)
+	
+	endpoint := fmt.Sprintf("/characters/%d/location/?datasource=tranquility", characterID)
+	resp, err := c.doRequest("GET", endpoint, nil, true)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		body, _ := io.ReadAll(resp.Body)
+		return nil, fmt.Errorf("failed to get location, status: %d body: %s", resp.StatusCode, string(body))
+	}
+
+var data LocationData
+        if err := json.NewDecoder(resp.Body).Decode(&data); err != nil {
+                return nil, err
+        }
+
+        return &data, nil
+}
+
+func (c *EsiClient) SetWaypoints(waypoints []int) (*WaypointResult, error) {
+	res := &WaypointResult{
+		RequestedCount: len(waypoints),
+		Success:        true,
+	}
+
+	for i, wp := range waypoints {
+		clearOther := "false"
+		if i == 0 {
+			clearOther = "true"
+		}
+		
+		endpoint := fmt.Sprintf("/ui/autopilot/waypoint/?add_to_beginning=false&clear_other_waypoints=%s&destination_id=%d&datasource=tranquility", clearOther, wp)
+		
+		resp, err := c.doRequest("POST", endpoint, nil, true)
+		if err != nil {
+			res.FailedWaypoints = append(res.FailedWaypoints, wp)
+			res.Errors = append(res.Errors, err.Error())
+			res.Success = false
+			continue
+		}
+		
+		if resp.StatusCode >= 200 && resp.StatusCode < 300 {
+			res.SuccessCount++
+			res.AppliedWaypoints = append(res.AppliedWaypoints, wp)
+		} else {
+			body, _ := io.ReadAll(resp.Body)
+			res.Errors = append(res.Errors, fmt.Sprintf("status %d body %s", resp.StatusCode, string(body)))
+			res.FailedWaypoints = append(res.FailedWaypoints, wp)
+			res.Success = false
+		}
+		resp.Body.Close()
+		time.Sleep(50 * time.Millisecond) // Rate limiting
+	}
+
+	res.Success = len(res.FailedWaypoints) == 0
+	return res, nil
+}
+
+func (c *EsiClient) GetWalletTransactions(fromID *int) ([]WalletTransaction, error) {
+	characterIDStr := os.Getenv("character_id")
+	if characterIDStr == "" {
+		return nil, fmt.Errorf("character_id not set in environment variables")
+	}
+	characterID, _ := strconv.Atoi(characterIDStr)
+	endpoint := fmt.Sprintf("/characters/%d/wallet/transactions/?datasource=tranquility", characterID)
+	if fromID != nil {
+		endpoint += fmt.Sprintf("&from_id=%d", *fromID)
+	}
+
+	resp, err := c.doRequest("GET", endpoint, nil, true)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		body, _ := io.ReadAll(resp.Body)
+		return nil, fmt.Errorf("failed to get transactions, status: %d body: %s", resp.StatusCode, string(body))
+	}
+
+	var baseTx []struct {
+		TransactionID int     `json:"transaction_id"`
+		Date          string  `json:"date"`
+		LocationID    int     `json:"location_id"`
+		TypeID        int     `json:"type_id"`
+		UnitPrice     float64 `json:"unit_price"`
+		Quantity      int     `json:"quantity"`
+		ClientID      int     `json:"client_id"`
+		IsBuy         bool    `json:"is_buy"`
+		IsPersonal    bool    `json:"is_personal"`
+		JournalRefID  int     `json:"journal_ref_id"`
+	}
+
+	if err := json.NewDecoder(resp.Body).Decode(&baseTx); err != nil {
+		return nil, err
+	}
+
+	var results []WalletTransaction
+	for _, bt := range baseTx {
+		// ESI dates look like `2026-04-26T01:23:45Z`
+		t, _ := time.Parse(time.RFC3339, bt.Date)
+		results = append(results, WalletTransaction{
+			TransactionID: bt.TransactionID,
+			Date:          t,
+			LocationID:    bt.LocationID,
+			TypeID:        bt.TypeID,
+			UnitPrice:     bt.UnitPrice,
+			Quantity:      bt.Quantity,
+			ClientID:      bt.ClientID,
+			IsBuy:         bt.IsBuy,
+			IsPersonal:    bt.IsPersonal,
+			JournalRefID:  bt.JournalRefID,
+		})
+	}
+	return results, nil
+}
+
+func (c *EsiClient) OpenMarketWindow(typeID int) error {
+	endpoint := fmt.Sprintf("/ui/openwindow/marketdetails/?datasource=tranquility&type_id=%d", typeID)
+	resp, err := c.doRequest("POST", endpoint, nil, true)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode >= 200 && resp.StatusCode < 300 {
+		return nil
+	}
+	body, _ := io.ReadAll(resp.Body)
+	return fmt.Errorf("failed to open market window, status: %d body: %s", resp.StatusCode, string(body))
+}
+
+func (c *EsiClient) GetRegionOrders(regionID int, page int) ([]map[string]interface{}, string, int, error) {
+        endpoint := fmt.Sprintf("/markets/%d/orders/?datasource=tranquility&order_type=all&page=%d", regionID, page)
+        resp, err := c.doRequest("GET", endpoint, nil, true)
+        if err != nil {
+                return nil, "", 0, err
+        }
+        defer resp.Body.Close()
+
+        if resp.StatusCode != 200 {
+                body, _ := io.ReadAll(resp.Body)
+                return nil, "", 0, fmt.Errorf("failed to get region orders, status: %d body: %s", resp.StatusCode, string(body))
+        }
+
+        var orders []map[string]interface{}
+        if err := json.NewDecoder(resp.Body).Decode(&orders); err != nil {
+                return nil, "", 0, err
+        }
+
+        expires := resp.Header.Get("Expires")
+        totalPagesStr := resp.Header.Get("X-Pages")
+        totalPages, _ := strconv.Atoi(totalPagesStr)
+        if totalPages == 0 {
+                totalPages = 1
+        }
+
+        // Add RegionID and drop 0 volume
+        var filtered []map[string]interface{}
+        for _, o := range orders {
+                volRemain, _ := o["volume_remain"].(float64)
+                if volRemain > 0 {
+                        o["region_id"] = regionID
+                        filtered = append(filtered, o)
+                }
+        }
+
+        return filtered, expires, totalPages, nil
+}
diff --git a/backend-go/internal/esi/client.go b/backend-go/internal/esi/client.go
new file mode 100644
index 0000000..6a3b5fd
--- /dev/null
+++ b/backend-go/internal/esi/client.go
@@ -0,0 +1,203 @@
+package esi
+
+import (
+	"bytes"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+)
+
+const (
+	EsiBaseURL        = "https://esi.evetech.net/latest"
+	UserAgent         = "Haul (Hyperspace Asset Unloading and Loading) - Go Port"
+	ErrorLimitThresh  = 50
+)
+
+type AuthData struct {
+	AccessToken  string  `json:"access_token"`
+	RefreshToken string  `json:"refresh_token"`
+	ExpiresAt    float64 `json:"expires_at"`
+}
+
+type EsiClient struct {
+	HttpClient   *http.Client
+	AuthFilePath string
+	TokenMutex   sync.Mutex
+	ClientID     string
+	SecretKey    string
+}
+
+func NewEsiClient(authFilePath string) *EsiClient {
+	clientID := os.Getenv("CLIENT_ID")
+	secretKey := os.Getenv("SECRET_KEY")
+	
+	// Default to generic timeout
+	client := &http.Client{
+		Timeout: 10 * time.Second,
+	}
+
+	return &EsiClient{
+		HttpClient:   client,
+		AuthFilePath: authFilePath,
+		ClientID:     clientID,
+		SecretKey:    secretKey,
+	}
+}
+
+// GetAccessToken checks if the token is valid, refreshing if needed or forced.
+func (c *EsiClient) GetAccessToken(forceRefresh bool) (string, error) {
+	c.TokenMutex.Lock()
+	defer c.TokenMutex.Unlock()
+
+	data, err := os.ReadFile(c.AuthFilePath)
+	if err != nil {
+		return "", fmt.Errorf("failed to read auth file: %w", err)
+	}
+
+	var auth AuthData
+	if err := json.Unmarshal(data, &auth); err != nil {
+		return "", fmt.Errorf("failed to parse auth file: %w", err)
+	}
+
+	now := float64(time.Now().Unix())
+	// Refresh if expired or soon to expire (within 20 mins)
+	if forceRefresh || auth.ExpiresAt < now+1200 {
+		return c.refreshAccessToken(auth.RefreshToken)
+	}
+
+	return auth.AccessToken, nil
+}
+
+func (c *EsiClient) refreshAccessToken(refreshToken string) (string, error) {
+	if c.ClientID == "" || c.SecretKey == "" {
+		return "", errors.New("CLIENT_ID and SECRET_KEY environment variables not set")
+	}
+
+	tokenURL := "https://login.eveonline.com/v2/oauth/token"
+	data := url.Values{}
+	data.Set("grant_type", "refresh_token")
+	data.Set("refresh_token", refreshToken)
+
+	req, err := http.NewRequest("POST", tokenURL, strings.NewReader(data.Encode()))
+	if err != nil {
+		return "", err
+	}
+
+	authStr := base64.StdEncoding.EncodeToString([]byte(fmt.Sprintf("%s:%s", c.ClientID, c.SecretKey)))
+	req.Header.Add("Authorization", "Basic "+authStr)
+	req.Header.Add("Content-Type", "application/x-www-form-urlencoded")
+	req.Header.Add("Host", "login.eveonline.com")
+
+	resp, err := c.HttpClient.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		bodyBytes, _ := io.ReadAll(resp.Body)
+		return "", fmt.Errorf("failed to refresh token, status %d: %s", resp.StatusCode, string(bodyBytes))
+	}
+
+	var respData struct {
+		AccessToken  string `json:"access_token"`
+		RefreshToken string `json:"refresh_token"`
+		ExpiresIn    int64  `json:"expires_in"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&respData); err != nil {
+		return "", err
+	}
+
+	// Update auth file
+	newAuth := AuthData{
+		AccessToken:  respData.AccessToken,
+		RefreshToken: respData.RefreshToken,
+		ExpiresAt:    float64(time.Now().Unix() + respData.ExpiresIn),
+	}
+
+	// Ensure cache dir exists
+	os.MkdirAll(filepath.Dir(c.AuthFilePath), 0755)
+
+	outBytes, err := json.MarshalIndent(newAuth, "", "  ")
+	if err != nil {
+		return "", err
+	}
+	if err := os.WriteFile(c.AuthFilePath, outBytes, 0644); err != nil {
+		return "", err
+	}
+
+	return newAuth.AccessToken, nil
+}
+
+func (c *EsiClient) doRequest(method, endpoint string, body []byte, allowRetry bool) (*http.Response, error) {
+	url := fmt.Sprintf("%s%s", EsiBaseURL, endpoint)
+
+	for attempt := 1; attempt <= 3; attempt++ {
+		token, err := c.GetAccessToken(false)
+		if err != nil {
+			return nil, err
+		}
+
+		var reqBody io.Reader
+		if body != nil {
+			reqBody = bytes.NewReader(body)
+		}
+
+		req, err := http.NewRequest(method, url, reqBody)
+		if err != nil {
+			return nil, err
+		}
+
+		req.Header.Set("Accept", "application/json")
+		req.Header.Set("Cache-Control", "no-cache")
+		req.Header.Set("Authorization", "Bearer "+token)
+		req.Header.Set("User-Agent", UserAgent)
+		if body != nil {
+			req.Header.Set("Content-Type", "application/json")
+		}
+
+		resp, err := c.HttpClient.Do(req)
+		if err != nil {
+			return nil, err
+		}
+
+		// Check ESI Error Limit
+		if remainStr := resp.Header.Get("x-esi-error-limit-remain"); remainStr != "" {
+			if remain, err := strconv.Atoi(remainStr); err == nil && remain < ErrorLimitThresh {
+				resp.Body.Close()
+				return nil, fmt.Errorf("ESI error limit threshold reached: %d remaining", remain)
+			}
+		}
+
+		if resp.StatusCode == 401 && allowRetry && attempt == 1 {
+			resp.Body.Close()
+			_, _ = c.GetAccessToken(true) // Force refresh
+			continue
+		}
+
+		if resp.StatusCode == 429 && allowRetry {
+			resp.Body.Close()
+			time.Sleep(time.Duration(2*attempt) * time.Second)
+			continue
+		}
+
+		if resp.StatusCode == 403 {
+			resp.Body.Close()
+			return nil, errors.New("permission denied (403). Check ESI scopes")
+		}
+
+		return resp, nil
+	}
+
+	return nil, errors.New("max retries exceeded")
+}
\ No newline at end of file