feat(go-services): inventory-go Phase A — read-side scaffold + simple endpoints

First slice of the inventory-service port, running in parallel READ-ONLY against
the production inventory_db (never written):
- main.go/store.go: pgx pool (forced read-only), enum-DB loader extracting
  AttributeSetInfo for set-name resolution, /health, /sets/list, /characters/list.
- Dockerfile + compose service inventory-go (127.0.0.1:8772, enum JSON mounted).

Validated vs the Python service on the same DB: /characters/list 167 chars exact
counts; /sets/list 76 sets EXACT match (ids, names, counts).

Remaining (large): /search/items (40+ filters + enrich_db_item), inventory
fetch, item-processing ingestion (extract_item_properties), and the suitbuilder
solver.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

go-services/docker-compose.go.yml

@@ -124,5 +124,33 @@ services:
         max-size: "10m"
         max-file: "3"
 
+  # Go port of inventory-service. Phase A: read side, READ-ONLY against the
+  # production inventory_db, validated vs the Python service. Loopback :8772.
+  inventory-go:
+    build:
+      context: ./go-services/inventory-go
+      args:
+        BUILD_VERSION: ${BUILD_VERSION:-dev}
+    image: inventory-go:local
+    container_name: inventory-go
+    ports:
+      - "127.0.0.1:8772:8772"
+    environment:
+      PORT: "8772"
+      DATABASE_URL: "postgresql://inventory_user:${INVENTORY_DB_PASSWORD}@inventory-db:5432/inventory_db"
+      READ_ONLY: "true"
+      ENUM_DB_PATH: "/enums/comprehensive_enum_database_v2.json"
+      LOG_LEVEL: "INFO"
+    volumes:
+      - ./inventory-service/comprehensive_enum_database_v2.json:/enums/comprehensive_enum_database_v2.json:ro
+    depends_on:
+      - inventory-db
+    restart: unless-stopped
+    logging:
+      driver: "json-file"
+      options:
+        max-size: "10m"
+        max-file: "3"
+
 volumes:
   dereth-go-data:

go-services/inventory-go/Dockerfile

@@ -0,0 +1,12 @@
+FROM golang:1.25-bookworm AS build
+WORKDIR /src
+COPY . .
+RUN go mod tidy
+ARG BUILD_VERSION=dev
+RUN CGO_ENABLED=0 GOOS=linux go build \
+    -trimpath -ldflags "-s -w -X main.buildVersion=${BUILD_VERSION}" -o /out/inventory-go .
+
+FROM gcr.io/distroless/static-debian12:nonroot
+COPY --from=build /out/inventory-go /inventory-go
+EXPOSE 8772
+ENTRYPOINT ["/inventory-go"]

go-services/inventory-go/go.mod

@@ -0,0 +1,5 @@
+module git.snakedesert.se/SawatoMosswartsEnjoyersClub/MosswartOverlord/go-services/inventory-go
+
+go 1.25
+
+require github.com/jackc/pgx/v5 v5.10.0

go-services/inventory-go/main.go

@@ -0,0 +1,202 @@
+// Command inventory-go is a Go reimplementation of the MosswartOverlord
+// inventory-service (FastAPI), deployed in parallel for comparison.
+//
+// Phase A: read side. Connects READ-ONLY to the existing inventory_db and
+// reimplements the read endpoints, validated against the Python service on the
+// same data. The heavy item-processing ingestion and the suitbuilder solver
+// follow in later phases.
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"log/slog"
+	"net/http"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+var buildVersion = "dev"
+
+type Server struct {
+	pool          *pgxpool.Pool
+	attributeSets map[string]string // AttributeSetInfo: set-id -> set name
+	log           *slog.Logger
+}
+
+func main() {
+	logger := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{Level: slog.LevelInfo}))
+	slog.SetDefault(logger)
+
+	addr := ":" + envOr("PORT", "8772")
+	dsn := os.Getenv("DATABASE_URL")
+	enumPath := envOr("ENUM_DB_PATH", "comprehensive_enum_database_v2.json")
+	readOnly := envOr("READ_ONLY", "true") != "false"
+
+	logger.Info("starting inventory-go", "version", buildVersion, "addr", addr, "read_only", readOnly)
+
+	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
+	defer stop()
+
+	srv := &Server{log: logger, attributeSets: map[string]string{}}
+
+	if sets, err := loadAttributeSets(enumPath); err != nil {
+		logger.Warn("could not load enum AttributeSetInfo (set names will be unknown)", "err", err, "path", enumPath)
+	} else {
+		srv.attributeSets = sets
+		logger.Info("loaded enum AttributeSetInfo", "sets", len(sets))
+	}
+
+	if dsn == "" {
+		logger.Error("DATABASE_URL is required")
+		os.Exit(1)
+	}
+	connectCtx, cancel := context.WithTimeout(ctx, 15*time.Second)
+	pool, err := newPool(connectCtx, dsn, readOnly)
+	cancel()
+	if err != nil {
+		logger.Error("db pool init failed", "err", err)
+		os.Exit(1)
+	}
+	defer pool.Close()
+	srv.pool = pool
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("GET /health", srv.handleHealth)
+	mux.HandleFunc("GET /sets/list", srv.handleSetsList)
+	mux.HandleFunc("GET /characters/list", srv.handleCharactersList)
+
+	httpSrv := &http.Server{Addr: addr, Handler: withLogging(mux), ReadHeaderTimeout: 10 * time.Second}
+	go func() {
+		if err := httpSrv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
+			logger.Error("http server failed", "err", err)
+			os.Exit(1)
+		}
+	}()
+	logger.Info("listening", "addr", addr)
+
+	<-ctx.Done()
+	shutdownCtx, c := context.WithTimeout(context.Background(), 10*time.Second)
+	defer c()
+	_ = httpSrv.Shutdown(shutdownCtx)
+	logger.Info("stopped")
+}
+
+// GET /health (main.py:2674)
+func (s *Server) handleHealth(w http.ResponseWriter, r *http.Request) {
+	ctx, cancel := context.WithTimeout(r.Context(), 3*time.Second)
+	defer cancel()
+	dbOK := s.pool.Ping(ctx) == nil
+	status := "healthy"
+	if !dbOK {
+		status = "degraded"
+	}
+	writeJSON(w, http.StatusOK, map[string]any{
+		"status":             status,
+		"timestamp":          pyISO(time.Now()),
+		"database_connected": dbOK,
+		"version":            "1.0.0",
+	})
+}
+
+// GET /sets/list (main.py:2712)
+func (s *Server) handleSetsList(w http.ResponseWriter, r *http.Request) {
+	ctx, cancel := context.WithTimeout(r.Context(), 15*time.Second)
+	defer cancel()
+	rows, err := queryRowsAsMaps(ctx, s.pool, `
+		SELECT enh.item_set, COUNT(*) AS item_count
+		FROM item_enhancements enh
+		WHERE enh.item_set IS NOT NULL AND enh.item_set != ''
+		GROUP BY enh.item_set
+		ORDER BY item_count DESC, enh.item_set`)
+	if err != nil {
+		s.dbErr(w, "sets/list", err)
+		return
+	}
+	sets := make([]map[string]any, 0, len(rows))
+	for _, row := range rows {
+		setID := toStr(row["item_set"])
+		name, ok := s.attributeSets[setID]
+		if !ok {
+			name = "Unknown Set " + setID
+		}
+		sets = append(sets, map[string]any{"id": setID, "name": name, "item_count": row["item_count"]})
+	}
+	writeJSON(w, http.StatusOK, map[string]any{"sets": sets})
+}
+
+// GET /characters/list (main.py:4291)
+func (s *Server) handleCharactersList(w http.ResponseWriter, r *http.Request) {
+	ctx, cancel := context.WithTimeout(r.Context(), 15*time.Second)
+	defer cancel()
+	rows, err := queryRowsAsMaps(ctx, s.pool, `
+		SELECT character_name, COUNT(*) AS item_count, MAX(timestamp) AS last_updated
+		FROM items GROUP BY character_name ORDER BY character_name`)
+	if err != nil {
+		s.dbErr(w, "characters/list", err)
+		return
+	}
+	formatTimes(rows, "last_updated")
+	chars := make([]map[string]any, 0, len(rows))
+	for _, row := range rows {
+		chars = append(chars, map[string]any{
+			"character_name": row["character_name"],
+			"item_count":     row["item_count"],
+			"last_updated":   row["last_updated"],
+		})
+	}
+	writeJSON(w, http.StatusOK, map[string]any{"characters": chars, "total_characters": len(chars)})
+}
+
+func (s *Server) dbErr(w http.ResponseWriter, where string, err error) {
+	s.log.Error("db query failed", "where", where, "err", err)
+	writeJSON(w, http.StatusInternalServerError, map[string]any{"detail": "Internal server error"})
+}
+
+// loadAttributeSets reads the comprehensive enum DB and extracts AttributeSetInfo
+// (set-id -> name), mirroring load_comprehensive_enums (dictionaries first, then
+// enums). Only the slice needed for /sets/list is decoded.
+func loadAttributeSets(path string) (map[string]string, error) {
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	var db struct {
+		Dictionaries map[string]struct {
+			Values map[string]string `json:"values"`
+		} `json:"dictionaries"`
+		Enums map[string]struct {
+			Values map[string]string `json:"values"`
+		} `json:"enums"`
+	}
+	if err := json.Unmarshal(b, &db); err != nil {
+		return nil, err
+	}
+	if d, ok := db.Dictionaries["AttributeSetInfo"]; ok && len(d.Values) > 0 {
+		return d.Values, nil
+	}
+	if e, ok := db.Enums["AttributeSetInfo"]; ok {
+		return e.Values, nil
+	}
+	return map[string]string{}, nil
+}
+
+func envOr(key, def string) string {
+	if v := os.Getenv(key); v != "" {
+		return v
+	}
+	return def
+}
+
+func withLogging(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		start := time.Now()
+		next.ServeHTTP(w, r)
+		slog.Info("http", "method", r.Method, "path", r.URL.Path, "dur_ms", time.Since(start).Milliseconds())
+	})
+}

go-services/inventory-go/store.go

@@ -0,0 +1,83 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"time"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// newPool creates a pgx pool. When readOnly (the default in parallel mode), every
+// connection is forced into read-only transactions so the Go service can never
+// mutate the production inventory_db it shares with the Python service.
+func newPool(ctx context.Context, dsn string, readOnly bool) (*pgxpool.Pool, error) {
+	cfg, err := pgxpool.ParseConfig(dsn)
+	if err != nil {
+		return nil, fmt.Errorf("parse DATABASE_URL: %w", err)
+	}
+	cfg.MaxConns = 10
+	cfg.MaxConnIdleTime = 5 * time.Minute
+	if readOnly {
+		cfg.AfterConnect = func(ctx context.Context, conn *pgx.Conn) error {
+			_, err := conn.Exec(ctx, "SET default_transaction_read_only = on")
+			return err
+		}
+	}
+	return pgxpool.NewWithConfig(ctx, cfg)
+}
+
+func queryRowsAsMaps(ctx context.Context, pool *pgxpool.Pool, sql string, args ...any) ([]map[string]any, error) {
+	rows, err := pool.Query(ctx, sql, args...)
+	if err != nil {
+		return nil, err
+	}
+	out, err := pgx.CollectRows(rows, pgx.RowToMap)
+	if err != nil {
+		return nil, err
+	}
+	if out == nil {
+		out = []map[string]any{}
+	}
+	return out, nil
+}
+
+// pyISO mirrors Python datetime.isoformat() for a UTC value (matches FastAPI's
+// jsonable_encoder). Note the inventory-service stores naive datetimes (no tz),
+// so isoformat has no offset — we format without one.
+func pyISO(t time.Time) string {
+	t = t.UTC()
+	if t.Nanosecond() == 0 {
+		return t.Format("2006-01-02T15:04:05")
+	}
+	return t.Format("2006-01-02T15:04:05") + fmt.Sprintf(".%06d", t.Nanosecond()/1000)
+}
+
+func formatTimes(rows []map[string]any, keys ...string) {
+	for _, m := range rows {
+		for _, k := range keys {
+			if t, ok := m[k].(time.Time); ok {
+				m[k] = pyISO(t)
+			}
+		}
+	}
+}
+
+func toStr(v any) string {
+	if s, ok := v.(string); ok {
+		return s
+	}
+	return ""
+}
+
+func writeJSON(w http.ResponseWriter, status int, v any) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	if err := json.NewEncoder(w).Encode(v); err != nil {
+		slog.Error("json encode failed", "err", err)
+	}
+}