// Command api-server 是 visionA-backend 的對前端 REST + WebSocket 伺服器。
//
// 雛形雙 binary 架構（Q1 裁決）：
//   - api-server **無狀態**：所有 session 狀態都在 remote-proxy 那邊
//   - 透過 ProxyClientStore + Forwarder 走 internal HTTP 跟 remote-proxy 溝通
//
// 對應文件：
//   - `.autoflow/04-architecture/TDD.md` §2.4（雙 binary 部署）/ §10（前端資料流）
//   - `.autoflow/04-architecture/api/api-spec.md`（前端用的 REST API）
//   - `.autoflow/04-architecture/api/api-internal.md`（api-server ↔ remote-proxy）
//   - `.autoflow/04-architecture/tunnel.md` §5
package main

import (
	"context"
	"errors"
	"net"
	"net/http"
	"os"
	"os/signal"
	"strconv"
	"syscall"
	"time"

	"github.com/gin-gonic/gin"

	"visiona-backend/internal/api"
	"visiona-backend/internal/auth"
	"visiona-backend/internal/config"
	"visiona-backend/internal/conversion"
	"visiona-backend/internal/converter"
	"visiona-backend/internal/device"
	"visiona-backend/internal/logger"
	"visiona-backend/internal/model"
	"visiona-backend/internal/oidc"
	"visiona-backend/internal/session"
	"visiona-backend/internal/storage"
	"visiona-backend/internal/usersession"
)

// defaultSigningSecret 與 config/load.go 保持一致 — 用於啟動警告。
const defaultSigningSecret = "dev-signing-secret-do-not-use-in-prod"

// shutdownTimeout 是收到 SIGINT/SIGTERM 後等待進行中請求完成的最長時間。
const shutdownTimeout = 10 * time.Second

// sessionCleanupInterval 是 OIDC user session store 的後台清理頻率。
// 設 5 分鐘是 dev / prod 都合理的值：足夠頻繁讓 idle session 不久留，
// 又不會過度消耗 CPU。
const sessionCleanupInterval = 5 * time.Minute

func main() {
	cfg := config.Load()
	log := logger.New(cfg.Logger.Level).With("service", "api-server")

	// Validate config（特別是 OIDC 啟用時的必填欄位）。
	if err := cfg.Validate(); err != nil {
		log.Error("invalid config", "error", err)
		os.Exit(1)
	}

	// 啟動警告：signing secret 為預設值（同 remote-proxy 行為）。
	// 此 secret 同時給 storage presigned URL 與（未來）pairing token hash 用。
	if cfg.Auth.SigningSecret == defaultSigningSecret {
		log.Warn("signing secret 仍為預設 dev 值（storage/pairing 共用）",
			"action", "請在生產環境設定環境變數 VISIONA_STORAGE_SIGNING_SECRET",
			"affects", "storage presigned URL, pairing token hash (phase 1)")
	}

	// ===== Storage =====
	// 用 LocalFS（Phase 0 雛形）；signing secret 共用同一份。
	storageStore, err := storage.NewLocalFSStore(cfg.Storage.RootDir, cfg.Storage.BaseURL, cfg.Auth.SigningSecret)
	if err != nil {
		log.Error("failed to init storage", "error", err)
		os.Exit(1)
	}
	log.Info("storage initialized",
		"backend", cfg.Storage.Backend,
		"root", cfg.Storage.RootDir,
		"base_url", cfg.Storage.BaseURL)

	// ===== Pairing / Session Token（OIDC 之外的雛形 token store） =====
	pairingStore := auth.NewInMemoryPairingStore()
	sessionTokenStore := auth.NewInMemorySessionTokenStore()

	// ===== OIDC + User Session（OB5：唯一認證路徑） =====
	// cfg.Validate() 已確保所有必填欄位存在，這裡可以放心 wire。
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	oidcProvider, err := oidc.NewProvider(ctx, oidc.ProviderConfig{
		IssuerURL:    cfg.OIDC.IssuerURL,
		ClientID:     cfg.OIDC.ClientID,
		ClientSecret: cfg.OIDC.ClientSecret,
		RedirectURL:  cfg.OIDC.RedirectURL,
	})
	cancel()
	if err != nil {
		log.Error("failed to init OIDC provider",
			"error", err,
			"issuer", cfg.OIDC.IssuerURL,
			"hint", "確認 IdP discovery (.well-known/openid-configuration) 可達")
		os.Exit(1)
	}

	userSessionStore := usersession.NewInMemoryStore()
	userSessionMgr := usersession.NewManager(userSessionStore, usersession.CookieConfig{
		Name:       cfg.UserSession.CookieName,
		Domain:     cfg.UserSession.CookieDomain,
		Path:       "/",
		Secure:     cfg.UserSession.CookieSecure,
		HTTPOnly:   true,
		SameSite:   http.SameSiteLaxMode,
		MaxAge:     int(cfg.UserSession.AbsoluteTTL.Seconds()),
		SigningKey: []byte(cfg.UserSession.Secret),
	})
	log.Info("OIDC initialized",
		"issuer", cfg.OIDC.IssuerURL,
		"client_id", cfg.OIDC.ClientID,
		"redirect_url", cfg.OIDC.RedirectURL,
		"frontend_url", cfg.OIDC.PostLoginURL,
		"cookie_secure", cfg.UserSession.CookieSecure,
		"absolute_ttl", cfg.UserSession.AbsoluteTTL,
		"idle_ttl", cfg.UserSession.IdleTTL,
	)

	// ===== Session（api-server 端透過 ProxyClient 走 internal HTTP） =====
	proxyClient := session.NewHTTPProxyClient(cfg.Session.ProxyInternalURL, log)
	forwarder := session.NewForwarder(cfg.Session.ProxyInternalURL, log)
	sessionStore := session.NewProxyClientStore(proxyClient, forwarder)
	log.Info("session store initialized",
		"backend", "proxy-client",
		"proxy_internal_url", cfg.Session.ProxyInternalURL)

	// ===== Repositories（in-memory，雛形） =====
	deviceRepo := device.NewInMemoryRepository()
	modelRepo := model.NewInMemoryRepository()

	// ===== Converter（stub，Phase 2 才實作） =====
	converterClient := converter.NewStubClient()

	// ===== Phase 0.8 / 0.8b Conversion（轉檔功能整合） =====
	// 對齊 .autoflow/04-architecture/conversion.md、ADR-015。
	//
	// 啟用條件：cfg.Conversion.Enabled() —
	// ConverterBaseURL + FAABaseURL + ConverterAPIKey + FAAAPIKey 全部非空。
	// 不啟用時 deps.Conversion 為 nil，5 個 endpoint 自動回 501（registerConversionRoutes 處理）。
	//
	// **Phase 0.8b T5**：完全切換至 pre-shared API key 認證 — 不再 wire MCTokenClient、
	// 不再讀 OIDCConfig.ServiceClientID/Secret、不再有 tenant_id / delegated_ttl_sec
	// 概念。參見 ADR-015 §6 變更影響清單。
	var conversionService conversion.Service
	if cfg.Conversion.Enabled() {
		// 不再檢查 ServiceClientID/Secret —— Phase 0.8b 起 conversion 不依賴 OIDC service client。
		// （OIDCConfig.ServiceClientID/Secret 兩欄位仍保留供 backward compat，但非 conversion 必需。）

		converterAPIClient := conversion.NewConverterClient(conversion.ConverterClientOpts{
			BaseURL: cfg.Conversion.ConverterBaseURL,
			APIKey:  cfg.Conversion.ConverterAPIKey,
			Logger:  log,
		})
		faaAPIClient := conversion.NewFAAClient(conversion.FAAClientOpts{
			BaseURL: cfg.Conversion.FAABaseURL,
			APIKey:  cfg.Conversion.FAAAPIKey,
			Logger:  log,
		})
		ownership := conversion.NewOwnership(converterAPIClient, log)

		// narrow adapter（避免 conversion 直接 import internal/model / internal/storage）
		modelStoreAdapter := newConversionModelStoreAdapter(modelRepo)
		storageAdapter := newConversionStorageAdapter(storageStore)

		var convErr error
		conversionService, convErr = conversion.NewService(conversion.FlowOpts{
			Converter:  converterAPIClient,
			FAA:        faaAPIClient,
			Ownership:  ownership,
			ModelStore: modelStoreAdapter,
			Storage:    storageAdapter,
			Logger:     log,
		})
		if convErr != nil {
			log.Error("failed to init conversion service", "error", convErr)
			os.Exit(1)
		}
		log.Info("conversion service initialized",
			"converter_base_url", cfg.Conversion.ConverterBaseURL,
			"faa_base_url", cfg.Conversion.FAABaseURL,
			// 安全：絕不印 key 全文 — 對齊 ADR-015 §3.5.3 部署檢查清單 #4
			"converter_api_key_set", cfg.Conversion.ConverterAPIKey != "",
			"faa_api_key_set", cfg.Conversion.FAAAPIKey != "")
	} else {
		log.Info("conversion service disabled (set VISIONA_CONVERTER_BASE_URL + VISIONA_FAA_BASE_URL + VISIONA_CONVERTER_API_KEY + VISIONA_FAA_API_KEY to enable)")
	}

	// ===== Seed demo data（可選） =====
	if cfg.Server.SeedDemoData {
		if err := seedDemoData(deviceRepo, modelRepo, pairingStore, cfg.Auth.StaticUserID, log); err != nil {
			log.Warn("seed demo data failed", "error", err)
		}
	}

	// ===== API Router =====
	gin.SetMode(gin.ReleaseMode)
	// Phase 0.7 security fix C1：StaticUserID 不再注入 Deps（見 .autoflow/05-implementation/review/phase-0.7-security-audit.md）
	// dev seed 仍直接讀 cfg.Auth.StaticUserID；stage/prod 不影響（VISIONA_SEED_DEMO_DATA=false）。
	router := api.NewRouter(api.Deps{
		Logger:             log,
		PairingStore:       pairingStore,
		SessionTokenStore:  sessionTokenStore,
		SessionStore:       sessionStore,
		Forwarder:          forwarder,
		DeviceRepo:         deviceRepo,
		ModelRepo:          modelRepo,
		Storage:            storageStore,
		Converter:          converterClient,
		Conversion:         conversionService, // Phase 0.8（nil 時 /api/conversion/* 回 501）
		MaxUploadSizeMB:    cfg.Model.MaxSizeMB,
		CORSAllowedOrigins: cfg.CORS.AllowedOrigins,
		RelayPublicURL:     cfg.Server.RelayPublicURL,

		// OIDC（OB5：唯一認證路徑）
		OIDCProvider:     oidcProvider,
		SessionManager:   userSessionMgr,
		OIDCPostLoginURL: cfg.OIDC.PostLoginURL,
	})

	addr := net.JoinHostPort(cfg.Server.Host, strconv.Itoa(cfg.Server.Port))
	srv := &http.Server{
		Addr:              addr,
		Handler:           router,
		ReadHeaderTimeout: 10 * time.Second, // 防 slow-loris（對齊 security.md）
	}

	// ===== User session cleanup goroutine =====
	cleanupCtx, cleanupCancel := context.WithCancel(context.Background())
	defer cleanupCancel()
	go runUserSessionCleanup(cleanupCtx, userSessionStore, cfg.UserSession.IdleTTL, cfg.UserSession.AbsoluteTTL, log)

	// ===== 啟動 server =====
	errCh := make(chan error, 1)
	go func() {
		log.Info("api-server listening",
			"addr", addr,
			"proxy_internal_url", cfg.Session.ProxyInternalURL,
			"seed_demo_data", cfg.Server.SeedDemoData,
			"oidc_issuer", cfg.OIDC.IssuerURL,
		)
		if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
			errCh <- err
		}
	}()

	// 等 signal 或錯誤
	quit := make(chan os.Signal, 1)
	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
	select {
	case <-quit:
		log.Info("shutdown signal received")
	case err := <-errCh:
		log.Error("api-server error, shutting down", "error", err)
	}

	// Graceful shutdown
	shutdownCtx, cancel := context.WithTimeout(context.Background(), shutdownTimeout)
	defer cancel()
	if err := srv.Shutdown(shutdownCtx); err != nil {
		log.Warn("api-server shutdown error", "error", err)
	}
	cleanupCancel() // 停掉 user session cleanup goroutine
	log.Info("api-server stopped")
}

// runUserSessionCleanup 是 OIDC user session store 的 background cleanup 迴圈。
//
// 每 sessionCleanupInterval 跑一次 store.CleanupExpired，把 idle / absolute timeout
// 的 session 清掉。失敗只 log 不 panic（cleanup 不應拖垮主 process）。
//
// ctx 取消（process shutdown）即退出。
func runUserSessionCleanup(ctx context.Context, store usersession.Store, idleTTL, absTTL time.Duration, log loggerLike) {
	ticker := time.NewTicker(sessionCleanupInterval)
	defer ticker.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			cctx, cancel := context.WithTimeout(ctx, 10*time.Second)
			removed, err := store.CleanupExpired(cctx, idleTTL, absTTL)
			cancel()
			if err != nil {
				log.Warn("user session cleanup failed", "error", err)
				continue
			}
			if removed > 0 {
				log.Info("user session cleanup", "removed", removed)
			}
		}
	}
}

// loggerLike 是 runUserSessionCleanup 需要的最小 logger 介面，避免直接綁 *slog.Logger
// 而能在 test 中 stub。
type loggerLike interface {
	Info(msg string, args ...any)
	Warn(msg string, args ...any)
}