package http

import (
	"crypto/sha256"
	"encoding/hex"
	"errors"
	"fmt"
	"strconv"
	"strings"
	"time"

	"github.com/lixenwraith/chess/internal/server/core"
	"github.com/lixenwraith/chess/internal/server/processor"
	"github.com/lixenwraith/chess/internal/server/service"

	"github.com/gofiber/fiber/v2"
	"github.com/gofiber/fiber/v2/middleware/cors"
	"github.com/gofiber/fiber/v2/middleware/limiter"
	"github.com/gofiber/fiber/v2/middleware/logger"
	"github.com/gofiber/fiber/v2/middleware/recover"
)

const rateLimitRate = 10 // req/sec

// HTTPHandler handles HTTP requests and routes them to the processor
type HTTPHandler struct {
	proc    *processor.Processor
	svc     *service.Service
	version string
}

func NewHTTPHandler(proc *processor.Processor, svc *service.Service, version string) *HTTPHandler {
	return &HTTPHandler{proc: proc, svc: svc, version: version}
}

// Options configures the API application.
type Options struct {
	DevMode     bool
	LogRequests bool
	// TrustedProxies lists reverse-proxy IPs or CIDRs whose ProxyHeader value
	// is the client address. Empty means the TCP peer is the client.
	TrustedProxies []string
	// ProxyHeader names a single-address header the proxy overwrites, such as
	// X-Real-IP (nginx: proxy_set_header X-Real-IP $remote_addr). Avoid
	// X-Forwarded-For: its first entry is supplied by the client.
	ProxyHeader string
	// Version is the build identifier /health reports.
	Version string
}

// appConfig returns the Fiber configuration. Client-IP resolution only honors
// ProxyHeader on connections from a trusted proxy, so rate-limit keys cannot be
// chosen by a client that reaches the API directly.
func appConfig(opts Options) fiber.Config {
	config := fiber.Config{
		ErrorHandler: customErrorHandler,
		ReadTimeout:  15 * time.Second,
		WriteTimeout: 35 * time.Second,
		IdleTimeout:  60 * time.Second,
	}
	if len(opts.TrustedProxies) > 0 && opts.ProxyHeader != "" {
		config.EnableTrustedProxyCheck = true
		config.TrustedProxies = opts.TrustedProxies
		config.ProxyHeader = opts.ProxyHeader
		config.EnableIPValidation = true
	}
	return config
}

// clientIP is the rate-limit key: the proxy-reported address from a trusted
// proxy, otherwise the TCP peer.
func clientIP(c *fiber.Ctx) string {
	if ip := c.IP(); ip != "" {
		return ip
	}
	return c.Context().RemoteIP().String()
}

func NewFiberApp(proc *processor.Processor, svc *service.Service, opts Options) *fiber.App {
	// Create handler
	h := NewHTTPHandler(proc, svc, opts.Version)
	devMode := opts.DevMode

	// Initialize Fiber app
	app := fiber.New(appConfig(opts))

	// Global middleware (order matters)
	app.Use(recover.New())
	if opts.LogRequests {
		app.Use(logger.New(logger.Config{
			Format:     "${time} HTTP ${status} ${method} ${path} ${latency}\n",
			TimeFormat: time.RFC3339,
			TimeZone:   "UTC",
		}))
	}
	// ETag and Content-Disposition are not CORS-safelisted: a browser client
	// on another origin (the embedded web server's port, in development) can
	// only revalidate histories and name PGN downloads when they are exposed.
	app.Use(cors.New(cors.Config{
		AllowOrigins:  "*",
		AllowMethods:  "GET,POST,PUT,DELETE,OPTIONS",
		AllowHeaders:  "Origin,Content-Type,Accept,Authorization,If-None-Match",
		ExposeHeaders: "ETag,Content-Disposition",
	}))

	// Health check (no rate limit)
	app.Get("/health", h.Health)

	// API routes
	api := app.Group("/api")

	// Auth routes with specific rate limiting
	auth := api.Group("/auth")

	// Register: 5 req/min per IP
	auth.Post("/register", limiter.New(limiter.Config{
		Max:          5,
		Expiration:   1 * time.Minute,
		KeyGenerator: clientIP,
		LimitReached: func(c *fiber.Ctx) error {
			return c.Status(fiber.StatusTooManyRequests).JSON(core.ErrorResponse{
				Error:   "rate limit exceeded",
				Code:    core.ErrRateLimitExceeded,
				Details: "5 registrations per minute allowed",
			})
		},
	}), h.RegisterHandler)

	// Login: 10 req/min per IP
	auth.Post("/login", limiter.New(limiter.Config{
		Max:          10,
		Expiration:   1 * time.Minute,
		KeyGenerator: clientIP,
		LimitReached: func(c *fiber.Ctx) error {
			return c.Status(fiber.StatusTooManyRequests).JSON(core.ErrorResponse{
				Error:   "rate limit exceeded",
				Code:    core.ErrRateLimitExceeded,
				Details: "10 login attempts per minute allowed",
			})
		},
	}), h.LoginHandler)

	// Create token validator closure
	validateToken := svc.ValidateToken

	// Current user (requires auth)
	auth.Get("/me", AuthRequired(validateToken), h.GetCurrentUserHandler)

	// Logout
	auth.Post("/logout", AuthRequired(validateToken), h.LogoutHandler)

	// Delete own account: 5 req/min per IP. It takes a password, so it is
	// limited like login; authentication runs first, so only a signed-in
	// caller reaches the password check.
	auth.Delete("/me", AuthRequired(validateToken), limiter.New(limiter.Config{
		Max:          5,
		Expiration:   1 * time.Minute,
		KeyGenerator: clientIP,
		LimitReached: func(c *fiber.Ctx) error {
			return c.Status(fiber.StatusTooManyRequests).JSON(core.ErrorResponse{
				Error:   "rate limit exceeded",
				Code:    core.ErrRateLimitExceeded,
				Details: "5 account deletion attempts per minute allowed",
			})
		},
	}), h.DeleteAccountHandler)

	// Game routes with standard rate limiting
	maxReq := rateLimitRate
	if devMode {
		maxReq = rateLimitRate * 2
	}
	api.Use(limiter.New(limiter.Config{
		Max:          maxReq,
		Expiration:   1 * time.Second,
		KeyGenerator: clientIP,
		LimitReached: func(c *fiber.Ctx) error {
			return c.Status(fiber.StatusTooManyRequests).JSON(core.ErrorResponse{
				Error:   "rate limit exceeded",
				Code:    core.ErrRateLimitExceeded,
				Details: fmt.Sprintf("%d requests per second allowed", maxReq),
			})
		},
	}))

	// Content-Type validation for POST and PUT requests
	api.Use(contentTypeValidator)

	// Middleware validation for sanitization
	api.Use(validationMiddleware)

	// Register game routes with auth middleware
	api.Post("/games", OptionalAuth(validateToken), h.CreateGame) // Optional auth for player ID association
	api.Get("/games/:gameId/history", h.GetGameHistory)
	api.Get("/games/:gameId/pgn", h.GetGamePGN)
	api.Put("/games/:gameId/players", OptionalAuth(validateToken), h.ConfigurePlayers)
	api.Get("/games/:gameId", h.GetGame)
	api.Delete("/games/:gameId", OptionalAuth(validateToken), h.DeleteGame)
	api.Post("/games/:gameId/moves", OptionalAuth(validateToken), h.MakeMove)
	api.Post("/games/:gameId/undo", OptionalAuth(validateToken), h.UndoMove)
	api.Post("/games/:gameId/resign", OptionalAuth(validateToken), h.Resign)
	api.Post("/games/:gameId/draw", OptionalAuth(validateToken), h.Draw)
	api.Get("/games/:gameId/board", h.GetBoard)
	api.Get("/users/me/games", AuthRequired(validateToken), h.GetCurrentUserGames)

	return app
}

// contentTypeValidator ensures POST and PUT requests have application/json
func contentTypeValidator(c *fiber.Ctx) error {
	method := c.Method()
	if method == fiber.MethodPost || method == fiber.MethodPut {
		contentType := c.Get("Content-Type")
		if contentType != "application/json" && contentType != "" {
			return c.Status(fiber.StatusUnsupportedMediaType).JSON(core.ErrorResponse{
				Error:   "unsupported media type",
				Code:    core.ErrInvalidContent,
				Details: "Content-Type must be application/json",
			})
		}
	}
	return c.Next()
}

// customErrorHandler provides consistent error responses
func customErrorHandler(c *fiber.Ctx, err error) error {
	code := fiber.StatusInternalServerError
	response := core.ErrorResponse{
		Error: "internal server error",
		Code:  core.ErrInternalError,
	}

	// Check if it's a Fiber error
	if e, ok := err.(*fiber.Error); ok {
		code = e.Code
		response.Error = e.Message

		// Map HTTP status to error codes
		// An unknown route is not a missing game: a client newer than the
		// server must not report "game not found" for an endpoint the server
		// predates.
		switch code {
		case fiber.StatusNotFound:
			response.Code = core.ErrRouteNotFound
		case fiber.StatusBadRequest:
			response.Code = core.ErrInvalidRequest
		case fiber.StatusTooManyRequests:
			response.Code = core.ErrRateLimitExceeded
		}
	}

	return c.Status(code).JSON(response)
}

// Health check endpoint with storage status
func (h *HTTPHandler) Health(c *fiber.Ctx) error {
	storageHealth := h.svc.GetStorageHealth()
	status := "healthy"
	if storageHealth == "degraded" {
		status = "degraded"
	}
	return c.JSON(fiber.Map{
		"status":  status,
		"time":    time.Now().Unix(),
		"storage": storageHealth,
		"version": h.version,
	})
}

// CreateGame creates a new game with specified player types
func (h *HTTPHandler) CreateGame(c *fiber.Ctx) error {
	// Ensure middleware validation ran
	validated, ok := c.Locals("validated").(bool)
	if !ok || !validated {
		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
			Error: "validation bypass detected",
			Code:  core.ErrInternalError,
		})
	}

	// Retrieve validated parsed body
	validatedBody := c.Locals("validatedBody")
	if validatedBody == nil {
		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
			Error: "validation data missing",
			Code:  core.ErrInternalError,
		})
	}
	var req core.CreateGameRequest
	req = *(validatedBody.(*core.CreateGameRequest))

	// Retrieve authenticated user ID if available
	userID, _ := c.Locals("userID").(string)

	// Generate game ID via service with optional user context
	cmd := processor.NewCreateGameCommand(req)
	cmd.UserID = userID // Add user ID to command if authenticated

	resp := h.proc.Execute(cmd)

	// Return appropriate HTTP response
	if !resp.Success {
		return c.Status(fiber.StatusBadRequest).JSON(resp.Error)
	}

	return c.Status(fiber.StatusCreated).JSON(resp.Data)
}

// ConfigurePlayers updates player configuration mid-game
func (h *HTTPHandler) ConfigurePlayers(c *fiber.Ctx) error {
	gameID := c.Params("gameId")

	// Validate UUID format
	if !isValidUUID(gameID) {
		return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
			Error:   "invalid game ID format",
			Code:    core.ErrInvalidRequest,
			Details: "game ID must be a valid UUID",
		})
	}

	// Ensure middleware validation ran
	validated, ok := c.Locals("validated").(bool)
	if !ok || !validated {
		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
			Error: "validation bypass detected",
			Code:  core.ErrInternalError,
		})
	}

	// Retrieve validated parsed body
	validatedBody := c.Locals("validatedBody")
	if validatedBody == nil {
		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
			Error: "validation data missing",
			Code:  core.ErrInternalError,
		})
	}
	var req core.ConfigurePlayersRequest
	req = *(validatedBody.(*core.ConfigurePlayersRequest))

	// Create command and execute
	cmd := processor.NewConfigurePlayersCommand(gameID, req)
	cmd.UserID, _ = c.Locals("userID").(string)
	resp := h.proc.Execute(cmd)

	// Return appropriate HTTP response
	if !resp.Success {
		return c.Status(statusForCode(resp.Error.Code)).JSON(resp.Error)
	}

	return c.JSON(resp.Data)
}

// GetGame retrieves current game state
func (h *HTTPHandler) GetGame(c *fiber.Ctx) error {
	gameID := c.Params("gameId")

	// Validate UUID format
	if !isValidUUID(gameID) {
		return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
			Error:   "invalid game ID format",
			Code:    core.ErrInvalidRequest,
			Details: "game ID must be a valid UUID",
		})
	}

	// Check for long-polling parameters
	waitStr := c.Query("wait", "false")
	moveCountStr := c.Query("moveCount", "-1")

	// Non-wait path - existing behavior
	if waitStr != "true" {
		// Create command and execute
		cmd := processor.NewGetGameCommand(gameID)
		resp := h.proc.Execute(cmd)

		// Return appropriate HTTP response
		if !resp.Success {
			return c.Status(fiber.StatusNotFound).JSON(resp.Error)
		}

		return c.JSON(resp.Data)
	}

	// Long-polling path
	moveCount, err := strconv.Atoi(moveCountStr)
	if err != nil {
		moveCount = -1
	}

	// First check if game exists and get current state
	g, err := h.svc.GetGameView(gameID)
	if err != nil {
		return c.Status(fiber.StatusNotFound).JSON(core.ErrorResponse{
			Error: "game not found",
			Code:  core.ErrGameNotFound,
		})
	}

	currentMoveCount := len(g.Moves)
	st := g.State
	settled := st != core.StateOngoing && st != core.StatePending
	// If move count already different, return immediately
	if moveCount != currentMoveCount || settled {
		cmd := processor.NewGetGameCommand(gameID)
		resp := h.proc.Execute(cmd)
		if !resp.Success {
			return c.Status(fiber.StatusNotFound).JSON(resp.Error)
		}
		return c.JSON(resp.Data)
	}

	// Register wait with service
	ctx := c.Context()
	notify := h.svc.RegisterWait(gameID, moveCount, ctx)

	// Wait for notification, timeout, or client disconnect
	select {
	case <-notify:
		// State changed or timeout, get fresh game state
		cmd := processor.NewGetGameCommand(gameID)
		resp := h.proc.Execute(cmd)

		// Game might have been deleted
		if !resp.Success {
			return c.Status(fiber.StatusNotFound).JSON(resp.Error)
		}

		return c.JSON(resp.Data)

	case <-ctx.Done():
		// Client disconnected
		return nil
	}
}

// MakeMove submits a move
func (h *HTTPHandler) MakeMove(c *fiber.Ctx) error {
	gameID := c.Params("gameId")

	if !isValidUUID(gameID) {
		return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
			Error:   "invalid game ID format",
			Code:    core.ErrInvalidRequest,
			Details: "game ID must be a valid UUID",
		})
	}

	validated, ok := c.Locals("validated").(bool)
	if !ok || !validated {
		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
			Error: "validation bypass detected",
			Code:  core.ErrInternalError,
		})
	}

	validatedBody := c.Locals("validatedBody")
	if validatedBody == nil {
		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
			Error: "validation data missing",
			Code:  core.ErrInternalError,
		})
	}
	var req core.MoveRequest
	req = *(validatedBody.(*core.MoveRequest))

	// Get authenticated user ID if present
	userID, _ := c.Locals("userID").(string)

	cmd := processor.NewMakeMoveCommand(gameID, req)
	cmd.UserID = userID // Pass user context for authorization

	resp := h.proc.Execute(cmd)

	if !resp.Success {
		statusCode := fiber.StatusBadRequest
		switch resp.Error.Code {
		case core.ErrGameNotFound:
			statusCode = fiber.StatusNotFound
		case core.ErrUnauthorized:
			statusCode = fiber.StatusForbidden
		case core.ErrConflict:
			statusCode = fiber.StatusConflict
		}
		return c.Status(statusCode).JSON(resp.Error)
	}

	return c.JSON(resp.Data)
}

// UndoMove undoes one or more moves
func (h *HTTPHandler) UndoMove(c *fiber.Ctx) error {
	gameID := c.Params("gameId")

	// Validate UUID format
	if !isValidUUID(gameID) {
		return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
			Error:   "invalid game ID format",
			Code:    core.ErrInvalidRequest,
			Details: "game ID must be a valid UUID",
		})
	}

	// Ensure middleware validation ran
	validated, ok := c.Locals("validated").(bool)
	if !ok || !validated {
		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
			Error: "validation bypass detected",
			Code:  core.ErrInternalError,
		})
	}

	// Retrieve validated parsed body
	validatedBody := c.Locals("validatedBody")
	if validatedBody == nil {
		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
			Error: "validation data missing",
			Code:  core.ErrInternalError,
		})
	}
	var req core.UndoRequest
	req = *(validatedBody.(*core.UndoRequest))

	// Create command and execute
	cmd := processor.NewUndoMoveCommand(gameID, req)
	cmd.UserID, _ = c.Locals("userID").(string)
	resp := h.proc.Execute(cmd)

	// Return appropriate HTTP response
	if !resp.Success {
		return c.Status(statusForCode(resp.Error.Code)).JSON(resp.Error)
	}

	return c.JSON(resp.Data)
}

// Resign ends the game in the opponent's favor.
func (h *HTTPHandler) Resign(c *fiber.Ctx) error {
	return h.executeWithBody(c, func(gameID string, body any) processor.Command {
		return processor.NewResignCommand(gameID, *body.(*core.ResignRequest))
	})
}

// Draw offers, accepts, or declines a draw by agreement.
func (h *HTTPHandler) Draw(c *fiber.Ctx) error {
	return h.executeWithBody(c, func(gameID string, body any) processor.Command {
		return processor.NewDrawCommand(gameID, *body.(*core.DrawRequest))
	})
}

// executeWithBody runs a game command built from the validated request body,
// with the caller's user ID for slot authorization.
func (h *HTTPHandler) executeWithBody(c *fiber.Ctx, build func(gameID string, body any) processor.Command) error {
	gameID := c.Params("gameId")
	if !isValidUUID(gameID) {
		return invalidGameID(c)
	}
	body := c.Locals("validatedBody")
	if validated, _ := c.Locals("validated").(bool); !validated || body == nil {
		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
			Error: "validation bypass detected", Code: core.ErrInternalError,
		})
	}
	cmd := build(gameID, body)
	cmd.UserID, _ = c.Locals("userID").(string)

	resp := h.proc.Execute(cmd)
	if !resp.Success {
		return c.Status(statusForCode(resp.Error.Code)).JSON(resp.Error)
	}
	return c.JSON(resp.Data)
}

// statusForCode maps processor error codes to HTTP statuses.
func statusForCode(code string) int {
	switch code {
	case core.ErrGameNotFound:
		return fiber.StatusNotFound
	case core.ErrUnauthorized:
		return fiber.StatusForbidden
	case core.ErrConflict:
		return fiber.StatusConflict
	case core.ErrInternalError:
		return fiber.StatusInternalServerError
	}
	return fiber.StatusBadRequest
}

// DeleteGame unloads a live game while retaining its durable history.
func (h *HTTPHandler) DeleteGame(c *fiber.Ctx) error {
	gameID := c.Params("gameId")

	// Validate UUID format
	if !isValidUUID(gameID) {
		return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
			Error:   "invalid game ID format",
			Code:    core.ErrInvalidRequest,
			Details: "game ID must be a valid UUID",
		})
	}

	// Create command and execute
	cmd := processor.NewDeleteGameCommand(gameID)
	cmd.UserID, _ = c.Locals("userID").(string)
	resp := h.proc.Execute(cmd)

	// Return appropriate HTTP response
	if !resp.Success {
		return c.Status(statusForCode(resp.Error.Code)).JSON(resp.Error)
	}

	return c.SendStatus(fiber.StatusNoContent)
}

// GetBoard returns ASCII representation of the board
func (h *HTTPHandler) GetBoard(c *fiber.Ctx) error {
	gameID := c.Params("gameId")

	// Validate UUID format
	if !isValidUUID(gameID) {
		return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
			Error:   "invalid game ID format",
			Code:    core.ErrInvalidRequest,
			Details: "game ID must be a valid UUID",
		})
	}

	// Create command and execute
	cmd := processor.NewGetBoardCommand(gameID)
	resp := h.proc.Execute(cmd)

	// Return appropriate HTTP response
	if !resp.Success {
		return c.Status(fiber.StatusNotFound).JSON(resp.Error)
	}

	return c.JSON(resp.Data)
}

// GetGameHistory serves persisted replay data. Histories are public by game ID,
// matching the existing public live-game read model.
func (h *HTTPHandler) GetGameHistory(c *fiber.Ctx) error {
	gameID := c.Params("gameId")
	if !isValidUUID(gameID) {
		return invalidGameID(c)
	}

	history, err := h.svc.GetGameHistory(gameID)
	if err != nil {
		return storedGameError(c, err)
	}
	body, err := c.App().Config().JSONEncoder(history)
	if err != nil {
		return err
	}
	return sendRevalidated(c, fiber.MIMEApplicationJSON, body)
}

// GetGamePGN exports a stored game as a PGN attachment; ?ply=N stops after N
// plies. Same visibility as the history.
func (h *HTTPHandler) GetGamePGN(c *fiber.Ctx) error {
	gameID := c.Params("gameId")
	if !isValidUUID(gameID) {
		return invalidGameID(c)
	}
	ply, err := queryInt(c, "ply", -1, 0, 1_000_000)
	if err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
			Error: "invalid ply", Code: core.ErrInvalidRequest, Details: err.Error(),
		})
	}

	pgn, err := h.svc.GetGamePGN(gameID, ply)
	if err != nil {
		return storedGameError(c, err)
	}
	// The name is built from a date and the hexadecimal game ID only.
	c.Set(fiber.HeaderContentDisposition, `attachment; filename="`+pgn.Filename+`"`)
	return sendRevalidated(c, "application/x-chess-pgn; charset=utf-8", []byte(pgn.Text))
}

// sendRevalidated sends a stored-game representation with a strong ETag and
// answers a matching If-None-Match with 304. Stored games still change
// (moves, undo after a result), so caches must revalidate on every use
// rather than keep a copy for a fixed time.
func sendRevalidated(c *fiber.Ctx, contentType string, body []byte) error {
	sum := sha256.Sum256(body)
	etag := `"` + hex.EncodeToString(sum[:16]) + `"`
	c.Set(fiber.HeaderETag, etag)
	c.Set(fiber.HeaderCacheControl, "private, no-cache")
	if etagMatches(c.Get(fiber.HeaderIfNoneMatch), etag) {
		return c.SendStatus(fiber.StatusNotModified)
	}
	c.Set(fiber.HeaderContentType, contentType)
	return c.Send(body)
}

// etagMatches applies the weak comparison If-None-Match requires (RFC 9110
// section 13.1.2) to a comma-separated header value.
func etagMatches(header, etag string) bool {
	for _, candidate := range strings.Split(header, ",") {
		candidate = strings.TrimPrefix(strings.TrimSpace(candidate), "W/")
		if candidate == "*" || candidate == etag {
			return true
		}
	}
	return false
}

func invalidGameID(c *fiber.Ctx) error {
	return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
		Error: "invalid game ID format", Code: core.ErrInvalidRequest,
		Details: "game ID must be a valid UUID",
	})
}

func storedGameError(c *fiber.Ctx, err error) error {
	switch {
	case errors.Is(err, service.ErrStorageDisabled), errors.Is(err, service.ErrStorageUnavailable):
		return c.Status(fiber.StatusServiceUnavailable).JSON(core.ErrorResponse{
			Error: "game history storage unavailable", Code: core.ErrStorageUnavailable,
		})
	case errors.Is(err, service.ErrGameNotFound):
		return c.Status(fiber.StatusNotFound).JSON(core.ErrorResponse{
			Error: "game history not found", Code: core.ErrGameNotFound,
		})
	case errors.Is(err, service.ErrPlyOutOfRange):
		return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
			Error: "invalid ply", Code: core.ErrInvalidRequest, Details: err.Error(),
		})
	case errors.Is(err, service.ErrNotation):
		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
			Error: "game cannot be exported as PGN", Code: core.ErrInternalError,
		})
	default:
		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
			Error: "failed to load game history", Code: core.ErrInternalError,
		})
	}
}

// GetCurrentUserGames returns a bounded list suitable for CLI and web game
// pickers. The extra row used to detect a next page stays internal.
func (h *HTTPHandler) GetCurrentUserGames(c *fiber.Ctx) error {
	userID, ok := c.Locals("userID").(string)
	if !ok || userID == "" {
		return c.Status(fiber.StatusUnauthorized).JSON(core.ErrorResponse{
			Error: "unauthorized", Code: core.ErrUnauthorized,
		})
	}

	limit, err := queryInt(c, "limit", 50, 1, 100)
	if err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
			Error: "invalid pagination", Code: core.ErrInvalidRequest, Details: err.Error(),
		})
	}
	offset, err := queryInt(c, "offset", 0, 0, 1_000_000)
	if err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
			Error: "invalid pagination", Code: core.ErrInvalidRequest, Details: err.Error(),
		})
	}

	games, err := h.svc.GetUserGames(userID, service.UserGamesOptions{
		Limit:  limit,
		Offset: offset,
		Cursor: c.Query("cursor"),
		Color:  c.Query("color"),
		Status: c.Query("status"),
	})
	if err != nil {
		switch {
		case errors.Is(err, service.ErrInvalidListQuery):
			return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
				Error: "invalid list query", Code: core.ErrInvalidRequest, Details: err.Error(),
			})
		case errors.Is(err, service.ErrStorageDisabled), errors.Is(err, service.ErrStorageUnavailable):
			return c.Status(fiber.StatusServiceUnavailable).JSON(core.ErrorResponse{
				Error: "stored games unavailable", Code: core.ErrStorageUnavailable,
			})
		}
		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
			Error: "failed to load stored games", Code: core.ErrInternalError,
		})
	}
	return c.JSON(games)
}

func queryInt(c *fiber.Ctx, name string, defaultValue, minimum, maximum int) (int, error) {
	raw := c.Query(name)
	if raw == "" {
		return defaultValue, nil
	}
	value, err := strconv.Atoi(raw)
	if err != nil || value < minimum || value > maximum {
		return 0, fmt.Errorf("%s must be between %d and %d", name, minimum, maximum)
	}
	return value, nil
}