package handler

import (
	"context"
	"net/http"
	"net/url"
	"path/filepath"
	"strings"
	"time"

	"filefast/backend/internal/config"
	"filefast/backend/internal/model"
	"filefast/backend/internal/service"
	"filefast/backend/internal/storage"
	"filefast/backend/internal/store"
	"filefast/backend/internal/ws"

	"github.com/gin-gonic/gin"
	"log/slog"
)

type Dependencies struct {
	Config          config.Config
	Logger          *slog.Logger
	Store           *store.MemoryStore
	DeviceService   *service.DeviceService
	RoomService     *service.RoomService
	TransferService *service.TransferService
	AdminService    *service.AdminService
	MinIOClient     *storage.MinIOClient
	Hub             *ws.Hub
	StorageReady    bool
	RedisReady      bool
}

type HTTPHandler struct {
	deps Dependencies
}

func NewHTTPHandler(deps Dependencies) *HTTPHandler {
	return &HTTPHandler{deps: deps}
}

func (h *HTTPHandler) Router() *gin.Engine {
	router := gin.Default()

	router.GET("/healthz", h.handleHealth)
	router.GET("/ws", h.deps.Hub.Handle)

	api := router.Group("/api")
	{
		api.GET("/runtime/config", h.runtimeConfig)
		api.POST("/devices/register", h.registerDevice)
		api.POST("/admin/login", h.adminLogin)
	}

	device := api.Group("/")
	device.Use(h.requireDevice())
	{
		device.POST("/devices/heartbeat", h.deviceHeartbeat)
		device.GET("/devices/candidates", h.listCandidates)
		device.GET("/devices/:id/pending-downloads", h.pendingFallbackDownloads)

		device.POST("/rooms", h.createRoom)
		device.GET("/rooms/:code", h.getRoom)
		device.POST("/rooms/join", h.joinRoom)
		device.POST("/rooms/:code/cancel", h.cancelRoom)

		device.POST("/transfers", h.createTransfer)
		device.PATCH("/transfers/:id/status", h.updateTransferStatus)
		device.POST("/transfers/:id/fallback/presign", h.presignFallback)
		device.PUT("/transfers/:id/fallback/upload", h.uploadFallback)
		device.GET("/transfers/:id/fallback/download", h.downloadFallback)
	}

	admin := api.Group("/admin")
	admin.Use(h.requireAdmin())
	{
		admin.GET("/stats", h.adminStats)
		admin.GET("/config", h.adminConfig)
		admin.PUT("/config", h.updateAdminConfig)
		admin.GET("/transfers/recent", h.recentTransfers)
	}

	return router
}

func (h *HTTPHandler) handleHealth(c *gin.Context) {
	status := "ok"
	if !h.deps.StorageReady || !h.deps.RedisReady {
		status = "degraded"
	}

	c.JSON(http.StatusOK, gin.H{
		"status":           status,
		"minio_enabled":    h.deps.MinIOClient != nil && h.deps.MinIOClient.Enabled(),
		"storage_ready":    h.deps.StorageReady,
		"redis_ready":      h.deps.RedisReady,
		"turn_enabled":     len(h.deps.Store.RuntimeConfig().TURNURLs) > 0,
		"room_ttl_sec":     int(h.deps.Config.RoomTTL.Seconds()),
		"server_time_unix": time.Now().Unix(),
	})
}

func (h *HTTPHandler) runtimeConfig(c *gin.Context) {
	c.JSON(http.StatusOK, gin.H{"data": h.deps.Store.RuntimeConfig()})
}

func (h *HTTPHandler) registerDevice(c *gin.Context) {
	var input service.RegisterDeviceInput
	if err := c.ShouldBindJSON(&input); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	device, session := h.deps.DeviceService.Register(input, c.Request.UserAgent(), c.GetHeader("X-Device-Token"))
	c.JSON(http.StatusOK, gin.H{"data": gin.H{
		"id":                device.ID,
		"name":              device.Name,
		"type":              device.Type,
		"user_agent":        device.UserAgent,
		"network_group_key": device.NetworkGroupKey,
		"public_ip_hash":    device.PublicIPHash,
		"is_online":         device.IsOnline,
		"last_seen_at":      device.LastSeenAt,
		"created_at":        device.CreatedAt,
		"auth_token":        session.Token,
		"auth_expires_at":   session.ExpiresAt,
	}})
}

func (h *HTTPHandler) deviceHeartbeat(c *gin.Context) {
	var input struct {
		DeviceID string `json:"device_id" binding:"required"`
	}
	if err := c.ShouldBindJSON(&input); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	if !h.ensureAuthenticatedDevice(c, input.DeviceID) {
		return
	}

	device, ok := h.deps.DeviceService.Heartbeat(input.DeviceID)
	if !ok {
		c.JSON(http.StatusNotFound, gin.H{"error": "device not found"})
		return
	}

	c.JSON(http.StatusOK, gin.H{"data": device})
}

func (h *HTTPHandler) listCandidates(c *gin.Context) {
	deviceID := c.Query("deviceId")
	if deviceID == "" {
		c.JSON(http.StatusBadRequest, gin.H{"error": "deviceId is required"})
		return
	}
	if !h.ensureAuthenticatedDevice(c, deviceID) {
		return
	}

	c.JSON(http.StatusOK, gin.H{"data": h.deps.DeviceService.ListCandidates(deviceID)})
}

func (h *HTTPHandler) createRoom(c *gin.Context) {
	var input struct {
		CreatorDeviceID string `json:"creator_device_id" binding:"required"`
	}
	if err := c.ShouldBindJSON(&input); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}
	if !h.ensureAuthenticatedDevice(c, input.CreatorDeviceID) {
		return
	}

	room, err := h.deps.RoomService.CreateRoom(input.CreatorDeviceID)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	c.JSON(http.StatusOK, gin.H{"data": room})
}

func (h *HTTPHandler) getRoom(c *gin.Context) {
	room, ok := h.deps.Store.GetRoom(c.Param("code"))
	if !ok {
		c.JSON(http.StatusNotFound, gin.H{"error": "room not found"})
		return
	}
	deviceID := h.authenticatedDeviceID(c)
	if room.CreatorDeviceID != deviceID && room.JoinerDeviceID != deviceID {
		c.JSON(http.StatusForbidden, gin.H{"error": "room access denied"})
		return
	}

	c.JSON(http.StatusOK, gin.H{"data": room})
}

func (h *HTTPHandler) joinRoom(c *gin.Context) {
	var input struct {
		Code           string `json:"code" binding:"required"`
		JoinerDeviceID string `json:"joiner_device_id" binding:"required"`
	}
	if err := c.ShouldBindJSON(&input); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}
	if !h.ensureAuthenticatedDevice(c, input.JoinerDeviceID) {
		return
	}

	room, err := h.deps.RoomService.JoinRoom(input.Code, input.JoinerDeviceID)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	c.JSON(http.StatusOK, gin.H{"data": room})
}

func (h *HTTPHandler) cancelRoom(c *gin.Context) {
	var input struct {
		RequesterID string `json:"requester_id" binding:"required"`
	}
	if err := c.ShouldBindJSON(&input); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}
	if !h.ensureAuthenticatedDevice(c, input.RequesterID) {
		return
	}

	room, err := h.deps.RoomService.CancelRoom(c.Param("code"), input.RequesterID)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	c.JSON(http.StatusOK, gin.H{"data": room})
}

func (h *HTTPHandler) createTransfer(c *gin.Context) {
	var input service.CreateTransferInput
	if err := c.ShouldBindJSON(&input); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}
	if !h.ensureAuthenticatedDevice(c, input.SenderDeviceID) {
		return
	}

	transfer, err := h.deps.TransferService.Create(input)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	c.JSON(http.StatusOK, gin.H{"data": transfer})
}

func (h *HTTPHandler) updateTransferStatus(c *gin.Context) {
	transfer, ok := h.deps.Store.GetTransfer(c.Param("id"))
	if !ok {
		c.JSON(http.StatusNotFound, gin.H{"error": "transfer not found"})
		return
	}
	deviceID := h.authenticatedDeviceID(c)
	if transfer.SenderDeviceID != deviceID && transfer.ReceiverDeviceID != deviceID {
		c.JSON(http.StatusForbidden, gin.H{"error": "transfer access denied"})
		return
	}

	var input service.UpdateTransferStatusInput
	if err := c.ShouldBindJSON(&input); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	transfer, err := h.deps.TransferService.UpdateStatus(c.Param("id"), input)
	if err != nil {
		c.JSON(http.StatusNotFound, gin.H{"error": err.Error()})
		return
	}

	c.JSON(http.StatusOK, gin.H{"data": transfer})
}

func (h *HTTPHandler) presignFallback(c *gin.Context) {
	if h.deps.MinIOClient == nil || !h.deps.MinIOClient.Enabled() {
		c.JSON(http.StatusServiceUnavailable, gin.H{"error": "minio fallback is disabled"})
		return
	}

	transfer, ok := h.deps.Store.GetTransfer(c.Param("id"))
	if !ok {
		c.JSON(http.StatusNotFound, gin.H{"error": "transfer not found"})
		return
	}
	if transfer.SenderDeviceID != h.authenticatedDeviceID(c) {
		c.JSON(http.StatusForbidden, gin.H{"error": "transfer access denied"})
		return
	}

	transfer, object, err := h.deps.TransferService.PrepareFallback(c.Param("id"))
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	ctx, cancel := context.WithTimeout(c.Request.Context(), 10*time.Second)
	defer cancel()

	if err := h.ensureFallbackBucket(ctx, transfer.ID); err != nil {
		h.deps.Logger.Warn("minio ensure bucket failed", "transfer_id", transfer.ID, "error", err)
		c.JSON(http.StatusBadGateway, gin.H{"error": err.Error()})
		return
	}

	uploadURL, err := h.deps.MinIOClient.PresignUpload(ctx, object.ObjectKey)
	if err != nil {
		h.deps.Logger.Warn("minio presign upload failed", "transfer_id", transfer.ID, "object_key", object.ObjectKey, "error", err)
		c.JSON(http.StatusBadGateway, gin.H{"error": err.Error()})
		return
	}

	downloadURL, err := h.deps.MinIOClient.PresignDownload(ctx, object.ObjectKey)
	if err != nil {
		h.deps.Logger.Warn("minio presign download failed", "transfer_id", transfer.ID, "object_key", object.ObjectKey, "error", err)
		c.JSON(http.StatusBadGateway, gin.H{"error": err.Error()})
		return
	}

	c.JSON(http.StatusOK, gin.H{
		"data": gin.H{
			"transfer":      transfer,
			"upload_url":    uploadURL.String(),
			"download_url":  downloadURL.String(),
			"download_path": fallbackDownloadPath(transfer.ID),
			"expires_at":    object.ExpiresAt,
		},
	})
}

func (h *HTTPHandler) uploadFallback(c *gin.Context) {
	if h.deps.MinIOClient == nil || !h.deps.MinIOClient.Enabled() {
		c.JSON(http.StatusServiceUnavailable, gin.H{"error": "minio fallback is disabled"})
		return
	}

	transfer, ok := h.deps.Store.GetTransfer(c.Param("id"))
	if !ok {
		c.JSON(http.StatusNotFound, gin.H{"error": "transfer not found"})
		return
	}
	if transfer.ObjectKey == "" {
		c.JSON(http.StatusBadRequest, gin.H{"error": "fallback object is not prepared"})
		return
	}
	if transfer.SenderDeviceID != h.authenticatedDeviceID(c) {
		c.JSON(http.StatusForbidden, gin.H{"error": "transfer access denied"})
		return
	}

	ctx, cancel := context.WithTimeout(c.Request.Context(), 30*time.Minute)
	defer cancel()

	if err := h.ensureFallbackBucket(ctx, transfer.ID); err != nil {
		h.deps.Logger.Warn("minio ensure bucket failed", "transfer_id", transfer.ID, "error", err)
		c.JSON(http.StatusBadGateway, gin.H{"error": err.Error()})
		return
	}

	contentLength := c.Request.ContentLength
	if contentLength <= 0 {
		contentLength = transfer.SizeBytes
	}

	contentType := strings.TrimSpace(c.GetHeader("Content-Type"))
	if contentType == "" {
		contentType = "application/octet-stream"
	}

	if err := h.deps.MinIOClient.UploadObject(ctx, transfer.ObjectKey, c.Request.Body, contentLength, contentType); err != nil {
		h.deps.Logger.Warn("minio upload object failed", "transfer_id", transfer.ID, "object_key", transfer.ObjectKey, "error", err)
		c.JSON(http.StatusBadGateway, gin.H{"error": err.Error()})
		return
	}

	if object, ok := h.deps.Store.GetFallbackObject(transfer.ID); ok {
		object.SizeBytes = contentLength
		object.CleanupState = "ready"
		h.deps.Store.SaveFallbackObject(object)
	}

	downloadURL, err := h.deps.MinIOClient.PresignDownload(ctx, transfer.ObjectKey)
	if err != nil {
		h.deps.Logger.Warn("minio presign download failed after upload", "transfer_id", transfer.ID, "object_key", transfer.ObjectKey, "error", err)
		c.JSON(http.StatusBadGateway, gin.H{"error": err.Error()})
		return
	}

	c.JSON(http.StatusOK, gin.H{
		"data": gin.H{
			"download_url":  downloadURL.String(),
			"download_path": fallbackDownloadPath(transfer.ID),
			"object_key":    transfer.ObjectKey,
		},
	})
}

func (h *HTTPHandler) pendingFallbackDownloads(c *gin.Context) {
	deviceID := strings.TrimSpace(c.Param("id"))
	if deviceID == "" {
		c.JSON(http.StatusBadRequest, gin.H{"error": "device id is required"})
		return
	}
	if !h.ensureAuthenticatedDevice(c, deviceID) {
		return
	}

	c.JSON(http.StatusOK, gin.H{
		"data": h.deps.Store.ListPendingFallbackDownloads(deviceID, 20),
	})
}

func (h *HTTPHandler) downloadFallback(c *gin.Context) {
	if h.deps.MinIOClient == nil || !h.deps.MinIOClient.Enabled() {
		c.JSON(http.StatusServiceUnavailable, gin.H{"error": "minio fallback is disabled"})
		return
	}

	transfer, ok := h.deps.Store.GetTransfer(c.Param("id"))
	if !ok {
		c.JSON(http.StatusNotFound, gin.H{"error": "transfer not found"})
		return
	}
	if transfer.ObjectKey == "" {
		c.JSON(http.StatusBadRequest, gin.H{"error": "fallback object is not prepared"})
		return
	}
	if transfer.ReceiverDeviceID != h.authenticatedDeviceID(c) {
		c.JSON(http.StatusForbidden, gin.H{"error": "transfer access denied"})
		return
	}

	ctx, cancel := context.WithTimeout(c.Request.Context(), 5*time.Minute)
	defer cancel()

	filename := filepath.Base(transfer.Name)
	if filename == "." || filename == "" {
		filename = "download.bin"
	}

	downloadURL, err := h.deps.MinIOClient.PresignDownloadWithFilename(ctx, transfer.ObjectKey, filename)
	if err != nil {
		h.deps.Logger.Warn("minio presign download failed", "transfer_id", transfer.ID, "object_key", transfer.ObjectKey, "error", err)
		c.JSON(http.StatusBadGateway, gin.H{"error": err.Error()})
		return
	}

	c.Redirect(http.StatusTemporaryRedirect, downloadURL.String())
}

func (h *HTTPHandler) adminLogin(c *gin.Context) {
	var input struct {
		Username string `json:"username" binding:"required"`
		Password string `json:"password" binding:"required"`
	}
	if err := c.ShouldBindJSON(&input); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	session, err := h.deps.AdminService.Login(input.Username, input.Password)
	if err != nil {
		c.JSON(http.StatusUnauthorized, gin.H{"error": err.Error()})
		return
	}

	c.JSON(http.StatusOK, gin.H{"data": session})
}

func (h *HTTPHandler) adminStats(c *gin.Context) {
	c.JSON(http.StatusOK, gin.H{
		"data": gin.H{
			"stats": h.deps.Store.SnapshotStats(),
			"minio": h.deps.Store.SnapshotMinIOStorage(),
		},
	})
}

func (h *HTTPHandler) adminConfig(c *gin.Context) {
	c.JSON(http.StatusOK, gin.H{"data": h.deps.Store.RuntimeConfig()})
}

func (h *HTTPHandler) updateAdminConfig(c *gin.Context) {
	var input model.RuntimeConfig
	if err := c.ShouldBindJSON(&input); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	c.JSON(http.StatusOK, gin.H{"data": h.deps.Store.UpdateRuntimeConfig(input)})
}

func (h *HTTPHandler) recentTransfers(c *gin.Context) {
	c.JSON(http.StatusOK, gin.H{"data": h.deps.Store.ListRecentTransfers(20)})
}

func (h *HTTPHandler) requireAdmin() gin.HandlerFunc {
	return func(c *gin.Context) {
		header := c.GetHeader("Authorization")
		if header == "" {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "missing authorization header"})
			return
		}

		token := strings.TrimSpace(strings.TrimPrefix(header, "Bearer"))
		if token == "" || !h.deps.AdminService.ValidateToken(token) {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "invalid admin token"})
			return
		}

		c.Next()
	}
}

func (h *HTTPHandler) requireDevice() gin.HandlerFunc {
	return func(c *gin.Context) {
		deviceID := strings.TrimSpace(c.GetHeader("X-Device-ID"))
		token := strings.TrimSpace(c.GetHeader("X-Device-Token"))
		if deviceID == "" || token == "" {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "missing device credentials"})
			return
		}
		if !h.deps.DeviceService.ValidateSession(deviceID, token) {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "invalid device credentials"})
			return
		}
		c.Set("device_id", deviceID)
		c.Next()
	}
}

func (h *HTTPHandler) authenticatedDeviceID(c *gin.Context) string {
	value, ok := c.Get("device_id")
	if !ok {
		return ""
	}
	deviceID, _ := value.(string)
	return deviceID
}

func (h *HTTPHandler) ensureAuthenticatedDevice(c *gin.Context, expected string) bool {
	if h.authenticatedDeviceID(c) != strings.TrimSpace(expected) {
		c.JSON(http.StatusForbidden, gin.H{"error": "device access denied"})
		return false
	}
	return true
}

func fallbackDownloadPath(transferID string) string {
	return "/api/transfers/" + url.PathEscape(transferID) + "/fallback/download"
}

func contentDisposition(filename string) string {
	escaped := strings.ReplaceAll(filename, `"`, "")
	return `attachment; filename="` + escaped + `"`
}

func (h *HTTPHandler) ensureFallbackBucket(ctx context.Context, transferID string) error {
	if h.deps.MinIOClient == nil {
		return nil
	}

	err := h.deps.MinIOClient.EnsureBucket(ctx)
	if err == nil {
		return nil
	}

	// Some MinIO users can read/write objects in an existing bucket but cannot run
	// bucket-existence or bucket-creation checks. In that case we keep going.
	if strings.Contains(strings.ToLower(err.Error()), "access denied") {
		h.deps.Logger.Info("minio bucket ensure skipped due to limited permissions", "transfer_id", transferID)
		return nil
	}

	return err
}