package gateway

import (
	"context"
	"crypto/sha256"
	"database/sql"
	"encoding/hex"
	"encoding/json"
	"log/slog"
	"net/http"
	"strings"
	"time"

	"github.com/gorilla/websocket"
)

const (
	writeWait      = 10 * time.Second
	pongWait       = 60 * time.Second
	pingPeriod     = (pongWait * 9) / 10
	maxMessageSize = 4096
)

var upgrader = websocket.Upgrader{
	ReadBufferSize:  1024,
	WriteBufferSize: 1024,
	CheckOrigin:     func(r *http.Request) bool { return true },
}

// SetAllowedOrigins replaces the default upgrader with one that validates
// the Origin header. Accepts if:
// 1. Exact match in origins list, OR
// 2. Hostname matches a trusted hostname, OR
// 3. Hostname matches the request's own Host header (same-origin), OR
// 4. Localhost variant
func SetAllowedOrigins(origins []string) {
	originSet := make(map[string]struct{}, len(origins))
	hostSet := make(map[string]struct{}, len(origins))
	for _, o := range origins {
		originSet[o] = struct{}{}
		h := o
		if idx := strings.Index(h, "://"); idx >= 0 {
			h = h[idx+3:]
		}
		if idx := strings.Index(h, "/"); idx >= 0 {
			h = h[:idx]
		}
		if idx := strings.LastIndex(h, ":"); idx >= 0 {
			h = h[:idx]
		}
		if h != "" {
			hostSet[h] = struct{}{}
		}
	}
	upgrader = websocket.Upgrader{
		ReadBufferSize:  1024,
		WriteBufferSize: 1024,
		CheckOrigin: func(r *http.Request) bool {
			origin := r.Header.Get("Origin")
			if origin == "" {
				return true
			}
			if _, ok := originSet[origin]; ok {
				return true
			}
			oh := extractHostname(origin)

			// Match trusted hostnames
			if _, ok := hostSet[oh]; ok {
				return true
			}

			// Match request's own Host header (same-origin)
			reqHost := extractHostname(r.Host)
			if reqHost != "" && oh == reqHost {
				return true
			}

			// Localhost variants
			if oh == "localhost" || oh == "127.0.0.1" || oh == "::1" {
				return true
			}

			return false
		},
	}
}

func extractHostname(s string) string {
	h := s
	if idx := strings.Index(h, "://"); idx >= 0 {
		h = h[idx+3:]
	}
	if idx := strings.Index(h, "/"); idx >= 0 {
		h = h[:idx]
	}
	if idx := strings.LastIndex(h, ":"); idx >= 0 {
		h = h[:idx]
	}
	h = strings.TrimPrefix(h, "[")
	h = strings.TrimSuffix(h, "]")
	return h
}

// Client is a middleman between the websocket connection and the hub.
type Client struct {
	Hub      *Hub
	Conn     *websocket.Conn
	UserID   string
	Username string
	IsBot    bool
	BotID    string
	BotName  string
	send     chan []byte
}

// readPump pumps messages from the websocket connection to the hub.
func (c *Client) readPump() {
	defer func() {
		c.Hub.Unregister(c)
		c.Conn.Close()
	}()

	c.Conn.SetReadLimit(maxMessageSize)
	c.Conn.SetReadDeadline(time.Now().Add(pongWait))
	c.Conn.SetPongHandler(func(string) error {
		c.Conn.SetReadDeadline(time.Now().Add(pongWait))
		return nil
	})

	for {
		_, raw, err := c.Conn.ReadMessage()
		if err != nil {
			if websocket.IsUnexpectedCloseError(err, websocket.CloseGoingAway, websocket.CloseNormalClosure) {
				c.Hub.logger.Warn("websocket read error", "error", err, "user_id", c.UserID)
			}
			break
		}

		var event Event
		if err := json.Unmarshal(raw, &event); err != nil {
			c.Hub.logger.Warn("invalid event JSON", "error", err, "user_id", c.UserID)
			continue
		}

		c.Hub.RecordActivity(c.UserID)

		switch event.Type {
		case EventTypingStart:
			// Enrich with sender info so receivers know who is typing
			var data map[string]interface{}
			if raw, ok := event.Data.(json.RawMessage); ok {
				json.Unmarshal(raw, &data)
			}
			if data == nil {
				data = make(map[string]interface{})
			}
			data["user_id"] = c.UserID
			data["username"] = c.Username
			c.Hub.BroadcastEvent(Event{Type: event.Type, Data: data})
		case EventPresenceUpdate:
			c.Hub.BroadcastEvent(event)
		case EventVoiceJoin, EventVoiceLeave, EventVoiceMute, EventVoiceDeafen:
			// Broadcast voice state changes to all clients with sender info
			var vData map[string]interface{}
			if raw, ok := event.Data.(json.RawMessage); ok {
				json.Unmarshal(raw, &vData)
			}
			if vData == nil {
				vData = make(map[string]interface{})
			}
			vData["user_id"] = c.UserID
			vData["username"] = c.Username
			c.Hub.BroadcastEvent(Event{Type: event.Type, Data: vData})
		case EventVoiceWhisper:
			// Forward voice whispers only to the target user, not broadcast
			var whisperData struct {
				TargetUserID string `json:"target_user_id"`
				FromUserID   string `json:"from_user_id"`
				FromUsername string `json:"from_username"`
				Message      string `json:"message,omitempty"`
			}
			if raw, ok := event.Data.(json.RawMessage); ok {
				if err := json.Unmarshal(raw, &whisperData); err == nil {
					whisperData.FromUserID = c.UserID
					c.Hub.SendToUser(whisperData.TargetUserID, Event{
						Type: EventVoiceWhisper,
						Data: whisperData,
					})
				}
			}
		case BotSendMessage:
			if !c.IsBot {
				c.Hub.logger.Warn("non-bot client sent SEND_MESSAGE", "user_id", c.UserID)
				continue
			}
			c.handleBotSendMessage(event.Data)
		case BotDeleteMessage:
			if !c.IsBot {
				c.Hub.logger.Warn("non-bot client sent DELETE_MESSAGE", "user_id", c.UserID)
				continue
			}
			c.handleBotDeleteMessage(event.Data)
		default:
			c.Hub.logger.Info("received event from client", "type", event.Type, "user_id", c.UserID)
		}
	}
}

// writePump pumps messages from the hub to the websocket connection.
func (c *Client) writePump() {
	ticker := time.NewTicker(pingPeriod)
	defer func() {
		ticker.Stop()
		c.Conn.Close()
	}()

	for {
		select {
		case message, ok := <-c.send:
			c.Conn.SetWriteDeadline(time.Now().Add(writeWait))
			if !ok {
				c.Conn.WriteMessage(websocket.CloseMessage, []byte{})
				return
			}

			w, err := c.Conn.NextWriter(websocket.TextMessage)
			if err != nil {
				return
			}
			w.Write(message)

			n := len(c.send)
			for i := 0; i < n; i++ {
				w.Write([]byte{'\n'})
				w.Write(<-c.send)
			}

			if err := w.Close(); err != nil {
				return
			}

		case <-ticker.C:
			c.Conn.SetWriteDeadline(time.Now().Add(writeWait))
			if err := c.Conn.WriteMessage(websocket.PingMessage, nil); err != nil {
				return
			}
		}
	}
}

// authMessage is the first frame the client must send after connecting (for TUI/bot clients).
type authMessage struct {
	Token string `json:"token"`
}

// ServeWS handles websocket requests from the peer.
// It authenticates via cookie (browser) or message-frame (TUI/bots).
func ServeWS(db *sql.DB, hub *Hub, logger *slog.Logger, w http.ResponseWriter, r *http.Request, cookieName string) {
	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		logger.Error("websocket upgrade failed", "error", err)
		return
	}

	var userID, username string

	// Collect candidate tokens from Query param, Authorization header, and Cookies.
	var candidateTokens []string
	if qToken := r.URL.Query().Get("token"); qToken != "" {
		candidateTokens = append(candidateTokens, qToken)
	}
	authHeader := r.Header.Get("Authorization")
	if len(authHeader) > 7 && authHeader[:7] == "Bearer " {
		candidateTokens = append(candidateTokens, authHeader[7:])
	}
	for _, c := range r.Cookies() {
		if c.Name == cookieName && c.Value != "" {
			candidateTokens = append(candidateTokens, c.Value)
		}
	}

	// Test candidates against Postgres sessions (tokens are stored hashed)
	for _, token := range candidateTokens {
		err := db.QueryRowContext(context.Background(),
			`SELECT u.id, u.username FROM sessions s JOIN users u ON u.id = s.user_id WHERE s.token = $1 AND s.expires_at > NOW()`,
			hashToken(token),
		).Scan(&userID, &username)
		if err == nil && userID != "" {
			break
		}
	}

	// Fall back to message-frame auth if no candidate token authenticated (wait up to 5s)
	if userID == "" {
		conn.SetReadDeadline(time.Now().Add(5 * time.Second))
		_, raw, readErr := conn.ReadMessage()
		if readErr == nil {
			var auth authMessage
			if jsonErr := json.Unmarshal(raw, &auth); jsonErr == nil && auth.Token != "" {
				_ = db.QueryRowContext(context.Background(),
					`SELECT u.id, u.username FROM sessions s JOIN users u ON u.id = s.user_id WHERE s.token = $1 AND s.expires_at > NOW()`,
					hashToken(auth.Token),
				).Scan(&userID, &username)
			}
		}
	}

	if userID == "" {
		logger.Warn("ws auth: no valid session found")
		conn.WriteMessage(websocket.TextMessage, []byte(`{"type":"error","error":"invalid_session"}`))
		conn.Close()
		return
	}

	conn.SetReadDeadline(time.Time{})
	conn.WriteMessage(websocket.TextMessage, []byte(`{"type":"ready"}`))

	client := &Client{
		Hub:      hub,
		Conn:     conn,
		UserID:   userID,
		Username: username,
		send:     make(chan []byte, 256),
	}

	hub.Register(client)

	go client.writePump()
	go client.readPump()
}

// ServeBotWS handles websocket requests from bot clients.
// Authenticates via ?token= query param (bot token, hashed lookup).
func ServeBotWS(db *sql.DB, hub *Hub, logger *slog.Logger, w http.ResponseWriter, r *http.Request) {
	token := r.URL.Query().Get("token")
	if token == "" {
		http.Error(w, `{"error":"token query param required"}`, http.StatusBadRequest)
		return
	}

	// Hash the token and look up the bot.
	tokenHash := hashToken(token)

	var botID, botName, ownerID string
	err := db.QueryRowContext(r.Context(),
		`SELECT id, name, owner_id FROM bots WHERE token = $1`,
		tokenHash,
	).Scan(&botID, &botName, &ownerID)
	if err != nil {
		logger.Warn("bot ws auth: invalid token")
		http.Error(w, `{"error":"invalid bot token"}`, http.StatusUnauthorized)
		return
	}

	// Verify the bot is added to at least one server.
	var serverCount int
	err = db.QueryRowContext(r.Context(),
		`SELECT COUNT(*) FROM bot_servers WHERE bot_id = $1`, botID,
	).Scan(&serverCount)
	if err != nil || serverCount == 0 {
		logger.Warn("bot ws auth: bot not added to any server", "bot_id", botID)
		http.Error(w, `{"error":"bot not added to any server"}`, http.StatusForbidden)
		return
	}

	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		logger.Error("bot websocket upgrade failed", "error", err)
		return
	}

	// Load bot server memberships into hub so BroadcastToServer works.
	hub.RefreshUserServers(ownerID)

	conn.SetReadDeadline(time.Time{})
	conn.WriteMessage(websocket.TextMessage, []byte(`{"type":"ready","bot_id":"`+botID+`"}`))

	client := &Client{
		Hub:      hub,
		Conn:     conn,
		UserID:   ownerID,
		Username: botName,
		IsBot:    true,
		BotID:    botID,
		BotName:  botName,
		send:     make(chan []byte, 256),
	}

	hub.Register(client)

	go client.writePump()
	go client.readPump()
}

// hashToken returns the SHA-256 hex digest of a token.
func hashToken(token string) string {
	h := sha256.Sum256([]byte(token))
	return hex.EncodeToString(h[:])
}

// handleBotSendMessage processes a SEND_MESSAGE action from a bot client.
func (c *Client) handleBotSendMessage(data interface{}) {
	var payload struct {
		ChannelID string `json:"channel_id"`
		Content   string `json:"content"`
	}
	raw, ok := data.(json.RawMessage)
	if !ok {
		return
	}
	if err := json.Unmarshal(raw, &payload); err != nil || payload.ChannelID == "" || payload.Content == "" {
		c.Hub.logger.Warn("bot SEND_MESSAGE: invalid payload")
		return
	}
	if len(payload.Content) > 4000 {
		payload.Content = payload.Content[:4000]
	}

	// Verify the bot is in the server that owns this channel.
	serverID, err := c.Hub.ServerIDForChannel(context.Background(), payload.ChannelID)
	if err != nil {
		c.Hub.logger.Warn("bot SEND_MESSAGE: channel not found", "channel_id", payload.ChannelID)
		return
	}
	var inServer bool
	err = c.Hub.db.QueryRowContext(context.Background(),
		`SELECT EXISTS(SELECT 1 FROM bot_servers WHERE bot_id = $1 AND server_id = $2)`,
		c.BotID, serverID,
	).Scan(&inServer)
	if err != nil || !inServer {
		c.Hub.logger.Warn("bot SEND_MESSAGE: bot not in server", "bot_id", c.BotID, "server_id", serverID)
		return
	}

	// Insert the message with bot_id set.
	var msgID, createdAt string
	err = c.Hub.db.QueryRowContext(context.Background(),
		`INSERT INTO messages (channel_id, author_id, content, bot_id)
		 VALUES ($1, $2, $3, $4)
		 RETURNING id, created_at::text`,
		payload.ChannelID, c.UserID, payload.Content, c.BotID,
	).Scan(&msgID, &createdAt)
	if err != nil {
		c.Hub.logger.Error("bot SEND_MESSAGE: insert failed", "error", err)
		return
	}

	// Broadcast MESSAGE_CREATE to the server.
	c.Hub.BroadcastToServer(serverID, Event{
		Type: EventMessageCreate,
		Data: map[string]interface{}{
			"id":                   msgID,
			"channel_id":           payload.ChannelID,
			"author_id":            c.UserID,
			"author_username":      c.BotName,
			"author_display_name":  nil,
			"author_bot":           true,
			"bot_id":               c.BotID,
			"bot_name":             c.BotName,
			"content":              payload.Content,
			"reply_to":             nil,
			"edited_at":            nil,
			"pinned":               false,
			"created_at":           createdAt,
			"embeds":               []interface{}{},
			"reactions":            []interface{}{},
		},
	})
}

// handleBotDeleteMessage processes a DELETE_MESSAGE action from a bot client.
func (c *Client) handleBotDeleteMessage(data interface{}) {
	var payload struct {
		ChannelID string `json:"channel_id"`
		MessageID string `json:"message_id"`
	}
	raw, ok := data.(json.RawMessage)
	if !ok {
		return
	}
	if err := json.Unmarshal(raw, &payload); err != nil || payload.ChannelID == "" || payload.MessageID == "" {
		c.Hub.logger.Warn("bot DELETE_MESSAGE: invalid payload")
		return
	}

	// Verify the bot is in the server that owns this channel.
	serverID, err := c.Hub.ServerIDForChannel(context.Background(), payload.ChannelID)
	if err != nil {
		return
	}
	var inServer bool
	err = c.Hub.db.QueryRowContext(context.Background(),
		`SELECT EXISTS(SELECT 1 FROM bot_servers WHERE bot_id = $1 AND server_id = $2)`,
		c.BotID, serverID,
	).Scan(&inServer)
	if err != nil || !inServer {
		return
	}

	// Delete the message (only if it exists in this channel).
	result, err := c.Hub.db.ExecContext(context.Background(),
		`DELETE FROM messages WHERE id = $1 AND channel_id = $2`,
		payload.MessageID, payload.ChannelID,
	)
	if err != nil {
		c.Hub.logger.Error("bot DELETE_MESSAGE: delete failed", "error", err)
		return
	}
	rows, _ := result.RowsAffected()
	if rows == 0 {
		return
	}

	// Broadcast MESSAGE_DELETE.
	c.Hub.BroadcastToServer(serverID, Event{
		Type: EventMessageDelete,
		Data: map[string]string{
			"id":         payload.MessageID,
			"channel_id": payload.ChannelID,
		},
	})
}