package message

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"log/slog"
	"net/http"
	"strconv"

	"git.dustin.coffee/hobokenchicken/dumpsterChat/internal/gateway"
	"git.dustin.coffee/hobokenchicken/dumpsterChat/internal/middleware"
	"git.dustin.coffee/hobokenchicken/dumpsterChat/internal/push"
	"github.com/go-chi/chi/v5"
)

type Handler struct {
	db       *sql.DB
	hub      *gateway.Hub
	mentions *MentionHandler
}

func NewHandler(db *sql.DB, hub *gateway.Hub, pushHandler *push.Handler, logger *slog.Logger) *Handler {
	return &Handler{
		db:       db,
		hub:      hub,
		mentions: NewMentionHandler(db, pushHandler, logger),
	}
}

func (h *Handler) RegisterRoutes(r chi.Router) {
	r.Get("/{channelID}/messages", h.List)
	r.Post("/{channelID}/messages", h.Create)
	r.Patch("/{messageID}", h.Update)
	r.Delete("/{messageID}", h.Delete)
}

type messageResponse struct {
	ID           string  `json:"id"`
	ChannelID    string  `json:"channel_id"`
	AuthorID     string  `json:"author_id"`
	AuthorName   string  `json:"author_username"`
	DisplayName  *string `json:"author_display_name"`
	Content      string  `json:"content"`
	EditedAt     *string `json:"edited_at"`
	CreatedAt    string  `json:"created_at"`
}

// isMember checks whether the given user is a member of the given server.
func (h *Handler) isMember(ctx context.Context, userID, serverID string) (bool, error) {
	var exists bool
	err := h.db.QueryRowContext(ctx, `
		SELECT EXISTS(SELECT 1 FROM members WHERE user_id = $1 AND server_id = $2)
	`, userID, serverID).Scan(&exists)
	return exists, err
}

type createMessageRequest struct {
	Content string  `json:"content"`
	ReplyTo *string `json:"reply_to,omitempty"`
}

// @Summary Create a message
// @Description Send a message to a channel
// @Tags messages
// @Accept json
// @Produce json
// @Security SessionAuth
// @Param channelID path string true "Channel ID"
// @Param body body createMessageRequest true "Message data"
// @Success 201 {object} messageResponse
// @Failure 400 {object} map[string]string
// @Failure 401 {object} map[string]string
// @Failure 403 {object} map[string]string
// @Router /channels/{channelID}/messages [post]
func (h *Handler) Create(w http.ResponseWriter, r *http.Request) {
	channelID := chi.URLParam(r, "channelID")
	userID, ok := h.requireChannelAccess(w, r, channelID)
	if !ok {
		return
	}

	var req createMessageRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		http.Error(w, `{"error":"invalid request"}`, http.StatusBadRequest)
		return
	}
	if req.Content == "" {
		http.Error(w, `{"error":"content is required"}`, http.StatusBadRequest)
		return
	}

	var msg messageResponse
	var editedAt sql.NullString
	var createdAt sql.NullString
	var replyTo sql.NullString
	if req.ReplyTo != nil {
		replyTo = sql.NullString{String: *req.ReplyTo, Valid: true}
	}
	err := h.db.QueryRowContext(r.Context(), `
		INSERT INTO messages (channel_id, author_id, content, reply_to)
		VALUES ($1, $2, $3, $4)
		RETURNING id, channel_id, author_id, content, edited_at::text, created_at::text
	`, channelID, userID, req.Content, replyTo).Scan(
		&msg.ID, &msg.ChannelID, &msg.AuthorID, &msg.Content, &editedAt, &createdAt,
	)
	if err != nil {
		http.Error(w, `{"error":"failed to create message"}`, http.StatusInternalServerError)
		return
	}

	// Fetch author info
	err = h.db.QueryRowContext(r.Context(), `
		SELECT username, display_name FROM users WHERE id = $1
	`, userID).Scan(&msg.AuthorName, &msg.DisplayName)
	if err != nil {
		http.Error(w, `{"error":"server error"}`, http.StatusInternalServerError)
		return
	}

	if editedAt.Valid {
		msg.EditedAt = &editedAt.String
	}
	msg.CreatedAt = createdAt.String

	// Broadcast MESSAGE_CREATE event via WebSocket
	h.hub.BroadcastEvent(gateway.Event{
		Type: gateway.EventMessageCreate,
		Data: msg,
	})

	// Dispatch push notifications for @mentions
	go h.mentions.ParseAndNotify(r.Context(), channelID, userID, req.Content)

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusCreated)
	json.NewEncoder(w).Encode(msg)
}

type updateMessageRequest struct {
	Content string `json:"content"`
}

// @Summary Update a message
// @Description Edit a message (author only)
// @Tags messages
// @Accept json
// @Produce json
// @Security SessionAuth
// @Param channelID path string true "Channel ID"
// @Param messageID path string true "Message ID"
// @Param body body updateMessageRequest true "Message update data"
// @Success 200 {object} messageResponse
// @Failure 400 {object} map[string]string
// @Failure 401 {object} map[string]string
// @Failure 404 {object} map[string]string
// @Router /channels/{channelID}/messages/{messageID} [patch]
func (h *Handler) Update(w http.ResponseWriter, r *http.Request) {
	messageID := chi.URLParam(r, "messageID")
	userID, ok := middleware.UserIDFromContext(r.Context())
	if !ok {
		http.Error(w, `{"error":"unauthorized"}`, http.StatusUnauthorized)
		return
	}

	var req updateMessageRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		http.Error(w, `{"error":"invalid request"}`, http.StatusBadRequest)
		return
	}
	if req.Content == "" {
		http.Error(w, `{"error":"content is required"}`, http.StatusBadRequest)
		return
	}

	var msg messageResponse
	var editedAt sql.NullString
	var createdAt sql.NullString
	err := h.db.QueryRowContext(r.Context(), `
		UPDATE messages SET content = $1, edited_at = NOW()
		WHERE id = $2 AND author_id = $3
		RETURNING id, channel_id, author_id, content, edited_at::text, created_at::text
	`, req.Content, messageID, userID).Scan(
		&msg.ID, &msg.ChannelID, &msg.AuthorID, &msg.Content, &editedAt, &createdAt,
	)
	if err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			http.Error(w, `{"error":"message not found or not authorized"}`, http.StatusNotFound)
			return
		}
		http.Error(w, `{"error":"failed to update message"}`, http.StatusInternalServerError)
		return
	}

	err = h.db.QueryRowContext(r.Context(), `
		SELECT username, display_name FROM users WHERE id = $1
	`, userID).Scan(&msg.AuthorName, &msg.DisplayName)
	if err != nil {
		http.Error(w, `{"error":"server error"}`, http.StatusInternalServerError)
		return
	}

	if editedAt.Valid {
		msg.EditedAt = &editedAt.String
	}
	msg.CreatedAt = createdAt.String

	h.hub.BroadcastEvent(gateway.Event{
		Type: gateway.EventMessageUpdate,
		Data: msg,
	})

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(msg)
}

// @Summary Delete a message
// @Description Delete a message (author only)
// @Tags messages
// @Security SessionAuth
// @Param channelID path string true "Channel ID"
// @Param messageID path string true "Message ID"
// @Success 204
// @Failure 401 {object} map[string]string
// @Failure 404 {object} map[string]string
// @Router /channels/{channelID}/messages/{messageID} [delete]
func (h *Handler) Delete(w http.ResponseWriter, r *http.Request) {
	messageID := chi.URLParam(r, "messageID")
	userID, ok := middleware.UserIDFromContext(r.Context())
	if !ok {
		http.Error(w, `{"error":"unauthorized"}`, http.StatusUnauthorized)
		return
	}

	var channelID string
	err := h.db.QueryRowContext(r.Context(), `
		DELETE FROM messages WHERE id = $1 AND author_id = $2
		RETURNING channel_id
	`, messageID, userID).Scan(&channelID)
	if err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			http.Error(w, `{"error":"message not found or not authorized"}`, http.StatusNotFound)
			return
		}
		http.Error(w, `{"error":"failed to delete message"}`, http.StatusInternalServerError)
		return
	}

	h.hub.BroadcastEvent(gateway.Event{
		Type: gateway.EventMessageDelete,
		Data: map[string]string{
			"id":          messageID,
			"channel_id":  channelID,
		},
	})

	w.WriteHeader(http.StatusNoContent)
}

// @Summary List messages
// @Description List messages in a channel with pagination
// @Tags messages
// @Produce json
// @Security SessionAuth
// @Param channelID path string true "Channel ID"
// @Param limit query int false "Max messages to return (1-100, default 50)"
// @Param before query string false "Message ID to fetch messages before"
// @Success 200 {array} messageResponse
// @Failure 401 {object} map[string]string
// @Failure 403 {object} map[string]string
// @Router /channels/{channelID}/messages [get]
func (h *Handler) List(w http.ResponseWriter, r *http.Request) {
	channelID := chi.URLParam(r, "channelID")
	userID, ok := h.requireChannelAccess(w, r, channelID)
	if !ok {
		return
	}

	limitStr := r.URL.Query().Get("limit")
	limit := 50
	if limitStr != "" {
		if l, err := strconv.Atoi(limitStr); err == nil && l > 0 && l <= 100 {
			limit = l
		}
	}

	before := r.URL.Query().Get("before")

	var rows *sql.Rows
	var err error
	if before != "" {
		rows, err = h.db.QueryContext(r.Context(), `
			SELECT m.id, m.channel_id, m.author_id, u.username, u.display_name, m.content, m.edited_at::text, m.created_at::text
			FROM messages m
			JOIN users u ON m.author_id = u.id
			WHERE m.channel_id = $1 AND m.created_at < (SELECT created_at FROM messages WHERE id = $2)
			ORDER BY m.created_at DESC
			LIMIT $3
		`, channelID, before, limit)
	} else {
		rows, err = h.db.QueryContext(r.Context(), `
			SELECT m.id, m.channel_id, m.author_id, u.username, u.display_name, m.content, m.edited_at::text, m.created_at::text
			FROM messages m
			JOIN users u ON m.author_id = u.id
			WHERE m.channel_id = $1
			ORDER BY m.created_at DESC
			LIMIT $2
		`, channelID, limit)
	}
	if err != nil {
		http.Error(w, `{"error":"failed to list messages"}`, http.StatusInternalServerError)
		return
	}
	defer rows.Close()

	messages := make([]messageResponse, 0)
	for rows.Next() {
		var msg messageResponse
		var editedAt sql.NullString
		var createdAt sql.NullString
		err := rows.Scan(&msg.ID, &msg.ChannelID, &msg.AuthorID, &msg.AuthorName, &msg.DisplayName, &msg.Content, &editedAt, &createdAt)
		if err != nil {
			continue
		}
		if editedAt.Valid {
			msg.EditedAt = &editedAt.String
		}
		msg.CreatedAt = createdAt.String
		messages = append(messages, msg)
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(messages)

	_ = userID
}

// requireChannelAccess checks if user is authenticated and is a member of the channel's server.
func (h *Handler) requireChannelAccess(w http.ResponseWriter, r *http.Request, channelID string) (string, bool) {
	userID, ok := middleware.UserIDFromContext(r.Context())
	if !ok {
		http.Error(w, `{"error":"unauthorized"}`, http.StatusUnauthorized)
		return "", false
	}

	var serverID string
	err := h.db.QueryRowContext(r.Context(), `SELECT server_id FROM channels WHERE id = $1`, channelID).Scan(&serverID)
	if err != nil {
		http.Error(w, `{"error":"channel not found"}`, http.StatusNotFound)
		return "", false
	}

	isMember, err := h.isMember(r.Context(), userID, serverID)
	if err != nil || !isMember {
		http.Error(w, `{"error":"not a member"}`, http.StatusForbidden)
		return "", false
	}

	return userID, true
}