package message

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

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

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

func NewHandler(db *sql.DB, hub *gateway.Hub) *Handler {
	return &Handler{db: db, hub: hub}
}

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
}

// serverIDForChannel returns the server_id that owns the given channel.
func (h *Handler) serverIDForChannel(ctx context.Context, channelID string) (string, error) {
	var serverID string
	err := h.db.QueryRowContext(ctx, `
		SELECT server_id FROM channels WHERE id = $1
	`, channelID).Scan(&serverID)
	return serverID, err
}

// requireChannelAccess verifies the user is a member of the server owning the channel,
// returning the server_id if successful.
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
	}

	serverID, err := h.serverIDForChannel(r.Context(), channelID)
	if err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			http.Error(w, `{"error":"channel not found"}`, http.StatusNotFound)
		} else {
			http.Error(w, `{"error":"server error"}`, http.StatusInternalServerError)
		}
		return "", false
	}

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

	return userID, true
}

func (h *Handler) List(w http.ResponseWriter, r *http.Request) {
	channelID := chi.URLParam(r, "channelID")
	if _, ok := h.requireChannelAccess(w, r, channelID); !ok {
		return
	}

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

	var rows *sql.Rows
	var err error

	if before != "" {
		// Fetch the created_at of the cursor message
		var cursorTime sql.NullString
		err = h.db.QueryRowContext(r.Context(), `
			SELECT created_at::text FROM messages WHERE id = $1
		`, before).Scan(&cursorTime)
		if err != nil {
			if errors.Is(err, sql.ErrNoRows) {
				http.Error(w, `{"error":"cursor message not found"}`, http.StatusBadRequest)
				return
			}
			http.Error(w, `{"error":"server error"}`, http.StatusInternalServerError)
			return
		}

		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
			INNER JOIN users u ON u.id = m.author_id
			WHERE m.channel_id = $1 AND m.created_at < $2::timestamptz
			ORDER BY m.created_at DESC
			LIMIT $3
		`, channelID, cursorTime.String, 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
			INNER JOIN users u ON u.id = m.author_id
			WHERE m.channel_id = $1
			ORDER BY m.created_at DESC
			LIMIT $2
		`, channelID, limit)
	}
	if err != nil {
		http.Error(w, `{"error":"server error"}`, http.StatusInternalServerError)
		return
	}
	defer rows.Close()

	messages := make([]messageResponse, 0)
	for rows.Next() {
		var msg messageResponse
		var editedAt, createdAt sql.NullString
		if err := rows.Scan(
			&msg.ID, &msg.ChannelID, &msg.AuthorID, &msg.AuthorName, &msg.DisplayName,
			&msg.Content, &editedAt, &createdAt,
		); err != nil {
			http.Error(w, `{"error":"server error"}`, http.StatusInternalServerError)
			return
		}
		if editedAt.Valid {
			msg.EditedAt = &editedAt.String
		}
		msg.CreatedAt = createdAt.String
		messages = append(messages, msg)
	}
	if err := rows.Err(); err != nil {
		http.Error(w, `{"error":"server error"}`, http.StatusInternalServerError)
		return
	}

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

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

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
	err := h.db.QueryRowContext(r.Context(), `
		INSERT INTO messages (channel_id, author_id, content)
		VALUES ($1, $2, $3)
		RETURNING id, channel_id, author_id, content, edited_at::text, created_at::text
	`, channelID, userID, req.Content).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,
	})

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

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

func (h *Handler) Update(w http.ResponseWriter, r *http.Request) {
	userID, ok := middleware.UserIDFromContext(r.Context())
	if !ok {
		http.Error(w, `{"error":"unauthorized"}`, http.StatusUnauthorized)
		return
	}

	messageID := chi.URLParam(r, "messageID")

	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
	}

	// Verify authorship
	var authorID string
	err := h.db.QueryRowContext(r.Context(), `
		SELECT author_id FROM messages WHERE id = $1
	`, messageID).Scan(&authorID)
	if err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			http.Error(w, `{"error":"message not found"}`, http.StatusNotFound)
			return
		}
		http.Error(w, `{"error":"server error"}`, http.StatusInternalServerError)
		return
	}
	if authorID != userID {
		http.Error(w, `{"error":"forbidden"}`, http.StatusForbidden)
		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
		RETURNING id, channel_id, author_id, content, edited_at::text, created_at::text
	`, req.Content, messageID).Scan(
		&msg.ID, &msg.ChannelID, &msg.AuthorID, &msg.Content, &editedAt, &createdAt,
	)
	if err != nil {
		http.Error(w, `{"error":"failed to update message"}`, http.StatusInternalServerError)
		return
	}

	// Fetch author info
	err = h.db.QueryRowContext(r.Context(), `
		SELECT username, display_name FROM users WHERE id = $1
	`, msg.AuthorID).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_UPDATE event via WebSocket
	h.hub.BroadcastEvent(gateway.Event{
		Type: gateway.EventMessageUpdate,
		Data: msg,
	})

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

func (h *Handler) Delete(w http.ResponseWriter, r *http.Request) {
	userID, ok := middleware.UserIDFromContext(r.Context())
	if !ok {
		http.Error(w, `{"error":"unauthorized"}`, http.StatusUnauthorized)
		return
	}

	messageID := chi.URLParam(r, "messageID")

	// Verify authorship and get channel_id for the broadcast
	var authorID, channelID string
	err := h.db.QueryRowContext(r.Context(), `
		SELECT author_id, channel_id FROM messages WHERE id = $1
	`, messageID).Scan(&authorID, &channelID)
	if err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			http.Error(w, `{"error":"message not found"}`, http.StatusNotFound)
			return
		}
		http.Error(w, `{"error":"server error"}`, http.StatusInternalServerError)
		return
	}
	if authorID != userID {
		http.Error(w, `{"error":"forbidden"}`, http.StatusForbidden)
		return
	}

	_, err = h.db.ExecContext(r.Context(), `
		DELETE FROM messages WHERE id = $1
	`, messageID)
	if err != nil {
		http.Error(w, `{"error":"failed to delete message"}`, http.StatusInternalServerError)
		return
	}

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

	w.WriteHeader(http.StatusNoContent)
}