package main

import (
	"context"
	"net/http"
	"strings"
)

func (s *Server) markChatConversationRead(
	ctx context.Context,
	conversationID string,
	userID string,
) error {
	_, err := s.db.Exec(
		ctx,
		`
		INSERT INTO conversation_members (
			conversation_id,
			user_id,
			last_read_at
		)
		VALUES ($1, $2, now())
		ON CONFLICT (conversation_id, user_id)
		DO UPDATE SET last_read_at = EXCLUDED.last_read_at
		`,
		conversationID,
		userID,
	)
	return err
}

func (s *Server) getChatUnreadCount(ctx context.Context, userID string) (int, error) {
	var unreadCount int
	err := s.db.QueryRow(
		ctx,
		`
		SELECT COUNT(*)::INT
		FROM messages m
		JOIN conversations c ON c.id = m.conversation_id
		LEFT JOIN conversation_members cm
			ON cm.conversation_id = c.id
			AND cm.user_id = $1
		WHERE m.deleted_at IS NULL
		  AND (m.expires_at IS NULL OR m.expires_at > now())
		  AND m.sender_id IS DISTINCT FROM $1::UUID
		  AND m.created_at > COALESCE(cm.last_read_at, '-infinity'::TIMESTAMPTZ)
		  AND cm.user_id IS NOT NULL
		`,
		userID,
	).Scan(&unreadCount)
	return unreadCount, err
}

func (s *Server) handleGetChatUnreadCount(w http.ResponseWriter, r *http.Request) {
	user, ok := userFromContext(r.Context())
	if !ok {
		writeError(w, http.StatusUnauthorized, "Unauthorized")
		return
	}

	if err := s.ensureTeamGroupConversations(r.Context()); err != nil {
		writeError(w, http.StatusInternalServerError, "Team-Gruppenchats konnten nicht vorbereitet werden")
		return
	}
	if err := s.ensureAllUserChannels(r.Context(), user.ID); err != nil {
		writeError(w, http.StatusInternalServerError, "Channels konnten nicht vorbereitet werden")
		return
	}

	unreadCount, err := s.getChatUnreadCount(r.Context(), user.ID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "Ungelesene Nachrichten konnten nicht geladen werden")
		return
	}

	writeJSON(w, http.StatusOK, map[string]any{
		"unreadCount": unreadCount,
	})
}

func (s *Server) handleMarkChatConversationRead(w http.ResponseWriter, r *http.Request) {
	user, ok := userFromContext(r.Context())
	if !ok {
		writeError(w, http.StatusUnauthorized, "Unauthorized")
		return
	}

	conversationID := strings.TrimSpace(r.PathValue("id"))
	if !s.canAccessConversation(r.Context(), conversationID, user.ID) {
		writeError(w, http.StatusForbidden, "Kein Zugriff auf diesen Chat")
		return
	}

	if err := s.markChatConversationRead(r.Context(), conversationID, user.ID); err != nil {
		writeError(w, http.StatusInternalServerError, "Lesestatus konnte nicht gespeichert werden")
		return
	}

	unreadCount, err := s.getChatUnreadCount(r.Context(), user.ID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "Ungelesene Nachrichten konnten nicht geladen werden")
		return
	}

	writeJSON(w, http.StatusOK, map[string]any{
		"unreadCount": unreadCount,
	})
}