import { NextRequest, NextResponse } from "next/server";
import { getServerSession } from "next-auth/next";
import { authOptions } from "@/app/api/auth/options";
import { prisma } from "@/lib/prisma";
import { logger } from "@/lib/logger";

/**
 * Handles GET requests to retrieve a calendar by its ID.
 *
 * @param req - The incoming request object.
 * @param params - An object containing the route parameters.
 * @param params.id - The ID of the calendar to retrieve.
 * @returns A JSON response containing the calendar data if found and authorized,
 *          or an error message with the appropriate HTTP status code.
 *
 * - 401: If the user is not authenticated.
 * - 403: If the user is not authorized to access the calendar.
 * - 404: If the calendar is not found.
 * - 500: If there is a server error during the retrieval process.
 */
export async function GET(
  req: NextRequest,
  { params }: { params: Promise<{ id: string }> }
) {
  const session = await getServerSession(authOptions);

  if (!session?.user?.username) {
    return NextResponse.json({ error: "Non authentifié" }, { status: 401 });
  }

  try {
    const { id } = await params;
    
    const calendar = await prisma.calendar.findUnique({
      where: {
        id: id,
      },
    });

    if (!calendar) {
      return NextResponse.json(
        { error: "Calendrier non trouvé" },
        { status: 404 }
      );
    }

    // Vérification que l'utilisateur est bien le propriétaire
    if (calendar.userId !== session.user.username) {
      return NextResponse.json({ error: "Non autorisé" }, { status: 403 });
    }

    return NextResponse.json(calendar);
  } catch (error) {
    console.error("Erreur lors de la récupération du calendrier:", error);
    return NextResponse.json({ error: "Erreur serveur" }, { status: 500 });
  }
}

/**
 * Handles the PUT request to update a calendar.
 *
 * @param req - The incoming request object.
 * @param params - An object containing the route parameters.
 * @param params.id - The ID of the calendar to update.
 * @returns A JSON response with the updated calendar data or an error message.
 *
 * @throws {401} If the user is not authenticated.
 * @throws {404} If the calendar is not found.
 * @throws {403} If the user is not authorized to update the calendar.
 * @throws {400} If the calendar name is not provided.
 * @throws {500} If there is a server error during the update process.
 */
export async function PUT(
  req: NextRequest,
  { params }: { params: Promise<{ id: string }> }
) {
  const session = await getServerSession(authOptions);

  if (!session?.user?.username) {
    return NextResponse.json({ error: "Non authentifié" }, { status: 401 });
  }

  try {
    const { id } = await params;
    
    // Vérifier que le calendrier existe et appartient à l'utilisateur
    const existingCalendar = await prisma.calendar.findUnique({
      where: {
        id: id,
      },
    });

    if (!existingCalendar) {
      return NextResponse.json(
        { error: "Calendrier non trouvé" },
        { status: 404 }
      );
    }

    if (existingCalendar.userId !== session.user.username) {
      return NextResponse.json({ error: "Non autorisé" }, { status: 403 });
    }

    const { name, color, description } = await req.json();

    // Validation
    if (!name) {
      return NextResponse.json(
        { error: "Le nom du calendrier est requis" },
        { status: 400 }
      );
    }

    const updatedCalendar = await prisma.calendar.update({
      where: {
        id: id,
      },
      data: {
        name,
        color,
        description,
      },
    });

    return NextResponse.json(updatedCalendar);
  } catch (error) {
    console.error("Erreur lors de la mise à jour du calendrier:", error);
    return NextResponse.json({ error: "Erreur serveur" }, { status: 500 });
  }
}

/**
 * Handles the DELETE request to remove a calendar by its ID.
 *
 * @param req - The incoming Next.js request object.
 * @param params - An object containing the route parameters.
 * @param params.id - The ID of the calendar to be deleted.
 * @returns A JSON response indicating the result of the deletion operation.
 *
 * - If the user is not authenticated, returns a 401 status with an error message.
 * - If the calendar does not exist, returns a 404 status with an error message.
 * - If the calendar does not belong to the authenticated user, returns a 403 status with an error message.
 * - If the calendar is successfully deleted, returns a 204 status with no content.
 * - If an error occurs during the deletion process, returns a 500 status with an error message.
 */
export async function DELETE(
  req: NextRequest,
  { params }: { params: Promise<{ id: string }> }
) {
  const session = await getServerSession(authOptions);

  if (!session?.user?.id) {
    return NextResponse.json({ error: "Non authentifié" }, { status: 401 });
  }

  try {
    const { id } = await params;
    
    const calendar = await prisma.calendar.findUnique({
      where: { id },
      include: {
        mission: true,
      },
    });

    if (!calendar) {
      return NextResponse.json(
        { error: "Calendrier non trouvé" },
        { status: 404 }
      );
    }

    // Check permissions
    // Allow deletion if:
    // 1. User owns the calendar
    // 2. OR it's a group calendar (starts with "Groupe:")
    // 3. OR user created the associated mission
    const isOwner = calendar.userId === session.user.id;
    const isGroupCalendar = calendar.name.startsWith("Groupe:");
    const isMissionCreator = calendar.mission && calendar.mission.creatorId === session.user.id;

    if (!isOwner && !isGroupCalendar && !isMissionCreator) {
      return NextResponse.json(
        { error: "Vous n'avez pas la permission de supprimer ce calendrier" },
        { status: 403 }
      );
    }

    // For group calendars, log the deletion
    if (isGroupCalendar) {
      logger.info('Deleting group calendar', { 
        calendarId: id, 
        calendarName: calendar.name,
        userId: session.user.id 
      });
    }

    // Delete the calendar (cascade will delete events)
    await prisma.calendar.delete({
      where: { id },
    });

    logger.info('Calendar deleted successfully', { 
      calendarId: id, 
      calendarName: calendar.name 
    });

    return NextResponse.json({ success: true, message: "Calendrier supprimé avec succès" });
  } catch (error) {
    logger.error('Error deleting calendar', { error });
    console.error("Erreur lors de la suppression du calendrier:", error);
    return NextResponse.json({ error: "Erreur serveur" }, { status: 500 });
  }
}