import { NextRequest, NextResponse } from "next/server";
import { getSupabaseAdminClient } from "@/lib/supabase/admin";
import { getCurrentUser } from "@/lib/auth/current-user";
import { deleteGroupAndData } from "@/lib/groups/delete-group";

/** POST /api/groups/[id]/leave — Leave a group */
export async function POST(request: NextRequest, { params }: { params: Promise<{ id: string }> }) {
  try {
    const { id } = await params;
    const user = await getCurrentUser(request);
    if (!user) {
      return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
    }

    const admin = getSupabaseAdminClient();

    const { data: membership } = await admin
      .from("group_members")
      .select("role")
      .eq("group_id", id)
      .eq("user_id", user.id)
      .maybeSingle();

    if (!membership) {
      return NextResponse.json({ error: "Not a member of this group" }, { status: 403 });
    }

    const { count } = await admin
      .from("group_members")
      .select("*", { count: "exact", head: true })
      .eq("group_id", id);

    const isLastMember = count === 1;

    // If admin with other members, must transfer first
    if (membership.role === "admin" && !isLastMember) {
      return NextResponse.json(
        { error: "Transfer admin role before leaving. Use /api/groups/[id]/transfer first." },
        { status: 400 },
      );
    }

    if (isLastMember) {
      await deleteGroupAndData(id);
      return NextResponse.json({ success: true, groupDeleted: true });
    }

    const { error } = await admin
      .from("group_members")
      .delete()
      .eq("group_id", id)
      .eq("user_id", user.id);

    if (error) {
      return NextResponse.json({ error: "Failed to leave group" }, { status: 500 });
    }

    return NextResponse.json({ success: true, groupDeleted: false });
  } catch {
    return NextResponse.json({ error: "Internal server error" }, { status: 500 });
  }
}