import { NextResponse } from "next/server";
import { prisma } from "@/lib/prisma";
import { requireRole } from "@/lib/auth";
import { LIBRARY_FINE_PER_DAY } from "@/lib/constants";

type Params = { params: Promise<{ id: string }> };

/** Return an issued book — calculates the overdue fine and restores availability. */
export async function PUT(_req: Request, { params }: Params) {
  const session = await requireRole("INSTITUTION_ADMIN");
  if (!session || !session.institutionId) {
    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
  }
  const { id } = await params;

  try {
    const issue = await prisma.bookIssue.findFirst({
      where: { id: Number(id), institutionId: session.institutionId },
      include: { book: true },
    });
    if (!issue) return NextResponse.json({ error: "Not found" }, { status: 404 });
    if (issue.status === "RETURNED") {
      return NextResponse.json({ error: "Already returned" }, { status: 400 });
    }

    const today = new Date(new Date().toISOString().slice(0, 10));
    const overdueDays =
      today > issue.dueDate
        ? Math.ceil((today.getTime() - issue.dueDate.getTime()) / 86400000)
        : 0;
    const fine = overdueDays * LIBRARY_FINE_PER_DAY;

    await prisma.$transaction([
      prisma.bookIssue.update({
        where: { id: issue.id },
        data: { status: "RETURNED", returnDate: today, fine },
      }),
      prisma.book.update({
        where: { id: issue.bookId },
        data: {
          availableCopies: Math.min(issue.book.totalCopies, issue.book.availableCopies + 1),
        },
      }),
    ]);

    return NextResponse.json({ success: true, overdueDays, fine });
  } catch {
    return NextResponse.json({ error: "Could not return book" }, { status: 500 });
  }
}