import { Buffer } from "node:buffer";
import { auth } from "@clerk/nextjs/server";
import { NextResponse } from "next/server";
import * as XLSX from "xlsx";
import { prisma } from "@/lib/prisma";
import { getNumericParam } from "@/lib/route-params";

type AssignmentRouteParams = { assignmentId: string | string[] | undefined };

const EXPORTABLE_COLUMNS = {
  studentId: { header: "学号", getter: (submission: any) => submission.studentId },
  studentName: { header: "姓名", getter: (submission: any) => submission.studentName },
  originalFilename: {
    header: "文件名",
    getter: (submission: any) => submission.originalFilename,
  },
  fileUrl: { header: "文件地址", getter: (submission: any) => submission.fileUrl },
  submittedAt: {
    header: "提交时间",
    getter: (submission: any) =>
      submission.submittedAt ? new Date(submission.submittedAt).toISOString() : "",
  },
  evaluationScore: {
    header: "得分",
    getter: (submission: any) =>
      typeof submission.evaluationScore === "number"
        ? submission.evaluationScore
        : "",
  },
  evaluationComment: {
    header: "评价评语",
    getter: (submission: any) => submission.evaluationComment ?? "",
  },
  evaluatedAt: {
    header: "评价时间",
    getter: (submission: any) =>
      submission.evaluatedAt ? new Date(submission.evaluatedAt).toISOString() : "",
  },
} as const;

const DEFAULT_COLUMNS = ["studentId", "evaluationScore"] as Array<keyof typeof EXPORTABLE_COLUMNS>;

export async function GET(
  request: Request,
  { params }: { params: Promise<AssignmentRouteParams> },
) {
  const resolvedParams = await params;
  const assignmentId = getNumericParam(resolvedParams.assignmentId);
  if (Number.isNaN(assignmentId)) {
    return NextResponse.json({ error: "作业不存在" }, { status: 400 });
  }

  const { userId } = await auth();
  if (!userId) {
    return NextResponse.json({ error: "未授权" }, { status: 401 });
  }

  const assignment = await prisma.assignment.findFirst({
    where: { id: assignmentId, teacherId: userId },
    select: { id: true, title: true },
  });

  if (!assignment) {
    return NextResponse.json({ error: "未找到作业" }, { status: 404 });
  }

  const url = new URL(request.url);
  const columnsParam = url.searchParams.get("columns");
  const requestedColumns = columnsParam
    ? columnsParam
        .split(",")
        .map((item) => item.trim())
        .filter((item) => item.length > 0)
    : null;

  const selectedColumns =
    requestedColumns && requestedColumns.length > 0
      ? requestedColumns.filter(
          (key): key is keyof typeof EXPORTABLE_COLUMNS => key in EXPORTABLE_COLUMNS,
        )
      : DEFAULT_COLUMNS;

  if (!selectedColumns.length) {
    return NextResponse.json({ error: "请选择有效的导出列" }, { status: 400 });
  }

  const submissions = await prisma.submission.findMany({
    where: { assignmentId },
    orderBy: { submittedAt: "asc" },
  });

  const worksheetData = submissions.map((submission) => {
    const row: Record<string, unknown> = {};
    for (const column of selectedColumns) {
      const { header, getter } = EXPORTABLE_COLUMNS[column];
      row[header] = getter(submission);
    }
    return row;
  });

  if (worksheetData.length === 0) {
    worksheetData.push(
      Object.fromEntries(
        selectedColumns.map((column) => [
          EXPORTABLE_COLUMNS[column].header,
          "",
        ]),
      ),
    );
  }

  const worksheet = XLSX.utils.json_to_sheet(worksheetData);
  const workbook = XLSX.utils.book_new();
  XLSX.utils.book_append_sheet(workbook, worksheet, "Submissions");
  const buffer = XLSX.write(workbook, { bookType: "xlsx", type: "buffer" }) as Buffer;

  const filenameSafeTitle = assignment.title
    ? assignment.title.replace(/[^\w\s-]/g, "").replace(/\s+/g, "_")
    : `assignment_${assignmentId}`;
  const filename = `${filenameSafeTitle}_submissions.xlsx`;

  return new NextResponse(buffer, {
    status: 200,
    headers: {
      "Content-Type": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
      "Content-Disposition": `attachment; filename="${encodeURIComponent(filename)}"`,
      "Content-Length": buffer.length.toString(),
      "Cache-Control": "no-store",
    },
  });
}