douyin-archive/app/api/comments/[awemeId]/route.ts

import { getFileUrl } from "@/lib/minio";
import { prisma } from "@/lib/prisma";
import { Prisma } from "@prisma/client";
import { NextRequest, NextResponse } from "next/server";

export async function GET(
  request: NextRequest,
  { params }: { params: Promise<{ awemeId: string }> }
) {
  const awemeId = (await params).awemeId;
  const searchParams = request.nextUrl.searchParams;
  const skip = parseInt(searchParams.get("skip") || "0", 10);
  const take = parseInt(searchParams.get("take") || "20", 10);

  // ranked 模式参数（均为可选，提供合理默认值）
  const seed = searchParams.get("seed") || new Date().toISOString().slice(0, 10); // 默认按日期稳定
  const snapshotIso = searchParams.get("snapshot");
  const snapshot = snapshotIso ? new Date(snapshotIso) : new Date(); // 用于时间衰减的基准时间，确保单次会话稳定
  const halfLifeHours = parseFloat(searchParams.get("halfLifeHours") || "24");
  const wPop = parseFloat(searchParams.get("wPop") || "1"); // 热度权重
  const wTime = parseFloat(searchParams.get("wTime") || "2"); // 时间衰减权重
  const wJit = parseFloat(searchParams.get("wJit") || "10"); // 随机扰动权重（稳定随机）



  try {
    // 查找是视频还是图文
    const [video, post] = await Promise.all([
      prisma.video.findUnique({
        where: { aweme_id: awemeId },
        select: { aweme_id: true },
      }),
      prisma.imagePost.findUnique({
        where: { aweme_id: awemeId },
        select: { aweme_id: true },
      }),
    ]);

    if (!video && !post) {
      return NextResponse.json({ error: "作品不存在" }, { status: 404 });
    }

    // 构建查询条件
    const where = video
      ? { videoId: awemeId }
      : { imagePostId: awemeId };

    // 按「热度 + 时间衰减 + 稳定随机扰动」打分排序；否则使用稳定的时间排序
    const total = await prisma.comment.count({ where });

    // 计算稳定随机扰动：基于 (cid, seed) 的 md5 -> 取前4字节 -> 映射到 [0,1)
    const jitterExpr = Prisma.sql`(
        (
          get_byte(decode(md5(c."cid" || ':' || ${seed}), 'hex'), 0)::double precision * 16777216.0 +
          get_byte(decode(md5(c."cid" || ':' || ${seed}), 'hex'), 1)::double precision * 65536.0 +
          get_byte(decode(md5(c."cid" || ':' || ${seed}), 'hex'), 2)::double precision * 256.0 +
          get_byte(decode(md5(c."cid" || ':' || ${seed}), 'hex'), 3)::double precision
        ) / 4294967295.0
      )`;

    const snapshotTs = snapshot.toISOString();

    // popularity: ln(1 + digg_count)
    // time decay: exp(- age_hours / halfLifeHours)，使用固定 snapshot 基准保证会话内稳定
    const scoreExpr = Prisma.sql`(
        ${wPop} * ln(1 + c."digg_count"::numeric) +
        ${wTime} * exp(- (extract(epoch from (${snapshotTs}::timestamptz - c."created_at")) / 3600.0) / ${halfLifeHours}) +
        ${wJit} * ${jitterExpr}
      )`;

    const whereField = (await video) ? Prisma.sql`c."videoId"` : Prisma.sql`c."imagePostId"`;

    const rows: Array<{
      cid: string;
      text: string;
      created_at: Date;
      digg_count: bigint;
      nickname: string;
      avatar_url: string | null;
    }> = await prisma.$queryRaw(
      Prisma.sql`
          SELECT
            c."cid",
            c."text",
            c."created_at",
            c."digg_count",
            u."nickname",
            u."avatar_url"
          FROM "Comment" c
          JOIN "CommentUser" u ON u."id" = c."userId"
          WHERE ${whereField} = ${awemeId}
          ORDER BY ${scoreExpr} DESC, c."created_at" DESC, c."cid" ASC
          OFFSET ${skip}
          LIMIT ${take}
        `
    );

    // 批量查询每条评论的配图/贴纸
    const cids = rows.map(r => r.cid);
    const images = cids.length
      ? await prisma.commentImage.findMany({
        where: { commentId: { in: cids } },
        orderBy: { order: 'asc' },
        select: { commentId: true, url: true, width: true, height: true, order: true },
      })
      : [];
    const group = new Map<string, { url: string; width?: number | null; height?: number | null; order: number }[]>();
    for (const img of images) {
      const arr = group.get(img.commentId) || [];
      arr.push({ url: img.url, width: img.width, height: img.height, order: img.order });
      group.set(img.commentId, arr);
    }
    const formattedComments = rows.map((c) => ({
      cid: c.cid,
      text: c.text,
      created_at: c.created_at,
      digg_count: Number(c.digg_count),
      user: {
        nickname: c.nickname,
        avatar_url: getFileUrl(c.avatar_url || 'default_avatar.png'),
      },
      images: (group.get(c.cid) || []).sort((a, b) => a.order - b.order).map(i => ({ url: getFileUrl(i.url), width: i.width ?? undefined, height: i.height ?? undefined })),
    }));

    return NextResponse.json({
      comments: formattedComments,
      total,
      hasMore: skip + take < total,
      // 回传用于稳定排序的参数，前端可在后续请求中透传
      seed,
      snapshot: snapshotTs,
      weights: { wPop, wTime, wJit, halfLifeHours },
      mode: "ranked",
    });
  } catch (error) {
    console.error("获取评论失败:", error);
    return NextResponse.json(
      { error: "获取评论失败" },
      { status: 500 }
    );
  }
}