import { NextRequest, NextResponse } from "next/server";
import { auth } from "@/app/(auth)/auth";
import { uploadFile } from "@/lib/storage/service";
import { exec } from "child_process";
import { promisify } from "util";
import { writeFile, unlink, readFile, mkdir } from "fs/promises";
import { existsSync } from "fs";
import path from "path";
import os from "os";

const execAsync = promisify(exec);

// 最大文件大小：500MB
const MAX_FILE_SIZE = 500 * 1024 * 1024;

// 支持的视频格式
const SUPPORTED_FORMATS = [
  "video/mp4",
  "video/quicktime",
  "video/x-msvideo",
  "video/x-matroska",
  "video/webm",
  "video/mpeg",
  "video/x-m4v",
];

// 检查 FFmpeg 是否可用
async function checkFFmpeg(): Promise<boolean> {
  try {
    await execAsync("ffmpeg -version");
    return true;
  } catch {
    return false;
  }
}

// 获取视频信息
async function getVideoInfo(
  inputPath: string
): Promise<{ duration: number; width: number; height: number; bitrate: number }> {
  try {
    const { stdout } = await execAsync(
      `ffprobe -v quiet -print_format json -show_format -show_streams "${inputPath}"`
    );
    const info = JSON.parse(stdout);
    const videoStream = info.streams?.find((s: any) => s.codec_type === "video");
    
    return {
      duration: parseFloat(info.format?.duration || "0"),
      width: videoStream?.width || 0,
      height: videoStream?.height || 0,
      bitrate: parseInt(info.format?.bit_rate || "0"),
    };
  } catch (error) {
    console.error("[Video Upload] Failed to get video info:", error);
    return { duration: 0, width: 0, height: 0, bitrate: 0 };
  }
}

// 使用 FFmpeg 压缩视频
async function compressVideo(
  inputPath: string,
  outputPath: string,
  options: {
    targetWidth?: number;
    crf?: number; // 质量因子，18-28 推荐，越低质量越高
    preset?: string; // 编码速度预设
    audioBitrate?: string;
  } = {}
): Promise<{ success: boolean; originalSize: number; compressedSize: number }> {
  const {
    targetWidth = 1280, // 默认 720p
    crf = 23, // 默认质量
    preset = "medium", // 编码速度
    audioBitrate = "128k",
  } = options;

  const videoInfo = await getVideoInfo(inputPath);
  const originalSize = (await readFile(inputPath)).length;

  // 构建 FFmpeg 命令 - 针对 Web 流式播放深度优化
  // 使用 H.264 (libx264) 编码器 + AAC 音频
  // 
  // 关键优化参数说明：
  // -movflags +faststart: 将 moov atom 移到文件开头，支持边下载边播放
  // -profile:v high: 使用 High Profile，更好的压缩率和兼容性
  // -level 4.1: 兼容大多数设备的 Level
  // -pix_fmt yuv420p: 确保最广泛的浏览器兼容性
  // -tune film/animation: 根据内容优化（这里用 film 作为通用选择）
  // -g 48: 关键帧间隔，约每2秒一个关键帧，优化 seek 体验
  // -keyint_min 24: 最小关键帧间隔
  // -sc_threshold 0: 禁用场景切换检测，保持稳定的关键帧间隔
  // -bf 2: B帧数量，提高压缩率
  // -b_strategy 2: B帧策略，动态选择
  
  let scaleFilter = "";
  if (videoInfo.width > targetWidth) {
    // 使用 lanczos 缩放算法，质量最好
    scaleFilter = `-vf "scale=${targetWidth}:-2:flags=lanczos"`;
  }

  const ffmpegCmd = `ffmpeg -i "${inputPath}" \
    -c:v libx264 \
    -preset ${preset} \
    -crf ${crf} \
    -profile:v high \
    -level 4.1 \
    -pix_fmt yuv420p \
    -g 48 \
    -keyint_min 24 \
    -sc_threshold 0 \
    -bf 2 \
    -b_strategy 2 \
    ${scaleFilter} \
    -c:a aac \
    -b:a ${audioBitrate} \
    -ar 44100 \
    -ac 2 \
    -movflags +faststart \
    -y \
    "${outputPath}"`;

  console.log("[Video Compress] Running FFmpeg:", ffmpegCmd);

  try {
    await execAsync(ffmpegCmd, { maxBuffer: 50 * 1024 * 1024 });
    const compressedSize = (await readFile(outputPath)).length;
    
    console.log(
      `[Video Compress] Original: ${(originalSize / 1024 / 1024).toFixed(2)}MB, ` +
      `Compressed: ${(compressedSize / 1024 / 1024).toFixed(2)}MB, ` +
      `Ratio: ${((1 - compressedSize / originalSize) * 100).toFixed(1)}%`
    );

    return { success: true, originalSize, compressedSize };
  } catch (error) {
    console.error("[Video Compress] FFmpeg error:", error);
    return { success: false, originalSize, compressedSize: 0 };
  }
}

export async function POST(request: NextRequest) {
  try {
    // 验证用户身份
    const session = await auth();
    if (!session?.user) {
      return NextResponse.json({ error: "未授权" }, { status: 401 });
    }

    // 只允许管理员上传教程视频
    if (session.user.type !== "admin") {
      return NextResponse.json({ error: "仅管理员可上传视频" }, { status: 403 });
    }

    // 检查 FFmpeg
    const hasFFmpeg = await checkFFmpeg();
    console.log("[Video Upload] FFmpeg available:", hasFFmpeg);

    // 解析上传的文件
    const formData = await request.formData();
    const file = formData.get("file") as File | null;
    const compress = formData.get("compress") !== "false"; // 默认压缩
    const quality = formData.get("quality") as string || "medium"; // low, medium, high

    if (!file) {
      return NextResponse.json({ error: "未找到视频文件" }, { status: 400 });
    }

    // 验证文件类型
    if (!SUPPORTED_FORMATS.includes(file.type)) {
      return NextResponse.json(
        { error: `不支持的视频格式: ${file.type}` },
        { status: 400 }
      );
    }

    // 验证文件大小
    if (file.size > MAX_FILE_SIZE) {
      return NextResponse.json(
        { error: `文件过大，最大支持 ${MAX_FILE_SIZE / 1024 / 1024}MB` },
        { status: 400 }
      );
    }

    console.log(
      `[Video Upload] Received file: ${file.name}, size: ${(file.size / 1024 / 1024).toFixed(2)}MB, type: ${file.type}`
    );

    // 创建临时目录
    const tempDir = path.join(os.tmpdir(), "video-upload");
    if (!existsSync(tempDir)) {
      await mkdir(tempDir, { recursive: true });
    }

    const timestamp = Date.now();
    const randomStr = Math.random().toString(36).slice(2, 8);
    const inputPath = path.join(tempDir, `input-${timestamp}-${randomStr}.mp4`);
    const outputPath = path.join(tempDir, `output-${timestamp}-${randomStr}.mp4`);

    // 写入临时文件
    const bytes = await file.arrayBuffer();
    await writeFile(inputPath, Buffer.from(bytes));

    let finalBuffer: Buffer;
    let compressionInfo = {
      compressed: false,
      originalSize: file.size,
      compressedSize: file.size,
      ratio: 0,
    };

    // 如果有 FFmpeg 且需要压缩
    if (hasFFmpeg && compress) {
      // 根据质量选择 CRF 值
      const crfMap: Record<string, number> = {
        low: 28, // 较低质量，文件更小
        medium: 23, // 中等质量（推荐）
        high: 18, // 高质量，文件较大
      };
      const crf = crfMap[quality] || 23;

      const result = await compressVideo(inputPath, outputPath, {
        crf,
        preset: quality === "low" ? "fast" : quality === "high" ? "slow" : "medium",
        targetWidth: quality === "low" ? 720 : quality === "high" ? 1920 : 1280,
      });

      if (result.success) {
        finalBuffer = await readFile(outputPath);
        compressionInfo = {
          compressed: true,
          originalSize: result.originalSize,
          compressedSize: result.compressedSize,
          ratio: Math.round((1 - result.compressedSize / result.originalSize) * 100),
        };
      } else {
        // 压缩失败，使用原文件
        finalBuffer = Buffer.from(bytes);
      }
    } else {
      // 不压缩，直接使用原文件
      finalBuffer = Buffer.from(bytes);
    }

    // 上传到存储
    const filename = `tutorial-${timestamp}-${randomStr}.mp4`;
    // 将 Buffer 转换为 ArrayBuffer
    const uint8Array = new Uint8Array(finalBuffer);
    const arrayBuffer = uint8Array.buffer.slice(
      uint8Array.byteOffset,
      uint8Array.byteOffset + uint8Array.byteLength
    ) as ArrayBuffer;
    const uploadResult = await uploadFile(filename, arrayBuffer);

    console.log(`[Video Upload] Uploaded to: ${uploadResult.url}`);

    // 清理临时文件
    try {
      await unlink(inputPath);
      if (existsSync(outputPath)) {
        await unlink(outputPath);
      }
    } catch {
      // 忽略清理错误
    }

    return NextResponse.json({
      success: true,
      url: uploadResult.url,
      filename: filename,
      compression: compressionInfo,
    });
  } catch (error) {
    console.error("[Video Upload] Error:", error);
    return NextResponse.json(
      { error: error instanceof Error ? error.message : "上传失败" },
      { status: 500 }
    );
  }
}

// App Router 配置：增加请求体大小限制
// 参考: https://nextjs.org/docs/app/api-reference/file-conventions/route-segment-config
export const maxDuration = 300; // 5分钟超时
export const dynamic = "force-dynamic";