using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;
using UnityEngine;

namespace Kill.Video
{
    /// <summary>
    /// 视频缓存管理:按 url 哈希缓存到 persistentDataPath/video_cache
    /// key=mp4(转码后),key=tmp.h264(下载中临时)
    /// </summary>
    public static class VideoCacheManager
    {
        private const string CacheSubDir = "video_cache";

        private static string CacheDir
        {
            get
            {
                string dir = Path.Combine(Application.persistentDataPath, CacheSubDir);
                if (!Directory.Exists(dir)) Directory.CreateDirectory(dir);
                return dir;
            }
        }

        /// <summary>已转码好的 mp4 缓存路径</summary>
        public static string GetCachedMp4Path(string url)
        {
            return Path.Combine(CacheDir, Hash(url) + ".mp4");
        }

        /// <summary>下载中的 .h264 临时路径</summary>
        public static string GetTempH264Path(string url)
        {
            return Path.Combine(CacheDir, Hash(url) + ".h264");
        }

        public static bool IsCached(string url)
        {
            var p = GetCachedMp4Path(url);
            return File.Exists(p) && new FileInfo(p).Length > 0;
        }

        public static void Clear()
        {
            string dir = Path.Combine(Application.persistentDataPath, CacheSubDir);
            if (Directory.Exists(dir))
            {
                try { Directory.Delete(dir, true); }
                catch (Exception e) { Debug.LogWarning("[VideoCacheManager] clear fail: " + e.Message); }
            }
        }

        private static string Hash(string s)
        {
            using var sha = SHA1.Create();
            var bytes = sha.ComputeHash(Encoding.UTF8.GetBytes(s));
            var sb = new StringBuilder(bytes.Length * 2);
            foreach (var b in bytes) sb.Append(b.ToString("x2"));
            return sb.ToString();
        }
    }
}