using dy.net.model.dto;

namespace dy.net.storage
{
    public class LocalMediaStorage : IMediaStorage
    {
        public StorageType StorageType => StorageType.Local;

        public Task EnsureDirectoryAsync(string path, CancellationToken cancellationToken = default)
        {
            if (!string.IsNullOrWhiteSpace(path)) Directory.CreateDirectory(path);
            return Task.CompletedTask;
        }

        public Task<bool> ExistsAsync(string path, CancellationToken cancellationToken = default) =>
            Task.FromResult(File.Exists(path));

        public Task<long?> GetLengthAsync(string path, CancellationToken cancellationToken = default) =>
            Task.FromResult<long?>(File.Exists(path) ? new FileInfo(path).Length : null);

        public async Task WriteAsync(string path, Stream source, long? contentLength = null, string contentType = null, CancellationToken cancellationToken = default)
        {
            var directory = Path.GetDirectoryName(path);
            if (!string.IsNullOrWhiteSpace(directory)) Directory.CreateDirectory(directory);

            var tempPath = path + ".part-" + Guid.NewGuid().ToString("N");
            try
            {
                await using (var output = new FileStream(tempPath, FileMode.CreateNew, FileAccess.Write, FileShare.None, 81920, true))
                {
                    await source.CopyToAsync(output, 81920, cancellationToken);
                    await output.FlushAsync(cancellationToken);
                }
                var actualLength = new FileInfo(tempPath).Length;
                if (actualLength <= 0) throw new IOException("本地写入后的临时文件为空");
                if (contentLength.HasValue && actualLength != contentLength.Value)
                    throw new IOException($"本地写入长度不一致：期望 {contentLength.Value}，实际 {actualLength}");
                File.Move(tempPath, path, true);
                var finalLength = new FileInfo(path).Length;
                if (finalLength != actualLength) throw new IOException($"本地最终文件长度不一致：期望 {actualLength}，实际 {finalLength}");
            }
            finally
            {
                if (File.Exists(tempPath)) File.Delete(tempPath);
            }
        }

        public Task<StorageReadResult> OpenReadAsync(string path, long? from = null, long? to = null, CancellationToken cancellationToken = default)
        {
            if (!File.Exists(path)) throw new FileNotFoundException("媒体文件不存在", path);
            var file = new FileInfo(path);
            var start = Math.Max(0, from ?? 0);
            var end = Math.Min(file.Length - 1, to ?? file.Length - 1);
            var stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read, 81920, true);
            stream.Seek(start, SeekOrigin.Begin);
            return Task.FromResult(new StorageReadResult
            {
                Stream = stream,
                ContentLength = end - start + 1,
                ContentType = MimeType(path),
                ContentRange = from.HasValue ? $"bytes {start}-{end}/{file.Length}" : null,
                StatusCode = from.HasValue ? 206 : 200
            });
        }

        public Task DeleteAsync(string path, CancellationToken cancellationToken = default)
        {
            if (File.Exists(path)) File.Delete(path);
            return Task.CompletedTask;
        }

        private static string MimeType(string path) => Path.GetExtension(path).ToLowerInvariant() switch
        {
            ".mp4" => "video/mp4",
            ".jpg" or ".jpeg" => "image/jpeg",
            ".png" => "image/png",
            ".mp3" => "audio/mpeg",
            ".nfo" or ".xml" => "application/xml",
            _ => "application/octet-stream"
        };
    }
}