using Amazon.Runtime;
using Amazon.S3;
using Amazon.S3.Model;
using Microsoft.Extensions.Options;

namespace WordVersioning.Api.Services;

public interface IObjectStorageService
{
    /// <summary>อัปโหลด stream ไป bucket (content ต้อง seek ได้ — จะได้กำหนด ContentLength และ retry ได้)</summary>
    Task PutAsync(string bucket, string key, Stream content, string contentType, CancellationToken ct = default);

    /// <summary>ดึง object กลับมาเป็น stream (proxy ต่อให้ client) — stream นี้ dispose แล้วจะปิด S3 response ให้ด้วย</summary>
    Task<Stream> GetStreamAsync(string bucket, string key, CancellationToken ct = default);
}

/// <summary>Wrapper เรียก MinIO ผ่าน AWSSDK.S3 (S3-compatible API)</summary>
public class ObjectStorageService : IObjectStorageService
{
    private readonly IAmazonS3 _s3;
    private readonly ILogger<ObjectStorageService> _logger;

    public ObjectStorageService(IOptions<MinioOptions> options, ILogger<ObjectStorageService> logger)
    {
        var opt = options.Value;
        var config = new AmazonS3Config
        {
            ServiceURL = (opt.UseSSL ? "https://" : "http://") + opt.Endpoint,
            ForcePathStyle = true, // จำเป็นสำหรับ MinIO (path-style bucket)
        };
        _s3 = new AmazonS3Client(new BasicAWSCredentials(opt.AccessKey, opt.SecretKey), config);
        _logger = logger;
    }

    public async Task PutAsync(string bucket, string key, Stream content, string contentType, CancellationToken ct = default)
    {
        var request = new PutObjectRequest
        {
            BucketName = bucket,
            Key = key,
            InputStream = content,
            ContentType = contentType,
        };
        if (content.CanSeek)
        {
            // ระบุความยาวชัดๆ ไม่ต้องให้ SDK ไป buffer ทั้ง stream
            request.Headers.ContentLength = content.Length;
        }

        await _s3.PutObjectAsync(request, ct);
        _logger.LogInformation("Uploaded object {Bucket}/{Key} ({Length} bytes)", bucket, key, content.Length);
    }

    public async Task<Stream> GetStreamAsync(string bucket, string key, CancellationToken ct = default)
    {
        GetObjectResponse response;
        try
        {
            response = await _s3.GetObjectAsync(new GetObjectRequest { BucketName = bucket, Key = key }, ct);
        }
        catch (AmazonS3Exception ex) when (ex.StatusCode == System.Net.HttpStatusCode.NotFound)
        {
            throw new KeyNotFoundException($"Object {bucket}/{key} not found");
        }

        _logger.LogInformation("Fetching object {Bucket}/{Key} ({Length} bytes)", bucket, key, response.ContentLength);
        return new S3ResponseStream(response);
    }

    /// <summary>Stream ที่ครอบ GetObjectResponse — dispose stream = dispose response ทั้งอัน
    /// (ไม่งั้น controller ต้องรับ response มาด้วยแล้วจัดการ lifetime เอง ยุ่ง)</summary>
    private sealed class S3ResponseStream(GetObjectResponse response) : Stream
    {
        private readonly Stream _inner = response.ResponseStream;

        public override bool CanRead => _inner.CanRead;
        public override bool CanSeek => _inner.CanSeek;
        public override bool CanWrite => _inner.CanWrite;
        public override long Length => _inner.Length;
        public override long Position { get => _inner.Position; set => _inner.Position = value; }

        public override int Read(byte[] buffer, int offset, int count) => _inner.Read(buffer, offset, count);
        public override Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken ct) =>
            _inner.ReadAsync(buffer, offset, count, ct);
        public override ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken ct = default) => _inner.ReadAsync(buffer, ct);
        public override long Seek(long offset, SeekOrigin origin) => _inner.Seek(offset, origin);
        public override void Flush() => _inner.Flush();
        public override void SetLength(long value) => _inner.SetLength(value);
        public override void Write(byte[] buffer, int offset, int count) => _inner.Write(buffer, offset, count);

        protected override void Dispose(bool disposing)
        {
            if (disposing) response.Dispose();
            base.Dispose(disposing);
        }
    }
}