using Amazon;
using Amazon.S3;
using Amazon.S3.Model;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using OFACScraper.Configuration;

namespace OFACScraper.Services;

public class S3UploadService : IDisposable
{
    private readonly S3Options _options;
    private readonly ILogger<S3UploadService> _logger;
    private readonly IAmazonS3? _s3Client;

    public S3UploadService(IOptions<S3Options> options, ILogger<S3UploadService> logger)
    {
        _options = options.Value;
        _logger = logger;

        if (_options.IsConfigured)
        {
            var config = new AmazonS3Config
            {
                RegionEndpoint = RegionEndpoint.GetBySystemName(_options.Region)
            };
            _s3Client = new AmazonS3Client(_options.AccessKeyId, _options.SecretAccessKey, config);
            _logger.LogInformation("S3 configured: bucket={Bucket} region={Region} prefix={Prefix}",
                _options.BucketName, _options.Region, _options.Prefix);
        }
        else
        {
            _logger.LogWarning("S3 not configured — uploads will be skipped.");
        }
    }

    public void Dispose() => (_s3Client as IDisposable)?.Dispose();

    public async Task<bool> UploadFileAsync(string localPath, string s3Key)
    {
        if (_s3Client == null) return false;

        try
        {
            await _s3Client.PutObjectAsync(new PutObjectRequest
            {
                BucketName = _options.BucketName,
                Key = s3Key,
                FilePath = localPath
            });
            _logger.LogDebug("Uploaded {Path} → s3://{Bucket}/{Key}", localPath, _options.BucketName, s3Key);
            return true;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to upload {Path}", localPath);
            return false;
        }
    }

    /// <summary>
    /// Syncs localDirectory to S3 under s3Prefix, skipping files whose MD5 matches existing S3 ETag.
    /// Uploads metadata.json last so CGSH processing triggers only after all documents are present.
    /// </summary>
    public async Task<S3SyncResult> SyncDirectoryAsync(string localDirectory, string s3Prefix)
    {
        var result = new S3SyncResult();

        if (_s3Client == null)
        {
            _logger.LogWarning("S3 not configured, skipping sync of {Path}", localDirectory);
            result.NotConfigured = true;
            return result;
        }

        if (!Directory.Exists(localDirectory))
        {
            result.Error = $"Directory not found: {localDirectory}";
            return result;
        }

        // List existing objects to skip unchanged files
        var existing = new Dictionary<string, string>();
        var listRequest = new ListObjectsV2Request { BucketName = _options.BucketName, Prefix = s3Prefix + "/" };
        ListObjectsV2Response listResponse;
        do
        {
            listResponse = await _s3Client.ListObjectsV2Async(listRequest);
            foreach (var obj in listResponse.S3Objects ?? [])
                existing[obj.Key] = obj.ETag?.Trim('"') ?? "";
            listRequest.ContinuationToken = listResponse.NextContinuationToken;
        } while (listResponse.IsTruncated == true);

        // metadata.json last — CGSH triggers on its arrival
        var files = Directory.GetFiles(localDirectory, "*", SearchOption.AllDirectories)
            .OrderBy(f => Path.GetFileName(f) == "metadata.json" ? 1 : 0)
            .ThenBy(f => f)
            .ToArray();

        foreach (var file in files)
        {
            var relativePath = Path.GetRelativePath(localDirectory, file).Replace('\\', '/');
            var s3Key = $"{s3Prefix}/{relativePath}";

            if (existing.TryGetValue(s3Key, out var etag) && !string.IsNullOrEmpty(etag))
            {
                var localMd5 = Convert.ToHexString(
                    System.Security.Cryptography.MD5.HashData(File.ReadAllBytes(file))
                ).ToLowerInvariant();
                if (localMd5 == etag) { result.Skipped++; continue; }
            }

            if (await UploadFileAsync(file, s3Key))
                result.Uploaded++;
            else
                result.Failed++;
        }

        _logger.LogInformation("S3 sync: {Uploaded} uploaded, {Skipped} unchanged, {Failed} failed",
            result.Uploaded, result.Skipped, result.Failed);
        return result;
    }
}

public class S3SyncResult
{
    public int Uploaded { get; set; }
    public int Skipped { get; set; }
    public int Failed { get; set; }
    public bool NotConfigured { get; set; }
    public string? Error { get; set; }
}