DocumentService/DocumentService.Client/Clients/PdfAttachmentClient.cs

using DocumentService.Application.Common.DTOs;
using DocumentService.Client.Interfaces;
using DocumentService.Application.Common.DTOs.Requests;
using Microsoft.Extensions.Logging;
using System.IO.Compression;
using System.Net.Http;

namespace DocumentService.Client.Clients;

/// <summary>
/// Implementation of PDF attachment client.
/// </summary>
public class PdfAttachmentClient(HttpClient httpClient, ILogger<PdfAttachmentClient> logger)
    : BaseDocumentClient(httpClient, logger), IPdfAttachmentClient
{
    /// <inheritdoc />
    public async Task<AttachmentCheckResult> CheckAttachmentsAsync(Stream pdfStream, CancellationToken cancellationToken = default)
    {
        Logger.LogDebug("Checking PDF attachments from stream (multipart)");

        var result = await SendMultipartAsync<AttachmentCheckResult>(
            "/api/pdf/attachments/check",
            pdfStream,
            "document.pdf",
            cancellationToken);

        return result ?? throw new InvalidOperationException("API returned null response");
    }

    /// <inheritdoc />
    public async Task<AttachmentCheckResult> CheckAttachmentsAsync(byte[] pdfBytes, CancellationToken cancellationToken = default)
    {
        Logger.LogDebug("Checking PDF attachments from byte array (Base64 JSON)");

        var request = new CheckPdfAttachmentsRequest { Base64Pdf = ToBase64(pdfBytes) };

        var result = await SendJsonAsync<CheckPdfAttachmentsRequest, AttachmentCheckResult>(
            "/api/pdf/attachments/check",
            request,
            cancellationToken);

        return result ?? throw new InvalidOperationException("API returned null response");
    }

    /// <inheritdoc />
    public async Task<Dictionary<string, Stream>> ExtractAttachmentsAsync(Stream pdfStream, CancellationToken cancellationToken = default)
    {
        Logger.LogDebug("Extracting PDF attachments from stream (multipart)");

        var zipStream = await SendMultipartForStreamAsync(
            "/api/pdf/attachments/extract",
            pdfStream,
            "document.pdf",
            cancellationToken);

        return UnzipToStreams(zipStream);
    }

    /// <inheritdoc />
    public async Task<Dictionary<string, Stream>> ExtractAttachmentsAsync(byte[] pdfBytes, CancellationToken cancellationToken = default)
    {
        Logger.LogDebug("Extracting PDF attachments from byte array (Base64 JSON)");

        var request = new ExtractPdfAttachmentsRequest { Base64Pdf = ToBase64(pdfBytes) };

        var zipStream = await SendJsonForStreamAsync(
            "/api/pdf/attachments/extract",
            request,
            cancellationToken);

        return UnzipToStreams(zipStream);
    }

    /// <inheritdoc />
    [Obsolete("API endpoint not implemented yet")]
    public Task<Stream> AddAttachmentsAsync(Stream pdfStream, List<AttachmentRequestDto> attachments, CancellationToken cancellationToken = default)
    {
        Logger.LogWarning("AddAttachments endpoint is not implemented yet in API");
        throw new NotImplementedException("API endpoint /api/pdf/attachments/add is not implemented yet");
    }

    /// <inheritdoc />
    [Obsolete("API endpoint not implemented yet")]
    public Task<Stream> AddAttachmentsAsync(byte[] pdfBytes, List<AttachmentRequestDto> attachments, CancellationToken cancellationToken = default)
    {
        Logger.LogWarning("AddAttachments endpoint is not implemented yet in API");
        throw new NotImplementedException("API endpoint /api/pdf/attachments/add is not implemented yet");
    }

    // ?????????????????????????????????????????????????????????????????????????
    // Private helpers
    // ?????????????????????????????????????????????????????????????????????????

    /// <summary>
    /// Reads a ZIP stream and returns a dictionary mapping each entry's full name
    /// to an in-memory <see cref="MemoryStream"/> containing the decompressed bytes.
    /// The caller owns the returned streams and is responsible for disposing them.
    /// </summary>
    private static Dictionary<string, Stream> UnzipToStreams(Stream zipStream)
    {
        var result = new Dictionary<string, Stream>(StringComparer.OrdinalIgnoreCase);

        using var archive = new ZipArchive(zipStream, ZipArchiveMode.Read, leaveOpen: false);

        foreach (var entry in archive.Entries)
        {
            // Skip directory entries (name ends with '/')
            if (string.IsNullOrEmpty(entry.Name))
                continue;

            var ms = new MemoryStream((int)entry.Length);

            using (var entryStream = entry.Open())
            {
                entryStream.CopyTo(ms);
            }

            ms.Position = 0;
            result[entry.FullName] = ms;
        }

        return result;
    }
}