DocumentService/DocumentService.Client/Clients/BaseDocumentClient.cs

using Microsoft.Extensions.Logging;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Net.Http.Json;

namespace DocumentService.Client.Clients;

/// <summary>
/// Base class for all DocumentService HTTP clients.
/// Provides common HTTP operations and error handling.
/// </summary>
/// <remarks>
/// 
/// </remarks>
/// <param name="HttpClient"></param>
/// <param name="logger"></param>
/// <exception cref="ArgumentNullException"></exception>
public abstract class BaseDocumentClient(HttpClient HttpClient, ILogger logger)
{
    /// <summary>
    /// 
    /// </summary>
    protected readonly ILogger Logger = logger ?? throw new ArgumentNullException(nameof(logger));

    /// <summary>
    /// Sends a multipart/form-data POST with a single file and deserializes the JSON response.
    /// </summary>
    protected async Task<TResponse?> SendMultipartAsync<TResponse>(
        string endpoint,
        Stream fileStream,
        string fileName = "file.pdf",
        CancellationToken cancellationToken = default)
    {
        using var content = new MultipartFormDataContent();
        var streamContent = new StreamContent(fileStream);
        streamContent.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");
        content.Add(streamContent, "file", fileName);

        var response = await HttpClient.PostAsync(endpoint, content, cancellationToken);
        response.EnsureSuccessStatusCode();

        return await response.Content.ReadFromJsonAsync<TResponse>(cancellationToken);
    }

    /// <summary>
    /// Sends a multipart/form-data POST with a single file and returns the response as a stream.
    /// </summary>
    protected async Task<Stream> SendMultipartForStreamAsync(
        string endpoint,
        Stream fileStream,
        string fileName = "file.pdf",
        CancellationToken cancellationToken = default)
    {
        using var content = new MultipartFormDataContent();
        var streamContent = new StreamContent(fileStream);
        streamContent.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");
        content.Add(streamContent, "file", fileName);

        var response = await HttpClient.PostAsync(endpoint, content, cancellationToken);
        response.EnsureSuccessStatusCode();

#if NETFRAMEWORK
        return await response.Content.ReadAsStreamAsync();
#else
        return await response.Content.ReadAsStreamAsync(cancellationToken);
#endif
    }

    /// <summary>
    /// Sends a multipart/form-data POST with a single file and returns the raw byte array.
    /// </summary>
    protected async Task<byte[]> SendMultipartForBinaryAsync(
        string endpoint,
        Stream fileStream,
        string fileName = "file.pdf",
        CancellationToken cancellationToken = default)
    {
        using var content = new MultipartFormDataContent();
        var streamContent = new StreamContent(fileStream);
        streamContent.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");
        content.Add(streamContent, "file", fileName);

        var response = await HttpClient.PostAsync(endpoint, content, cancellationToken);
        response.EnsureSuccessStatusCode();

#if NETFRAMEWORK
        return await response.Content.ReadAsByteArrayAsync();
#else
        return await response.Content.ReadAsByteArrayAsync(cancellationToken);
#endif
    }

    /// <summary>
    /// Sends a caller-built <see cref="MultipartFormDataContent"/> and returns the response as a stream.
    /// Use this overload when the multipart body contains more than one file (e.g., merge).
    /// </summary>
    protected async Task<Stream> SendMultipartContentForStreamAsync(
        string endpoint,
        MultipartFormDataContent content,
        CancellationToken cancellationToken = default)
    {
        var response = await HttpClient.PostAsync(endpoint, content, cancellationToken);
        response.EnsureSuccessStatusCode();

#if NETFRAMEWORK
        return await response.Content.ReadAsStreamAsync();
#else
        return await response.Content.ReadAsStreamAsync(cancellationToken);
#endif
    }

    /// <summary>
    /// Serializes <paramref name="request"/> as JSON, POSTs it, and deserializes the response.
    /// </summary>
    protected async Task<TResponse?> SendJsonAsync<TRequest, TResponse>(
        string endpoint,
        TRequest request,
        CancellationToken cancellationToken = default)
    {
        var response = await HttpClient.PostAsJsonAsync(endpoint, request, cancellationToken);
        response.EnsureSuccessStatusCode();

        return await response.Content.ReadFromJsonAsync<TResponse>(cancellationToken);
    }

    /// <summary>
    /// Serializes <paramref name="request"/> as JSON, POSTs it, and returns the response as a stream.
    /// </summary>
    protected async Task<Stream> SendJsonForStreamAsync<TRequest>(
        string endpoint,
        TRequest request,
        CancellationToken cancellationToken = default)
    {
        var response = await HttpClient.PostAsJsonAsync(endpoint, request, cancellationToken);
        response.EnsureSuccessStatusCode();

#if NETFRAMEWORK
        return await response.Content.ReadAsStreamAsync();
#else
        return await response.Content.ReadAsStreamAsync(cancellationToken);
#endif
    }

    /// <summary>
    /// Serializes <paramref name="request"/> as JSON, POSTs it, and returns the raw byte array.
    /// </summary>
    protected async Task<byte[]> SendJsonForBinaryAsync<TRequest>(
        string endpoint,
        TRequest request,
        CancellationToken cancellationToken = default)
    {
        var response = await HttpClient.PostAsJsonAsync(endpoint, request, cancellationToken);
        response.EnsureSuccessStatusCode();

#if NETFRAMEWORK
        return await response.Content.ReadAsByteArrayAsync();
#else
        return await response.Content.ReadAsByteArrayAsync(cancellationToken);
#endif
    }

    /// <summary>Converts a byte array to a Base64 string.</summary>
    protected static string ToBase64(byte[] bytes) => Convert.ToBase64String(bytes);

    /// <summary>Reads a stream fully into a byte array.</summary>
    protected static async Task<byte[]> StreamToBytesAsync(Stream stream, CancellationToken cancellationToken = default)
    {
        if (stream is MemoryStream ms)
            return ms.ToArray();

        using var memoryStream = new MemoryStream();
#if NET8_0
        await stream.CopyToAsync(memoryStream, cancellationToken);
#else
        await stream.CopyToAsync(memoryStream);
#endif
        return memoryStream.ToArray();
    }
}