EnvelopeGenerator/EnvelopeGenerator.ReceiverUI/EnvelopeGenerator.ReceiverUI.Client/Services/Base/ApiServiceBase.cs

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

namespace EnvelopeGenerator.ReceiverUI.Client.Services.Base;

/// <summary>
/// Basisklasse für ALLE API-Services.
/// 
/// WARUM eine Basisklasse?
/// - Einheitliches Error-Handling: Jeder API-Aufruf wird gleich behandelt
/// - DRY (Don't Repeat Yourself): Logging, Fehlerbehandlung, Serialisierung nur einmal
/// - Einfache Erweiterung: Retry-Logik, Token-Refresh etc. nur hier ändern
/// </summary>
public abstract class ApiServiceBase
{
    protected readonly HttpClient Http;
    protected readonly ILogger Logger;

    protected ApiServiceBase(HttpClient http, ILogger logger)
    {
        Http = http;
        Logger = logger;
    }

    /// <summary>
    /// GET-Request mit Deserialisierung.
    /// Alle API GET-Aufrufe gehen durch diese Methode.
    /// </summary>
    protected async Task<ApiResponse<T>> GetAsync<T>(string endpoint, CancellationToken ct = default)
    {
        try
        {
            var response = await Http.GetAsync(endpoint, ct);

            if (!response.IsSuccessStatusCode)
            {
                var errorBody = await response.Content.ReadAsStringAsync(ct);
                Logger.LogWarning("GET {Endpoint} failed: {Status} - {Body}",
                    endpoint, (int)response.StatusCode, errorBody);
                return ApiResponse<T>.Failure((int)response.StatusCode, errorBody);
            }

            var data = await response.Content.ReadFromJsonAsync<T>(cancellationToken: ct);
            return ApiResponse<T>.Success(data!, (int)response.StatusCode);
        }
        catch (HttpRequestException ex)
        {
            Logger.LogError(ex, "HTTP error calling GET {Endpoint}", endpoint);
            return ApiResponse<T>.Failure(0, "Verbindung zum Server fehlgeschlagen.");
        }
        catch (TaskCanceledException)
        {
            Logger.LogWarning("GET {Endpoint} was cancelled", endpoint);
            return ApiResponse<T>.Failure(0, "Anfrage abgebrochen.");
        }
    }

    /// <summary>
    /// POST-Request mit Body und Response-Deserialisierung.
    /// </summary>
    protected async Task<ApiResponse<TResponse>> PostAsync<TRequest, TResponse>(
        string endpoint, TRequest body, CancellationToken ct = default)
    {
        try
        {
            var response = await Http.PostAsJsonAsync(endpoint, body, ct);

            if (!response.IsSuccessStatusCode)
            {
                var errorBody = await response.Content.ReadAsStringAsync(ct);
                Logger.LogWarning("POST {Endpoint} failed: {Status} - {Body}",
                    endpoint, (int)response.StatusCode, errorBody);
                return ApiResponse<TResponse>.Failure((int)response.StatusCode, errorBody);
            }

            var data = await response.Content.ReadFromJsonAsync<TResponse>(cancellationToken: ct);
            return ApiResponse<TResponse>.Success(data!, (int)response.StatusCode);
        }
        catch (HttpRequestException ex)
        {
            Logger.LogError(ex, "HTTP error calling POST {Endpoint}", endpoint);
            return ApiResponse<TResponse>.Failure(0, "Verbindung zum Server fehlgeschlagen.");
        }
    }

    /// <summary>
    /// POST-Request ohne Response-Body (z.B. Logout).
    /// </summary>
    protected async Task<ApiResponse> PostAsync<TRequest>(
        string endpoint, TRequest body, CancellationToken ct = default)
    {
        try
        {
            var response = await Http.PostAsJsonAsync(endpoint, body, ct);

            if (!response.IsSuccessStatusCode)
            {
                var errorBody = await response.Content.ReadAsStringAsync(ct);
                return ApiResponse.Failure((int)response.StatusCode, errorBody);
            }

            return ApiResponse.Success((int)response.StatusCode);
        }
        catch (HttpRequestException ex)
        {
            Logger.LogError(ex, "HTTP error calling POST {Endpoint}", endpoint);
            return ApiResponse.Failure(0, "Verbindung zum Server fehlgeschlagen.");
        }
    }
}