Wollmilchsau/Wollmilchsau/Services/Moodle/MoodleService.cs

using System.Net.Http.Json;
using Microsoft.AspNetCore.Http.Extensions;
using Microsoft.AspNetCore.WebUtilities;
using Microsoft.Extensions.Options;
using Wollmilchsau.Models;

namespace Wollmilchsau.Services.Moodle;

public sealed class MoodleService(HttpClient httpClient, IOptions<MoodleOptions> options) : IMoodleService
{
    private readonly MoodleOptions _options = options.Value;

    public async Task<IReadOnlyCollection<MoodleUser>> GetAllUsers(CancellationToken cancellationToken = default)
    {
        var requestUri = QueryHelpers.AddQueryString(
            string.Empty,
            new Dictionary<string, string?>
            {
                ["wstoken"] = _options.WsToken,
                ["wsfunction"] = "core_user_get_users",
                ["moodlewsrestformat"] = "json",
                ["criteria[0][key]"] = "lastname",
                ["criteria[0][value]"] = "%"
            });

        using var response = await httpClient.GetAsync(requestUri, cancellationToken);
        response.EnsureSuccessStatusCode();

        var result = await response.Content.ReadFromJsonAsync<MoodleUserSearchResponse>(cancellationToken);
        if (result is null)
        {
            throw new InvalidOperationException("Moodle returned an empty user search response.");
        }

        if (!string.IsNullOrWhiteSpace(result.Exception))
        {
            throw new InvalidOperationException($"Moodle user search failed with {result.ErrorCode ?? "an unspecified error"}: {result.Message ?? result.Exception}.");
        }

        return result.Users ?? throw new InvalidOperationException("Moodle user search response did not contain users.");
    }

    public async Task DeleteUsers(IReadOnlyCollection<int> userIds, CancellationToken cancellationToken = default)
    {
        if (userIds.Count == 0)
        {
            throw new ArgumentException("At least one Moodle user ID is required.", nameof(userIds));
        }

        var query = new QueryBuilder
        {
            { "wstoken", _options.WsToken },
            { "wsfunction", "core_user_delete_users" },
            { "moodlewsrestformat", "json" }
        };

        foreach (var (userId, index) in userIds.Distinct().Select((userId, index) => (userId, index)))
        {
            query.Add($"userids[{index}]", userId.ToString());
        }

        using var response = await httpClient.GetAsync(query.ToQueryString().Value, cancellationToken);
        response.EnsureSuccessStatusCode();

        var result = await response.Content.ReadFromJsonAsync<MoodleDeletionResponse>(cancellationToken);
        if (!string.IsNullOrWhiteSpace(result?.Exception))
        {
            throw new InvalidOperationException($"Moodle user deletion failed with {result.ErrorCode ?? "an unspecified error"}: {result.Message ?? result.Exception}.");
        }
    }

    private sealed record MoodleUserSearchResponse(
        IReadOnlyCollection<MoodleUser>? Users,
        string? Exception,
        string? ErrorCode,
        string? Message);

    private sealed record MoodleDeletionResponse(
        string? Exception,
        string? ErrorCode,
        string? Message);
}