OllamaApiClientExtensions that use Reflection to modified setting of httpClient

OllamaApiClientExtensions.cs

using System.Reflection;
using OllamaSharp;

namespace OllamaSharp.Custom.Extensions;

/// <summary>
/// Extension methods for OllamaApiClient providing enhanced configuration capabilities,
/// specifically focusing on timeout management for long-running LLM operations.
/// </summary>
public static class OllamaApiClientExtensions
{
    // Cache the FieldInfo to avoid repeated reflection overhead
    private static readonly FieldInfo? HttpClientField = typeof(OllamaApiClient)
        .GetField("_client", BindingFlags.NonPublic | BindingFlags.Instance);

    /// <summary>
    /// Sets the timeout for the OllamaApiClient's underlying HttpClient.
    /// </summary>
    /// <param name="client">The OllamaApiClient instance.</param>
    /// <param name="timeout">The timeout duration to set.</param>
    /// <returns>The same OllamaApiClient instance for method chaining.</returns>
    /// <exception cref="ArgumentNullException">Thrown when client is null.</exception>
    /// <exception cref="ArgumentOutOfRangeException">Thrown when timeout is zero or negative.</exception>
    /// <exception cref="InvalidOperationException">Thrown when the internal HttpClient cannot be accessed.</exception>
    public static OllamaApiClient SetTimeout(this OllamaApiClient client, TimeSpan timeout)
    {
        ArgumentNullException.ThrowIfNull(client);
        
        if (timeout <= TimeSpan.Zero)
            throw new ArgumentOutOfRangeException(nameof(timeout), "Timeout must be greater than zero.");

        if (GetInternalClient(client) is not HttpClient httpClient)
            throw new InvalidOperationException("Unable to access the internal HttpClient of OllamaApiClient. The library structure may have changed.");

        httpClient.Timeout = timeout;
        return client;
    }

    /// <summary>
    /// Gets the current timeout setting from the OllamaApiClient's underlying HttpClient.
    /// </summary>
    public static TimeSpan? GetTimeout(this OllamaApiClient client)
    {
        ArgumentNullException.ThrowIfNull(client);
        return GetInternalClient(client)?.Timeout;
    }

    /// <summary>
    /// Configures the timeout using a functional approach.
    /// </summary>
    public static OllamaApiClient ConfigureTimeout(this OllamaApiClient client, Func<TimeSpan?, TimeSpan> configure)
    {
        ArgumentNullException.ThrowIfNull(client);
        ArgumentNullException.ThrowIfNull(configure);

        var newTimeout = configure(client.GetTimeout());
        return client.SetTimeout(newTimeout);
    }

    /// <summary>
    /// Sets a 2-minute timeout for quick responses.
    /// </summary>
    public static OllamaApiClient WithQuickTimeout(this OllamaApiClient client) => client.SetTimeout(TimeSpan.FromMinutes(2));

    /// <summary>
    /// Sets a 5-minute timeout for standard operations.
    /// </summary>
    public static OllamaApiClient WithStandardTimeout(this OllamaApiClient client) => client.SetTimeout(TimeSpan.FromMinutes(5));

    /// <summary>
    /// Sets a 10-minute timeout for long generations.
    /// </summary>
    public static OllamaApiClient WithLongTimeout(this OllamaApiClient client) => client.SetTimeout(TimeSpan.FromMinutes(10));

    /// <summary>
    /// Sets a 30-minute timeout for heavy models or complex tasks.
    /// </summary>
    public static OllamaApiClient WithExtendedTimeout(this OllamaApiClient client) => client.SetTimeout(TimeSpan.FromMinutes(30));

    /// <summary>
    /// Internal helper to extract the HttpClient using cached reflection data.
    /// </summary>
    private static HttpClient? GetInternalClient(OllamaApiClient client) 
        => HttpClientField?.GetValue(client) as HttpClient;
}