meeting-assistant/MeetingAssistant.Tests/LiteLlmResponsesChatClientTests.cs

using MeetingAssistant.Summary;
using Microsoft.Extensions.AI;
using System.Net;

namespace MeetingAssistant.Tests;

public sealed class LiteLlmResponsesChatClientTests
{
    [Fact]
    public void ParserIgnoresReasoningItemsWithNullStatusAndReadsText()
    {
        const string json = """
            {
              "id": "resp_test",
              "created_at": 1779147100,
              "model": "gpt-5.5-2026-04-23",
              "output": [
                {
                  "type": "reasoning",
                  "summary": [],
                  "status": null
                },
                {
                  "type": "message",
                  "role": "assistant",
                  "status": "completed",
                  "content": [
                    {
                      "type": "output_text",
                      "text": "OK"
                    }
                  ]
                }
              ]
            }
            """;

        var response = LiteLlmResponsesChatClient.ParseResponseJson(json);

        Assert.Equal("OK", response.Text);
        Assert.Equal("resp_test", response.ResponseId);
        Assert.Equal("gpt-5.5-2026-04-23", response.ModelId);
    }

    [Fact]
    public void ParserReadsFunctionCalls()
    {
        const string json = """
            {
              "output": [
                {
                  "type": "function_call",
                  "call_id": "call_1",
                  "name": "write_summary",
                  "arguments": "{\"markdown\":\"# Summary\\nDone\"}",
                  "status": "completed"
                }
              ]
            }
            """;

        var response = LiteLlmResponsesChatClient.ParseResponseJson(json);
        var call = Assert.IsType<FunctionCallContent>(Assert.Single(response.Messages[0].Contents));

        Assert.Equal("call_1", call.CallId);
        Assert.Equal("write_summary", call.Name);
        Assert.NotNull(call.Arguments);
        Assert.Equal("# Summary\nDone", call.Arguments["markdown"]);
    }

    [Fact]
    public void ParserReadsUsage()
    {
        const string json = """
            {
              "usage": {
                "input_tokens": 123,
                "output_tokens": 45,
                "total_tokens": 168
              },
              "output": [
                {
                  "type": "message",
                  "content": [
                    {
                      "type": "output_text",
                      "text": "OK"
                    }
                  ]
                }
              ]
            }
            """;

        var response = LiteLlmResponsesChatClient.ParseResponseJson(json);

        Assert.NotNull(response.Usage);
        Assert.Equal(123, response.Usage.InputTokenCount);
        Assert.Equal(45, response.Usage.OutputTokenCount);
        Assert.Equal(168, response.Usage.TotalTokenCount);
    }

    [Fact]
    public async Task ClientRetriesTransientServerFailure()
    {
        var handler = new SequencedHttpMessageHandler(
            new HttpResponseMessage(HttpStatusCode.InternalServerError)
            {
                Content = new StringContent("Internal Server Error")
            },
            new HttpResponseMessage(HttpStatusCode.OK)
            {
                Content = new StringContent("""
                    {
                      "output": [
                        {
                          "type": "message",
                          "content": [
                            {
                              "type": "output_text",
                              "text": "Done."
                            }
                          ]
                        }
                      ]
                    }
                    """)
            });
        using var client = CreateClient(handler, reconnectionAttempts: 1);

        var response = await client.GetResponseAsync([new ChatMessage(ChatRole.User, "write summary")]);

        Assert.Equal("Done.", response.Text);
        Assert.Equal(2, handler.RequestCount);
    }

    [Fact]
    public async Task ClientDoesNotRetryNonTransientClientFailure()
    {
        var handler = new SequencedHttpMessageHandler(
            new HttpResponseMessage(HttpStatusCode.BadRequest)
            {
                Content = new StringContent("bad request")
            });
        using var client = CreateClient(handler, reconnectionAttempts: 3);

        var exception = await Assert.ThrowsAsync<InvalidOperationException>(
            () => client.GetResponseAsync([new ChatMessage(ChatRole.User, "write summary")]));

        Assert.Contains("400", exception.Message);
        Assert.Equal(1, handler.RequestCount);
    }

    [Fact]
    public async Task ClientUsesResponsesCompactionEndpointWhenContextThresholdIsReached()
    {
        var handler = new RecordingHttpMessageHandler(request =>
        {
            if (request.RequestUri?.PathAndQuery == "/v1/responses/compact")
            {
                return new HttpResponseMessage(HttpStatusCode.OK)
                {
                    Content = new StringContent("""
                        {
                          "input": [
                            {
                              "role": "user",
                              "content": "compacted"
                            }
                          ]
                        }
                        """)
                };
            }

            return new HttpResponseMessage(HttpStatusCode.OK)
            {
                Content = new StringContent("""
                    {
                      "output": [
                        {
                          "type": "message",
                          "content": [
                            {
                              "type": "output_text",
                              "text": "Done."
                            }
                          ]
                        }
                      ]
                    }
                    """)
            };
        });
        using var client = CreateClient(
            handler,
            reconnectionAttempts: 0,
            new LiteLlmResponsesCompactionOptions
            {
                Enabled = true,
                ContextWindowTokens = 100,
                MaxOutputTokens = 10,
                RemainingRatio = 0.10,
                CompactPath = "responses/compact"
            });

        var response = await client.GetResponseAsync([new ChatMessage(ChatRole.User, new string('x', 800))]);

        Assert.Equal("Done.", response.Text);
        Assert.Equal(["/v1/responses/compact", "/v1/responses"], handler.RequestPaths);
        Assert.Contains("\"content\":\"compacted\"", handler.RequestBodies[1]);
    }

    [Fact]
    public async Task ClientFallsBackToAgentFrameworkCompactionWhenResponsesCompactionFails()
    {
        var handler = new RecordingHttpMessageHandler(request =>
        {
            if (request.RequestUri?.PathAndQuery == "/v1/responses/compact")
            {
                return new HttpResponseMessage(HttpStatusCode.NotFound)
                {
                    Content = new StringContent("missing")
                };
            }

            return new HttpResponseMessage(HttpStatusCode.OK)
            {
                Content = new StringContent("""
                    {
                      "output": [
                        {
                          "type": "message",
                          "content": [
                            {
                              "type": "output_text",
                              "text": "Done."
                            }
                          ]
                        }
                      ]
                    }
                    """)
            };
        });
        using var client = CreateClient(
            handler,
            reconnectionAttempts: 0,
            new LiteLlmResponsesCompactionOptions
            {
                Enabled = true,
                ContextWindowTokens = 100,
                MaxOutputTokens = 10,
                RemainingRatio = 0.10,
                CompactPath = "responses/compact",
                FallbackStrategy = OpenAiMeetingSummaryAgentPipeline.CreateFallbackCompactionStrategyForTests(
                    contextWindowTokens: 100,
                    maxOutputTokens: 10,
                    remainingRatio: 0.10,
                    summaryClient: null)
            });

        var response = await client.GetResponseAsync(
            Enumerable.Range(0, 8)
                .Select(index => new ChatMessage(ChatRole.User, $"turn {index} {new string('x', 200)}")));

        Assert.Equal("Done.", response.Text);
        Assert.Equal(["/v1/responses/compact", "/v1/responses"], handler.RequestPaths);
        Assert.DoesNotContain("turn 0", handler.RequestBodies[1]);
    }

    private static LiteLlmResponsesChatClient CreateClient(
        HttpMessageHandler handler,
        int reconnectionAttempts,
        LiteLlmResponsesCompactionOptions? compactionOptions = null)
    {
        return new LiteLlmResponsesChatClient(
            new HttpClient(handler)
            {
                BaseAddress = new Uri("https://litellm.example/v1/")
            },
            "test-key",
            "test-model",
            enableThinking: false,
            reasoningEffort: "none",
            reconnectionAttempts,
            TimeSpan.Zero,
            compactionOptions);
    }

    private sealed class SequencedHttpMessageHandler : HttpMessageHandler
    {
        private readonly Queue<HttpResponseMessage> responses;

        public SequencedHttpMessageHandler(params HttpResponseMessage[] responses)
        {
            this.responses = new Queue<HttpResponseMessage>(responses);
        }

        public int RequestCount { get; private set; }

        protected override Task<HttpResponseMessage> SendAsync(
            HttpRequestMessage request,
            CancellationToken cancellationToken)
        {
            RequestCount++;
            return Task.FromResult(responses.Dequeue());
        }
    }

    private sealed class RecordingHttpMessageHandler : HttpMessageHandler
    {
        private readonly Func<HttpRequestMessage, HttpResponseMessage> handler;

        public RecordingHttpMessageHandler(Func<HttpRequestMessage, HttpResponseMessage> handler)
        {
            this.handler = handler;
        }

        public List<string> RequestPaths { get; } = [];

        public List<string> RequestBodies { get; } = [];

        protected override async Task<HttpResponseMessage> SendAsync(
            HttpRequestMessage request,
            CancellationToken cancellationToken)
        {
            RequestPaths.Add(request.RequestUri?.PathAndQuery ?? string.Empty);
            RequestBodies.Add(request.Content is null
                ? string.Empty
                : await request.Content.ReadAsStringAsync(cancellationToken));
            return handler(request);
        }
    }
}