using MeetingAssistant.MacOs;
using MeetingAssistant.Workflow;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;

namespace MeetingAssistant.Tests;

public sealed class MacOsWorkflowRulesEditorSessionTests
{
    [Fact]
    public async Task ApprovedWorkflowStartsOnceInOwnSessionWithoutReplacingDefaultConversation()
    {
        var pipeline = new ReplyPipeline();
        using var lifetime = new TestApplicationLifetime();
        var sessions = CreateSessions(pipeline, lifetime);
        Assert.True(sessions.TryGetSession(null, out var normal));
        await normal.SendAsync("My existing conversation", CancellationToken.None);
        const string prompt = "Given Alpha in the title,\nwhen metadata arrives, then associate project Alpha.";

        sessions.OpenWithPrompt(prompt);

        var window = Assert.Single(sessions.GetAgentWindows());
        Assert.EndsWith($"/diagnostics/settings-and-logs?session={window.Id}", window.Url);
        Assert.True(sessions.TryGetSession(window.Id, out var requested));
        var snapshot = await WaitForCompletionAsync(requested);
        Assert.Equal(
            [new MacOsWorkflowRulesEditorMessage("user", prompt), new MacOsWorkflowRulesEditorMessage("agent", "Agent response.")],
            snapshot.Messages);
        for (var index = 0; index < 3; index++)
        {
            Assert.Equal(snapshot.Messages, requested.GetSnapshot().Messages);
            Assert.False(requested.GetSnapshot().IsThinking);
            Assert.Single(sessions.GetAgentWindows());
        }
        Assert.Equal(
            [new MacOsWorkflowRulesEditorMessage("user", "My existing conversation"), new MacOsWorkflowRulesEditorMessage("agent", "Agent response.")],
            normal.GetSnapshot().Messages);
        Assert.NotSame(normal, requested);
    }

    [Fact]
    public async Task ClosingAResponseConnectionKeepsAcceptedChatWorkingAndSnapshotsRemainReadable()
    {
        var pipeline = new BlockingPipeline();
        using var lifetime = new TestApplicationLifetime();
        var sessions = CreateSessions(pipeline, lifetime);
        Assert.True(sessions.TryGetSession(null, out var session));
        using var responseConnection = new CancellationTokenSource();
        var response = session.SendAsync("Continue the approved change", responseConnection.Token);
        await pipeline.Started.Task.WaitAsync(TimeSpan.FromSeconds(2));
        var pending = session.GetSnapshot();
        Assert.True(pending.IsThinking);
        Assert.Equal([new MacOsWorkflowRulesEditorMessage("user", "Continue the approved change")], pending.Messages);

        responseConnection.Cancel();
        await Assert.ThrowsAnyAsync<OperationCanceledException>(() => response);

        Assert.True(session.GetSnapshot().IsThinking);
        pipeline.Release.TrySetResult();
        var completed = await WaitForCompletionAsync(session);
        Assert.False(completed.IsThinking);
        Assert.Equal("Agent response.", completed.Messages.Last().Content);
        Assert.Single(pending.Messages);
        Assert.True(pending.IsThinking);
    }

    [Fact]
    public async Task ApprovedWorkflowWindowOpensWithoutWaitingForItsAgentResponse()
    {
        var pipeline = new BlockingPipeline();
        using var lifetime = new TestApplicationLifetime();
        var sessions = CreateSessions(pipeline, lifetime);
        IWorkflowRulesEditorWindowService editor = new MacOsWorkflowRulesEditorWindowService(
            Options.Create(new MeetingAssistantOptions()), () => sessions);
        try
        {
            await Task.Run(() => editor.ShowWithPrompt("Apply the approved workflow scenario."))
                .WaitAsync(TimeSpan.FromSeconds(2));
            await pipeline.Started.Task.WaitAsync(TimeSpan.FromSeconds(2));
            var window = Assert.Single(sessions.GetAgentWindows());
            Assert.True(sessions.TryGetSession(window.Id, out var session));
            Assert.True(session.GetSnapshot().IsThinking);
        }
        finally
        {
            pipeline.Release.TrySetResult();
        }
    }

    [Fact]
    public void ConstructingTheWindowServiceDoesNotStartOrResolveAnAgentConversation()
    {
        using var lifetime = new TestApplicationLifetime();
        var sessions = CreateSessions(new ReplyPipeline(), lifetime);
        var resolutions = 0;
        IWorkflowRulesEditorWindowService editor = new MacOsWorkflowRulesEditorWindowService(
            Options.Create(new MeetingAssistantOptions()), () =>
            {
                resolutions++;
                return sessions;
            });

        Assert.Equal(0, resolutions);
        Assert.Empty(sessions.GetAgentWindows());

        editor.ShowWithPrompt("An explicitly approved scenario.");

        Assert.Equal(1, resolutions);
        Assert.Single(sessions.GetAgentWindows());
    }

    [Fact]
    public async Task TwoApprovedWorkflowsAndTheirFollowUpsRemainIndependent()
    {
        using var lifetime = new TestApplicationLifetime();
        var sessions = CreateSessions(new ReplyPipeline(), lifetime);
        sessions.OpenWithPrompt("First approved scenario.");
        sessions.OpenWithPrompt("Second approved scenario.");
        var windows = sessions.GetAgentWindows();
        Assert.Equal(2, windows.Count);
        Assert.Equal(2, windows.Select(window => window.Id).Distinct().Count());
        var conversations = new List<MacOsWorkflowRulesEditorSession>();
        foreach (var window in windows)
        {
            Assert.True(sessions.TryGetSession(window.Id, out var conversation));
            conversations.Add(conversation);
        }
        var snapshots = await Task.WhenAll(conversations.Select(WaitForCompletionAsync));
        Assert.Equal(
            ["First approved scenario.", "Second approved scenario."],
            snapshots.Select(snapshot => snapshot.Messages[0].Content).Order());

        var updated = await conversations[0].SendAsync("A follow-up in just this conversation.", CancellationToken.None);

        Assert.Equal(4, updated.Messages.Count);
        Assert.Equal(2, conversations[1].GetSnapshot().Messages.Count);
        Assert.True(sessions.TryGetSession(null, out var normal));
        Assert.Empty(normal.GetSnapshot().Messages);
    }

    [Fact]
    public async Task ApplicationShutdownCancelsBackgroundConversationAndPreventsNewWindows()
    {
        var pipeline = new BlockingPipeline();
        using var lifetime = new TestApplicationLifetime();
        var sessions = CreateSessions(pipeline, lifetime);
        sessions.OpenWithPrompt("Apply the approved scenario.");
        await pipeline.Started.Task.WaitAsync(TimeSpan.FromSeconds(2));
        var window = Assert.Single(sessions.GetAgentWindows());
        Assert.True(sessions.TryGetSession(window.Id, out var conversation));

        lifetime.StopApplication();

        using var deadline = new CancellationTokenSource(TimeSpan.FromSeconds(2));
        while (conversation.GetSnapshot().IsThinking) await Task.Delay(10, deadline.Token);
        Assert.Empty(sessions.GetAgentWindows());
        Assert.Single(conversation.GetSnapshot().Messages);
        Assert.ThrowsAny<OperationCanceledException>(() => sessions.OpenWithPrompt("A stale approval."));
    }

    private static MacOsWorkflowRulesEditorSessions CreateSessions(
        IWorkflowRulesEditorChatPipeline pipeline,
        IHostApplicationLifetime lifetime) => new(
            pipeline,
            Options.Create(new MeetingAssistantOptions()),
            lifetime,
            NullLogger<MacOsWorkflowRulesEditorSessions>.Instance);

    private static async Task<MacOsWorkflowRulesEditorChatResponse> WaitForCompletionAsync(
        MacOsWorkflowRulesEditorSession session)
    {
        using var deadline = new CancellationTokenSource(TimeSpan.FromSeconds(2));
        while (true)
        {
            var snapshot = session.GetSnapshot();
            if (snapshot.Messages.Count >= 2 && !snapshot.IsThinking) return snapshot;
            await Task.Delay(10, deadline.Token);
        }
    }

    private sealed class ReplyPipeline : IWorkflowRulesEditorChatPipeline
    {
        public Task<WorkflowRulesEditorChatResult> SendAsync(
            IReadOnlyList<WorkflowRulesEditorChatMessage> conversation,
            string userMessage,
            CancellationToken cancellationToken,
            Action<WorkflowRulesEditorActivityUpdate>? activityChanged = null) =>
            Task.FromResult(new WorkflowRulesEditorChatResult("Agent response."));
    }

    private sealed class BlockingPipeline : IWorkflowRulesEditorChatPipeline
    {
        public TaskCompletionSource Started { get; } = new(TaskCreationOptions.RunContinuationsAsynchronously);
        public TaskCompletionSource Release { get; } = new(TaskCreationOptions.RunContinuationsAsynchronously);

        public async Task<WorkflowRulesEditorChatResult> SendAsync(
            IReadOnlyList<WorkflowRulesEditorChatMessage> conversation,
            string userMessage,
            CancellationToken cancellationToken,
            Action<WorkflowRulesEditorActivityUpdate>? activityChanged = null)
        {
            Started.TrySetResult();
            await Release.Task.WaitAsync(cancellationToken);
            return new WorkflowRulesEditorChatResult("Agent response.");
        }
    }

    private sealed class TestApplicationLifetime : IHostApplicationLifetime, IDisposable
    {
        private readonly CancellationTokenSource stopping = new();
        public CancellationToken ApplicationStarted => CancellationToken.None;
        public CancellationToken ApplicationStopping => stopping.Token;
        public CancellationToken ApplicationStopped => stopping.Token;
        public void StopApplication() => stopping.Cancel();
        public void Dispose()
        {
            stopping.Cancel();
            stopping.Dispose();
        }
    }
}