using MeetingAssistant.Notifications;
using MeetingAssistant.Workflow;
using System.Threading.Channels;

namespace MeetingAssistant.Summary;

public sealed class WorkflowChangeRequestService(
    AgentApprovalService approvals,
    IWorkflowRulesEditorWindowService editor,
    ILogger<WorkflowChangeRequestService> logger) : BackgroundService
{
    private readonly Channel<RequestDetails> requests = Channel.CreateUnbounded<RequestDetails>(
        new UnboundedChannelOptions { SingleReader = true });

    public string Request(string intention, string detailedPrompt, string meetingNotePath)
    {
        if (string.IsNullOrWhiteSpace(intention) || intention.Length > 100 || intention.Contains('\r') || intention.Contains('\n'))
            return "Refused: intention must be a nonempty single line of at most 100 characters.";
        if (string.IsNullOrWhiteSpace(detailedPrompt))
            return "Refused: supply a detailed change prompt, preferably a scenario or specification.";
        var request = new RequestDetails(Guid.NewGuid().ToString("N"), intention, detailedPrompt, meetingNotePath);
        return requests.Writer.TryWrite(request) ? $"Requested: {request.Id}. User approval is pending."
            : "Refused: application is stopping.";
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        var pending = new List<Task>();
        try
        {
            await foreach (var request in requests.Reader.ReadAllAsync(stoppingToken))
            {
                pending.RemoveAll(task => task.IsCompleted);
                pending.Add(HandleAsync(request, stoppingToken));
            }
        }
        catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested) { }
        finally
        {
            await Task.WhenAll(pending);
        }
    }

    private async Task HandleAsync(RequestDetails request, CancellationToken cancellationToken)
    {
        try
        {
            if (await approvals.ConfirmAsync($"Workflow change requested: {request.Intention}",
                $"The summarizer for {Path.GetFileName(request.MeetingNotePath)} requests a workflow change. Open the settings agent to apply it?",
                cancellationToken))
            {
                cancellationToken.ThrowIfCancellationRequested();
                editor.ShowWithPrompt(request.DetailedPrompt);
            }
        }
        catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested) { }
        catch (Exception exception)
        {
            logger.LogWarning(exception, "Workflow request {RequestId} could not be handled", request.Id);
        }
    }

    public override Task StopAsync(CancellationToken cancellationToken)
    {
        requests.Writer.TryComplete();
        return base.StopAsync(cancellationToken);
    }

    private sealed record RequestDetails(string Id, string Intention, string DetailedPrompt, string MeetingNotePath);
}