using System.Threading.Channels;
using Luna.Shared;
using Microsoft.AspNetCore.SignalR.Client;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace Luna.Cli;

public class ChatClientService(IHostApplicationLifetime lifetime) : IHostedService
{
    private HubConnection? connection;
    private readonly Guid conversationId = Guid.NewGuid();
    private Channel<ChatStreamUpdate>? responseChannel;

    public async Task StartAsync(CancellationToken cancellationToken)
    {
        var serverUrl = Environment.GetEnvironmentVariable("LUNA_SERVER_URL") ?? "http://localhost:5000";
        var hubUrl = $"{serverUrl.TrimEnd('/')}/chat";

        connection = new HubConnectionBuilder()
            .WithUrl(hubUrl)
            .WithAutomaticReconnect()
            .AddJsonProtocol(options =>
            {
                options.PayloadSerializerOptions.Converters.Add(
                    new System.Text.Json.Serialization.JsonStringEnumConverter(System.Text.Json.JsonNamingPolicy.CamelCase));
            })
            .Build();

        connection.On<ChatStreamUpdate>("OnMessageStreamReceived", update =>
        {
            responseChannel?.Writer.TryWrite(update);

            if (update.IsComplete)
                responseChannel?.Writer.TryComplete();
        });

        connection.Closed += error =>
        {
            Console.WriteLine(error != null
                ? $"[connection closed: {error.Message}]"
                : "[connection closed]");
            responseChannel?.Writer.TryComplete(error);
            return Task.CompletedTask;
        };

        connection.Reconnecting += error =>
        {
            Console.WriteLine($"[reconnecting... {error?.Message}]");
            responseChannel?.Writer.TryComplete(error);
            return Task.CompletedTask;
        };

        connection.Reconnected += connectionId =>
        {
            Console.WriteLine($"[reconnected: {connectionId}]");
            return Task.CompletedTask;
        };

        try
        {
            await connection.StartAsync(cancellationToken);
        }
        catch (Exception ex)
        {
            Console.WriteLine($"[failed to connect to {hubUrl}: {ex.Message}]");
            lifetime.StopApplication();
            return;
        }

        // Print startup banner
        Console.WriteLine("=== Luna CLI ===");
        Console.WriteLine($"Connected to {hubUrl}");
        Console.WriteLine("Type messages and press Enter to send.");
        Console.WriteLine("Commands: /exit (quit), /clear (clear screen)");
        Console.WriteLine();

        // Start input loop in background
        _ = Task.Run(() => InputLoopAsync(lifetime.ApplicationStopping), lifetime.ApplicationStopping);
    }

    private async Task InputLoopAsync(CancellationToken cancellationToken)
    {
        while (!cancellationToken.IsCancellationRequested)
        {
            try
            {
                Console.ForegroundColor = ConsoleColor.Green;
                Console.Write("you> ");
                Console.ResetColor();

                var input = await Task.Run(() => Console.ReadLine(), cancellationToken);

                if (input is null || string.Equals(input.Trim(), "/exit", StringComparison.OrdinalIgnoreCase))
                {
                    lifetime.StopApplication();
                    break;
                }

                if (string.Equals(input.Trim(), "/clear", StringComparison.OrdinalIgnoreCase))
                {
                    Console.Clear();
                    continue;
                }

                if (string.IsNullOrWhiteSpace(input))
                {
                    continue;
                }

                var message = new ChannelMessage(
                    MessageId: Guid.NewGuid().ToString(),
                    ConversationId: conversationId.ToString(),
                    SenderId: "cli-user",
                    SenderName: "User",
                    Content: input.Trim(),
                    Timestamp: DateTimeOffset.UtcNow
                );

                await StreamResponseAsync(message, cancellationToken);
            }
            catch (OperationCanceledException)
            {
                break;
            }
            catch (Exception ex)
            {
                Console.WriteLine($"[error] {ex.Message}");
            }
        }
    }

    private async Task StreamResponseAsync(ChannelMessage message, CancellationToken cancellationToken)
    {
        if (connection is null) return;

        responseChannel = Channel.CreateUnbounded<ChatStreamUpdate>();

        var assistantLabelPrinted = false;
        var thinkingLabelPrinted = false;

        try
        {
            await connection.InvokeAsync("OnMessageReceived", message, cancellationToken);

            await foreach (var update in responseChannel.Reader.ReadAllAsync(cancellationToken))
            {
                if (update.IsComplete)
                {
                    if (assistantLabelPrinted || thinkingLabelPrinted)
                        Console.WriteLine();
                    break;
                }

                switch (update.Type)
                {
                    case ChatStreamUpdateType.Thinking:
                        if (!thinkingLabelPrinted)
                        {
                            Console.ForegroundColor = ConsoleColor.DarkGray;
                            Console.Write("thinking> ");
                            Console.ResetColor();
                            thinkingLabelPrinted = true;
                        }
                        if (update.Content != null)
                        {
                            Console.ForegroundColor = ConsoleColor.DarkGray;
                            Console.Write(update.Content);
                            Console.ResetColor();
                        }
                        break;

                    case ChatStreamUpdateType.Text:
                        if (!assistantLabelPrinted)
                        {
                            Console.ForegroundColor = ConsoleColor.Magenta;
                            Console.Write("assistant> ");
                            Console.ResetColor();
                            assistantLabelPrinted = true;
                        }
                        Console.Write(update.Content);
                        break;
                    case ChatStreamUpdateType.Usage:
                        Console.WriteLine($"\n[{update.Type.ToString().ToLower()}: {update.Content}]");
                        break;
                }
            }

            // Ensure newline if stream ended without IsComplete flag
            if (assistantLabelPrinted || thinkingLabelPrinted)
                Console.WriteLine();
        }
        catch (OperationCanceledException)
        {
            Console.WriteLine();
        }
        catch (Exception ex)
        {
            Console.WriteLine($"\n[stream error] {ex.Message}");
        }
    }

    public async Task StopAsync(CancellationToken cancellationToken)
    {
        if (connection != null)
        {
            await connection.DisposeAsync();
            connection = null;
        }
    }
}