using System.IO;
using System.Net.WebSockets;
using System.Text;
using System.Text.Json;
using Backend;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc.Testing;
using Xunit;

namespace Backend.Tests;

public class EndToEndSmokeTests : IClassFixture<WebApplicationFactory<Program>>
{
    private readonly WebApplicationFactory<Program> _factory;

    public EndToEndSmokeTests(WebApplicationFactory<Program> factory)
    {
        _factory = factory.WithWebHostBuilder(b =>
        {
            // Prevent MVC picking up assemblies; force env vars if needed.
            b.UseEnvironment("Development");
        });
    }

    [Fact]
    public async Task WebSocket_ReceivesInitAndStateFrames()
    {
        // Prerequisites: publish/GameCli/GameCli and models/ppo_lander.onnx must exist.
        var repoRoot = FindRepoRoot();
        Assert.True(File.Exists(Path.Combine(repoRoot, "publish", "GameCli", "GameCli")),
            "run `dotnet publish GameCli -c Release -o publish/GameCli` before this test");
        Assert.True(File.Exists(Path.Combine(repoRoot, "models", "ppo_lander.onnx")),
            "run `python Training/export_onnx.py ...` before this test");

        var client = _factory.Server.CreateWebSocketClient();
        var baseUri = _factory.Server.BaseAddress;
        var wsUri = new UriBuilder(baseUri) { Scheme = "ws", Path = "/ws/game" }.Uri;

        using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(15));
        using var ws = await client.ConnectAsync(wsUri, cts.Token);

        var initText = await ReceiveTextAsync(ws, cts.Token);
        using var initDoc = JsonDocument.Parse(initText);
        Assert.Equal("init", initDoc.RootElement.GetProperty("type").GetString());

        // Send a cursor and receive at least one state frame.
        var cursorPayload = """{"type":"cursor","x":0.3,"y":0.7}""";
        await ws.SendAsync(Encoding.UTF8.GetBytes(cursorPayload),
            WebSocketMessageType.Text, true, cts.Token);

        // Read up to N frames looking for a state frame; the ticker runs at 50 Hz.
        for (int i = 0; i < 100; i++)
        {
            var text = await ReceiveTextAsync(ws, cts.Token);
            using var doc = JsonDocument.Parse(text);
            if (doc.RootElement.GetProperty("type").GetString() == "state")
            {
                Assert.True(doc.RootElement.TryGetProperty("x",      out _));
                Assert.True(doc.RootElement.TryGetProperty("y",      out _));
                Assert.True(doc.RootElement.TryGetProperty("angle",  out _));
                Assert.True(doc.RootElement.TryGetProperty("engine", out _));
                Assert.True(doc.RootElement.TryGetProperty("target", out _));
                Assert.True(doc.RootElement.TryGetProperty("step",   out _));
                return;
            }
        }
        Assert.Fail("did not receive a state frame in 100 messages");
    }

    private static async Task<string> ReceiveTextAsync(WebSocket ws, CancellationToken ct)
    {
        var buffer = new byte[16 * 1024];
        var sb = new StringBuilder();
        WebSocketReceiveResult result;
        do
        {
            result = await ws.ReceiveAsync(buffer, ct);
            sb.Append(Encoding.UTF8.GetString(buffer, 0, result.Count));
        } while (!result.EndOfMessage);
        return sb.ToString();
    }

    private static string FindRepoRoot()
    {
        var dir = AppContext.BaseDirectory;
        while (dir is not null)
        {
            if (File.Exists(Path.Combine(dir, "GameCli.sln"))) return dir;
            var parent = Directory.GetParent(dir);
            if (parent is null) break;
            dir = parent.FullName;
        }
        throw new InvalidOperationException("repo root not found");
    }
}