using System.Buffers.Binary;
using System.Net;
using System.Text;
using AcDream.Core.Chat;
using AcDream.Core.Net;
using AcDream.Core.Net.Messages;
using AcDream.Headless.Configuration;
using AcDream.Headless.Credentials;
using AcDream.Headless.Diagnostics;
using AcDream.Headless.Hosting;
using AcDream.Plugin.Abstractions;
using AcDream.Runtime;
using AcDream.Runtime.Chat;
using AcDream.Runtime.Session;

namespace AcDream.Headless.Tests;

/// <summary>
/// docs/plans/2026-09-07-headless-console.md — the headless interactive
/// console. Two layers: <see cref="HeadlessConsoleInputReader"/> /
/// <see cref="HeadlessConsoleController"/> tested in isolation (no live
/// server, no <see cref="HeadlessSessionHost"/>), then
/// <see cref="HeadlessSessionHost.SubmitConsoleLine"/> tested against a real
/// host wired to <see cref="FixtureSessionOperations"/> — the same
/// no-network fixture pattern <c>HeadlessSessionHostTests</c> already uses
/// for <c>LoginCommandSequence</c>, proving the console reuses the EXACT
/// same pipeline rather than a second parser.
/// </summary>
public sealed class HeadlessConsoleTests
{
    // ── HeadlessConsoleOptions (typed option resolution) ─────────────────

    [Theory]
    [InlineData(true, "0", false, true)]   // CLI flag always wins
    [InlineData(false, "1", false, true)]  // env var wins over terminal default
    [InlineData(false, "0", true, true)]   // env var "0" does not disable the terminal default
    [InlineData(false, null, true, true)]  // no flag/env -> terminal-shaped default (on)
    [InlineData(false, null, false, false)] // no flag/env -> terminal-shaped default (off)
    public void ResolvePrefersFlagThenEnvironmentThenTerminalDefault(
        bool commandLineFlag,
        string? environmentValue,
        bool standardInputIsTerminal,
        bool expected)
    {
        bool resolved = HeadlessConsoleOptions.Resolve(
            commandLineFlag,
            _ => environmentValue,
            standardInputIsTerminal);

        Assert.Equal(expected, resolved);
    }

    [Fact]
    public void CommandLineParsesTheBareConsoleFlag()
    {
        HeadlessCommandLine parsed = HeadlessCommandLine.Parse(
            ["run", "--config", "bot.json", "--console"]);

        Assert.True(parsed.Console);
        Assert.Equal("bot.json", parsed.ConfigurationPath);
    }

    [Fact]
    public void CommandLineWithoutTheFlagDefaultsConsoleOff()
    {
        HeadlessCommandLine parsed = HeadlessCommandLine.Parse(
            ["run", "--config", "bot.json"]);

        Assert.False(parsed.Console);
    }

    // ── HeadlessConsoleInputReader: reader-thread/ordering ───────────────

    /// <summary>
    /// The required reader-thread test: lines produced by the background
    /// thread are drained, in FIFO order, entirely on the CALLING thread.
    /// The reader thread itself never runs anything beyond
    /// <c>ConcurrentQueue.Enqueue</c> — there is no dispatch code it could
    /// execute — so this also structurally proves "never executed on the
    /// reader thread," not just orders the output.
    /// </summary>
    [Fact]
    public void LinesQueuedByTheReaderThreadDrainInOrderOnTheCallingThread()
    {
        using var input = new System.IO.StringReader(
            "one" + Environment.NewLine
            + "two" + Environment.NewLine
            + "three" + Environment.NewLine);
        using var reader = new HeadlessConsoleInputReader(input);

        Assert.True(
            reader.EndOfInput.Wait(TimeSpan.FromSeconds(5)),
            "the reader thread never reached EOF");

        int callingThread = Environment.CurrentManagedThreadId;
        var drained = new List<string>();
        while (reader.TryDequeue(out string line))
        {
            drained.Add(line);
            // Proves the dequeue (and everything a caller does with the
            // line) runs on THIS thread, not the reader thread.
            Assert.Equal(callingThread, Environment.CurrentManagedThreadId);
        }

        Assert.Equal(["one", "two", "three"], drained);
    }

    // ── HeadlessConsoleController: /quit, /status, dispatch ordering ─────

    [Fact]
    public void ControllerDrainsEveryLineQueuedSinceTheLastTickInOrderOnOneCall()
    {
        // Simulates "input queued during a busy tick": every line is
        // enqueued by the reader thread before DrainDue is ever called —
        // one DrainDue call must still process all of them, in order.
        using var input = new System.IO.StringReader(
            "alpha" + Environment.NewLine
            + "beta" + Environment.NewLine
            + "gamma" + Environment.NewLine);
        var handled = new List<string>();
        using var quit = new CancellationTokenSource();
        using var controller = new HeadlessConsoleController(
            input,
            TextWriter.Null,
            line =>
            {
                handled.Add(line);
                return SubmitOutcome.Sent;
            },
            () => string.Empty,
            quit);

        Assert.True(
            WaitForEndOfInput(controller),
            "the reader thread never reached EOF");
        controller.DrainDue();

        Assert.Equal(["alpha", "beta", "gamma"], handled);
        Assert.Equal(3, controller.LastDrainCount);

        // A second drain with nothing queued does nothing — proves DrainDue
        // does not re-process already-handled lines.
        controller.DrainDue();
        Assert.Equal(["alpha", "beta", "gamma"], handled);
        Assert.Equal(0, controller.LastDrainCount);
    }

    [Fact]
    public void QuitRequestsCancellationAndNeverReachesSubmit()
    {
        using var input = new System.IO.StringReader("/quit" + Environment.NewLine);
        var submitted = new List<string>();
        var output = new StringWriter();
        using var quit = new CancellationTokenSource();
        using var controller = new HeadlessConsoleController(
            input,
            output,
            line =>
            {
                submitted.Add(line);
                return SubmitOutcome.Sent;
            },
            () => string.Empty,
            quit);

        Assert.True(WaitForEndOfInput(controller));
        controller.DrainDue();

        Assert.True(quit.IsCancellationRequested);
        Assert.Empty(submitted);
        Assert.Contains("quitting", output.ToString(), StringComparison.OrdinalIgnoreCase);
    }

    [Fact]
    public void StatusPrintsTheProvidedStatusTextAndNeverReachesSubmit()
    {
        using var input = new System.IO.StringReader("/status" + Environment.NewLine);
        var submitted = new List<string>();
        var output = new StringWriter();
        using var quit = new CancellationTokenSource();
        using var controller = new HeadlessConsoleController(
            input,
            output,
            line =>
            {
                submitted.Add(line);
                return SubmitOutcome.Sent;
            },
            () => "generation=1 position=unknown plugins=0 loaded",
            quit);

        Assert.True(WaitForEndOfInput(controller));
        controller.DrainDue();

        Assert.Empty(submitted);
        Assert.Contains(
            "generation=1 position=unknown plugins=0 loaded",
            output.ToString());
    }

    // ── HeadlessConsoleChatFormatter: channel-prefixed rendering ─────────

    [Theory]
    [InlineData("Bob", 0x50000010u, "hi", "[Local] Bob: hi")]
    [InlineData("", 0u, "hi", "[Local] You: hi")]
    public void FormatsLocalSpeechWithTheLocalLabel(
        string sender, uint senderGuid, string text, string expected)
    {
        var entry = new RuntimeChatEntry(
            Revision: 1,
            SenderGuid: senderGuid,
            Kind: (int)ChatKind.LocalSpeech,
            Sender: sender,
            Text: text,
            ChannelName: string.Empty);

        Assert.Equal(expected, HeadlessConsoleChatFormatter.Format(entry));
    }

    [Fact]
    public void FormatsChannelBroadcastWithItsFriendlyName()
    {
        var entry = new RuntimeChatEntry(
            Revision: 1,
            SenderGuid: 0x50000010u,
            Kind: (int)ChatKind.Channel,
            Sender: "Bob",
            Text: "group up",
            ChannelName: "Fellowship");

        Assert.Equal(
            "[Fellowship] Bob: group up",
            HeadlessConsoleChatFormatter.Format(entry));
    }

    [Theory]
    [InlineData(0x50000010u, "Bob", "hi", "[Tell] Bob: hi")]
    [InlineData(0u, "Bob", "hi", "[Tell] You -> Bob: hi")]
    public void FormatsTellWithDirection(
        uint senderGuid, string sender, string text, string expected)
    {
        var entry = new RuntimeChatEntry(
            Revision: 1,
            SenderGuid: senderGuid,
            Kind: (int)ChatKind.Tell,
            Sender: sender,
            Text: text,
            ChannelName: string.Empty);

        Assert.Equal(expected, HeadlessConsoleChatFormatter.Format(entry));
    }

    // ── HeadlessSessionHost.SubmitConsoleLine: the real dispatch pipeline ─

    [Fact]
    public void SlashSayProducesTheSameOutboundTalkActionTheGraphicalRouteSends()
    {
        var captured = new List<byte[]>();
        var operations = new FixtureSessionOperations
        {
            GameActionCapture = body => captured.Add(body),
        };
        using var credential = new HeadlessCredentialSecret("fixture", "password");
        using var host = new HeadlessSessionHost(
            Descriptor(),
            credential,
            new HeadlessDiagnosticWriter(TextWriter.Null),
            operations);
        Assert.Equal(
            RuntimeSessionStartStatus.Connected,
            host.Start().Status);

        SubmitOutcome outcome = host.SubmitConsoleLine("/say hello", _ => { });

        Assert.Equal(SubmitOutcome.Sent, outcome);
        byte[] body = Assert.Single(captured);
        Assert.Equal(ChatRequests.TalkOpcode, ActionOpcode(body));
        Assert.Equal("hello", TalkText(body));
    }

    [Fact]
    public void PlainTextProducesTheSameOutboundTalkActionAsSlashSay()
    {
        var captured = new List<byte[]>();
        var operations = new FixtureSessionOperations
        {
            GameActionCapture = body => captured.Add(body),
        };
        using var credential = new HeadlessCredentialSecret("fixture", "password");
        using var host = new HeadlessSessionHost(
            Descriptor(),
            credential,
            new HeadlessDiagnosticWriter(TextWriter.Null),
            operations);
        Assert.Equal(
            RuntimeSessionStartStatus.Connected,
            host.Start().Status);

        SubmitOutcome outcome = host.SubmitConsoleLine("hello", _ => { });

        Assert.Equal(SubmitOutcome.Sent, outcome);
        byte[] body = Assert.Single(captured);
        Assert.Equal(ChatRequests.TalkOpcode, ActionOpcode(body));
        Assert.Equal("hello", TalkText(body));
    }

    [Fact]
    public void PluginVerbReachesTheRegisteredPluginCommandWithoutTouchingTheWire()
    {
        var captured = new List<byte[]>();
        var operations = new FixtureSessionOperations
        {
            GameActionCapture = body => captured.Add(body),
        };
        using var credential = new HeadlessCredentialSecret("fixture", "password");
        using var host = new HeadlessSessionHost(
            Descriptor(),
            credential,
            new HeadlessDiagnosticWriter(TextWriter.Null),
            operations);
        Assert.Equal(
            RuntimeSessionStartStatus.Connected,
            host.Start().Status);
        var received = new List<PluginCommand>();
        using IDisposable registration = host.PluginCommands.Register(
            "vt",
            command => received.Add(command));

        SubmitOutcome outcome = host.SubmitConsoleLine("/vt start", _ => { });

        Assert.Equal(SubmitOutcome.ClientHandled, outcome);
        PluginCommand command = Assert.Single(received);
        Assert.Equal("vt", command.Verb);
        Assert.Equal("start", command.Arguments);
        Assert.Empty(captured);
    }

    [Fact]
    public void UnknownVerbProducesTheSameInterfaceTextTheChatBoxShows()
    {
        var operations = new FixtureSessionOperations();
        using var credential = new HeadlessCredentialSecret("fixture", "password");
        using var host = new HeadlessSessionHost(
            Descriptor(),
            credential,
            new HeadlessDiagnosticWriter(TextWriter.Null),
            operations);
        Assert.Equal(
            RuntimeSessionStartStatus.Connected,
            host.Start().Status);
        var interfaceText = new List<string>();

        // A bare "/" is retail's degenerate-prefix case (no letter verb) —
        // ChatCommandRouter refuses it locally instead of sending it to the
        // server or speech (ChatCommandRouterTests.
        // DegeneratePrefix_UnknownCommand_ShowsRefusal_ViaInterfaceTextSeam
        // pins the exact same text for the graphical route).
        SubmitOutcome outcome = host.SubmitConsoleLine(
            "/",
            interfaceText.Add);

        Assert.Equal(SubmitOutcome.UnknownCommand, outcome);
        string text = Assert.Single(interfaceText);
        Assert.Contains("Unknown command:", text);
    }

    private static bool WaitForEndOfInput(HeadlessConsoleController controller) =>
        controller.Reader.EndOfInput.Wait(TimeSpan.FromSeconds(5));

    private static uint ActionOpcode(byte[] body) =>
        BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(8, sizeof(uint)));

    private static string TalkText(byte[] body)
    {
        ushort length = BinaryPrimitives.ReadUInt16LittleEndian(
            body.AsSpan(12, sizeof(ushort)));
        return Encoding.ASCII.GetString(body, 14, length);
    }

    private static HeadlessSessionDescriptor Descriptor() => new()
    {
        Id = "console-bot",
        Endpoint = new HeadlessEndpointDescriptor
        {
            Host = "127.0.0.1",
            Port = 9000,
        },
        Account = "account",
        Character = new HeadlessCharacterSelector
        {
            Name = "headless",
        },
        Policy = new HeadlessBotPolicyDescriptor
        {
            Id = "idle",
        },
        Credential = new HeadlessCredentialReference
        {
            Provider = HeadlessCredentialProviderKind.Environment,
            Reference = "CONSOLE_BOT_PASSWORD",
        },
    };

    private sealed class FixtureSessionOperations : ILiveSessionOperations
    {
        public Action<byte[]>? GameActionCapture { get; init; }

        public CharacterList.Parsed? Characters { get; init; } = new(
            0u,
            [
                new CharacterList.Character(0x50000001u, "Other", 0u),
                new CharacterList.Character(0x50000002u, "Headless", 0u),
            ],
            [],
            11,
            "account",
            true,
            true);

        public IPEndPoint ResolveEndpoint(string host, int port) =>
            new(IPAddress.Loopback, port);

        public WorldSession CreateSession(IPEndPoint endpoint)
        {
            var session = new WorldSession(endpoint);
            session.GameActionCapture = GameActionCapture;
            return session;
        }

        public void Connect(WorldSession session, string user, string password)
        {
        }

        public CharacterList.Parsed? GetCharacters(WorldSession session) =>
            Characters;

        public void EnterWorld(WorldSession session, int activeCharacterIndex)
        {
        }

        public void Tick(WorldSession session)
        {
        }

        public void DisposeSession(WorldSession session) => session.Dispose();
    }
}