using AcDream.Headless.Configuration;
using AcDream.Runtime;

namespace AcDream.Headless.Policies;

internal interface IHeadlessBotPolicy : IRuntimeEventObserver, IDisposable
{
    bool IsComplete { get; }

    void Tick(IGameRuntimeView view, IGameRuntimeCommands commands);
}

internal static class HeadlessBotPolicyFactory
{
    internal static IHeadlessBotPolicy Create(string id) =>
        id switch
        {
            "idle" => new IdleHeadlessBotPolicy(),
            "lifecycle-smoke" => new LifecycleSmokeHeadlessBotPolicy(),
            _ => throw new HeadlessConfigurationException(
                $"Unknown headless bot policy '{id}'."),
        };
}

internal sealed class IdleHeadlessBotPolicy : IHeadlessBotPolicy
{
    public bool IsComplete => false;

    public void Tick(
        IGameRuntimeView view,
        IGameRuntimeCommands commands)
    {
        ArgumentNullException.ThrowIfNull(view);
        ArgumentNullException.ThrowIfNull(commands);
    }

    public void OnLifecycle(in RuntimeLifecycleDelta delta)
    {
    }

    public void OnCommand(in RuntimeCommandDelta delta)
    {
    }

    public void OnEntity(in RuntimeEntityDelta delta)
    {
    }

    public void OnInventory(in RuntimeInventoryDelta delta)
    {
    }

    public void OnChat(in RuntimeChatDelta delta)
    {
    }

    public void OnMovement(in RuntimeMovementDelta delta)
    {
    }

    public void OnPortal(in RuntimePortalDelta delta)
    {
    }

    public void OnCombat(in RuntimeCombatDelta delta)
    {
    }

    public void Dispose()
    {
    }
}

/// <summary>
/// Explicit connected-gate policy: wait for the local player, issue one
/// harmless local-speech command and one lifestone recall, reconnect after
/// the exact portal completes, then terminate after the new generation has
/// materialized the player. It is never selected implicitly.
/// </summary>
internal sealed class LifecycleSmokeHeadlessBotPolicy
    : IHeadlessBotPolicy
{
    private int _stage;
    private ulong _firstGeneration;

    public bool IsComplete => _stage == 3;

    public void Tick(
        IGameRuntimeView view,
        IGameRuntimeCommands commands)
    {
        ArgumentNullException.ThrowIfNull(view);
        ArgumentNullException.ThrowIfNull(commands);
        switch (_stage)
        {
            case 0:
                if (!HasLocalPlayer(view))
                    return;
                Require(commands.Chat.Execute(
                    view.Generation,
                    new RuntimeChatCommand(
                        RuntimeChatChannel.Say,
                        "[acdream headless lifecycle gate]")));
                Require(commands.Portal.Execute(
                    view.Generation,
                    RuntimePortalCommand.RecallLifestone));
                _firstGeneration = view.Generation.Value;
                _stage = 1;
                break;
            case 1:
                if (view.Portal.Snapshot.Kind
                        is not RuntimePortalKind.Portal
                    || !view.Portal.Snapshot.Completed)
                {
                    return;
                }
                RuntimeSessionStartResult reconnect =
                    commands.Session.Reconnect(view.Generation);
                if (reconnect.Status
                    is not (
                        RuntimeSessionStartStatus.Connected
                        or RuntimeSessionStartStatus.Deferred))
                {
                    throw new InvalidOperationException(
                        $"Lifecycle gate reconnect was rejected with {reconnect.Status}.");
                }
                _stage = 2;
                break;
            case 2:
                if (view.Generation.Value <= _firstGeneration
                    || !HasLocalPlayer(view))
                {
                    return;
                }
                _stage = 3;
                break;
        }
    }

    public void OnLifecycle(in RuntimeLifecycleDelta delta)
    {
    }

    public void OnCommand(in RuntimeCommandDelta delta)
    {
    }

    public void OnEntity(in RuntimeEntityDelta delta)
    {
    }

    public void OnInventory(in RuntimeInventoryDelta delta)
    {
    }

    public void OnChat(in RuntimeChatDelta delta)
    {
    }

    public void OnMovement(in RuntimeMovementDelta delta)
    {
    }

    public void OnPortal(in RuntimePortalDelta delta)
    {
    }

    public void OnCombat(in RuntimeCombatDelta delta)
    {
    }

    public void Dispose()
    {
    }

    private static bool HasLocalPlayer(IGameRuntimeView view) =>
        view.Lifecycle.State is RuntimeLifecycleState.InWorld
        && view.Lifecycle.PlayerGuid != 0u
        && view.Entities.TryGet(
            view.Lifecycle.PlayerGuid,
            out _);

    private static void Require(in RuntimeCommandResult result)
    {
        if (!result.Accepted)
        {
            throw new InvalidOperationException(
                $"Lifecycle gate command was rejected with {result.Status}.");
        }
    }
}