using System;
using System.Numerics;
using AcDream.App.Input;
using AcDream.Core.Physics;
using Xunit;

namespace AcDream.Core.Tests.Input;

public class PlayerMovementControllerTests
{
    private static PhysicsEngine MakeFlatEngine()
    {
        var engine = new PhysicsEngine();
        var heights = new byte[81];
        Array.Fill(heights, (byte)50);
        var heightTable = new float[256];
        for (int i = 0; i < 256; i++) heightTable[i] = i * 1f;
        var terrain = new TerrainSurface(heights, heightTable);
        engine.AddLandblock(0xA9B4FFFFu, terrain, Array.Empty<CellSurface>(),
            worldOffsetX: 0f, worldOffsetY: 0f);
        return engine;
    }

    [Fact]
    public void Update_NoInput_PositionUnchanged()
    {
        var engine = MakeFlatEngine();
        var controller = new PlayerMovementController(engine);
        controller.SetPosition(new Vector3(96f, 96f, 50f), 0x0001);

        var result = controller.Update(0.016f, new MovementInput());

        Assert.Equal(96f, result.Position.X, precision: 1);
        Assert.Equal(96f, result.Position.Y, precision: 1);
    }

    [Fact]
    public void Update_ForwardInput_MovesInFacingDirection()
    {
        var engine = MakeFlatEngine();
        var controller = new PlayerMovementController(engine);
        controller.SetPosition(new Vector3(96f, 96f, 50f), 0x0001);
        controller.Yaw = 0f;  // facing +X

        var input = new MovementInput { Forward = true };
        var result = controller.Update(1.0f, input);  // 1 second

        // Should have moved ~4 units in +X (walk speed).
        Assert.True(result.Position.X > 96f + 2f, $"X={result.Position.X} should have moved forward");
    }

    [Fact]
    public void Update_RunForward_MoveFasterThanWalk()
    {
        var engine = MakeFlatEngine();
        var controller = new PlayerMovementController(engine);
        controller.SetPosition(new Vector3(96f, 96f, 50f), 0x0001);
        controller.Yaw = 0f;

        var walkInput = new MovementInput { Forward = true };
        var walkResult = controller.Update(1.0f, walkInput);
        float walkDist = walkResult.Position.X - 96f;

        controller.SetPosition(new Vector3(96f, 96f, 50f), 0x0001);

        var runInput = new MovementInput { Forward = true, Run = true };
        var runResult = controller.Update(1.0f, runInput);
        float runDist = runResult.Position.X - 96f;

        Assert.True(runDist > walkDist, $"Run ({runDist}) should be faster than walk ({walkDist})");
    }

    [Fact]
    public void Update_TurnInput_ChangesYaw()
    {
        var engine = MakeFlatEngine();
        var controller = new PlayerMovementController(engine);
        controller.SetPosition(new Vector3(96f, 96f, 50f), 0x0001);
        float initialYaw = controller.Yaw;

        var input = new MovementInput { TurnRight = true };
        controller.Update(0.5f, input);

        Assert.NotEqual(initialYaw, controller.Yaw);
    }

    [Fact]
    public void MotionStateChanged_WhenStartingToWalk()
    {
        var engine = MakeFlatEngine();
        var controller = new PlayerMovementController(engine);
        controller.SetPosition(new Vector3(96f, 96f, 50f), 0x0001);

        // First frame: idle (no input).
        controller.Update(0.016f, new MovementInput());

        // Second frame: start walking.
        var input = new MovementInput { Forward = true };
        var result = controller.Update(0.016f, input);

        Assert.True(result.MotionStateChanged);
    }
}