using UnityEngine;
using UnityEngine.UIElements;

/// <summary>
/// Adds a small UI Toolkit control panel for adjusting Time.timeScale at runtime.
/// Buttons: Pause (0x), 0.5x, 1x (normal), 2x.
/// Camera movement is independent of Time.timeScale (uses unscaledDeltaTime),
/// so the simulation can be paused/slowed without affecting navigation.
/// </summary>
public class SimulationControlsUIPanel : MonoBehaviour
{
    [Header("Speed Options")]
    [SerializeField] private float pausedScale = 0f;
    [SerializeField] private float halfScale = 0.5f;
    [SerializeField] private float normalScale = 1f;
    [SerializeField] private float doubleScale = 2f;

    private VisualElement root;
    private Button pauseButton;
    private Button halfButton;
    private Button normalButton;
    private Button doubleButton;
    private Label statusLabel;

    private float lastSpeedBeforePause = 1f;

    void Start()
    {
        InitializeUI();
        ApplySpeed(normalScale);
    }

    void OnDestroy()
    {
        // Always restore normal speed when leaving the scene/play mode
        Time.timeScale = 1f;
    }

    private void InitializeUI()
    {
        var uiDocument = FindAnyObjectByType<UIDocument>();
        if (uiDocument == null)
        {
            var docGO = new GameObject("UIDocument");
            uiDocument = docGO.AddComponent<UIDocument>();
        }

        root = uiDocument.rootVisualElement;

        // Container - bottom-center
        var panel = new VisualElement();
        panel.name = "SimulationControlsPanel";
        panel.style.position = Position.Absolute;
        panel.style.bottom = 20;
        panel.style.left = new StyleLength(new Length(50, LengthUnit.Percent));
        panel.style.translate = new StyleTranslate(new Translate(new Length(-50, LengthUnit.Percent), 0));
        panel.style.flexDirection = FlexDirection.Row;
        panel.style.alignItems = Align.Center;
        panel.style.backgroundColor = new Color(0.1f, 0.1f, 0.1f, 0.85f);
        panel.style.borderBottomLeftRadius = 6;
        panel.style.borderBottomRightRadius = 6;
        panel.style.borderTopLeftRadius = 6;
        panel.style.borderTopRightRadius = 6;
        panel.style.paddingBottom = 6;
        panel.style.paddingTop = 6;
        panel.style.paddingLeft = 10;
        panel.style.paddingRight = 10;

        var title = new Label("Speed:");
        title.style.color = Color.white;
        title.style.fontSize = 13;
        title.style.unityFontStyleAndWeight = FontStyle.Bold;
        title.style.marginRight = 10;
        panel.Add(title);

        pauseButton = MakeButton("Pause", () => ApplySpeed(pausedScale));
        halfButton = MakeButton("0.5x", () => ApplySpeed(halfScale));
        normalButton = MakeButton("1x", () => ApplySpeed(normalScale));
        doubleButton = MakeButton("2x", () => ApplySpeed(doubleScale));

        panel.Add(pauseButton);
        panel.Add(halfButton);
        panel.Add(normalButton);
        panel.Add(doubleButton);

        statusLabel = new Label("1x");
        statusLabel.style.color = new Color(0.7f, 0.9f, 1f);
        statusLabel.style.fontSize = 12;
        statusLabel.style.marginLeft = 10;
        statusLabel.style.minWidth = 50;
        statusLabel.style.unityTextAlign = TextAnchor.MiddleLeft;
        panel.Add(statusLabel);

        root.Add(panel);
    }

    private Button MakeButton(string text, System.Action onClick)
    {
        var btn = new Button(onClick) { text = text };
        btn.style.width = 60;
        btn.style.height = 28;
        btn.style.marginLeft = 4;
        btn.style.marginRight = 4;
        btn.style.fontSize = 12;
        btn.style.color = Color.white;
        btn.style.backgroundColor = new Color(0.25f, 0.25f, 0.28f, 1f);
        btn.style.borderBottomLeftRadius = 4;
        btn.style.borderBottomRightRadius = 4;
        btn.style.borderTopLeftRadius = 4;
        btn.style.borderTopRightRadius = 4;
        return btn;
    }

    private void ApplySpeed(float scale)
    {
        if (scale > 0f)
            lastSpeedBeforePause = scale;

        Time.timeScale = scale;
        UpdateButtonHighlight(scale);
        if (statusLabel != null)
            statusLabel.text = scale <= 0f ? "PAUSED" : $"{scale}x";
    }

    private void UpdateButtonHighlight(float scale)
    {
        SetActive(pauseButton, Mathf.Approximately(scale, pausedScale));
        SetActive(halfButton, Mathf.Approximately(scale, halfScale));
        SetActive(normalButton, Mathf.Approximately(scale, normalScale));
        SetActive(doubleButton, Mathf.Approximately(scale, doubleScale));
    }

    private void SetActive(Button btn, bool active)
    {
        if (btn == null) return;
        btn.style.backgroundColor = active
            ? new Color(0.2f, 0.6f, 0.9f, 1f)   // highlighted
            : new Color(0.25f, 0.25f, 0.28f, 1f);
        btn.style.unityFontStyleAndWeight = active ? FontStyle.Bold : FontStyle.Normal;
    }

    void Update()
    {
        // Keyboard shortcuts: Space = pause/resume, 1/2/3/4 = speed presets
        var kb = UnityEngine.InputSystem.Keyboard.current;
        if (kb == null) return;

        if (kb.spaceKey.wasPressedThisFrame)
        {
            if (Time.timeScale > 0f)
                ApplySpeed(0f);
            else
                ApplySpeed(lastSpeedBeforePause);
        }
        else if (kb.digit1Key.wasPressedThisFrame) ApplySpeed(pausedScale);
        else if (kb.digit2Key.wasPressedThisFrame) ApplySpeed(halfScale);
        else if (kb.digit3Key.wasPressedThisFrame) ApplySpeed(normalScale);
        else if (kb.digit4Key.wasPressedThisFrame) ApplySpeed(doubleScale);
    }
}