using System;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
#if ENABLE_INPUT_SYSTEM
using UnityEngine.InputSystem.UI;
#endif

/// <summary>
/// In-game paint UI. Builds its own Screen Space - Overlay canvas (and an EventSystem
/// if the scene has none) entirely in code and binds the widgets directly to the live
/// <see cref="MeshPainter"/> fields, so changes apply immediately. The panel is shown
/// only while the active <see cref="GameMode"/> is <see cref="PaintMode"/> (it follows
/// the manager's ModeChanged event).
///
/// First, simple pass: channel toggles, an HSV colour picker for albedo, metallic /
/// smoothness / occlusion sliders, an HSV picker + intensity for emission, and brush
/// size. Attach to an empty GameObject; everything else is generated at runtime.
/// </summary>
[DisallowMultipleComponent]
public class PaintHud : MonoBehaviour
{
    [Tooltip("Mode manager driving visibility. Empty = found automatically.")]
    public GameModeManager modeManager;

    [Tooltip("Painter the HUD edits. Empty = the manager's painter, else found automatically.")]
    public MeshPainter painter;

    private static readonly Color PanelColor = new Color(0.09f, 0.09f, 0.11f, 0.9f);
    private static readonly Color Accent = new Color(0.40f, 0.75f, 1f, 1f);
    private static readonly Color BoxColor = new Color(0.20f, 0.20f, 0.24f, 1f);

    private GameObject _panel;
    private Font _font;

    private void Awake()
    {
        if (!modeManager) modeManager = FindFirstObjectByType<GameModeManager>();
    }

    private void OnEnable()
    {
        if (modeManager) modeManager.ModeChanged += OnModeChanged;
    }

    private void OnDisable()
    {
        if (modeManager) modeManager.ModeChanged -= OnModeChanged;
    }

    private void Start()
    {
        if (!painter) painter = modeManager ? modeManager.Painter : null;
        if (!painter) painter = FindFirstObjectByType<MeshPainter>();

        _font = Resources.GetBuiltinResource<Font>("LegacyRuntime.ttf");
        if (!_font) _font = Resources.GetBuiltinResource<Font>("Arial.ttf");

        EnsureEventSystem();
        BuildUi();

        // Set initial visibility (the manager's first SwitchTo may have fired before this Start).
        OnModeChanged(modeManager ? modeManager.ActiveMode : null);
    }

    private void OnModeChanged(GameMode mode)
    {
        if (_panel) _panel.SetActive(mode is PaintMode);
    }

    // --- UI construction ---

    private void BuildUi()
    {
        var canvas = GetComponent<Canvas>();
        if (!canvas) canvas = gameObject.AddComponent<Canvas>();
        canvas.renderMode = RenderMode.ScreenSpaceOverlay;
        canvas.sortingOrder = 100;

        var scaler = GetComponent<CanvasScaler>();
        if (!scaler) scaler = gameObject.AddComponent<CanvasScaler>();
        scaler.uiScaleMode = CanvasScaler.ScaleMode.ScaleWithScreenSize;
        scaler.referenceResolution = new Vector2(1920f, 1080f);
        scaler.matchWidthOrHeight = 0.5f;

        if (!GetComponent<GraphicRaycaster>()) gameObject.AddComponent<GraphicRaycaster>();

        // Panel (this is what gets shown/hidden per mode).
        var panel = NewRect("Panel", transform);
        _panel = panel.gameObject;
        panel.anchorMin = panel.anchorMax = new Vector2(0f, 1f);
        panel.pivot = new Vector2(0f, 1f);
        panel.anchoredPosition = new Vector2(16f, -16f);
        panel.sizeDelta = new Vector2(296f, 0f); // width fixed; height from the ContentSizeFitter
        AddImage(panel.gameObject, PanelColor);

        var vlg = panel.gameObject.AddComponent<VerticalLayoutGroup>();
        vlg.padding = new RectOffset(12, 12, 12, 12);
        vlg.spacing = 8f;
        vlg.childAlignment = TextAnchor.UpperLeft;
        vlg.childControlWidth = true;
        vlg.childControlHeight = true;
        vlg.childForceExpandWidth = true;
        vlg.childForceExpandHeight = false;

        var fitter = panel.gameObject.AddComponent<ContentSizeFitter>();
        fitter.verticalFit = ContentSizeFitter.FitMode.PreferredSize;

        AddSectionLabel(panel, "PAINT", 15, FontStyle.Bold);

        // Channels.
        AddSectionLabel(panel, "Channels", 13, FontStyle.Bold);
        AddToggle(panel, "Albedo", painter && painter.paintAlbedo, v => { if (painter) painter.paintAlbedo = v; });
        AddToggle(panel, "Metallic + Smoothness", painter && painter.paintMetallicSmoothness, v => { if (painter) painter.paintMetallicSmoothness = v; });
        AddToggle(panel, "Occlusion", painter && painter.paintOcclusion, v => { if (painter) painter.paintOcclusion = v; });
        AddToggle(panel, "Emission", painter && painter.paintEmission, v => { if (painter) painter.paintEmission = v; });

        // Albedo colour.
        AddSectionLabel(panel, "Albedo Color", 13, FontStyle.Bold);
        var albedo = AddColorPicker(panel);
        albedo.SetColor(painter ? painter.brushColor : Color.red);
        albedo.Changed += c => { if (painter) painter.brushColor = new Color(c.r, c.g, c.b, painter.brushColor.a); };

        // Metallic / smoothness / occlusion.
        AddSlider(panel, "Metallic", 0f, 1f, false, painter ? painter.metallic : 0f, v => { if (painter) painter.metallic = v; });
        AddSlider(panel, "Smoothness", 0f, 1f, false, painter ? painter.smoothness : 0.5f, v => { if (painter) painter.smoothness = v; });
        AddSlider(panel, "Occlusion", 0f, 1f, false, painter ? painter.occlusion : 0.5f, v => { if (painter) painter.occlusion = v; });

        // Emission.
        AddSectionLabel(panel, "Emission Color", 13, FontStyle.Bold);
        var emission = AddColorPicker(panel);
        emission.SetColor(painter ? painter.emissionColor : Color.black);
        emission.Changed += c => { if (painter) painter.emissionColor = new Color(c.r, c.g, c.b, painter.emissionColor.a); };
        AddSlider(panel, "Emission Intensity", 0f, 8f, false, painter ? painter.emissionIntensity : 1f, v => { if (painter) painter.emissionIntensity = v; });

        // Brush size.
        AddSlider(panel, "Brush Size", 1f, 256f, true, painter ? painter.brushSize : 16f, v => { if (painter) painter.brushSize = Mathf.RoundToInt(v); });
    }

    private void EnsureEventSystem()
    {
        if (FindFirstObjectByType<EventSystem>()) return;

        var es = new GameObject("EventSystem", typeof(EventSystem));
#if ENABLE_INPUT_SYSTEM
        var module = es.AddComponent<InputSystemUIInputModule>();
        if (!module.actionsAsset) module.AssignDefaultActions();
#else
        es.AddComponent<StandaloneInputModule>();
#endif
    }

    // --- Widgets ---

    private void AddSectionLabel(RectTransform panel, string text, int size, FontStyle style)
    {
        var rt = NewRect("Label", panel);
        var le = rt.gameObject.AddComponent<LayoutElement>();
        le.minHeight = le.preferredHeight = 18f;

        var t = MakeText(rt.gameObject, text, size, style, new Color(0.85f, 0.85f, 0.9f, 1f), TextAnchor.MiddleLeft);
        t.raycastTarget = false;
    }

    private void AddToggle(RectTransform panel, string label, bool value, Action<bool> onChanged)
    {
        var rt = NewRect("Toggle", panel);
        var le = rt.gameObject.AddComponent<LayoutElement>();
        le.minHeight = le.preferredHeight = 22f;

        var toggle = rt.gameObject.AddComponent<Toggle>();

        var box = NewRect("Box", rt);
        box.anchorMin = box.anchorMax = new Vector2(0f, 0.5f);
        box.pivot = new Vector2(0f, 0.5f);
        box.anchoredPosition = Vector2.zero;
        box.sizeDelta = new Vector2(18f, 18f);
        var boxImg = AddImage(box.gameObject, BoxColor);

        var check = NewRect("Check", box);
        check.anchorMin = Vector2.zero;
        check.anchorMax = Vector2.one;
        check.offsetMin = new Vector2(3f, 3f);
        check.offsetMax = new Vector2(-3f, -3f);
        var checkImg = AddImage(check.gameObject, Accent);
        checkImg.raycastTarget = false;

        var lbl = NewRect("Label", rt);
        lbl.anchorMin = Vector2.zero;
        lbl.anchorMax = Vector2.one;
        lbl.offsetMin = new Vector2(24f, 0f);
        lbl.offsetMax = Vector2.zero;
        var t = MakeText(lbl.gameObject, label, 14, FontStyle.Normal, Color.white, TextAnchor.MiddleLeft);
        t.raycastTarget = false;

        toggle.targetGraphic = boxImg;
        toggle.graphic = checkImg;
        toggle.isOn = value;
        toggle.onValueChanged.AddListener(v => onChanged(v));
    }

    private void AddSlider(RectTransform panel, string label, float min, float max, bool whole, float value, Action<float> onChanged)
    {
        var rt = NewRect("Slider", panel);
        var le = rt.gameObject.AddComponent<LayoutElement>();
        le.minHeight = le.preferredHeight = 34f;

        // Caption row (label left, value right), pinned to the top of the cell.
        var lbl = NewRect("Label", rt);
        lbl.anchorMin = new Vector2(0f, 1f);
        lbl.anchorMax = new Vector2(1f, 1f);
        lbl.pivot = new Vector2(0f, 1f);
        lbl.offsetMin = new Vector2(0f, -16f);
        lbl.offsetMax = new Vector2(-48f, 0f);
        var lt = MakeText(lbl.gameObject, label, 13, FontStyle.Normal, new Color(0.8f, 0.8f, 0.85f, 1f), TextAnchor.MiddleLeft);
        lt.raycastTarget = false;

        var valRt = NewRect("Value", rt);
        valRt.anchorMin = new Vector2(1f, 1f);
        valRt.anchorMax = new Vector2(1f, 1f);
        valRt.pivot = new Vector2(1f, 1f);
        valRt.anchoredPosition = Vector2.zero;
        valRt.sizeDelta = new Vector2(56f, 16f);
        var vt = MakeText(valRt.gameObject, "", 13, FontStyle.Normal, Color.white, TextAnchor.MiddleRight);
        vt.raycastTarget = false;

        // Track, pinned to the bottom of the cell.
        var track = NewRect("Track", rt);
        track.anchorMin = new Vector2(0f, 0f);
        track.anchorMax = new Vector2(1f, 0f);
        track.pivot = new Vector2(0.5f, 0f);
        track.anchoredPosition = Vector2.zero;
        track.sizeDelta = new Vector2(0f, 16f);
        var slider = track.gameObject.AddComponent<Slider>();

        var bg = NewRect("Background", track);
        bg.anchorMin = new Vector2(0f, 0.5f);
        bg.anchorMax = new Vector2(1f, 0.5f);
        bg.pivot = new Vector2(0.5f, 0.5f);
        bg.anchoredPosition = Vector2.zero;
        bg.sizeDelta = new Vector2(0f, 5f);
        AddImage(bg.gameObject, BoxColor); // raycast target so clicking the bar jumps the value

        var fillArea = NewRect("Fill Area", track);
        fillArea.anchorMin = new Vector2(0f, 0.5f);
        fillArea.anchorMax = new Vector2(1f, 0.5f);
        fillArea.pivot = new Vector2(0.5f, 0.5f);
        fillArea.anchoredPosition = Vector2.zero;
        fillArea.sizeDelta = new Vector2(-16f, 5f);
        var fill = NewRect("Fill", fillArea);
        fill.anchorMin = Vector2.zero;
        fill.anchorMax = Vector2.one;
        fill.offsetMin = Vector2.zero;
        fill.offsetMax = Vector2.zero;
        var fillImg = AddImage(fill.gameObject, Accent);
        fillImg.raycastTarget = false;

        var handleArea = NewRect("Handle Slide Area", track);
        handleArea.anchorMin = Vector2.zero;
        handleArea.anchorMax = Vector2.one;
        handleArea.offsetMin = new Vector2(8f, 0f);
        handleArea.offsetMax = new Vector2(-8f, 0f);
        var handle = NewRect("Handle", handleArea);
        handle.sizeDelta = new Vector2(14f, 0f);
        var handleImg = AddImage(handle.gameObject, Color.white);

        slider.fillRect = fill;
        slider.handleRect = handle;
        slider.targetGraphic = handleImg;
        slider.direction = Slider.Direction.LeftToRight;
        slider.minValue = min;
        slider.maxValue = max;
        slider.wholeNumbers = whole;
        slider.value = value;

        Action<float> setText = v => vt.text = whole
            ? Mathf.RoundToInt(v).ToString()
            : v.ToString("0.00");
        setText(slider.value); // show the actual (clamped) value, not the unclamped input
        slider.onValueChanged.AddListener(v => { setText(v); onChanged(v); });
    }

    private HsvColorPicker AddColorPicker(RectTransform panel)
    {
        const float square = 120f;
        const float hueH = 14f;

        var rt = NewRect("ColorPicker", panel);
        var le = rt.gameObject.AddComponent<LayoutElement>();
        le.minHeight = le.preferredHeight = square + 6f + hueH;

        var picker = rt.gameObject.AddComponent<HsvColorPicker>();
        picker.Build(square, hueH);
        return picker;
    }

    private Text MakeText(GameObject go, string text, int size, FontStyle style, Color color, TextAnchor anchor)
    {
        var t = go.AddComponent<Text>();
        t.font = _font;
        t.fontSize = size;
        t.fontStyle = style;
        t.color = color;
        t.alignment = anchor;
        t.text = text;
        t.horizontalOverflow = HorizontalWrapMode.Overflow;
        t.verticalOverflow = VerticalWrapMode.Truncate;
        return t;
    }

    // --- Static UI factory (shared with HsvColorPicker) ---

    public static RectTransform NewRect(string name, Transform parent)
    {
        var go = new GameObject(name, typeof(RectTransform));
        go.transform.SetParent(parent, false);
        return (RectTransform)go.transform;
    }

    public static Image AddImage(GameObject go, Color color)
    {
        var img = go.AddComponent<Image>();
        img.color = color;
        return img;
    }

    /// <summary>Adds a full-rect, non-raycasting overlay image with the given sprite.</summary>
    public static Image AddOverlay(RectTransform parent, Sprite sprite)
    {
        var rt = NewRect("Overlay", parent);
        rt.anchorMin = Vector2.zero;
        rt.anchorMax = Vector2.one;
        rt.offsetMin = Vector2.zero;
        rt.offsetMax = Vector2.zero;
        var img = rt.gameObject.AddComponent<Image>();
        img.sprite = sprite;
        img.type = Image.Type.Simple;
        img.raycastTarget = false;
        return img;
    }

    // Cached gradient sprites for the colour picker.
    private static Sprite _satSprite, _valSprite, _hueSprite;

    /// <summary>Horizontal white-out: opaque white (left) -> transparent (right) = saturation.</summary>
    public static Sprite SaturationSprite()
    {
        if (_satSprite) return _satSprite;
        const int n = 64;
        var tex = NewGradientTex(n, 1);
        for (int x = 0; x < n; x++)
        {
            byte a = (byte)Mathf.RoundToInt(255f * (1f - x / (float)(n - 1)));
            tex.SetPixel(x, 0, new Color32(255, 255, 255, a));
        }
        tex.Apply(false);
        _satSprite = ToSprite(tex);
        return _satSprite;
    }

    /// <summary>Vertical black-out: opaque black (bottom) -> transparent (top) = value.</summary>
    public static Sprite ValueSprite()
    {
        if (_valSprite) return _valSprite;
        const int n = 64;
        var tex = NewGradientTex(1, n);
        for (int y = 0; y < n; y++)
        {
            byte a = (byte)Mathf.RoundToInt(255f * (1f - y / (float)(n - 1)));
            tex.SetPixel(0, y, new Color32(0, 0, 0, a));
        }
        tex.Apply(false);
        _valSprite = ToSprite(tex);
        return _valSprite;
    }

    /// <summary>Horizontal full-saturation hue ramp 0..1.</summary>
    public static Sprite HueSprite()
    {
        if (_hueSprite) return _hueSprite;
        const int n = 64;
        var tex = NewGradientTex(n, 1);
        for (int x = 0; x < n; x++)
            tex.SetPixel(x, 0, Color.HSVToRGB(x / (float)(n - 1), 1f, 1f));
        tex.Apply(false);
        _hueSprite = ToSprite(tex);
        return _hueSprite;
    }

    private static Texture2D NewGradientTex(int w, int h)
    {
        return new Texture2D(w, h, TextureFormat.RGBA32, false, false) // sRGB sampling for correct colours
        {
            name = "PaintHud_Gradient",
            wrapMode = TextureWrapMode.Clamp,
            filterMode = FilterMode.Bilinear,
            hideFlags = HideFlags.HideAndDontSave
        };
    }

    private static Sprite ToSprite(Texture2D tex)
    {
        var s = Sprite.Create(tex, new Rect(0f, 0f, tex.width, tex.height), new Vector2(0.5f, 0.5f), 100f);
        s.hideFlags = HideFlags.HideAndDontSave;
        return s;
    }
}