using System;
using System.Collections.Generic;
using System.IO;
using UnityEngine;
using UnityEngine.SceneManagement;

public partial class PaintHud
{
    // --- Persistence: panel positions + the widget-bound painter values ---
    //
    // Saved on quit / play-stop and restored on the next start, so the HUD opens where you left it
    // with the brush settings you last used. This is small structured state (a handful of positions
    // and scalars), so it goes to a human-readable JSON file - unlike the painter's bulk pixel maps
    // (MeshPainter.Persistence) which use a raw byte dump. The two saves are independent: this one
    // owns the HUD layout + brush values, the painter owns the canvas pixels.

    [Header("Persistence")]
    [Tooltip("Save the panel positions and their values on quit / play-stop and restore them on the " +
             "next start. Off = the HUD opens at its authored layout / painter defaults every session.")]
    public bool persistHud = true;

    [Tooltip("Save file identifier. Empty = derived from the active scene name. Set explicitly to keep " +
             "the layout stable across scene renames or to share one layout between scenes.")]
    public string hudSaveId = "";

    private const int HudFileVersion = 1;
    private bool _hudSavedOnTeardown; // guards a double save across OnApplicationQuit + OnDestroy

    private static string HudSaveDir => Path.Combine(Application.persistentDataPath, "MeshPaint");

    private string HudSavePath()
    {
        string key = string.IsNullOrEmpty(hudSaveId)
            ? SanitizeHudKey(SceneManager.GetActiveScene().name + "_hud")
            : SanitizeHudKey(hudSaveId);
        return Path.Combine(HudSaveDir, key + ".hudlayout");
    }

    private static string SanitizeHudKey(string s)
    {
        foreach (char c in Path.GetInvalidFileNameChars()) s = s.Replace(c, '_');
        return s.Replace(' ', '_');
    }

    [Serializable]
    private class HudState
    {
        public int version = HudFileVersion;
        public bool hasValues; // false = no painter was bound when saved -> restore positions only
        public List<PanelPos> panels = new List<PanelPos>();
        public HudValues values = new HudValues();
    }

    [Serializable]
    private struct PanelPos
    {
        public string name;
        public Vector2 pos; // anchoredPosition (point-anchored panels -> fully determines placement)
    }

    // Mirrors exactly the painter fields the HUD widgets bind to (PaintHud.WirePanel).
    [Serializable]
    private class HudValues
    {
        public bool paintAlbedo, paintMetallicSmoothness, paintOcclusion, paintEmission, spray;
        public Color brushColor;
        public float metallic, smoothness, metallicSmoothnessOpacity, occlusion, occlusionOpacity;
        public Color emissionColor;
        public float emissionIntensity;
        public int brushSize;
        public int sprayDots;
        public float sprayDotSizeMin, sprayDotSizeMax, sprayDotAlphaMin, sprayDotAlphaMax;
    }

    private void OnApplicationQuit() => SaveHudOnTeardown();

    /// <summary>Saves once during teardown (OnApplicationQuit and OnDestroy both call this; only the first writes).</summary>
    private void SaveHudOnTeardown()
    {
        if (_hudSavedOnTeardown) return;
        _hudSavedOnTeardown = true;
        SaveHudState();
    }

    /// <summary>Writes the current panel positions and bound painter values to disk.</summary>
    public void SaveHudState()
    {
        if (!persistHud || !_panel) return;

        try
        {
            var state = new HudState();
            var panel = _panel.transform;

            foreach (var name in DraggablePanels)
            {
                if (FindDeep(panel, name) is RectTransform rt)
                    state.panels.Add(new PanelPos { name = name, pos = rt.anchoredPosition });
            }

            if (painter)
            {
                state.hasValues = true;
                var v = state.values;
                v.paintAlbedo = painter.paintAlbedo;
                v.paintMetallicSmoothness = painter.paintMetallicSmoothness;
                v.paintOcclusion = painter.paintOcclusion;
                v.paintEmission = painter.paintEmission;
                v.spray = painter.spray;
                v.brushColor = painter.brushColor;
                v.metallic = painter.metallic;
                v.smoothness = painter.smoothness;
                v.metallicSmoothnessOpacity = painter.metallicSmoothnessOpacity;
                v.occlusion = painter.occlusion;
                v.occlusionOpacity = painter.occlusionOpacity;
                v.emissionColor = painter.emissionColor;
                v.emissionIntensity = painter.emissionIntensity;
                v.brushSize = painter.brushSize;
                v.sprayDots = painter.sprayDots;
                v.sprayDotSizeMin = painter.sprayDotSizeMin;
                v.sprayDotSizeMax = painter.sprayDotSizeMax;
                v.sprayDotAlphaMin = painter.sprayDotAlphaMin;
                v.sprayDotAlphaMax = painter.sprayDotAlphaMax;
            }

            Directory.CreateDirectory(HudSaveDir);
            File.WriteAllText(HudSavePath(), JsonUtility.ToJson(state, true));
        }
        catch (Exception e)
        {
            Debug.LogWarning($"[PaintHud] Saving HUD state failed: {e.Message}", this);
        }
    }

    /// <summary>
    /// Restores the saved panel positions and brush values. Values are written into the painter (the
    /// source of truth the widgets read) and then pushed to every widget via <see cref="SyncFromPainter"/>,
    /// reusing the exact same painter -> HUD path the pipette pick uses. Positions are applied last.
    /// </summary>
    public void RestoreHudState()
    {
        if (!persistHud || !_panel) return;

        var state = LoadHudState();
        if (state == null) return;

        if (painter && state.hasValues && state.values != null)
        {
            var v = state.values;
            painter.paintAlbedo = v.paintAlbedo;
            painter.paintMetallicSmoothness = v.paintMetallicSmoothness;
            painter.paintOcclusion = v.paintOcclusion;
            painter.paintEmission = v.paintEmission;
            painter.spray = v.spray;
            painter.brushColor = v.brushColor;
            painter.metallic = v.metallic;
            painter.smoothness = v.smoothness;
            painter.metallicSmoothnessOpacity = v.metallicSmoothnessOpacity;
            painter.occlusion = v.occlusion;
            painter.occlusionOpacity = v.occlusionOpacity;
            painter.emissionColor = v.emissionColor;
            painter.emissionIntensity = v.emissionIntensity;
            painter.brushSize = v.brushSize;
            painter.sprayDots = v.sprayDots;
            painter.sprayDotSizeMin = v.sprayDotSizeMin;
            painter.sprayDotSizeMax = v.sprayDotSizeMax;
            painter.sprayDotAlphaMin = v.sprayDotAlphaMin;
            painter.sprayDotAlphaMax = v.sprayDotAlphaMax;
            SyncFromPainter();
        }

        // Point-anchored panels: anchoredPosition is resolution-independent under the canvas'
        // ScaleWithScreenSize scaler, so the raw saved value places them identically next session.
        var root = _panel.transform;
        if (state.panels != null)
            foreach (var p in state.panels)
                if (FindDeep(root, p.name) is RectTransform rt)
                    rt.anchoredPosition = p.pos;
    }

    private HudState LoadHudState()
    {
        string path = HudSavePath();
        if (!File.Exists(path)) return null;

        try
        {
            var state = JsonUtility.FromJson<HudState>(File.ReadAllText(path));
            if (state == null || state.version != HudFileVersion) return null;
            return state;
        }
        catch (Exception e)
        {
            Debug.LogWarning($"[PaintHud] Loading HUD state failed: {e.Message}", this);
            return null;
        }
    }

    /// <summary>Deletes the saved HUD layout (next start opens at the authored layout / defaults). Editor convenience.</summary>
    [ContextMenu("Clear Saved HUD Layout")]
    public void ClearSavedHudState()
    {
        try
        {
            string path = HudSavePath();
            if (File.Exists(path)) File.Delete(path);
            Debug.Log($"[PaintHud] Cleared saved HUD layout: {path}", this);
        }
        catch (Exception e)
        {
            Debug.LogWarning($"[PaintHud] Clearing saved HUD layout failed: {e.Message}", this);
        }
    }
}