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

public partial class MeshPainter
{
    // --- Persistence: named paint slots, saved/loaded explicitly from the HUD ---
    //
    // The painter no longer auto-loads on start or auto-saves on quit; painting is volatile until the
    // player explicitly saves it to a named slot, and a fresh session always starts from the material
    // seed. Saved slots live in a single global library folder (role/object independent), so any avatar
    // can load any saved painting as a camouflage preset.

    // Raw, bit-exact map dump: 'CHMP' magic + version + name + width + height + map count, then each
    // map's canonical Color32 bytes. Raw (not PNG) avoids any sRGB/alpha-premultiply ambiguity and
    // round-trips the exact canonical bytes ReadCanonical produces.
    private const uint PaintFileMagic = 0x504D4843; // 'CHMP' little-endian
    private const int PaintFileVersion = 4;         // v3: emission + camo scalars; v4: + painted-height knobs
    private const string PaintFileExt = ".paint";

    /// <summary>
    /// Per-player material scalars stored alongside the maps from v3 on. These are NOT baked into the
    /// painted pixels (a global emission multiplier + the PlayerCamoLit knobs), so they ride the slot
    /// header and are re-applied onto the painter when the slot loads.
    /// </summary>
    private struct PaintScalars
    {
        public bool has;        // false = legacy v2 slot with no scalars -> leave the painter's values untouched
        public bool hasHeight;  // v4+ painted-height knobs present (occlusion threshold + normal/parallax intensity)
        public float emissionIntensity;
        public float camoHalfLambert, camoHalfLambertBrightness, camoSpecularDampen;
        public float occlusionThreshold, heightNormalIntensity, parallaxIntensity;
    }

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

    /// <summary>Filesystem-safe key: invalid filename characters and spaces become underscores.</summary>
    internal static string SanitizeFileKey(string s)
    {
        foreach (char c in Path.GetInvalidFileNameChars()) s = s.Replace(c, '_');
        return s.Replace(' ', '_');
    }

    private static string SanitizeKey(string s) =>
        string.IsNullOrEmpty(s) ? "unnamed" : SanitizeFileKey(s);

    /// <summary>Disk path for a slot. The display name lives inside the file; the file name is a sanitized key.</summary>
    private static string PathForName(string name) =>
        Path.Combine(PaintLibraryDir, SanitizeKey(name) + PaintFileExt);

    /// <summary>True if a slot with this name already exists (used to block overwriting on save).</summary>
    public static bool PaintExists(string name) =>
        !string.IsNullOrWhiteSpace(name) && File.Exists(PathForName(name));

    /// <summary>Display names of every saved slot, sorted alphabetically. Each name is read from the file header.</summary>
    public static List<string> ListSavedPaintings()
    {
        var names = new List<string>();
        try
        {
            if (!Directory.Exists(PaintLibraryDir)) return names;
            foreach (string path in Directory.GetFiles(PaintLibraryDir, "*" + PaintFileExt))
            {
                string n = ReadHeaderName(path);
                if (!string.IsNullOrEmpty(n)) names.Add(n);
            }
        }
        catch (System.Exception e)
        {
            Debug.LogWarning($"[MeshPainter] Listing saved paintings failed: {e.Message}");
        }
        names.Sort(System.StringComparer.CurrentCultureIgnoreCase);
        return names;
    }

    /// <summary>
    /// Writes the current painted maps to a named slot. Returns false without writing if the painter is
    /// not ready. An existing slot of the same name is overwritten only when <paramref name="overwrite"/>
    /// is true; otherwise the call fails rather than clobbering it.
    /// </summary>
    public bool SavePaintAs(string name, bool overwrite = false)
    {
        if (!_setupValid || string.IsNullOrWhiteSpace(name)) return false;
        name = name.Trim();
        if (!overwrite && PaintExists(name)) return false;

        try
        {
            Directory.CreateDirectory(PaintLibraryDir);

            using (var fs = new FileStream(PathForName(name), FileMode.Create, FileAccess.Write))
            using (var w = new BinaryWriter(fs))
            {
                w.Write(PaintFileMagic);
                w.Write(PaintFileVersion);
                w.Write(name);                 // length-prefixed UTF8 (BinaryWriter.Write(string))
                w.Write(textureSize);
                w.Write(textureSize);
                w.Write(MAP_COUNT);

                // v3: per-player material scalars that are NOT baked into the maps (a global emission
                // multiplier + the PlayerCamoLit knobs). The painter is ready here (_setupValid), so the
                // material-backed camo getters return the live values rather than the not-ready 0.
                w.Write(emissionIntensity);
                w.Write(CamoHalfLambert);
                w.Write(CamoHalfLambertBrightness);
                w.Write(CamoSpecularDampen);

                // v4: the painted-height knobs (same material-instance source of truth as the camo knobs).
                w.Write(OcclusionThreshold);
                w.Write(HeightNormalIntensity);
                w.Write(ParallaxIntensity);

                WriteCanonicalMaps(w);
            }
            return true;
        }
        catch (System.Exception e)
        {
            Debug.LogWarning($"[MeshPainter] Saving paint '{name}' failed: {e.Message}", this);
            return false;
        }
    }

    /// <summary>
    /// Loads a named slot and re-seeds the active backend with it, replacing the current painting.
    /// Returns false if the slot is missing or incompatible (the current painting is left untouched).
    /// </summary>
    public bool LoadPaintByName(string name)
    {
        if (!_setupValid) return false;

        Color32[][] canonical = ReadMaps(PathForName(name), out PaintScalars scalars);
        if (canonical == null) return false;

        ReseedCanonical(canonical);

        // A load replaces the whole painting and is NOT undoable: the loaded maps become the new history
        // baseline, clearing any prior undo/redo. Peers reset to the same baseline via the load broadcast.
        ResetHistoryToCurrent(canonical);

        // v3 slots also carry the per-player material scalars; apply them so the loaded look is complete.
        // Legacy v2 slots have none -> leave the current emission/camo untouched. The painter is ready here
        // (_setupValid), so the material-backed camo setters take effect; PlayerPaintSync replicates the
        // changed values to peers via their owner-authoritative NetworkVariables on its next LateUpdate.
        if (scalars.has)
        {
            emissionIntensity = scalars.emissionIntensity;
            RefreshEmissionColor();
            CamoHalfLambert = scalars.camoHalfLambert;
            CamoHalfLambertBrightness = scalars.camoHalfLambertBrightness;
            CamoSpecularDampen = scalars.camoSpecularDampen;
        }
        // v4 slots also carry the painted-height knobs; older slots (v2/v3) leave them at the current value.
        if (scalars.hasHeight)
        {
            OcclusionThreshold = scalars.occlusionThreshold;
            HeightNormalIntensity = scalars.heightNormalIntensity;
            ParallaxIntensity = scalars.parallaxIntensity;
        }
        return true;
    }

    /// <summary>Deletes a named slot. Returns true if a file was removed.</summary>
    public static bool DeletePaint(string name)
    {
        try
        {
            string path = PathForName(name);
            if (!File.Exists(path)) return false;
            File.Delete(path);
            return true;
        }
        catch (System.Exception e)
        {
            Debug.LogWarning($"[MeshPainter] Deleting paint '{name}' failed: {e.Message}");
            return false;
        }
    }

    /// <summary>Reads just the display-name header of a slot file (or the file name as a fallback).</summary>
    private static string ReadHeaderName(string path)
    {
        try
        {
            using (var fs = new FileStream(path, FileMode.Open, FileAccess.Read))
            using (var r = new BinaryReader(fs, Encoding.UTF8))
            {
                if (!TryReadPaintVersion(r, out _)) return null;
                return r.ReadString();
            }
        }
        catch
        {
            return Path.GetFileNameWithoutExtension(path);
        }
    }

    /// <summary>
    /// Reads all maps from a slot file in canonical layout, or null if missing / incompatible. Per-map
    /// null entries are tolerated by both backends (they fall back to the material seed).
    /// </summary>
    private Color32[][] ReadMaps(string path, out PaintScalars scalars)
    {
        scalars = default;
        if (!File.Exists(path)) return null;

        try
        {
            using (var fs = new FileStream(path, FileMode.Open, FileAccess.Read))
            using (var r = new BinaryReader(fs, Encoding.UTF8))
            {
                if (!TryReadPaintVersion(r, out int ver)) return null;
                r.ReadString(); // display name (header only; not needed for the pixel load)
                int w = r.ReadInt32();
                int h = r.ReadInt32();
                int maps = r.ReadInt32();

                // v3+: the per-player material scalars sit between the header and the pixel maps.
                if (ver >= 3)
                {
                    scalars.has = true;
                    scalars.emissionIntensity = r.ReadSingle();
                    scalars.camoHalfLambert = r.ReadSingle();
                    scalars.camoHalfLambertBrightness = r.ReadSingle();
                    scalars.camoSpecularDampen = r.ReadSingle();
                }

                // v4+: the painted-height knobs follow the camo scalars.
                if (ver >= 4)
                {
                    scalars.hasHeight = true;
                    scalars.occlusionThreshold = r.ReadSingle();
                    scalars.heightNormalIntensity = r.ReadSingle();
                    scalars.parallaxIntensity = r.ReadSingle();
                }

                // Resolution change -> ignore rather than smear mismatched data; the brush re-seeds
                // from the material instead.
                if (w != textureSize || h != textureSize)
                {
                    Debug.LogWarning($"[MeshPainter] Saved paint ignored (got {w}x{h}, expected " +
                                     $"{textureSize}x{textureSize}).", this);
                    return null;
                }

                return ReadCanonicalMaps(r, maps);
            }
        }
        catch (System.Exception e)
        {
            Debug.LogWarning($"[MeshPainter] Loading paint failed: {e.Message}", this);
            return null;
        }
    }

    /// <summary>Validates the paint-file magic and version range (legacy v2 .. current).</summary>
    private static bool TryReadPaintVersion(BinaryReader r, out int ver)
    {
        if (r.ReadUInt32() != PaintFileMagic) { ver = 0; return false; }
        ver = r.ReadInt32();
        return ver >= 2 && ver <= PaintFileVersion;
    }

    /// <summary>Writes every map's canonical Color32 bytes to the stream (shared by slot save + net snapshot).</summary>
    private void WriteCanonicalMaps(BinaryWriter w)
    {
        int n = textureSize * textureSize;
        var bytes = new byte[n * 4];
        for (int mi = 0; mi < MAP_COUNT; mi++)
        {
            Color32[] px = ReadCanonical(mi);
            int count = Mathf.Min(n, px.Length);
            for (int i = 0; i < count; i++)
            {
                int o = i * 4;
                bytes[o] = px[i].r;
                bytes[o + 1] = px[i].g;
                bytes[o + 2] = px[i].b;
                bytes[o + 3] = px[i].a;
            }
            w.Write(bytes, 0, count * 4);
        }
    }

    /// <summary>Reads up to MAP_COUNT canonical map blocks; a truncated stream leaves the remaining maps null (seeded).</summary>
    private Color32[][] ReadCanonicalMaps(BinaryReader r, int mapsInFile)
    {
        int n = textureSize * textureSize;
        var result = new Color32[MAP_COUNT][];
        int load = Mathf.Min(mapsInFile, MAP_COUNT);
        for (int mi = 0; mi < load; mi++)
        {
            byte[] raw = r.ReadBytes(n * 4);
            if (raw.Length != n * 4) break; // truncated -> remaining maps stay at the material seed

            var px = new Color32[n];
            for (int i = 0; i < n; i++)
            {
                int o = i * 4;
                px[i] = new Color32(raw[o], raw[o + 1], raw[o + 2], raw[o + 3]);
            }
            result[mi] = px;
        }
        return result;
    }
}