using System.Collections.Generic;
using UnityEngine;

/// <summary>
/// 运行时美术生成（普通类）：
/// 不读取任何预制体/资源文件，用代码生成棋子圆底图、空心圆环等 Sprite
/// </summary>
public static class ChessArtFactory
{
    private static readonly Dictionary<string, Sprite> cache = new Dictionary<string, Sprite>();

    /// <summary>
    /// 实心圆（棋子底图：米色主体 + 深棕外圈，边缘抗锯齿）
    /// </summary>
    public static Sprite GetCircleSprite(int size = 128)
    {
        return GetCached("circle_" + size, size, (x, y, c, r) =>
        {
            float d = Vector2.Distance(new Vector2(x, y), new Vector2(c, c));
            float alpha = Mathf.Clamp01(r + 0.5f - d);
            if (alpha <= 0) return Color.clear;
            Color fill = new Color32(0xF7, 0xEB, 0xD3, 0xFF);
            Color rim = new Color32(0x4E, 0x34, 0x2E, 0xFF);
            float rimWidth = r * 0.08f;
            Color col = d > r - rimWidth ? rim : fill;
            col.a = alpha;
            return col;
        });
    }

    /// <summary>
    /// 空心圆环（选中圈 / 吃子提示，白色，由 Image.color 上色）
    /// </summary>
    public static Sprite GetRingSprite(int size = 128)
    {
        return GetCached("ring_" + size, size, (x, y, c, r) =>
        {
            float d = Vector2.Distance(new Vector2(x, y), new Vector2(c, c));
            float inner = r * 0.78f;
            float outer = r * 0.98f;
            float alpha = Mathf.Clamp01(d - inner + 1.5f) * Mathf.Clamp01(outer - d + 1.5f);
            return alpha <= 0 ? Color.clear : new Color(1f, 1f, 1f, alpha);
        });
    }

    /// <summary>
    /// 实心小圆点（白色，由 Image.color 上色）
    /// </summary>
    public static Sprite GetDotSprite(int size = 64)
    {
        return GetCached("dot_" + size, size, (x, y, c, r) =>
        {
            float d = Vector2.Distance(new Vector2(x, y), new Vector2(c, c));
            float alpha = Mathf.Clamp01(r + 0.5f - d);
            return alpha <= 0 ? Color.clear : new Color(1f, 1f, 1f, alpha);
        });
    }

    /// <summary>
    /// 走子提示点（绿色实心圆，颜色已烘焙进图里，使用时不再染色）
    /// </summary>
    public static Sprite GetHintDotSprite(int size = 64)
    {
        return GetCached("hintdot_" + size, size, (x, y, c, r) =>
        {
            float d = Vector2.Distance(new Vector2(x, y), new Vector2(c, c));
            float alpha = Mathf.Clamp01(r + 0.5f - d) * 0.90f;
            return alpha <= 0 ? Color.clear : new Color(0.26f, 0.66f, 0.31f, alpha);
        });
    }

    /// <summary>
    /// 吃子提示圈（红色空心圆环，颜色已烘焙进图里，使用时不再染色）
    /// </summary>
    public static Sprite GetCaptureRingSprite(int size = 128)
    {
        return GetCached("capturering_" + size, size, (x, y, c, r) =>
        {
            float d = Vector2.Distance(new Vector2(x, y), new Vector2(c, c));
            float inner = r * 0.78f;
            float outer = r * 0.98f;
            float alpha = Mathf.Clamp01(d - inner + 1.5f) * Mathf.Clamp01(outer - d + 1.5f) * 0.95f;
            return alpha <= 0 ? Color.clear : new Color(0.91f, 0.25f, 0.20f, alpha);
        });
    }

    private delegate Color PixelFunc(int x, int y, float center, float radius);

    private static Sprite GetCached(string key, int size, PixelFunc func)
    {
        Sprite sp;
        if (cache.TryGetValue(key, out sp) && sp != null) return sp;

        var tex = new Texture2D(size, size, TextureFormat.RGBA32, false)
        {
            wrapMode = TextureWrapMode.Clamp,
            filterMode = FilterMode.Bilinear
        };
        float c = (size - 1) * 0.5f;
        float r = size * 0.5f - 1f;

        var pixels = new Color[size * size];
        for (int y = 0; y < size; y++)
            for (int x = 0; x < size; x++)
                pixels[y * size + x] = func(x, y, c, r);
        tex.SetPixels(pixels);
        tex.Apply();

        sp = Sprite.Create(tex, new Rect(0, 0, size, size), new Vector2(0.5f, 0.5f), 100f);
        cache[key] = sp;
        return sp;
    }
}