using System;
using System.Numerics;
using System.Text;
using UnityEngine;

public static class Utility
{
    static StringBuilder _stringBuilder = new StringBuilder();

    public static StringBuilder StringBuilder => _stringBuilder;

    public static string Color2StringWithoutAlpha(Color color)
    {
        string red = ((int)(color.r * 255)).ToString("X2");
        string green = ((int)(color.g * 255)).ToString("X2");
        string blue = ((int)(color.b * 255)).ToString("X2");

        _stringBuilder.Clear();
        _stringBuilder.Append(red);
        _stringBuilder.Append(green);
        _stringBuilder.Append(blue);

        return _stringBuilder.ToString();
    }

    public static Color String2Color(string colorString)
    {
        Color result = Color.white;
        colorString = colorString.ToUpper();

        const int stride = 2;
        int[] rgba = new int[] { 0, 0, 0, 0 };

        int offset = 0;
        for (int i = 0; i < colorString.Length; i++)
        {
            char c = colorString[i];

            if (c >= 'A' && c <= 'F')
            {
                rgba[offset / stride] += (int)Mathf.Pow(16, (stride - (offset % stride) - 1)) * (10 + (c - 'A'));
                offset++;
            }
            else if (c >= '0' && c <= '9')
            {
                rgba[offset / stride] += (int)Mathf.Pow(16, (stride - (offset % stride) - 1)) * (c - '0');
                offset++;
            }
        }

        result.r = rgba[0] / 255f;
        result.g = rgba[1] / 255f;
        result.b = rgba[2] / 255f;
        result.a = rgba[3] / 255f;

        return result;
    }

    public static string GetMergeStringWithColor(Color color, string targetStr)
    {
        string colorStr = Color2StringWithoutAlpha(color);

        _stringBuilder.Clear();
        _stringBuilder.AppendFormat("<color=#{0}>{1}</color>", colorStr, targetStr);

        return _stringBuilder.ToString();
    }

    public static bool IsLittleEndian()
    {
        uint tmp = 0x000000ff;
        byte[] bytes = System.BitConverter.GetBytes(tmp);
        return bytes[0] == 0xff;
    }

    public static uint PermutationAdd(uint goal, uint start = 1)
    {
        if(start != 1)
            return PermutationAdd(goal) - PermutationAdd(start - 1);
        else
            return goal * (goal + 1) / 2;
    }

    public static BigInteger PermutationAdd(BigInteger goal, BigInteger start)
    {
        if(goal < 0 || start < 0)
            throw new ArgumentException("goal and start must be positive number.");

        if(start != 1)
            return PermutationAdd(goal, 1) - PermutationAdd(start - 1, 1);
        else
            return goal * (goal + 1) / 2;
    }
}

[Serializable]
public struct EditableKeyValue<TKey, TValue>
{
    public TKey key;
    public TValue value;
}