using System;
using System.Collections.Generic;
using System.Text;

namespace NPinyin
{
  public static class Pinyin
  {
    /// <summary>
    /// 取中文文本的拼音首字母
    /// </summary>
    /// <param name="text">编码为UTF8的文本</param>
    /// <returns>返回中文对应的拼音首字母</returns>
 
    public static string GetInitials(string text)
    {
      text = text.Trim();
      StringBuilder chars = new StringBuilder();
      for (var i = 0; i < text.Length; ++i)
      {
        string py = GetPinyin(text[i]);
        if (py != "") chars.Append(py[0]);
      }

      return chars.ToString().ToUpper();
    }


    /// <summary>
    /// 取中文文本的拼音首字母
    /// </summary>
    /// <param name="text">文本</param>
    /// <param name="encoding">源文本的编码</param>
    /// <returns>返回encoding编码类型中文对应的拼音首字母</returns>
    public static string GetInitials(string text, Encoding encoding)
    {
      string temp = ConvertEncoding(text, encoding, Encoding.UTF8);
      return ConvertEncoding(GetInitials(temp), Encoding.UTF8, encoding);
    }



    /// <summary>
    /// 取中文文本的拼音
    /// </summary>
    /// <param name="text">编码为UTF8的文本</param>
    /// <returns>返回中文文本的拼音</returns>
 
    public static string GetPinyin(string text)
    {
      StringBuilder sbPinyin = new StringBuilder();
      for (var i = 0; i < text.Length; ++i)
      {
        string py = GetPinyin(text[i]);
        if (py != "") sbPinyin.Append(py);
        sbPinyin.Append(" ");
      }

      return sbPinyin.ToString().Trim();
    }

    /// <summary>
    /// 取中文文本的拼音
    /// </summary>
    /// <param name="text">编码为UTF8的文本</param>
    /// <param name="encoding">源文本的编码</param>
    /// <returns>返回encoding编码类型的中文文本的拼音</returns>
    public static string GetPinyin(string text, Encoding encoding)
    {
      string temp = ConvertEncoding(text.Trim(), encoding, Encoding.UTF8);
      return ConvertEncoding(GetPinyin(temp), Encoding.UTF8, encoding);
    }

    /// <summary>
    /// 取和拼音相同的汉字列表
    /// </summary>
    /// <param name="pinyin">编码为UTF8的拼音</param>
    /// <returns>取拼音相同的汉字列表，如拼音“ai”将会返回“唉爱……”等</returns>
    public static string GetChineseText(string pinyin)
    {
      string key = pinyin.Trim().ToLower();

      foreach (string str in PyCode.codes)
      {
        if (str.StartsWith(key + " ") || str.StartsWith(key + ":"))
         return str.Substring(7);
      }

      return "";
    }


    /// <summary>
    /// 取和拼音相同的汉字列表，编码同参数encoding
    /// </summary>
    /// <param name="pinyin">编码为encoding的拼音</param>
    /// <param name="encoding">编码</param>
    /// <returns>返回编码为encoding的拼音为pinyin的汉字列表，如拼音“ai”将会返回“唉爱……”等</returns>
    public static string GetChineseText(string pinyin, Encoding encoding)
    {
      string text = ConvertEncoding(pinyin, encoding, Encoding.UTF8);
      return ConvertEncoding(GetChineseText(text), Encoding.UTF8, encoding);
    }



    /// <summary>
    /// 返回单个字符的汉字拼音
    /// </summary>
    /// <param name="ch">编码为UTF8的中文字符</param>
    /// <returns>ch对应的拼音</returns>
    public static string GetPinyin(char ch)
    {
      short hash = GetHashIndex(ch);
      for (var i = 0; i < PyHash.hashes[hash].Length; ++i)
      {
        short index = PyHash.hashes[hash][i];
        var pos = PyCode.codes[index].IndexOf(ch, 7);
        if (pos != -1)
          return PyCode.codes[index].Substring(0, 6).Trim();
      }
      return ch.ToString();
    }

    /// <summary>
    /// 返回单个字符的汉字拼音
    /// </summary>
    /// <param name="ch">编码为encoding的中文字符</param>
    /// <returns>编码为encoding的ch对应的拼音</returns>
    public static string GetPinyin(char ch, Encoding encoding)
    {
      ch = ConvertEncoding(ch.ToString(), encoding, Encoding.UTF8)[0];
      return ConvertEncoding(GetPinyin(ch), Encoding.UTF8, encoding);
    }

    /// <summary>
    /// 转换编码 
    /// </summary>
    /// <param name="text">文本</param>
    /// <param name="srcEncoding">源编码</param>
    /// <param name="dstEncoding">目标编码</param>
    /// <returns>目标编码文本</returns>
    public static string ConvertEncoding(string text, Encoding srcEncoding,  Encoding dstEncoding)
    {
      byte[] srcBytes = srcEncoding.GetBytes(text);
      byte[] dstBytes = Encoding.Convert(srcEncoding, dstEncoding, srcBytes);
      return dstEncoding.GetString(dstBytes);
    }

    /// <summary>
    /// 取文本索引值
    /// </summary>
    /// <param name="ch">字符</param>
    /// <returns>文本索引值</returns>
    private static short GetHashIndex(char ch)
    {
      return (short)((uint)ch % PyCode.codes.Length);
    }
  }
}