module app;
import std.algorithm,
       std.string,
       std.random,
       std.stdio,
       std.range,
       std.file;
import manakasi.mecab;

class Markov{
  private{
    static immutable begin = "_BEGIN_",
                     end   = "_END_";
    //連鎖時数
    static immutable d = 3;
    string[][] dic;
  }

  void study(string seed){
    string[] ss = segment(seed);
    ss = begin ~ ss ~ end;
    //d+1次の組の生成
    for(int offset; offset < ss.length - (d - 2); offset++)
      dic ~= (d + 1).iota.map!(i => ss[offset+i]).array;
  }

  void showDic(){
    foreach(e; dic)
      e.writeln;
  }

  string build(){
    string[][] begins;
    string result;
    int sentLeng = getRand % 100 + 10;

    foreach(e; dic)
      if(e[0] == begin)
        if(!this.find(begins, e[1..$]))
          begins ~= e[1..$];

    string[] current = randomGet(begins);

    result = current.join;

    while(){
      string targets = current[1 .. $];
      string[] sugs;

      foreach(e; dic)
        if(e[0..$ - 1] == targets)
          if(!this.find(sugs, e))
            sugs ~= e[$ - 1];

      string sug = randomGet(sugs);
      current = current[1..$ - 1] ~ sug;

      if(current[$ - 1] == end){
        break;
      }
      result ~= sug;
    }
    return result;
  }

  private{
    bool find(T)(T[] array, T elem){
      foreach(e; array)
        if(e == elem)
          return true;
      return false;
    }

    T randomGet(T)(T[] base){
      return base[cast(uint)(getRand % base.length)];
    }

    auto getRand(){
      Mt19937 gen;
      gen.seed(map!((a) => unpredictableSeed)(repeat(0)));
      return gen.front;
    }
  }
}

void main(){
  Markov markov = new Markov;
  string data = cast(string)read("./merosu.txt");

  foreach(s; data.split("\n"))
    markov.study(s);
  markov.build.writeln;
}