package com.stuffwithstuff.magpie.interpreter.builtin;

import com.stuffwithstuff.magpie.interpreter.Interpreter;
import com.stuffwithstuff.magpie.interpreter.Obj;

public class StringBuiltIns {
  @Signature("call(index Int -> String)")
  public static class Call implements BuiltInCallable {
    public Obj invoke(Interpreter interpreter, Obj thisObj, Obj arg) {
      int index = arg.asInt();
      String c = thisObj.asString().substring(index, index + 1);
      return interpreter.createString(c);
    }
  }
  
  // TODO(bob): May want to strongly-type arg at some point.
  @Signature("compareTo(other -> Int)")
  public static class CompareTo implements BuiltInCallable {
    public Obj invoke(Interpreter interpreter, Obj thisObj, Obj arg) {
      return interpreter.createInt(thisObj.asString().compareTo(arg.asString()));
    }
  }
  
  // TODO(bob): May want to strongly-type arg at some point.
  @Signature("concatenate(other -> String)")
  public static class Concatenate implements BuiltInCallable {
    public Obj invoke(Interpreter interpreter, Obj thisObj, Obj arg) {
      String left = thisObj.asString();
      String right = arg.asString();
      
      return interpreter.createString(left + right);
    }
  }
  
  @Getter("count Int")
  public static class Count implements BuiltInCallable {
    public Obj invoke(Interpreter interpreter, Obj thisObj, Obj arg) {
      return interpreter.createInt(thisObj.asString().length());
    }
  }
  
  @Signature("substring(arg -> String)")
  public static class Substring implements BuiltInCallable {
    public Obj invoke(Interpreter interpreter, Obj thisObj, Obj arg) {
      // TODO(bob): Hackish way to see if we have one or two arguments to this.
      if (arg.getTupleField(0) != null) {
        int startIndex = arg.getTupleField(0).asInt();
        int endIndex = arg.getTupleField(1).asInt();
        String substring = thisObj.asString().substring(startIndex, endIndex);
        return interpreter.createString(substring);
      } else {
        int startIndex = arg.asInt();
        String substring = thisObj.asString().substring(startIndex);
        return interpreter.createString(substring);
      }
    }
  }
}

package com.stuffwithstuff.magpie.interpreter.builtin;

import java.util.ArrayList;
import java.util.List;

import com.stuffwithstuff.magpie.interpreter.Interpreter;
import com.stuffwithstuff.magpie.interpreter.Obj;

public class StringBuiltIns {
  @Signature("call(index Int -> String)")
  public static class Call implements BuiltInCallable {
    public Obj invoke(Interpreter interpreter, Obj thisObj, Obj arg) {
      int index = arg.asInt();
      String c = thisObj.asString().substring(index, index + 1);
      return interpreter.createString(c);
    }
  }
  
  // TODO(bob): May want to strongly-type arg at some point.
  @Signature("compareTo(other -> Int)")
  public static class CompareTo implements BuiltInCallable {
    public Obj invoke(Interpreter interpreter, Obj thisObj, Obj arg) {
      return interpreter.createInt(thisObj.asString().compareTo(arg.asString()));
    }
  }
  
  @Signature("concatenate(other String -> String)")
  public static class Concatenate implements BuiltInCallable {
    public Obj invoke(Interpreter interpreter, Obj thisObj, Obj arg) {
      String left = thisObj.asString();
      String right = arg.asString();
      
      return interpreter.createString(left + right);
    }
  }
  
  @Getter("count Int")
  public static class Count implements BuiltInCallable {
    public Obj invoke(Interpreter interpreter, Obj thisObj, Obj arg) {
      return interpreter.createInt(thisObj.asString().length());
    }
  }
  
  @Signature("split(delimiter String -> List(String))")
  public static class Split implements BuiltInCallable {
    public Obj invoke(Interpreter interpreter, Obj thisObj, Obj arg) {
      String string = thisObj.asString();
      String delimiter = arg.asString();
      
      // Note: We're not using String#split because we don't want to split on
      // a regex, just a literal delimiter.
      List<Obj> substrings = new ArrayList<Obj>();
      int start = 0;
      while (start != -1) {
        int end = string.indexOf(delimiter, start);
        String substring;
        if (end != -1) {
          substring = string.substring(start, end);
          start = end + delimiter.length();
        } else {
          substring = string.substring(start);
          start = -1;
        }
        substrings.add(interpreter.createString(substring));
      }
      
      return interpreter.createArray(substrings);
    }
  }

  @Signature("substring(arg -> String)")
  public static class Substring implements BuiltInCallable {
    public Obj invoke(Interpreter interpreter, Obj thisObj, Obj arg) {
      // TODO(bob): Hackish way to see if we have one or two arguments to this.
      if (arg.getTupleField(0) != null) {
        int startIndex = arg.getTupleField(0).asInt();
        int endIndex = arg.getTupleField(1).asInt();
        String substring = thisObj.asString().substring(startIndex, endIndex);
        return interpreter.createString(substring);
      } else {
        int startIndex = arg.asInt();
        String substring = thisObj.asString().substring(startIndex);
        return interpreter.createString(substring);
      }
    }
  }
}

Add "split" method on String.