node-haxball/examples/libraries/mathExpr.js

The most powerful and lightweight API that allows you to develop your original Haxball(www.haxball.com) host, client, and standalone applications both on node.js and browser environments and also includes every possible hack and functionality that you can

module.exports = function(API){
  const { OperationType, VariableType, ConnectionState, AllowFlags, Direction, CollisionFlags, CameraFollow, BackgroundType, GamePlayState, BanEntryType, Callback, Utils, Room, Replay, Query, Library, RoomConfig, Plugin, Renderer, Errors, Language, EventFactory, Impl } = API;

  Object.setPrototypeOf(this, Library.prototype);
  Library.call(this, "mathExpr", { // "mathExpr" is library's name. Every library should have a unique name.
    version: 0.1,
    author: "abc",
    description: `This is a small library to parse mathematical expressions that only contains constant integers and paranthesis. Example: (5-(1+2)/10)*(5-8*3)`
  });
  
  function Expression(parent){
    this.parent = parent;
    this.operands = [];
    this.operations = [];
  }
  
  Expression.parse = function(str){
    var num = "", root = new Expression(), current = root;
    for (var i=0;i<str.length;i++){
      var ch = str[i];
      switch(ch){
        case "(":
          num = "";
          var newExpr = new Expression(current);
          current.operands.push(newExpr);
          current = newExpr;
          break;
        case ")":
          if (num.length>0){
            var n = parseInt(num);
            if (isNaN(n))
              throw "illegal character at index "+i;
            current.operands.push(n);
            num="";
          }
          current = current.parent;
          if (!current)
            throw "depth<0 at index "+i;
          break;
        case "0":
        case "1":
        case "2":
        case "3":
        case "4":
        case "5":
        case "6":
        case "7":
        case "8":
        case "9":
          num+=ch;
          break;
        case "+":
        case "-":
        case "*":
        case "/":
          if (str[i-1]!=")"){
            var n = parseInt(num);
            if (isNaN(n))
              throw "illegal character at index "+i;
            current.operands.push(n);
          }
          current.operations.push(ch);
          num="";
          break;
        case " ":
        case "\t":
          break;
        default:
          throw "illegal character at index "+i;
      }
    }
    if (current!=root)
      throw "missing paranthesis at the end";
    if (num.length>0){
      var n = parseInt(num);
      if (isNaN(n))
        throw "illegal character at index "+i;
      current.operands.push(n);
    }
    return root;
  };
  
  Expression.prototype = {
    simplify: function(){
      var v = this.operands[0];
      if (v==null)
        return;
      if (typeof v=="object"){
        v.simplify();
        if (v.operands.length==1)
          this.operands[0] = v.operands[0];
        else{
          var op = this.operations[0];
          if (op=="+" || op=="-"){
            this.operands.splice(0, 1, ...v.operands);
            this.operations.splice(0, 0, ...v.operations);
          }
        }
      }
      if (this.operands.length==1){
        if (typeof v=="object"){
          this.operands = v.operands;
          this.operations = v.operations;
        }
        return this;
      }
      for (var i=0;i<this.operations.length;i++){
        v = this.operands[i+1];
        if (typeof v=="object"){
          v.simplify();
          if (v.operands.length==1)
            this.operands[i+1] = v.operands[0];
          else if (v.operations.filter((x)=>(x=="+" || x=="-")).length==0){
            this.operands.splice(i+1, 1, ...v.operands);
            this.operations.splice(i+1, 0, ...v.operations);
          }
          else{
            var op1 = this.operations[i], op2 = this.operations[i+1];
            if (op2!="*" && op2!="/"){
              if (op1=="+"){
                this.operands.splice(i+1, 1, ...v.operands);
                this.operations.splice(i+1, 0, ...v.operations);
              }
              else if (op1=="-"){
                this.operands.splice(i+1, 1, ...v.operands);
                this.operations.splice(i+1, 0, ...v.operations.map((x)=>(((x=="+")?"-":((x=="-")?"+":x)))));
              }
            }
          }
        }
      }
      return this;
    },
    clone: function(){
      var exp = new Expression(this.parent);
      for (var i=0;i<this.operations.length;i++)
        exp.operations.push(this.operations[i]);
      for (var i=0;i<this.operands.length;i++){
        var value = this.operands[i];
        if (typeof value!="number")
          value = value.clone();
        exp.operands.push(value);
      }
      return exp;
    },
    toString: function(){
      var value = this.operands[0], str = typeof value=="number" ? value : ("(" + value.toString() + ")");
      for (var i=0;i<this.operations.length;i++){
        value = this.operands[i+1];
        str += this.operations[i] + (typeof value=="number" ? value : ("(" + value.toString() + ")"));
      }
      return str;
    },
    evaluate: function(){
      for (var i=0;i<this.operations.length;i++){
        var op = this.operations[i];
        if (op=="*" || op=="/"){
          var value1 = this.operands[i];
          if (typeof value1!="number")
            value1 = value1.evaluate();
          var value2 = this.operands[i+1];
          if (typeof value2!="number")
            value2 = value2.evaluate();
          var result = (op=="*") ? (value1*value2) : (value1/value2);
          this.operands.splice(i, 2, result);
          this.operations.splice(i, 1);
          i--;
        }
      }
      for (var i=0;i<this.operations.length;i++){
        var op = this.operations[i];
        if (op=="+" || op=="-"){
          var value1 = this.operands[i];
          if (typeof value1!="number")
            value1 = value1.evaluate();
          var value2 = this.operands[i+1];
          if (typeof value2!="number")
            value2 = value2.evaluate();
          var result = (op=="+") ? (value1+value2) : (value1-value2);
          this.operands.splice(i, 2, result);
          this.operations.splice(i, 1);
          i--;
        }
      }
      var val = this.operands[0];
      return (typeof val=="number") ? val : val.evaluate();
    }
  };
  
  this.Expression = Expression;
  
  this.isInteger = function(value){
    return isFinite(value) && (value === Math.round(value));
  };
};