AI Dungeon dice roller

/***
 *
 *  Author: Draco18s
 *
 *  call this from Input Modifier
 *  var r = MatchDiceAndParse(modifiedText, state);
 *  if(r.stop) return r;
 *  modifiedText = r.text;
 *
 *  /dice or /roll will display the results in a message.
 *  Syntax errors will display in a message and leave the input unaltered.
 *  /dice help will display the help text, reproduced here because it's unreadable in a message
 *  due to AI Dungeon's current CSS.
 *
 *  Wrap dice values in [].
 *  ndm: rolls n m-sided dice. +-/*% supported. < > compares two values as <= and >= respectively and the ternary
 *  operator can evaluate a truthy value to strings, eg [1d6>5?"hit":"miss"].
 *  {} creates a collection (eg {1,2,3}), dice rolled inside a collection are concatenated into the collection
 *  instead of being summed, eg [{3d6}] will create a collection of 3 random values
 *  Wrap in parens to evaluate the sum first, eg [{(3d6),(3d6)}].
 *  p and s will pick (without replacement) or select (with replacement) n values from a collection.
 *  /dice [...] will place the result in the message and not send to the AI.
 *
***/

function MatchDiceAndParse(modifiedText, state) {
  delete state.message;
  const regex = /\[((?:[dhlps \d?:*+,/(){}<>-]|(?:\?"[^"]*":"[^"]*")){3,})\]/i;
  var didMatch = false;
  while(modifiedText.match(regex) && state.message == undefined) {
    didMatch = true;
    modifiedText = modifiedText.replace(regex, function(v) {
      var m = v.match(regex);
      return ParseAndRollDice(m[1], state);
    });
  }
  const command = /\/dice|\/roll/i;
  if(modifiedText.match(command)) {
    if(modifiedText.match("help")) {
      state.message = "Wrap dice values in [].\nndm: rolls n m-sided dice. +-*/% supported. < > compares two values as <= and >= respectively and the ternary operator can evaluate a truthy value to strings, eg [1d6>5?\"hit\":\"miss\"].\n{} creates a collection (eg {1,2,3}), dice rolled inside a collection are concatenated into the collection instead of being summed, eg [{3d6}] will create a collection of 3 random values\nWrap in parens to evaluate the sum first, eg [{(3d6),(3d6)}].\np and s will pick (without replacement) or select (with replacement) n values from a collection.\n/dice [...] will place the result in the message and not send to the AI.";
      return { text: "", stop: true };
    }
    else if(didMatch) {
      if(state.message == undefined)
        state.message = modifiedText.replace(command,"");
      else
        return { text: modifiedText, stop: true };
      return { text: "", stop: true };
    }
  }
  return { text: modifiedText };
}

var OpPrecedence = {
    '(': 999,
    'd': 50,
    'p': 40,
    's': 40,
    '*': 20,
    '/': 20,
    '%': 20,
    'h': 15,
    'l': 15,
    '+': 10,
    '-': 10,
    '<': 5,
    '>': 5,
    ',': 5,
    '{': 2,
    '?': 1,
    ':': 1
}

function ParseAndRollDice(dice, state) {
  var output = [];
  var trainyard = [];
  var value = -1;
  var stringread = false;
  var tempString = "";
  for(var i=0; i<dice.length;i++) {
    var exp = dice[i];
    if(stringread) {
      if(exp == '"') {
        stringread = false;
        output.push(tempString);
      }
      else {
        tempString += exp;
      }
      continue;
    }
    if(exp == ' ' || exp == ':') continue;
    if(exp>='0' && exp<='9') {
      if(value == -1) value = 0;
      value = value*10+parseInt(exp.toString());
      continue;
    }
    else if(value != -1) {
      output.push(value);
      value = -1;
    }
    switch(exp) {
      case '"':
        tempString = "";
        stringread = true;
        break;
      case '{':
      case '(':
        output.push(exp);
      case '+':
      case '-':
      case '*':
      case '/':
      case '%':
      case 'd':
      case 'p':
      case 's':
      case 'h':
      case 'l':
      case '<':
      case '>':
      case ',':
      case '?':
        while(trainyard.length > 0 && trainyard[trainyard.length-1] != '(' && OpPrecedence[exp] <= OpPrecedence[trainyard[trainyard.length-1]]) {
          var pp = trainyard.pop();
          output.push(pp);
        }
        trainyard.push(exp);
        break;
      case '}':
        while(trainyard.length > 0) {
          var c = trainyard.pop();
          if(c == '{') break;
          if(c == '(') {
            state.message = "Unpaired (!";
            return "["+dice+"]";
          }
          output.push(c);
        }
        output.push(exp);
        break;
      case ')':
        while(trainyard.length > 0) {
          var c = trainyard.pop();
          if(c == '(') break;
          if(c == '{') {
            state.message = "Unpaired {!";
            return "["+dice+"]";
          }
          output.push(c);
        }
        output.push(exp);
        break;
      default:
        if(!(exp>='0' && exp<='9')) {
          state.message = "Unrecognized dice operation: " + exp;
          return "["+dice+"]";
        }
        break;
    }
  }
  if(value > -1) {
    output.push(value);
  }
  while(trainyard.length > 0) {
    output.push(trainyard.pop());
  }
  var ops = [];
  var v1=0;
  var v2=0;
  var collapse = 0;
  var retreat = [];
  while(output.length > 0) {
    exp = output.shift();
    switch(exp) {
      case '+':
        v1 = ParseArray(ops.pop());
        v2 = ParseArray(ops.pop());
        ops.push(v2+v1);
        break;
      case '-':
        v1 = ParseArray(ops.pop());
        v2 = ParseArray(ops.pop());
        ops.push(v2-v1);
        break;
      case '*':
        v1 = ParseArray(ops.pop());
        v2 = ParseArray(ops.pop());
        ops.push(v2*v1);
        break;
      case '/':
        v1 = ParseArray(ops.pop());
        v2 = ParseArray(ops.pop());
        ops.push(Math.floor(v2/v1));
        break;
      case '%':
        v1 = ParseArray(ops.pop());
        v2 = ParseArray(ops.pop());
        ops.push(Math.floor(v2%v1));
        break;
      case 'd':
        v1 = ParseArray(ops.pop());
        v2 = ParseArray(ops.pop());
        var r = [];
        for(var n=0; n < v2; n++) {
          r.push(Math.floor(Math.random()*v1)+1);
        }
        if(collapse == 0) {
          ops.push(ParseArray(r));
        }
        else {
          ops.push(r);
        }
        break;
      case ':':
        break;
      case '?':
        if(ops.length < 3) {
          state.message = "Invalid dice operation: " + exp + "\nInvalid number of operands.";
          return "["+dice+"]";
        }
        v3 = ops.pop();
        v2 = ops.pop();
        var v1 = ops.pop();
        if(v1) {
          ops.push(v2);
        }
        else {
          ops.push(v3);
        }
        break;
      case 'p':
      case 's':
        v1 = ParseArray(ops.pop());
        v2 = ops.pop();
        if(!Array.isArray(v2)) {
          state.message = "Unrecognized dice operation: " + exp + "\nValue " + v2 + " was not a collection.";
          return "["+dice+"]";
        }
        if(v2.length < v1) {
          state.message = "Invalid dice operation: " + exp + "\nValue " + v1 + " was larger than the size of the collection " + v2 + ".";
          return "["+dice+"]";
        }
        var r = [];
        for(var h=0;h<v1;h++) {
          var i = Math.floor(Math.random()*v2.length);
          r.push(v2[i]);
          if(exp == 'p')
            v2.splice(i,1);
        }
        if(collapse == 0) {
          ops.push(ParseArray(r));
        }
        else {
          ops.push(r);
        }
        break;
      case 'h':
        v1 = ParseArray(ops.pop());
        v2 = ops.pop();
        if(!Array.isArray(v2)) {
          state.message = "Unrecognized dice operation: " + exp + "\nValue " + v2 + " was not a collection.";
          return "["+dice+"]";
        }
        v2.sort(function(a, b){return a - b});
        v2.reverse();
        var r = [];
        for(var h=0;h<v1;h++) {
          r.push(v2[h]);
        }
        ops.push(r);
        break;
      case 'l':
        v1 = ParseArray(ops.pop());
        v2 = ops.pop();
        if(!Array.isArray(v2)) {
          state.message = "Unrecognized dice operation: " + exp + "\nValue " + v2 + " was not a collection.";
          return "["+dice+"]";
        }
        v2.sort(function(a, b){return a - b});
        var r = [];
        for(var h=0;h<v1;h++) {
          r.push(v2[h]);
        }
        ops.push(r);
        break;
      case '<':
        v1 = ParseArray(ops.pop());
        v2 = ParseArray(ops.pop());
        ops.push(v2 <= v1);
        break;
        break;
      case '>':
        v1 = ParseArray(ops.pop());
        v2 = ParseArray(ops.pop());
        ops.push(v2 >= v1);
        break;
      case '{':
        collapse++;
        break;
      case '}':
        collapse--;
        break;
      case '(':
        if(collapse > 0) {
          retreat.push(collapse);
          collapse = 0;
        }
        break;
      case ')':
        if(retreat.length > 0) {
          collapse = retreat.pop();
        }
        break;
      case ',':
        v1 = ops.pop();
        v2 = ops.pop();
        var p = [];
        if(collapse > 0 && v1 != null && v2 != null) {
          if(Array.isArray(v2)) {
            p = v2.concat(v1);
          }
          else if(Array.isArray(v1)) {
            var v3 = [];
            v3.push(v2);
            p = v3.concat(v1);
          }
          else {
            p = [v2, v1];
          }
          ops.push(p);
        }
        else if(v1 == null || v2 == null) {
          state.message = "Invalid operation: " + exp + "\nInvalid collection syntax!";
          return "["+dice+"]";
        }
        else {
          state.message = "Invalid operation: " + exp + "\nTo create a collection, use {a,b}.";
          return "["+dice+"]";
        }
        break;
      default:
        if(collapse > 0) {
          ops.push([exp]);
        }
        else {
          ops.push(exp);
        }
        break;
    }
  }
  var ret = ops.pop();
  if(ret === true) {
    return "[Success!]";
  }
  else if(ret === false) {
    return "[Failed!]";
  }
  if(Array.isArray(ret)) {
    return "(" + ret + ")";
  }
  return ParseArray(ret);
}

function ParseArray(val) {
  if(Array.isArray(val)) {
    var r = 0;
    for(var i = 0; i < val.length; i++) {
      r+=val[i];
    }
    return r;
  }
  else
    return val;
}