knight.js

window.Knight = (() => {
  let inputs = [];
  let output = '';

  class KnightError extends Error {}
  class ParseError extends KnightError {}
  class RuntimeError extends KnightError {}

  class Stream {
    constructor(source) {
      this.source = source;
    }

    stripWhitespace() {
      this.match(/^([\]\[\s(){}:]+|#[^\n]*(\n|$))*/);
    }

    peek() {
      return this.source[0] || null;
    }

    match(regex, group = 0) {
      const match = regex.exec(this.source);
      if (match === null) {
        return null;
      }
      this.source = this.source.substr(match[0].length);
      return match[group];
    }

    toString() {
      return this.source;
    }
  }

  const TYPES = [];
  class Value {
    static parse(stream) {
      stream.stripWhitespace();

      for (var i = 0; i < TYPES.length; i++) {
        const match = TYPES[i].parse(stream);

        if (match) {
          return match;
        }
      }

      return null;
    }

    run() {
      throw new Error();
    }

    debug() {
      throw new Error();
    }

    toString() {
      return this.run().toString();
    }

    toNumber() {
      return this.run().toNumber();
    }

    toBoolean() {
      return this.run().toBoolean();
    }
  }

  class Literal extends Value {
    _data;

    constructor(data) {
      super();

      this._data = data;
    }

    run() {
      return this;
    }

    toString() {
      return String(this._data);
    }

    toNumber() {
      return Number(this._data);
    }

    toBoolean() {
      return Boolean(this._data);
    }

    eql(rhs) {
      return rhs instanceof this.constructor && this._data === rhs._data;
    }
  }

  class Bool extends Literal {
    static parse(stream) {
      const match = stream.match(/^([TF])[A-Z]*/, 1);

      return match && new Bool(match === "T");
    }

    dump() {
      return `Boolean(${this})`;
    }

    lth(rhs) {
      return !this._data && rhs.toBoolean();
    }

    gth(rhs) {
      return this._data && !rhs.toBoolean();
    }
  }
  TYPES.push(Bool);

  const ENVIRONMENT = {};

  class Ident extends Value {
    static parse(stream) {
      const match = stream.match(/^[a-z_][a-z0-9_]*/);

      return match && new Ident(match);
    }

    constructor(ident) {
      super();

      this.ident = ident;
    }

    dump() {
      return `Identifier(${this.ident})`;
    }

    assign(value) {
      ENVIRONMENT[this.ident] = value;
    }

    run() {
      const value = ENVIRONMENT[this.ident];

      if (value === undefined) {
        throw new RuntimeError(`Unknown identifier '${this.ident}'`);
      } else {
        return value;
      }
    }
  }

  TYPES.push(Ident);

  class Int extends Literal {
    static parse(stream) {
      const match = stream.match(/^\d+/);

      return match && new Int(Number(match));
    }

    dump() {
      return `Number(${this})`;
    }

    add(rhs) {
      return new Int(this._data + rhs.toNumber());
    }

    sub(rhs) {
      return new Int(this._data - rhs.toNumber());
    }

    mul(rhs) {
      return new Int(this._data * rhs.toNumber());
    }

    div(rhs) {
      const rhsInt = rhs.toNumber();

      if (rhsInt === 0) {
        throw new RuntimeError("Cannot divide by zero");
      } else {
        return new Int(Math.trunc(this._data / rhsInt));
      }
    }

    mod(rhs) {
      const rhsInt = rhs.toNumber();

      if (rhsInt === 0) {
        throw new RuntimeError("Cannot modulo by zero");
      } else {
        return new Int(this._data % rhsInt);
      }
    }

    pow(rhs) {
      const rhsInt = rhs.toNumber();

      if (this._data === 0 && rhsInt < 0) {
        throw new RuntimeError("Cannot exponentiate zero to a negative power");
      } else {
        return new Int(Math.trunc(this._data ** rhsInt));
      }
    }

    lth(rhs) {
      return this._data < rhs.toNumber();
    }

    gth(rhs) {
      return this._data > rhs.toNumber();
    }
  }

  TYPES.push(Int);

  class Null extends Literal {
    static parse(stream) {
      return stream.match(/^N[A-Z]*/) && new Null();
    }

    constructor() {
      super(null);
    }

    dump() {
      return "Null()";
    }

    eql(rhs) {
      return rhs instanceof Null;
    }

    lth(_rhs) {
      throw new RuntimeError("Cannot compare Null.");
    }

    gth(_rhs) {
      throw new RuntimeError("Cannot compare Null.");
    }
  }

  TYPES.push(Null);

  class Str extends Literal {
    static parse(stream) {
      const match = stream.match(/^(["'])([\s\S]*?)\1/, 2);

      if (match !== null) {
        return new Str(match);
      }

      const first = stream.peek();
      if (first === "'" || first === '"') {
        throw new ParseError(`Unterminated quote encountered: ${stream}`);
      }
    }

    toNumber() {
      return parseInt(this._data, 10) || 0;
    }

    dump() {
      return `String(${this})`;
    }

    add(rhs) {
      return new Str(`${this}${rhs}`);
    }

    mul(rhs) {
      return new Str(this._data.repeat(rhs.toNumber()));
    }

    lth(rhs) {
      return this._data < rhs.toString();
    }

    gth(rhs) {
      return this._data > rhs.toString();
    }
  }

  TYPES.push(Str);

  const FUNCTIONS = {};

  class Func extends Value {
    static parse(stream) {
      const front = stream.peek();
      const func = FUNCTIONS[front];

      if (func === undefined) {
        return null;
      }

      stream.match(/^(?:[A-Z]+|.)/);

      let args = [];
      for (let i = 0; i < func.length; i++) {
        const arg = Value.parse(stream);

        if (!arg) {
          throw new ParseError(`Missing argument ${i + 1} for func '${front}'`);
        }

        args.push(arg);
      }

      return new Func(func, front, args);
    }

    constructor(func, name, args) {
      super();

      this.func = func;
      this.name = name;
      this.args = args;
    }

    run() {
      return this.func(...this.args);
    }

    dump() {
      let ret = "Function(" + this.name;

      for (let val of this.args) {
        ret += ", " + val.dump();
      }

      return ret + ")";
    }

    eql(rhs) {
      return Object.is(this, rhs);
    }
  }

  TYPES.push(Func);

  function register(name, func) {
    if (name.length !== 1) {
      throw new Error("Name must be exactly one character long.");
    }

    FUNCTIONS[name] = func;
  }

  register("P", () => {
    return inputs.length ? new Str(inputs.shift()) : new Null();
  });

  register("R", () => new Int(Math.floor(Math.random() * 0x1_0000_0000)));

  register("E", (string) => evalRun(string.toString()));

  register("A", (a) => {
    const b = a.run();
    return b instanceof Int
      ? new Str(String.fromCharCode(b.toNumber()))
      : new Int(b.toString().charCodeAt(0));
  });

  register("~", (a) => new Int(-a.toNumber()));

  register("B", (block) => block);

  register("C", (block) => block.run().run());

  register("`", (command) => {
		throw new RuntimeError('Run shell command not supported on DSO.');
	});

  register("Q", (status) => {
		throw new RuntimeError('Exit not supported on DSO.');
	});

  register("!", (arg) => new Bool(!arg.toBoolean()));

  register("L", (str) => new Int(str.toString().length));

  register("D", (value) => {
    const result = value.run();

    output += result.dump();

    return result;
  });

  register("O", (input) => {
    const str = input.toString();

    if (str.substr(-1) === "\\") {
      output += str.substr(0, str.length - 1);
    } else {
      output += `${str}\n`;
    }

    return new Null();
  });

  register("+", (lhs, rhs) => lhs.run().add(rhs.run()));

  register("-", (lhs, rhs) => lhs.run().sub(rhs.run()));

  register("*", (lhs, rhs) => lhs.run().mul(rhs.run()));

  register("/", (lhs, rhs) => lhs.run().div(rhs.run()));

  register("%", (lhs, rhs) => lhs.run().mod(rhs.run()));

  register("^", (lhs, rhs) => lhs.run().pow(rhs.run()));

  register("<", (lhs, rhs) => new Bool(lhs.run().lth(rhs.run())));

  register(">", (lhs, rhs) => new Bool(lhs.run().gth(rhs.run())));

  register("?", (lhs, rhs) => new Bool(lhs.run().eql(rhs.run())));

  register("&", (lhs, rhs) => {
    lhs = lhs.run();
    return lhs.toBoolean() ? rhs.run() : lhs;
  });

  register("|", (lhs, rhs) => {
    lhs = lhs.run();
    return lhs.toBoolean() ? lhs : rhs.run();
  });

  register(";", (lhs, rhs) => {
    lhs.run();
    return rhs.run();
  });

  register("=", (ident, value) => {
    if (!(ident instanceof Ident)) {
      ident = new Ident(ident.toString());
    }

    ident.assign((value = value.run()));
    return value;
  });

  register("W", (condition, body) => {
    while (condition.toBoolean()) {
      body.run();
    }

    return new Null();
  });

  register("I", (cond, iftrue, iffalse) => {
    return cond.toBoolean() ? iftrue.run() : iffalse.run();
  });

  register("G", (str, start, len) => {
    str = str.toString();
    start = start.toNumber();
    len = len.toNumber();

    return new Str(str.substr(start, len) || "");
  });

  register("S", (str, start, len, repl) => {
    str = str.toString();
    start = start.toNumber();
    len = len.toNumber();
    repl = repl.toString();

    if (str.length == start) {
      return new Str(str + repl);
    }

    return new Str(str.substr(0, start) + repl + str.substr(start + len));
  });

  function evalRun(input) {
    const value = Value.parse(new Stream(input.toString()));

    if (value === null) {
      throw new ParseError("No value could be parsed!");
    } else {
      return value.run();
    }
  }

  function run(input, inps = []) {
    inputs = [...inps];
    output = '';
    const value = Value.parse(new Stream(input.toString()));

    if (value === null) {
      throw new ParseError("No value could be parsed!");
    } else {
      value.run();
      return output;
    }
  }

  return { run };
})();