force-lang/src/token-stream.js

a modern forth lang compatible with NodeJS

import log from 'bunny-logger';

class TokenStream {
  constructor(tokens, filename) {
    if (!Array.isArray(tokens)) {
      // return false;
      throw new TypeError('tokens must be passed to TokenStream as an array.');
    }
    this._tokens = tokens;
    this._line = 1;
    this._col = 1;
    this._filename = filename;
  }

  set_filename(name) {
    this._filename = name;
  }

  lookahead(index) {
    if (this._tokens.length <= index) {
      return false;
      // throw new Error('Cannot read past the end of a stream');
    }
    return this._tokens[index];
  }

  peek() {
    if (this._tokens.length === 0) {
      return false;
      // throw new Error('Cannot read past the end of a stream');
    }
    return this._tokens[0];
  }

  advance() {
    if (this._tokens.length === 0) {
      return false;
      // throw new Error('Cannot read past the end of a stream');
    }
    this._col++;
    try {
      if (this.peek() == '\n') {
        this._col = 1;
        this._line++;
      }
    } catch (e) {
      // eof
      this._col--;
    }
    return this._tokens.shift();
  }

  defer(token) {
    this._col--;
    try {
      if (this.peek() == '\n') {
        this._col = 1;
        this._line--;
      }
    } catch (e) {}
    this._tokens.unshift(token);
  }

  print() {
    if (this._filename) {
      log.info(`in file ${this._filename}`);
    }
    log.info(`at line ${this._line} , col ${this._col}`);
  }

  print_err() {
    if (this._filename) {
      log.error(`in file ${this._filename}`);
    }
    log.error(`at line ${this._line} , col ${this._col}`);
  }
}

export default TokenStream;