moss/src/env.ts

import { AST } from './ast';
import { Error } from './error';
import Token from './token';

export class EnvError implements Error {
  public line: number;
  public message: string;
  public module?: string;

  public constructor(line: number, message: string, module?: string) {
    this.line = line;
    this.message = message;
    this.module = module;
  }
}

export default class Env {
  public data: { [name: string]: AST.Node };

  public constructor(parent = {}) {
    this.data = Object.assign({}, parent);
  }

  public get(name: Token): AST.Node | EnvError {
    if (this.data[name.value]) return this.data[name.value];
    return new EnvError(
      name.line,
      `Reference to unbound variable ${name.value}`
    );
  }

  public set(name: string, value: AST.Node): void {
    this.data[name] = value;
  }
}