/**
 * The environment in which a script runs. The environment holds
 * Netscript functions and arguments for that script.
 */
import { IMap } from "../types";

export class Environment {
  /**
   * Parent environment. Used to implement "scope"
   */
  parent: Environment | null = null;

  /**
   * Whether or not the script that uses this Environment should stop running
   */
  stopFlag = false;

  /**
   * Environment variables (currently only Netscript functions)
   */
  vars: IMap<any> = {};

  constructor(parent: Environment | null) {
    if (parent instanceof Environment) {
      this.vars = Object.assign({}, parent.vars);
    }

    this.parent = parent;
  }

  /**
   * Finds the scope where the variable with the given name is defined
   */
  lookup(name: string): Environment | null {
    // eslint-disable-next-line @typescript-eslint/no-this-alias
    let scope: Environment | null = this;
    while (scope) {
      if (Object.prototype.hasOwnProperty.call(scope.vars, name)) {
        return scope;
      }
      scope = scope.parent;
    }

    return null;
  }

  //Get the current value of a variable
  get(name: string): any {
    if (name in this.vars) {
      return this.vars[name];
    }

    throw new Error(`Undefined variable ${name}`);
  }

  //Sets the value of a variable in any scope
  // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types
  set(name: string, value: any): any {
    const scope = this.lookup(name);

    //If scope has a value, then this variable is already set in a higher scope, so
    //set is there. Otherwise, create a new variable in the local scope
    if (scope !== null) {
      return (scope.vars[name] = value);
    } else {
      return (this.vars[name] = value);
    }
  }

  //Creates (or overwrites) a variable in the current scope
  // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types
  def(name: string, value: any): any {
    return (this.vars[name] = value);
  }
}