class Printer extends Visitor {
  constructor() {
    super()
  }

  visitBinaryExpression(expr) {
    return this.prettyPrint(expr.operator, expr.left, expr.right)
  }

  visitLiteralExpression(expr) {
    if (expr.value === null) return 'null'

    return String(expr.value)
  }

  visitGroupingExpression(expr) {
    return this.prettyPrint('group', expr.expression)
  }

  visitUnaryExpression(expr) {
    return this.prettyPrint(expr.operator, expr.right)
  }

  prettyPrint(name, ...exprs) {
    let arr = []

    arr.push('(')
    arr.push(name)

    for (let expr in exprs) {
      arr.push(' ')
      arr.push(exprs[expr].handle(this))
    }

    arr.push(')')
    return arr.join('')
  }

  render(expr) {
    return expr.handle(this)
  }

  main() {
    const expr = new Binary(
      new Literal("12"),
      "*",
      new Binary(
        new Literal("10"),
        "-",
        new Literal("20")
      )
    )

    return this.render(expr)
  }
}