module Chervil
  RSpec.describe Parser do
    def parse(source)
      lexer = Lexer.new(source)
      parser = Parser.new(lexer)
      parser.parse
    end

    it 'parses a number' do
      expect(parse('1').first).to eq(AST::Number.new(1.0))
    end

    it 'parses a string' do
      expect(parse('"hello world"').first).to eq(AST::String.new('hello world'))
    end

    it 'parses an identifier' do
      expect(parse('+').first).to eq(AST::Identifier.new('+'))
    end

    it 'parses an application' do
      expect(parse('(+ 1 2)').first).to eq(
        AST::Application.new(
          AST::Identifier.new('+'),
          [AST::Number.new(1.0), AST::Number.new(2.0)]
        )
      )
    end

    it 'parses a definition' do
      expect(parse('(define x 5)').first).to eq(
        AST::Definition.new(AST::Identifier.new('x'), AST::Number.new(5.0))
      )
    end

    it 'parses a nested expression' do
      expect(parse('(+ (+ 1 2) (- 3 4))').first).to eq(
        AST::Application.new(
          AST::Identifier.new("+"),
          [
            AST::Application.new(
              AST::Identifier.new("+"),
              [
                AST::Number.new(1.0),
                AST::Number.new(2.0),
              ]
            ),
            AST::Application.new(
              AST::Identifier.new("-"),
              [
                AST::Number.new(3.0),
                AST::Number.new(4.0),
              ]
            ),
          ]
        )
      )
    end
  end
end