require_relative '../../spec_helper'
require 'strscan'

describe "StringScanner#peek" do
  before :each do
    @s = StringScanner.new('This is a test')
  end

  it "returns at most the specified number of bytes from the current position" do
    @s.peek(4).should == "This"
    @s.pos.should == 0
    @s.pos = 5
    @s.peek(2).should == "is"
    @s.peek(1000).should == "is a test"

    s = StringScanner.new("été")
    s.peek(2).should == "é"
  end

  it "returns an empty string when the passed argument is zero" do
    @s.peek(0).should == ""
  end

  it "raises a ArgumentError when the passed argument is negative" do
    -> { @s.peek(-2) }.should.raise(ArgumentError)
  end

  it "raises a RangeError when the passed argument is a Bignum" do
    -> { @s.peek(bignum_value) }.should.raise(RangeError)
  end

  it "returns an instance of String when passed a String subclass" do
    cls = Class.new(String)
    sub = cls.new("abc")

    s = StringScanner.new(sub)

    ch = s.peek(1)
    ch.should_not.is_a?(cls)
    ch.should.instance_of?(String)
  end
end
