module Shoulda
  class << self
    attr_accessor :contexts
    def contexts # :nodoc:
      @contexts ||= []
    end

    def current_context # :nodoc:
      self.contexts.last
    end

    def add_context(context) # :nodoc:
      self.contexts.push(context)
    end

    def remove_context # :nodoc:
      self.contexts.pop
    end
  end

  module ClassMethods
    # == Should statements
    #
    # Should statements are just syntactic sugar over normal Test::Unit test
    # methods.  A should block contains all the normal code and assertions
    # you're used to seeing, with the added benefit that they can be wrapped
    # inside context blocks (see below).
    #
    # === Example:
    #
    #  class UserTest < Test::Unit::TestCase
    #
    #    def setup
    #      @user = User.new("John", "Doe")
    #    end
    #
    #    should "return its full name"
    #      assert_equal 'John Doe', @user.full_name
    #    end
    #
    #  end
    #
    # ...will produce the following test:
    # * <tt>"test: User should return its full name. "</tt>
    #
    # Note: The part before <tt>should</tt> in the test name is gleamed from the name of the Test::Unit class.
    #
    # Should statements can also take a Proc as a <tt>:before </tt>option.  This proc runs after any
    # parent context's setups but before the current context's setup.
    #
    # === Example:
    #
    #  context "Some context" do
    #    setup { puts("I run after the :before proc") }
    #
    #    should "run a :before proc", :before => lambda { puts("I run before the setup") }  do
    #      assert true
    #    end
    #  end
    #
    # Should statements can also wrap matchers, making virtually any matcher
    # usable in a macro style. The matcher's description is used to generate a
    # test name and failure message, and the test will pass if the matcher
    # matches the subject.
    #
    # === Example:
    #
    #   should validate_presence_of(:first_name).with_message(/gotta be there/)
    #

    def should(name_or_matcher, options = {}, &blk)
      if Shoulda.current_context
        Shoulda.current_context.should(name_or_matcher, options, &blk)
      else
        context_name = self.name.gsub(/Test/, "")
        context = Shoulda::Context.new(context_name, self) do
          should(name_or_matcher, options, &blk)
        end
        context.build
      end
    end

    # Allows negative tests using matchers. The matcher's description is used
    # to generate a test name and negative failure message, and the test will
    # pass unless the matcher matches the subject.
    #
    # === Example:
    #
    #   should_not set_the_flash
    def should_not(matcher)
      if Shoulda.current_context
        Shoulda.current_context.should_not(matcher)
      else
        context_name = self.name.gsub(/Test/, "")
        context = Shoulda::Context.new(context_name, self) do
          should_not(matcher)
        end
        context.build
      end
    end

    # == Before statements
    #
    # Before statements are should statements that run before the current
    # context's setup. These are especially useful when setting expectations.
    #
    # === Example:
    #
    #  class UserControllerTest < Test::Unit::TestCase
    #    context "the index action" do
    #      setup do
    #        @users = [Factory(:user)]
    #        User.stubs(:find).returns(@users)
    #      end
    #
    #      context "on GET" do
    #        setup { get :index }
    #
    #        should_respond_with :success
    #
    #        # runs before "get :index"
    #        before_should "find all users" do
    #          User.expects(:find).with(:all).returns(@users)
    #        end
    #      end
    #    end
    #  end
    def before_should(name, &blk)
      should(name, :before => blk) { assert true }
    end

    # Just like should, but never runs, and instead prints an 'X' in the Test::Unit output.
    def should_eventually(name, options = {}, &blk)
      context_name = self.name.gsub(/Test/, "")
      context = Shoulda::Context.new(context_name, self) do
        should_eventually(name, &blk)
      end
      context.build
    end

    # == Contexts
    #
    # A context block groups should statements under a common set of setup/teardown methods.
    # Context blocks can be arbitrarily nested, and can do wonders for improving the maintainability
    # and readability of your test code.
    #
    # A context block can contain setup, should, should_eventually, and teardown blocks.
    #
    #  class UserTest < Test::Unit::TestCase
    #    context "A User instance" do
    #      setup do
    #        @user = User.find(:first)
    #      end
    #
    #      should "return its full name"
    #        assert_equal 'John Doe', @user.full_name
    #      end
    #    end
    #  end
    #
    # This code will produce the method <tt>"test: A User instance should return its full name. "</tt>.
    #
    # Contexts may be nested.  Nested contexts run their setup blocks from out to in before each
    # should statement.  They then run their teardown blocks from in to out after each should statement.
    #
    #  class UserTest < Test::Unit::TestCase
    #    context "A User instance" do
    #      setup do
    #        @user = User.find(:first)
    #      end
    #
    #      should "return its full name"
    #        assert_equal 'John Doe', @user.full_name
    #      end
    #
    #      context "with a profile" do
    #        setup do
    #          @user.profile = Profile.find(:first)
    #        end
    #
    #        should "return true when sent :has_profile?"
    #          assert @user.has_profile?
    #        end
    #      end
    #    end
    #  end
    #
    # This code will produce the following methods
    # * <tt>"test: A User instance should return its full name. "</tt>
    # * <tt>"test: A User instance with a profile should return true when sent :has_profile?. "</tt>
    #
    # <b>Just like should statements, a context block can exist next to normal <tt>def test_the_old_way; end</tt>
    # tests</b>.  This means you do not have to fully commit to the context/should syntax in a test file.

    def context(name, &blk)
      if Shoulda.current_context
        Shoulda.current_context.context(name, &blk)
      else
        context = Shoulda::Context.new(name, self, &blk)
        context.build
      end
    end

    # Returns the class being tested, as determined by the test class name.
    #
    #   class UserTest; described_type; end
    #   # => User
    def described_type
      self.name.gsub(/Test$/, '').constantize
    end

    # Sets the return value of the subject instance method:
    #
    #   class UserTest < Test::Unit::TestCase
    #     subject { User.first }
    #
    #     # uses the existing user
    #     should_validate_uniqueness_of :email
    #   end
    def subject(&block)
      @subject_block = block
    end

    def subject_block # :nodoc:
      @subject_block
    end
  end

  module InstanceMethods
    # Returns an instance of the class under test.
    #
    #   class UserTest
    #     should "be a user" do
    #       assert_kind_of User, subject # passes
    #     end
    #   end
    #
    # The subject can be explicitly set using the subject class method:
    #
    #   class UserTest
    #     subject { User.first }
    #     should "be an existing user" do
    #       assert !subject.new_record? # uses the first user
    #     end
    #   end
    #
    # The subject is used by all macros that require an instance of the class
    # being tested.
    def subject
      @shoulda_subject ||= construct_subject
    end

    def subject_block # :nodoc:
      (@shoulda_context && @shoulda_context.subject_block) || self.class.subject_block
    end

    def get_instance_of(object_or_klass) # :nodoc:
      if object_or_klass.is_a?(Class)
        object_or_klass.new
      else
        object_or_klass
      end
    end

    def instance_variable_name_for(klass) # :nodoc:
      klass.to_s.split('::').last.underscore
    end

    private

    def construct_subject
      if subject_block
        instance_eval(&subject_block)
      else
        get_instance_of(self.class.described_type)
      end
    end
  end

  class Context # :nodoc:

    attr_accessor :name               # my name
    attr_accessor :parent             # may be another context, or the original test::unit class.
    attr_accessor :subcontexts        # array of contexts nested under myself
    attr_accessor :setup_blocks       # blocks given via setup methods
    attr_accessor :teardown_blocks    # blocks given via teardown methods
    attr_accessor :shoulds            # array of hashes representing the should statements
    attr_accessor :should_eventuallys # array of hashes representing the should eventually statements
    attr_accessor :subject_block

    def initialize(name, parent, &blk)
      Shoulda.add_context(self)
      self.name               = name
      self.parent             = parent
      self.setup_blocks       = []
      self.teardown_blocks    = []
      self.shoulds            = []
      self.should_eventuallys = []
      self.subcontexts        = []

      merge_block(&blk)
      Shoulda.remove_context
    end

    def merge_block(&blk)
      blk.bind(self).call
    end

    def context(name, &blk)
      self.subcontexts << Context.new(name, self, &blk)
    end

    def setup(&blk)
      self.setup_blocks << blk
    end

    def teardown(&blk)
      self.teardown_blocks << blk
    end

    def should(name_or_matcher, options = {}, &blk)
      if name_or_matcher.respond_to?(:description) && name_or_matcher.respond_to?(:matches?)
        name = name_or_matcher.description
        blk = lambda { assert_accepts name_or_matcher, subject }
      else
        name = name_or_matcher
      end

      if blk
        self.shoulds << { :name => name, :before => options[:before], :block => blk }
      else
       self.should_eventuallys << { :name => name }
     end
    end

    def should_not(matcher)
      name = matcher.description
      blk = lambda { assert_rejects matcher, subject }
      self.shoulds << { :name => "not #{name}", :block => blk }
    end

    def should_eventually(name, &blk)
      self.should_eventuallys << { :name => name, :block => blk }
    end

    def subject(&block)
      self.subject_block = block
    end

    def subject_block
      return @subject_block if @subject_block
      parent.subject_block
    end

    def full_name
      parent_name = parent.full_name if am_subcontext?
      return [parent_name, name].join(" ").strip
    end

    def am_subcontext?
      parent.is_a?(self.class) # my parent is the same class as myself.
    end

    def test_unit_class
      am_subcontext? ? parent.test_unit_class : parent
    end

    def create_test_from_should_hash(should)
      test_name = ["test:", full_name, "should", "#{should[:name]}. "].flatten.join(' ').to_sym

      if test_unit_class.instance_methods.include?(test_name.to_s)
        warn "  * WARNING: '#{test_name}' is already defined"
      end

      context = self
      test_unit_class.send(:define_method, test_name) do
        @shoulda_context = context
        begin
          context.run_parent_setup_blocks(self)
          should[:before].bind(self).call if should[:before]
          context.run_current_setup_blocks(self)
          should[:block].bind(self).call
        ensure
          context.run_all_teardown_blocks(self)
        end
      end
    end

    def run_all_setup_blocks(binding)
      run_parent_setup_blocks(binding)
      run_current_setup_blocks(binding)
    end

    def run_parent_setup_blocks(binding)
      self.parent.run_all_setup_blocks(binding) if am_subcontext?
    end

    def run_current_setup_blocks(binding)
      setup_blocks.each do |setup_block|
        setup_block.bind(binding).call
      end
    end

    def run_all_teardown_blocks(binding)
      teardown_blocks.reverse.each do |teardown_block|
        teardown_block.bind(binding).call
      end
      self.parent.run_all_teardown_blocks(binding) if am_subcontext?
    end

    def print_should_eventuallys
      should_eventuallys.each do |should|
        test_name = [full_name, "should", "#{should[:name]}. "].flatten.join(' ')
        puts "  * DEFERRED: " + test_name
      end
    end

    def build
      shoulds.each do |should|
        create_test_from_should_hash(should)
      end

      subcontexts.each { |context| context.build }

      print_should_eventuallys
    end

    def method_missing(method, *args, &blk)
      test_unit_class.send(method, *args, &blk)
    end

  end
end