module Shoulda
  module Matchers
    module ActiveRecord
      # The `validate_uniqueness_of` matcher tests usage of the
      # `validates_uniqueness_of` validation. It first checks for an existing
      # instance of your model in the database, creating one if necessary. It
      # then takes a new instance of that model and asserts that it fails
      # validation if the attribute or attributes you've specified in the
      # validation are set to values which are the same as those of the
      # pre-existing record (thereby failing the uniqueness check).
      #
      #     class Post < ActiveRecord::Base
      #       validates_uniqueness_of :permalink
      #     end
      #
      #     # RSpec
      #     describe Post do
      #       it { should validate_uniqueness_of(:permalink) }
      #     end
      #
      #     # Test::Unit
      #     class PostTest < ActiveSupport::TestCase
      #       should validate_uniqueness_of(:permalink)
      #     end
      #
      # #### Caveat
      #
      # This matcher works a bit differently than other matchers. As noted
      # before, it will create an instance of your model if one doesn't already
      # exist. Sometimes this step fails, especially if you have database-level
      # restrictions on any attributes other than the one which is unique. In
      # this case, the solution is to populate these attributes with values
      # before you call `validate_uniqueness_of`.
      #
      # For example, say you have the following migration and model:
      #
      #     class CreatePosts < ActiveRecord::Migration
      #       def change
      #         create_table :posts do |t|
      #           t.string :title
      #           t.text :content, null: false
      #         end
      #       end
      #     end
      #
      #     class Post < ActiveRecord::Base
      #       validates :title, uniqueness: true
      #     end
      #
      # You may be tempted to test the model like this:
      #
      #     describe Post do
      #       it { should validate_uniqueness_of(:title) }
      #     end
      #
      # However, running this test will fail with something like:
      #
      #     Failures:
      #
      #       1) Post should require case sensitive unique value for title
      #          Failure/Error: it { should validate_uniqueness_of(:title) }
      #          ActiveRecord::StatementInvalid:
      #            SQLite3::ConstraintException: posts.content may not be NULL: INSERT INTO "posts" ("title") VALUES (?)
      #
      # This happens because `validate_uniqueness_of` tries to create a new post
      # but cannot do so because of the `content` attribute: though unrelated to
      # this test, it nevertheless needs to be filled in. The solution is to
      # build a custom Post object ahead of time with `content` filled in:
      #
      #     describe Post do
      #       describe "validations" do
      #         subject { Post.new(content: 'Here is the content') }
      #         it { should validate_uniqueness_of(:title) }
      #       end
      #     end
      #
      # Or, if you're using
      # [FactoryGirl](http://github.com/thoughtbot/factory_girl) and you have a
      # `post` factory defined which automatically fills in `content`, you can
      # say:
      #
      #     describe Post do
      #       describe "validations" do
      #         subject { FactoryGirl.build(:post) }
      #         it { should validate_uniqueness_of(:title) }
      #       end
      #     end
      #
      # #### Qualifiers
      #
      # ##### with_message
      #
      # Use `with_message` if you are using a custom validation message.
      #
      #     class Post < ActiveRecord::Base
      #       validates_uniqueness_of :title, message: 'Please choose another title'
      #     end
      #
      #     # RSpec
      #     describe Post do
      #       it do
      #         should validate_uniqueness_of(:title).
      #           with_message('Please choose another title')
      #       end
      #     end
      #
      #     # Test::Unit
      #     class PostTest < ActiveSupport::TestCase
      #       should validate_uniqueness_of(:title).
      #         with_message('Please choose another title')
      #     end
      #
      # ##### scoped_to
      #
      # Use `scoped_to` to test usage of the `:scope` option. This asserts that
      # a new record fails validation if not only the primary attribute is not
      # unique, but the scoped attributes are not unique either.
      #
      #     class Post < ActiveRecord::Base
      #       validates_uniqueness_of :slug, scope: :user_id
      #     end
      #
      #     # RSpec
      #     describe Post do
      #       it { should validate_uniqueness_of(:slug).scoped_to(:journal_id) }
      #     end
      #
      #     # Test::Unit
      #     class PostTest < ActiveSupport::TestCase
      #       should validate_uniqueness_of(:slug).scoped_to(:journal_id)
      #     end
      #
      # ##### case_insensitive
      #
      # Use `case_insensitive` to test usage of the `:case_sensitive` option
      # with a false value. This asserts that the uniquable attributes fail
      # validation even if their values are a different case than corresponding
      # attributes in the pre-existing record.
      #
      #     class Post < ActiveRecord::Base
      #       validates_uniqueness_of :key, case_sensitive: false
      #     end
      #
      #     # RSpec
      #     describe Post do
      #       it { should validate_uniqueness_of(:key).case_insensitive }
      #     end
      #
      #     # Test::Unit
      #     class PostTest < ActiveSupport::TestCase
      #       should validate_uniqueness_of(:key).case_insensitive
      #     end
      #
      # ##### allow_nil
      #
      # Use `allow_nil` to assert that the attribute allows nil.
      #
      #     class Post < ActiveRecord::Base
      #       validates_uniqueness_of :author_id, allow_nil: true
      #     end
      #
      #     # RSpec
      #     describe Post do
      #       it { should validate_uniqueness_of(:author_id).allow_nil }
      #     end
      #
      #     # Test::Unit
      #     class PostTest < ActiveSupport::TestCase
      #       should validate_uniqueness_of(:author_id).allow_nil
      #     end
      #
      # @return [ValidateUniquenessOfMatcher]
      #
      # ##### allow_blank
      #
      # Use `allow_blank` to assert that the attribute allows a blank value.
      #
      #     class Post < ActiveRecord::Base
      #       validates_uniqueness_of :author_id, allow_blank: true
      #     end
      #
      #     # RSpec
      #     describe Post do
      #       it { should validate_uniqueness_of(:author_id).allow_blank }
      #     end
      #
      #     # Test::Unit
      #     class PostTest < ActiveSupport::TestCase
      #       should validate_uniqueness_of(:author_id).allow_blank
      #     end
      #
      # @return [ValidateUniquenessOfMatcher]
      #
      def validate_uniqueness_of(attr)
        ValidateUniquenessOfMatcher.new(attr)
      end

      # @private
      class ValidateUniquenessOfMatcher < ActiveModel::ValidationMatcher
        include ActiveModel::Helpers

        def initialize(attribute)
          super(attribute)
          @options = {}
        end

        def scoped_to(*scopes)
          @options[:scopes] = [*scopes].flatten
          self
        end

        def with_message(message)
          @expected_message = message
          self
        end

        def case_insensitive
          @options[:case_insensitive] = true
          self
        end

        def allow_nil
          @options[:allow_nil] = true
          self
        end

        def allow_blank
          @options[:allow_blank] = true
          self
        end

        def description
          result = "require "
          result << "case sensitive " unless @options[:case_insensitive]
          result << "unique value for #{@attribute}"
          result << " scoped to #{@options[:scopes].join(', ')}" if @options[:scopes].present?
          result
        end

        def matches?(subject)
          @original_subject = subject
          @subject = subject.class.new
          @expected_message ||= :taken

          set_scoped_attributes &&
            validate_everything_except_duplicate_nils_or_blanks? &&
            validate_after_scope_change? &&
            allows_nil? &&
            allows_blank?
        ensure
          Uniqueness::TestModels.remove_all
        end

        private

        def allows_nil?
          if @options[:allow_nil]
            ensure_nil_record_in_database
            allows_value_of(nil, @expected_message)
          else
            true
          end
        end

        def allows_blank?
          if @options[:allow_blank]
            ensure_blank_record_in_database
            allows_value_of('', @expected_message)
          else
            true
          end
        end

        def existing_record
          @existing_record ||= first_instance
        end

        def first_instance
          @subject.class.first || create_record_in_database
        end

        def ensure_nil_record_in_database
          unless existing_record_is_nil?
            create_record_in_database(nil_value: true)
          end
        end

        def ensure_blank_record_in_database
          unless existing_record_is_blank?
            create_record_in_database(blank_value: true)
          end
        end

        def existing_record_is_nil?
          @existing_record.present? && existing_value.nil?
        end

        def existing_record_is_blank?
          @existing_record.present? && existing_value.strip == ''
        end

        def create_record_in_database(options = {})
          @original_subject.tap do |instance|
            instance.__send__("#{@attribute}=", value_for_new_record(options))
            ensure_secure_password_set(instance)
            instance.save(validate: false)
            @created_record = instance
          end
        end

        def ensure_secure_password_set(instance)
          if has_secure_password?
            instance.password = "password"
            instance.password_confirmation = "password"
          end
        end

        def value_for_new_record(options = {})
          case
            when options[:nil_value] then nil
            when options[:blank_value] then ''
            else 'a'
          end
        end

        def has_secure_password?
          @subject.class.ancestors.map(&:to_s).include?('ActiveModel::SecurePassword::InstanceMethodsOnActivation')
        end

        def set_scoped_attributes
          if @options[:scopes].present?
            @options[:scopes].all? do |scope|
              setter = :"#{scope}="
              if @subject.respond_to?(setter)
                @subject.__send__(setter, existing_record.__send__(scope))
                true
              else
                @failure_message = "#{class_name} doesn't seem to have a #{scope} attribute."
                false
              end
            end
          else
            true
          end
        end

        def validate_everything_except_duplicate_nils_or_blanks?
          if (@options[:allow_nil] && existing_value.nil?) ||
             (@options[:allow_blank] && existing_value.blank?)
            create_record_with_value
          end

          disallows_value_of(existing_value, @expected_message)
        end

        def create_record_with_value
          @existing_record = create_record_in_database
        end

        def model_class?(model_name)
          model_name.constantize.ancestors.include?(::ActiveRecord::Base)
        rescue NameError
          false
        end

        def validate_after_scope_change?
          if @options[:scopes].blank?
            true
          else
            all_records = @subject.class.all
            @options[:scopes].all? do |scope|
              previous_value = all_records.map(&scope).max

              # Assume the scope is a foreign key if the field is nil
              previous_value ||= correct_type_for_column(@subject.class.columns_hash[scope.to_s])

              next_value = next_value_for(scope, previous_value)

              @subject.__send__("#{scope}=", next_value)

              if allows_value_of(existing_value, @expected_message)
                @subject.__send__("#{scope}=", previous_value)

                @failure_message_when_negated <<
                  " (with different value of #{scope})"
                true
              else
                @failure_message << " (with different value of #{scope})"
                false
              end
            end
          end
        end

        def correct_type_for_column(column)
          if column.type == :string
            '0'
          elsif column.type == :datetime
            DateTime.now
          elsif column.type == :uuid
            SecureRandom.uuid
          else
            0
          end
        end

        def next_value_for(scope, previous_value)
          if @subject.class.respond_to?(:defined_enums) && @subject.defined_enums[scope.to_s]
            available_values = available_enum_values_for(scope, previous_value)
            available_values.keys.last
          elsif scope.to_s =~ /_type$/ && model_class?(previous_value)
            Uniqueness::TestModels.create(previous_value).to_s
          elsif previous_value.respond_to?(:next)
            previous_value.next
          elsif previous_value.respond_to?(:to_datetime)
            previous_value.to_datetime.next
          else
            previous_value.to_s.next
          end
        end

        def available_enum_values_for(scope, previous_value)
          @subject.defined_enums[scope.to_s].reject do |key, _|
            key == previous_value
          end
        end

        def class_name
          @subject.class.name
        end

        def existing_value
          value = existing_record.__send__(@attribute)
          if @options[:case_insensitive] && value.respond_to?(:swapcase!)
            value.swapcase!
          end
          value
        end
      end
    end
  end
end