module RSpec
  module Matchers
    module BuiltIn
      class Have
        def initialize(expected, relativity=:exactly)
          @expected = case expected
                      when :no then 0
                      when String then expected.to_i
                      else expected
                      end
          @relativity = relativity
          @actual = @collection_name = @plural_collection_name = nil
        end

        def relativities
          @relativities ||= {
            :exactly => "",
            :at_least => "at least ",
            :at_most => "at most "
          }
        end

        def matches?(collection_or_owner)
          collection = determine_collection(collection_or_owner)
          query_method = determine_query_method(collection)
          raise not_a_collection unless query_method
          @actual = collection.send(query_method)
          case @relativity
          when :at_least then @actual >= @expected
          when :at_most  then @actual <= @expected
          else                @actual == @expected
          end
        end
        alias == matches?

        def determine_collection(collection_or_owner)
          if collection_or_owner.respond_to?(@collection_name)
            collection_or_owner.send(@collection_name, *@args, &@block)
          elsif (@plural_collection_name && collection_or_owner.respond_to?(@plural_collection_name))
            collection_or_owner.send(@plural_collection_name, *@args, &@block)
          elsif determine_query_method(collection_or_owner)
            collection_or_owner
          else
            collection_or_owner.send(@collection_name, *@args, &@block)
          end
        end

        def determine_query_method(collection)
          [:size, :length, :count].detect {|m| collection.respond_to?(m)}
        end

        def not_a_collection
          "expected #{@collection_name} to be a collection but it does not respond to #length, #size or #count"
        end

        def failure_message_for_should
          "expected #{relative_expectation} #{@collection_name}, got #{@actual}"
        end

        def failure_message_for_should_not
          if @relativity == :exactly
            return "expected target not to have #{@expected} #{@collection_name}, got #{@actual}"
          elsif @relativity == :at_most
            return <<-EOF
Isn't life confusing enough?
Instead of having to figure out the meaning of this:
  should_not have_at_most(#{@expected}).#{@collection_name}
We recommend that you use this instead:
  should have_at_least(#{@expected + 1}).#{@collection_name}
EOF
          elsif @relativity == :at_least
            return <<-EOF
Isn't life confusing enough?
Instead of having to figure out the meaning of this:
  should_not have_at_least(#{@expected}).#{@collection_name}
We recommend that you use this instead:
  should have_at_most(#{@expected - 1}).#{@collection_name}
EOF
          end
        end

        def description
          "have #{relative_expectation} #{@collection_name}"
        end

        def respond_to?(m)
          @expected.respond_to?(m) || super
        end

        private

        def method_missing(method, *args, &block)
          @collection_name = method
          if inflector = (defined?(ActiveSupport::Inflector) && ActiveSupport::Inflector.respond_to?(:pluralize) ? ActiveSupport::Inflector : (defined?(Inflector) ? Inflector : nil))
            @plural_collection_name = inflector.pluralize(method.to_s)
          end
          @args = args
          @block = block
          self
        end

        def relative_expectation
          "#{relativities[@relativity]}#{@expected}"
        end
      end
    end
  end
end