TrustYouTest

##
# The IncludedResourceParams class is responsible for parsing a string containing
# a comma separated list of associated resources to include with a request. See
# http://jsonapi.org/format/#fetching-includes for additional details although
# this is not required knowledge for the task at hand.
#
# Our API requires specific inclusion of related resourses - that is we do NOT
# want to support wildcard inclusion (e.g. `foo.*`)
#
# The IncludedResourceParams class has three public methods making up its API.
#
# [included_resources]
#   returns an array of non-wildcard included elements.
# [has_included_resources?]
#   Returns true if our supplied param has included resources, false otherwise.
# [model_includes]
#   returns an array suitable to supply to ActiveRecord's `includes` method
#   (http://guides.rubyonrails.org/active_record_querying.html#eager-loading-multiple-associations)
#   The included_resources should be transformed as specified in the unit tests
#   included herein.
#
# All three public methods have unit tests written below that must pass. You are
# free to add additional classes/modules as necessary and/or private methods
# within the IncludedResourceParams class.
#
# Feel free to use the Ruby standard libraries available on codepad in your
# solution.
#
# Create your solution as a private fork, and send us the URL.
#
class IncludedResourceParams

  COMMA_ENDED          = /((\w{1,}\.){1,}\*{1,},)/.freeze
  COMMA_STARTED        = /(,(\w{1,}\.){1,}\*{1,})/.freeze
  NO_COMMA             = /((\w{1,}\.){1,}\*{1,})/.freeze
  WILDCARD_REGEX       = [COMMA_ENDED, COMMA_STARTED, NO_COMMA].join("|").freeze  

  def initialize(include_param)
    @include_param = include_param
  end

  ##
  # Does our IncludedResourceParams instance actually have any valid included
  # resources after parsing?
  #
  # @return [Boolean] whether this instance has included resources
  def has_included_resources?
    included_resources.any?
  end

  ##
  # Fetches the included resourcs as an Array containing only non-wildcard
  # resource specifiers.
  #
  # @example nil
  #   IncludedResourceParams.new(nil).included_resources => []
  #
  # @example "foo,foo.bar,baz.*"
  #   IncludedResourceParams.new("foo,bar,baz.*").included_resources => ["foo", "foo.bar"]   NOTE: I believe there's a typo here the example is "foo,foo.bar,baz.*" NOT "foo,bar,baz.*"
  #
  # @return [Array] an Array of Strings parsed from the include param with
  # wildcard includes removed
  def included_resources
    # only not empty string passes
    return Array.new if @include_param.nil?
    
    return Array.new unless @include_param.is_a?(String) && !@include_param.to_s.strip.empty?
    @_included_resources ||= @include_param.gsub(Regexp.new(WILDCARD_REGEX), "").split(",")
  end

  ##
  # Converts the resources to be included from their JSONAPI representation to
  # a structure compatible with ActiveRecord's `includes` methods. This can/should
  # be an Array in all cases. Does not do any verification that the resources
  # specified for inclusion are actual ActiveRecord classes.
  #
  # @example nil
  #   IncludedResourceParams.new(nil).model_includes => []
  #
  # @example "foo"
  #   IncludedResourceParams.new("foo").model_includes => [:foo]
  #
  # @see Following unit tests
  #
  # @return [Array] an Array of Symbols and/or Hashes compatible with ActiveRecord
  # `includes`
  def model_includes
    return Array.new unless included_resources.any?
    @_model_includes ||= generate_model_resources
  end

  private

  def generate_model_resources
    resources = Array.new
    included_resources.each do |element|
      element = element.split(".").map(&:to_sym)
      merge_elements!(resources, element)
    end
    resources
  end

  def merge_elements!(resources, element)
    matched = false

    resources.map.with_index do |resource, index|
      if element.empty?
        matched = true
        break
      end
      if resource.is_a? Symbol
        if resource == element.first
          matched = true
          element.size == 1 ? resources[index] = element.first : resources[index] = element.reverse.reduce { |x, y| { y => [x] } }
        end
      else
        if resource.keys.include? element.first
          matched = true
          resources[index][element.first] = merge_elements!(resource.values.flatten, element.drop(1))
        else
          next
        end
      end
    end
    if matched == false
      resources << element.reverse.reduce { |x, y| { y => [x] } }
    end
    resources
  end  
end

require 'test/unit'
class TestIncludedResourceParams < Test::Unit::TestCase
  # Tests for #has_included_resources?
  def test_has_included_resources_is_false_when_nil
    r = IncludedResourceParams.new(nil)
    assert r.has_included_resources? == false
  end

  def test_has_included_resources_is_false_when_only_wildcards
    include_string = 'foo.**'
    r = IncludedResourceParams.new(include_string)
    assert r.has_included_resources? == false
  end

  def test_has_included_resources_is_true_with_non_wildcard_params
    include_string = 'foo'
    r = IncludedResourceParams.new(include_string)
    assert r.has_included_resources?
  end

  def test_has_included_resources_is_true_with_both_wildcard_and_non_params
    include_string = 'foo,bar.**'
    r = IncludedResourceParams.new(include_string)
    assert r.has_included_resources?
  end

  # Tests for #included_resources
  def test_included_resources_always_returns_array
    r = IncludedResourceParams.new(nil)
    assert r.included_resources == []
  end

  def test_included_resources_returns_only_non_wildcards
    r = IncludedResourceParams.new('foo,foo.bar,baz.*,bat.**')
    assert r.included_resources == ['foo', 'foo.bar']
  end

  # Tests for #model_includes
  def test_model_includes_when_params_nil
    assert IncludedResourceParams.new(nil).model_includes == []
  end

  def test_model_includes_one_single_level_resource
    assert IncludedResourceParams.new('foo').model_includes == [:foo]
  end

  def test_model_includes_multiple_single_level_resources
    assert IncludedResourceParams.new('foo,bar').model_includes == [:foo, :bar]
  end

  def test_model_includes_single_two_level_resource
    assert IncludedResourceParams.new('foo.bar').model_includes == [{:foo => [:bar]}]
  end

  def test_model_includes_multiple_two_level_resources
    assert IncludedResourceParams.new('foo.bar,foo.bat').model_includes == [{:foo => [:bar, :bat]}]
    assert IncludedResourceParams.new('foo.bar,baz.bat').model_includes == [{:foo => [:bar]}, {:baz => [:bat]}]
  end

  def test_model_includes_three_level_resources
    assert IncludedResourceParams.new('foo.bar.baz').model_includes == [{:foo => [{:bar => [:baz]}]}]
  end

  def test_model_includes_multiple_three_level_resources
    assert IncludedResourceParams.new('foo.bar.baz,foo,foo.bar.bat,bar').model_includes == [{:foo => [{:bar => [:baz, :bat]}]}, :bar]
  end
end