TrustYou_test.rb

##
# 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
  def initialize(include_param)
    @include_param = []
    return unless include_param.is_a? String
    @include_param = include_param.split(',')
  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"]
  #
  # @return [Array] an Array of Strings parsed from the include param with
  # wildcard includes removed
  def included_resources
    @include_param.reject { |param| param.include? '*' }
  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
    includes_hash = includes_strings_to_hash(included_resources)
    result = []
    includes_hash.keys.each do |k|
      parsed_key = parse_key(k, includes_hash[k])
      result.push(parsed_key)
    end
    result
  end

  ##
  # Converts an array of strings using JSONAPI representation to
  # a standard Ruby hash object
  #
  # @example "foo.bar,foo.baz.bat"
  #   includes_strings_to_hash(['foo.bar','foo.baz.bat']) =>
  #     {:foo=>{:bar=>{}, :baz=>{:bat=>{}}}}
  #
  # @return [Hash] a Hash with symbol keys and hash values
  def includes_strings_to_hash(includes_strings)
    model_hash = {}
    includes_strings.each do |i_s|
      current = model_hash
      hierarchy = i_s.split('.').map(&:to_sym)
      hierarchy.each do |val|
        current[val] = {} unless current.key? val
        current = current[val]
      end
    end
    model_hash
  end

  ##
  # Constructs an ActiveRecord compatible hash, recursively
  #
  # @param [Symbol] key The original key
  #
  # @param [Hash] key_hash The original key's value
  #
  # @example ":foo, {bar: {}, baz: {bat: {}}"
  #   parse_key(:foo, {bar: {}, baz: {bat: {}}}) =>
  #     {:foo=>[:bar, {:baz=>[:bat]}]}
  #
  # @return [Symbol, Hash] A symbol if the key's hash is empty, or a Hash.
  def parse_key(key, key_hash)
    return key if key_hash.keys.empty?
    values = []
    key_hash.keys.each do |k|
      this_key = parse_key(k, key_hash[k])
      values.push(this_key)
    end
    { key => values }
  end

  private :includes_strings_to_hash, :parse_key
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