module Enumerable

def as_json(options = nil) # :nodoc:

:nodoc: 
def as_json(options = nil) # :nodoc:
  to_a.as_json(options)
end

def compact_blank

# => { b: 1, f: true }
{ a: "", b: 1, c: nil, d: [], e: false, f: true }.compact_blank

When called on a +Hash+, returns a new +Hash+ without the blank values.

# => [1]
Set.new([nil, "", 1, false]).compact_blank

# => [1, 2, true]
[1, "", nil, 2, " ", [], {}, false, true].compact_blank

Uses Object#blank? for determining if an item is blank.
Returns a new +Array+ without the blank items. 
def compact_blank
  reject(&:blank?)
end

def exclude?(object)

collection does not include the object.
The negative of the Enumerable#include?. Returns +true+ if the 
def exclude?(object)
  !include?(object)
end

def excluding(*elements)

# => {foo: 1, baz: 3}
{foo: 1, bar: 2, baz: 3}.excluding :bar

# => ["David", "Rafael"]
["David", "Rafael", "Aaron", "Todd"].excluding %w[ Aaron Todd ]

# => ["David", "Rafael"]
["David", "Rafael", "Aaron", "Todd"].excluding "Aaron", "Todd"

Returns a copy of the enumerable excluding the specified elements. 
def excluding(*elements)
  elements.flatten!(1)
  reject { |element| elements.include?(element) }
end

def in_order_of(key, series)

If the Enumerable has additional elements that aren't named in the +series+, these are not included in the result.
If the +series+ include keys that have no corresponding element in the Enumerable, these are ignored.

# => [ Person.find(1), Person.find(5), Person.find(3) ]
[ Person.find(5), Person.find(3), Person.find(1) ].in_order_of(:id, [ 1, 5, 3 ])

objects in the original enumerable.
Returns a new +Array+ where the order has been set to that provided in the +series+, based on the +key+ of the 
def in_order_of(key, series)
  group_by(&key).values_at(*series).flatten(1).compact
end

def including(*elements)

# => ["David", "Rafael", "Aaron", "Todd"]
["David", "Rafael"].including %w[ Aaron Todd ]

# => [ 1, 2, 3, 4, 5 ]
[ 1, 2, 3 ].including(4, 5)

Returns a new array that includes the passed elements. 
def including(*elements)
  to_a.including(*elements)
end

def index_by

# => { "Chade- Fowlersburg-e" => , "David Heinemeier Hansson" => , ...}
people.index_by { |person| "#{person.first_name} #{person.last_name}" }

# => { "nextangle" => , "chade-" => , ...}
people.index_by(&:login)

element as the value.
Convert an enumerable to a hash, using the block result as the key and the 
def index_by
  if block_given?
    result = {}
    each { |elem| result[yield(elem)] = elem }
    result
  else
    to_enum(:index_by) { size if respond_to?(:size) }
  end
end

def index_with(default = (no_default = true))

# => { created_at: 2020-03-09 22:31:47, updated_at: 2020-03-09 22:31:47 }
%i( created_at updated_at ).index_with(Time.now)

for all elements:
If an argument is passed instead of a block, it will be used as the value

# => { title: "hey there", body: "what's up?" }
%i( title body ).index_with { |attr_name| post.public_send(attr_name) }

post = Post.new(title: "hey there", body: "what's up?")

result as the value.
Convert an enumerable to a hash, using the element as the key and the block 
def index_with(default = (no_default = true))
  if block_given?
    result = {}
    each { |elem| result[elem] = yield(elem) }
    result
  elsif no_default
    to_enum(:index_with) { size if respond_to?(:size) }
  else
    result = {}
    each { |elem| result[elem] = default }
    result
  end
end

def many?

if more than one person is over 26.
much like any?, so people.many? { |p| p.age > 26 } returns +true+
equivalent to enum.to_a.size > 1. Can be called with a block too,
Returns +true+ if the enumerable has more than 1 element. Functionally 
def many?
  cnt = 0
  if block_given?
    any? do |*args|
      cnt += 1 if yield(*args)
      cnt > 1
    end
  else
    any? { (cnt += 1) > 1 }
  end
end

def maximum(key)

payments.maximum(:price) # => 15
payments = [Payment.new(5), Payment.new(15), Payment.new(10)]

Calculates the maximum from the extracted elements. 
def maximum(key)
  map(&key).max
end

def minimum(key)

payments.minimum(:price) # => 5
payments = [Payment.new(5), Payment.new(15), Payment.new(10)]

Calculates the minimum from the extracted elements. 
def minimum(key)
  map(&key).min
end

def pick(*keys)

# => [1, "David"]
[{ id: 1, name: "David" }, { id: 2, name: "Rafael" }].pick(:id, :name)

# => "David"
[{ name: "David" }, { name: "Rafael" }, { name: "Aaron" }].pick(:name)

Extract the given key from the first element in the enumerable. 
def pick(*keys)
  return if none?
  if keys.many?
    keys.map { |key| first[key] }
  else
    first[keys.first]
  end
end

def pluck(*keys)

# => [[1, "David"], [2, "Rafael"]]
[{ id: 1, name: "David" }, { id: 2, name: "Rafael" }].pluck(:id, :name)

# => ["David", "Rafael", "Aaron"]
[{ name: "David" }, { name: "Rafael" }, { name: "Aaron" }].pluck(:name)

Extract the given key from each element in the enumerable. 
def pluck(*keys)
  if keys.many?
    map { |element| keys.map { |key| element[key] } }
  else
    key = keys.first
    map { |element| element[key] }
  end
end

def sole

{ a: 1, b: 2 }.sole # => Enumerable::SoleItemExpectedError: multiple items found
Set.new.sole # => Enumerable::SoleItemExpectedError: no item found
["x"].sole # => "x"

than one item, raises +Enumerable::SoleItemExpectedError+.
Returns the sole item in the enumerable. If there are no items, or more 
def sole
  case count
  when 1   then return first # rubocop:disable Style/RedundantReturn
  when 0   then raise ActiveSupport::EnumerableCoreExt::SoleItemExpectedError, "no item found"
  when 2.. then raise ActiveSupport::EnumerableCoreExt::SoleItemExpectedError, "multiple items found"
  end
end