Class: Narabikae::Position

Inherits:
Object
  • Object
show all
Defined in:
lib/narabikae/position.rb

Instance Method Summary collapse

Constructor Details

#initialize(record, option) ⇒ Position

Initializes a new instance of the Position class.

Parameters:

  • record (Object) —

    Active Record object.

  • option (Option) 


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# File 'lib/narabikae/position.rb', line 7

def initialize(record, option)
  @record = record
  @option = option
end

Instance Method Details

#create_last_position ⇒ String

Generates a new key for the last position

Returns:

  • (String) —

    The newly generated key for the last position.



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# File 'lib/narabikae/position.rb', line 15

def create_last_position
  FractionalIndexer.generate_key(prev_key: current_last_position)
end

#find_position_after(target, **args) ⇒ String?

Finds the position after the specified target. If generated key is invalid(ex: it already exists), a new key is generated until the challenge count reaches the limit. challenge count is 10 by default.

Parameters:

  • target (#send(field))
  • args (Hash) —

    Additional arguments.

Options Hash (**args):

  • :challenge (Integer) —

    The number of times to attempt finding a valid position.

Returns:

  • (String, nil) —

    The generated key for the position after the target, or nil if no valid position is found.



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# File 'lib/narabikae/position.rb', line 28

def find_position_after(target, **args)
  merged_args = { challenge: 10 }.merge(args)
  # when target is nil, try to generate key from the last position
  key = FractionalIndexer.generate_key(
          prev_key: target&.send(option.field) || current_last_position
        )
  return key if valid?(key)

  (merged_args[:challenge] || 0).times do
    key += random_fractional
    return key if valid?(key)
  end

  nil
rescue FractionalIndexer::Error
  nil
end

#find_position_before(target, **args) ⇒ String?

Finds the position before the target position. If generated key is invalid(ex: it already exists), a new key is generated until the challenge count reaches the limit. challenge count is 10 by default.

Examples:

position = Position.new
position.find_position_before(target, challenge: 5)

Parameters:

  • target (#send(field))
  • args (Hash) —

    Additional arguments.

Options Hash (**args):

  • :challenge (Integer) —

    The number of times to attempt finding a valid position.

Returns:

  • (String, nil) —

    The generated key for the position before the target, or nil if no valid position is found.



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# File 'lib/narabikae/position.rb', line 60

def find_position_before(target, **args)
  merged_args = { challenge: 10 }.merge(args)
  # when target is nil, try to generate key from the first position
  key = FractionalIndexer.generate_key(
          next_key: target&.send(option.field) || current_first_position
        )
  return key if valid?(key)

  (merged_args[:challenge] || 0).times do
    key += random_fractional
    return key if valid?(key)
  end

  nil
rescue FractionalIndexer::Error
  nil
end

#find_position_between(prev_target, next_target, **args) ⇒ string?

Finds the position between two targets.

Parameters:

  • prev_target (#send(field)) —

    The previous target.

  • next_target (#send(field)) —

    The next target.

  • args (Hash) —

    Additional arguments.

Options Hash (**args):

  • :challenge (Integer) —

    The number of times to attempt finding a valid position.

Returns:

  • (string, nil) —

    The position between the two targets, or nil if no valid position is found.



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# File 'lib/narabikae/position.rb', line 85

def find_position_between(prev_target, next_target, **args)
  return find_position_before(next_target, **args) if prev_target.blank?
  return find_position_after(prev_target, **args)  if next_target.blank?

  merged_args = { challenge: 10 }.merge(args)

  prev_key, next_key = [ prev_target.send(option.field), next_target.send(option.field) ].minmax
  key = FractionalIndexer.generate_key(
          prev_key: prev_key,
          next_key: next_key,
        )
  return key if valid?(key)

  (merged_args[:challenge] || 0).times do
    key += random_fractional
    return key if valid?(key)
  end

  nil
rescue FractionalIndexer::Error
  nil
end