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# frozen_string_literal: true
module TTY
class Prompt
class Paginator
DEFAULT_PAGE_SIZE = 6
# The 0-based index of the first item on this page
attr_accessor :start_index
# The 0-based index of the last item on this page
attr_reader :end_index
# The 0-based index of the active item on this page
attr_reader :current_index
# The 0-based index of the previously active item on this page
attr_reader :last_index
# Create a Paginator
#
# @api private
def initialize(**options)
@last_index = Array(options[:default]).flatten.first || 0
@per_page = options[:per_page]
@start_index = Array(options[:default]).flatten.first
end
# Reset current page indexes
#
# @api private
def reset!
@start_index = nil
@end_index = nil
end
# Check if page size is valid
#
# @raise [InvalidArgument]
#
# @api private
def check_page_size!
raise InvalidArgument, "per_page must be > 0" if @per_page < 1
end
# Paginate collection given an active index
#
# @param [Array[Choice]] list
# a collection of choice items
# @param [Integer] active
# current choice active index
# @param [Integer] per_page
# number of choice items per page
#
# @return [Enumerable]
# the list between start and end index
#
# @api public
def paginate(list, active, per_page = nil, &block)
current_index = active - 1
default_size = (list.size <= DEFAULT_PAGE_SIZE ? list.size : DEFAULT_PAGE_SIZE)
@per_page = @per_page || per_page || default_size
check_page_size!
@start_index ||= (current_index / @per_page) * @per_page
@end_index ||= @start_index + @per_page - 1
# Don't paginate short lists
if list.size <= @per_page
@start_index = 0
@end_index = list.size - 1
if block
return list.each_with_index(&block)
else
return list.each_with_index.to_enum
end
end
step = (current_index - @last_index).abs
if current_index > @last_index # going up
if current_index >= @end_index && current_index < list.size - 1
last_page = list.size - @per_page
@start_index = [@start_index + step, last_page].min
end
elsif current_index < @last_index # going down
if current_index <= @start_index && current_index > 0
@start_index = [@start_index - step, 0].max
end
end
# Cycle list
if current_index.zero?
@start_index = 0
elsif current_index == list.size - 1
@start_index = list.size - 1 - (@per_page - 1)
end
@end_index = @start_index + (@per_page - 1)
@last_index = current_index
sliced_list = list[@start_index..@end_index]
page_range = (@start_index..@end_index)
return sliced_list.zip(page_range).to_enum unless block_given?
sliced_list.each_with_index do |item, index|
block[item, @start_index + index]
end
end
end # Paginator
end # Prompt
end # TTY
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