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require 'strscan'
module ActiveSupport
class Duration
# Parses a string formatted according to ISO 8601 Duration into the hash.
#
# See {ISO 8601}[http://en.wikipedia.org/wiki/ISO_8601#Durations] for more information.
#
# This parser allows negative parts to be present in pattern.
class ISO8601Parser # :nodoc:
class ParsingError < ::ArgumentError; end
PERIOD_OR_COMMA = /\.|,/
PERIOD = '.'.freeze
COMMA = ','.freeze
SIGN_MARKER = /\A\-|\+|/
DATE_MARKER = /P/
TIME_MARKER = /T/
DATE_COMPONENT = /(\-?\d+(?:[.,]\d+)?)(Y|M|D|W)/
TIME_COMPONENT = /(\-?\d+(?:[.,]\d+)?)(H|M|S)/
DATE_TO_PART = { 'Y' => :years, 'M' => :months, 'W' => :weeks, 'D' => :days }
TIME_TO_PART = { 'H' => :hours, 'M' => :minutes, 'S' => :seconds }
DATE_COMPONENTS = [:years, :months, :days]
TIME_COMPONENTS = [:hours, :minutes, :seconds]
attr_reader :parts, :scanner
attr_accessor :mode, :sign
def initialize(string)
@scanner = StringScanner.new(string)
@parts = {}
@mode = :start
@sign = 1
end
def parse!
while !finished?
case mode
when :start
if scan(SIGN_MARKER)
self.sign = (scanner.matched == '-') ? -1 : 1
self.mode = :sign
else
raise_parsing_error
end
when :sign
if scan(DATE_MARKER)
self.mode = :date
else
raise_parsing_error
end
when :date
if scan(TIME_MARKER)
self.mode = :time
elsif scan(DATE_COMPONENT)
parts[DATE_TO_PART[scanner[2]]] = number * sign
else
raise_parsing_error
end
when :time
if scan(TIME_COMPONENT)
parts[TIME_TO_PART[scanner[2]]] = number * sign
else
raise_parsing_error
end
end
end
validate!
parts
end
private
def finished?
scanner.eos?
end
# Parses number which can be a float with either comma or period.
def number
scanner[1] =~ PERIOD_OR_COMMA ? scanner[1].tr(COMMA, PERIOD).to_f : scanner[1].to_i
end
def scan(pattern)
scanner.scan(pattern)
end
def raise_parsing_error(reason = nil)
raise ParsingError, "Invalid ISO 8601 duration: #{scanner.string.inspect} #{reason}".strip
end
# Checks for various semantic errors as stated in ISO 8601 standard.
def validate!
raise_parsing_error('is empty duration') if parts.empty?
# Mixing any of Y, M, D with W is invalid.
if parts.key?(:weeks) && (parts.keys & DATE_COMPONENTS).any?
raise_parsing_error('mixing weeks with other date parts not allowed')
end
# Specifying an empty T part is invalid.
if mode == :time && (parts.keys & TIME_COMPONENTS).empty?
raise_parsing_error('time part marker is present but time part is empty')
end
fractions = parts.values.reject(&:zero?).select { |a| (a % 1) != 0 }
unless fractions.empty? || (fractions.size == 1 && fractions.last == @parts.values.reject(&:zero?).last)
raise_parsing_error '(only last part can be fractional)'
end
return true
end
end
end
end
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