Re: Time Window (#144)

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by Brian Candler

Write a Ruby class which can tell you whether the current time (or any given
time) is within a particular "time window". Time windows are defined by strings
in the following format:

# 0700-0900 # every day between these times
# Sat Sun # all day Sat and Sun, no other times
# Sat Sun 0700-0900 # 0700-0900 on Sat and Sun only
# Mon-Fri 0700-0900 # 0700-0900 on Monday to Friday only
# Mon-Fri 0700-0900; Sat Sun # ditto plus all day Sat and Sun
# Fri-Mon 0700-0900 # 0700-0900 on Fri Sat Sun Mon
# Sat 0700-0800; Sun 0800-0900 # 0700-0800 on Sat, plus 0800-0900 on Sun

Time ranges should exclude the upper bound, i.e. 0700-0900 is 07:00:00 to
08:59:59. An empty time window means "all times everyday". Here are some test
cases to make it clearer:

class TestTimeWindow < Test::Unit::TestCase
def test_window_1
w = TimeWindow.new("Sat-Sun; Mon Wed 0700-0900; Thu 0700-0900 1000-1200")

assert ! w.include?(Time.mktime(2007,9,25,8,0,0)) # Tue
assert w.include?(Time.mktime(2007,9,26,8,0,0)) # Wed
assert ! w.include?(Time.mktime(2007,9,26,11,0,0))
assert ! w.include?(Time.mktime(2007,9,27,6,59,59)) # Thu
assert w.include?(Time.mktime(2007,9,27,7,0,0))
assert w.include?(Time.mktime(2007,9,27,8,59,59))
assert ! w.include?(Time.mktime(2007,9,27,9,0,0))
assert w.include?(Time.mktime(2007,9,27,11,0,0))
assert w.include?(Time.mktime(2007,9,29,11,0,0)) # Sat
assert w.include?(Time.mktime(2007,9,29,0,0,0))
assert w.include?(Time.mktime(2007,9,29,23,59,59))
end

def test_window_2
w = TimeWindow.new("Fri-Mon")
assert ! w.include?(Time.mktime(2007,9,27)) # Thu
assert w.include?(Time.mktime(2007,9,28))
assert w.include?(Time.mktime(2007,9,29))
assert w.include?(Time.mktime(2007,9,30))
assert w.include?(Time.mktime(2007,10,1))
assert ! w.include?(Time.mktime(2007,10,2)) # Tue
end

def test_window_nil
w = RDS::TimeWindow.new("")
assert w.include?(Time.mktime(2007,9,25,1,2,3)) # all times
end
end

Like Gordon, I used Runt a bit for my solution. Unlike Gordon, I
didn't use Runt *directly*. I remembered seeing it some time ago and
used what I could recall of the general ideas of implementation to
roll my own (probably not as well as Runt itself). And I believe the
naming of "Unbound Time" comes from Martin Fowler.


require 'date'

class TimeWindow
attr_reader :intervals

def initialize(string)
@intervals = []

parse(string)
end

def include?(time)
intervals.any? { |int| int.include?(time) }
end

private

attr_writer :intervals

def parse(string)
parts = string.split(';')
parts = [''] if parts.empty?
@intervals = parts.collect { |str| TimeInterval.new(str) }
end

end

class TimeInterval
DAYS = %w(Sun Mon Tue Wed Thu Fri Sat)

UnboundTime = Struct.new(:hour, :minute) do
include Comparable

def <=>(time)
raise TypeError, "I need a real Time object for comparison"
unless time.is_a?(Time)

comp_date = Date.new(time.year, time.month, time.mday)
comp_date += 1 if hour == 24

Time.mktime(comp_date.year, comp_date.month, comp_date.day, hour
% 24, minute, 0) <=> time
end
end

UnboundTimeRange = Struct.new(:start, :end)

attr_reader :days, :times

def initialize(string)
@days = []
@times = []

parse(string)
end

def include?(time)
day_ok?(time) and time_ok?(time)
end

private

attr_writer :days, :times

def parse(string)
unless string.empty?
string.strip.split(' ').each do |segment|
if md = segment.match(/^(\d{4})-(\d{4})$/)
self.times +=
[ UnboundTimeRange.new(UnboundTime.new(*md[1].unpack('A2A2').collect
{ |elem| elem.to_i }), UnboundTime.new(*md[2].unpack('A2A2').collect
{ |elem| elem.to_i })) ]
elsif md = segment.match(/^(\w+)(-(\w+))?$/)
if md[2]
start_day = DAYS.index(md[1])
end_day = DAYS.index(md[3])

if start_day <= end_day
self.days += (start_day .. end_day).to_a
else
self.days += (start_day .. DAYS.length).to_a + (0 ..
end_day).to_a
end
else
self.days += [DAYS.index(md[1])]
end
else
raise ArgumentError, "Segment #{segment} of time window
incomprehensible"
end
end
end

self.days = 0..DAYS.length if days.empty?
self.times = [ UnboundTimeRange.new(UnboundTime.new(0, 0),
UnboundTime.new(24, 0)) ] if times.empty?
end

def day_ok?(time)
days.any? { |d| d == time.wday }
end

def time_ok?(time)
times.any? { |t| t.start <= time and t.end > time }
end
end


All tests pass, which at the moment is good enough for me.

--
-yossef


.

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