module CalInvite::IcalTimezone

# File lib/cal_invite/ical_timezone.rb
148 def fixed_observance_lines(period)
149   [
150     "BEGIN:STANDARD",
151     "DTSTART:16010101T000000",
152     "TZOFFSETFROM:#{format_offset(period.utc_total_offset)}",
153     "TZOFFSETTO:#{format_offset(period.utc_total_offset)}",
154     "TZNAME:#{period.abbreviation}",
155     "END:STANDARD"
156   ]
157 end

# File lib/cal_invite/ical_timezone.rb
172 def format_offset(seconds)
173   sign = seconds.negative? ? '-' : '+'
174   abs = seconds.abs
175   format('%<sign>s%<hours>02d%<minutes>02d', sign: sign, hours: abs / 3600, minutes: (abs % 3600) / 60)
176 end

# File lib/cal_invite/ical_timezone.rb
54 def local_time(tzid, utc_time)
55   return nil if utc?(tzid) || tzid.nil? || tzid.to_s.strip.empty?
56 
57   TZInfo::Timezone.get(tzid.to_s).utc_to_local(utc_time.utc)
58 rescue TZInfo::InvalidTimezoneIdentifier
59   nil
60 end

# File lib/cal_invite/ical_timezone.rb
133 def observance_lines(kind, from_period, to_period)
134   transition_time = period_local_ends_at(from_period).to_time
135 
136   [
137     "BEGIN:#{kind}",
138     "DTSTART:#{transition_time.strftime('%Y%m%dT%H%M%S')}",
139     "TZOFFSETFROM:#{format_offset(from_period.utc_total_offset)}",
140     "TZOFFSETTO:#{format_offset(to_period.utc_total_offset)}",
141     "TZNAME:#{to_period.abbreviation}",
142     rrule_line(transition_time),
143     "END:#{kind}"
144   ]
145 end

# File lib/cal_invite/ical_timezone.rb
110 def period_after(tz, period)
111   ends_at = period && period_ends_at(period)
112   return nil unless ends_at
113 
114   tz.period_for_utc(ends_at.to_time)
115 end

# File lib/cal_invite/ical_timezone.rb
102 def period_before(tz, period)
103   starts_at = period_starts_at(period)
104   return nil unless starts_at
105 
106   tz.period_for_utc(starts_at.to_time - 1)
107 end

# File lib/cal_invite/ical_timezone.rb
123 def period_ends_at(period)
124   period.respond_to?(:ends_at) ? period.ends_at : period.utc_end
125 end

# File lib/cal_invite/ical_timezone.rb
128 def period_local_ends_at(period)
129   period.respond_to?(:local_ends_at) ? period.local_ends_at : period.local_end
130 end

# File lib/cal_invite/ical_timezone.rb
118 def period_starts_at(period)
119   period.respond_to?(:starts_at) ? period.starts_at : period.utc_start
120 end

# File lib/cal_invite/ical_timezone.rb
162 def rrule_line(time)
163   wday_names = %w[SU MO TU WE TH FR SA]
164   days_in_month = Date.new(time.year, time.month, -1).day
165   nth = (time.day - 1) / 7 + 1
166   nth = -1 if time.day + 7 > days_in_month
167 
168   "RRULE:FREQ=YEARLY;BYMONTH=#{time.month};BYDAY=#{nth}#{wday_names[time.wday]}"
169 end

# File lib/cal_invite/ical_timezone.rb
29 def utc?(tzid)
30   tzid.to_s.upcase == 'UTC'
31 end

# File lib/cal_invite/ical_timezone.rb
39 def valid?(tzid)
40   return true if utc?(tzid)
41   return false if tzid.nil? || tzid.to_s.strip.empty?
42 
43   TZInfo::Timezone.get(tzid.to_s)
44   true
45 rescue TZInfo::InvalidTimezoneIdentifier
46   false
47 end

# File lib/cal_invite/ical_timezone.rb
69 def vtimezone_lines(tzid)
70   return nil if utc?(tzid) || tzid.nil? || tzid.to_s.strip.empty?
71 
72   tz = TZInfo::Timezone.get(tzid.to_s)
73   current = tz.period_for_utc(Time.now.utc)
74 
75   if current.dst?
76     dst_period = current
77     std_period = period_before(tz, dst_period)
78   else
79     std_period = current
80     dst_period = period_after(tz, std_period)
81     dst_period = nil unless dst_period&.dst?
82   end
83 
84   lines = ["BEGIN:VTIMEZONE", "TZID:#{tzid}"]
85 
86   if std_period && dst_period
87     lines.concat(observance_lines('STANDARD', dst_period, std_period))
88     lines.concat(observance_lines('DAYLIGHT', std_period, dst_period))
89   else
90     lines.concat(fixed_observance_lines(std_period || dst_period || current))
91   end
92 
93   lines << "END:VTIMEZONE"
94   lines
95 rescue StandardError
96   # Never let an exotic/edge-case timezone break calendar generation —
97   # worst case the VEVENT ends up without a VTIMEZONE definition.
98   nil
99 end