#!/usr/bin/env ruby
# -*- ruby -*-
#
# Looks up google calendars and prints today's schedule out in
# text mode.  You can also list the names of the calendars in ~/.ical.
# These values can be the names of calendars or the actual urls.
#
# Examples:
#
# ./today http://www.google.com/calendar/ical/s69iupuak9ll5d3tvct0io4pic%40group.calendar.google.com/public/basic.ics
# ./today s69iupuak9ll5d3tvct0io4pic@group.calendar.google.com
#
# Requires HTTParty.  To install
#
#  % sudo gem install httparty
#

require 'rubygems'
require 'httparty'
require 'cgi'

class CalendarEvent

  def initialize(dtstart,dtend,summary)
    @dtstart = dtstart
    @dtend = dtend
    @summary = summary
    @start_hours = @dtstart / 100
    @start_mins  = @dtstart % 100
    @end_hours   = @dtend   / 100
    @end_mins    = @dtend   % 100
  end

  # Returns 'true' if this event's range contains time.
  # 'time' is an integer between 0 and 2359
  def in_range(time)
    if @dtstart != @dtend
      return @dtstart-@start_mins <= time && time < @dtend
    else
      return @dtstart-@start_mins <= time && time <= @dtend
    end
  end

  def to_s
    time_str = sprintf "%02d:%02d - %02d:%02d", @start_hours, @start_mins, @end_hours, @end_mins
    return @summary + " (" + time_str + ")"
  end

end

class GoogleCalendar
  include HTTParty

  # cal_name is either a google calendar name or URL
  def self.find_calendar(cal_name)
    if /^http:\/\// !~ cal_name
      url = 'http://www.google.com/calendar/ical/' + CGI.escape(cal_name) + '/public/basic.ics'
    else
      url = cal_name
    end
    get url
  end

end

# Main entry
def main(argv)

  # Maybe look in ~/.ical for names on single lines
  if argv.empty?
    fname = ENV['HOME'] + '/.ical'
    if File.exist? fname
      IO.foreach fname do |line|
        argv.push line.strip
      end
    end
  end

  # Look up all the calendar names
  summarys2events = {}
  argv.map { |arg| summarys2events.update lookup(arg.downcase) }
  print_events summarys2events.values

end

# Looks up the google calendar with name 'cal_name' and prints to
# stdout.  Returns a map from summaries to events
def lookup(cal_name)
  ical = GoogleCalendar.find_calendar cal_name
  now = Time.now.strftime "%Y%m%d"
  start_token = 'DTSTART:' + now + 'T'
  end_token = 'DTEND:' + now + 'T'
  result = {}
  dtstart = -1
  dtend = -1
  summary = nil
  ical.each "\n" do |line|
    line = line.strip
    icolon = line.index ':'
    next if icolon == -1
    if /^#{start_token}/ =~ line
      dtstart = line[start_token.length..start_token.length+3].to_i
    elsif /^#{end_token}/ =~ line
      dtend = line[end_token.length..end_token.length+3].to_i
    elsif /^BEGIN:VEVENT/ =~ line
      dtstart = -1
      dtend = -1
      summary = nil
    elsif /^SUMMARY:.*/ =~ line
      summary = line[icolon+1..-1]
    elsif /^END:VEVENT/ =~ line
      if summary and dtstart > 0 and dtend > 0
        result.store summary, CalendarEvent.new(dtstart, dtend, summary)
      end      
    end
  end
  return result
end

# Prints an array of events
def print_events(events)
  (0..23).each do |hour|
    time = hour*100
    printf "%02d:00 ", hour
    printed_one = false
    events.each do |evt|
      if evt.in_range time
        print "\n      " if printed_one
        print evt
        printed_one = true
      end
    end
    print "\n"
  end
end


# Main
main ARGV