#!/usr/bin/env ruby
# coding: utf-8

require 'open-uri'
require 'nokogiri'
require 'erb'

def find_day s
  if s =~ /(\d+)\.(\d+)\./
    day = $1.to_i
    month = $2.to_i
    result = Time.now - 3 * 30 * 86400
    while result.year < 2100
      if result.month == month && result.day == day
        return result
      end
      result += 86400
    end
    STDERR.puts "Invalid day #{s.inspect}"
    nil
  else
    # STDERR.puts "Cannot parse day #{s.inspect}"
    nil
  end
end

def fmt_time t
  t.strftime "%Y%m%dT%H%M%S"
end

class Event
  attr_accessor :start, :stop, :location

  def initialize start, stop, location
    @start = start
    @stop = stop
    @location = location
  end
end

events = []
day = nil

url = "https://drksachsen.de/impfaktionen.html"
doc = Nokogiri::HTML URI.open(url)
doc.css(".o-accordion__navigation").each do |section|
  region = section.css(".o-accordion__title-wrap").text
  if region =~ /Dresden/
    section.css(".o-media__body").each do |list|
      list.children.each do |child|
        case child.name
        when "p"
          day = find_day child.text
        when "ul"
          child.css("li").each do |item|
            if day && item.text =~ /Impf\-?aktion[\s\u00A0]+(.+Dresden),?[\s\u00A0]*(\d+)[:\.]?(\d*)[\s\u00A0]*[\-bis]{1,3}[\s\u00A0]*(\d+)[:\.]?(\d*)/i
              start = Time.new day.year, day.month, day.day, $2.to_i, $3.to_i
              stop = Time.new day.year, day.month, day.day, $4.to_i, $5.to_i
              raise "Stuff is really broken" if start.hour == 0 || stop.hour == 0
              events << Event.new(start, stop, $1)
            elsif day
              STDERR.puts "Text not recognized: #{item.text.inspect}"
            else
              STDERR.puts "No day!"
            end
          end
        end
      end
    end
  end
end  

ical = ERB::new <<~EOF
  BEGIN:VCALENDAR
  VERSION:2.0
  METHOD:PUBLISH
  X-WR-TIMEZONE;VALUE=TEXT:Europe/Berlin
  <% events.each_with_index do |ev, i| %>
  BEGIN:VEVENT
  METHOD:PUBLISH
  CLASS:PUBLIC
  UID:<%= url %>#<%= i %>
  DTSTART:<%= fmt_time ev.start %>
  DTEND:<%= fmt_time ev.stop %>
  SUMMARY:Vor-Ort-Impfaktion
  URL:<%= url %>
  LOCATION:<%= ev.location %>
  END:VEVENT
  <% end %>
  END:VCALENDAR
EOF

puts ical.result