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

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

MONTHS = [
  "Jan", "Feb", "Mär", "Apr",
  "Mai", "Jun", "Jul", "Aug",
  "Sep", "Okt", "Nov", "Dez",
]

def fmt_time t
  if t.is_a? String
    t
  else
    t.strftime "%Y%m%dT%H%M%S"
  end
end

class Event
  attr_accessor :title, :url, :location
  attr_reader :date, :dtstart, :dtend

  def date=(s)
    if s =~ /(\d+)\.\s*(\S{3})\s+(.*)/
      day = $1.to_i
      month = MONTHS.index($2) + 1
      year = $3.to_i
      year_time = $3
      if year_time =~ /(\d{4})(.*)/
        year = $1.to_i
        time = $2
      else
        raise "Invalid year: #{year_time.inspect} in #{s.inspect}"
      end
      if time =~ /(\d+)[\.:](\d{2})/
        @dtstart = Time::local year, month, day, $1.to_i, $2.to_i, 0
        @dtend = @dtstart + 3600
      elsif time =~ /(\d+)\s+Uhr/
        @dtstart = Time::local year, month, day, $1.to_i, 0, 0
        @dtend = @dtstart + 3600
      else
        @dtstart = @dtend = "#{year}#{month.to_s.rjust(2, "0")}#{day.to_s.rjust(2, "0")}"
      end
    else
      raise "Invalid date: #{s.inspect}"
    end

  end
end

events = []

url = "https://kunsthausdresden.de/"
doc = Nokogiri::HTML URI.open(url)
doc.css(".events").each do |content|
  date = content.css(".meta.date").text.strip
  location = content.css(".meta.location").text.strip
               .sub(/^Ort:\s*/, "")
               .sub(/Ort:.*/, "")
  title_link = content.css(".article-header h1.title a")
  href = title_link.attr 'href'
  next unless href

  begin
    ev = Event::new
    ev.title = title_link.attr 'title'
    ev.url = URI.join url, href
    ev.date = date
    ev.location = location
    events << ev
  rescue
    STDERR.puts "Omitting: #{$!}"
    STDERR.puts $!.backtrace
  end
end

ical = ERB::new <<~EOF
  BEGIN:VCALENDAR
  VERSION:2.0
  METHOD:PUBLISH
  X-WR-TIMEZONE;VALUE=TEXT:Europe/Berlin
  <% events.each do |ev| %>
  BEGIN:VEVENT
  SUMMARY:<%= ev.title %>
  DTSTART:<%= fmt_time ev.dtstart %>
  DTEND:<%= fmt_time ev.dtend %>
  UID:<%= ev.url %>
  URL:<%= ev.url %>
  LOCATION:<%= ev.location %>
  END:VEVENT
  <% end %>
  END:VCALENDAR
EOF

puts ical.result