#!/bin/bash
# The epsi2ics project produces an ICS file from an EPSI school-year calendar.
# Copyright © 2019 Y. Gablin, under the GPL-3.0-or-later license.
# Full licensing information in the LICENSE file, or gnu.org/licences/gpl-3.0.txt if the file is missing.
#
# This script only works when executed in the timezone of the calendar, and only if this timezone offset
# is low enough to keep all events in the day they belong to in the web calendar (usually −6h ≤ TZ ≤ +8h).
#
# from EPSI “edtmobilityeng” to ICS, for the current school year
# $1: EPSI Login (firstname.lastname)
# $2: output file (else standard output)

if [ -n "$2" -a -d "$(dirname "$2")" -a -w "$(dirname "$2")" ]; then
  exec >"$2"
fi

(
  dtstamp=$(date -u +%Y%m%dT%H%M%SZ)
  currentYear=$(date +%Y)
  splitDay=$(date +%j -d "${currentYear}-08-01" | sed 's/^0*//') # XXXX-08-01 ∈ [1 … 366]
  dayOfYear=$(date +%j | sed 's/^0*//')                          #  this day  ∈ [1 … 366]
  if [ $dayOfYear -lt $splitDay ]; then
    offsetMax=$(( splitDay-dayOfYear ))
    offset=$(( offsetMax-365 ))
  else
    offset=$(( splitDay-dayOfYear ))
    offsetMax=$(( 365+offset ))
  fi
  dayOfWeek=$(date +%u -d "${offset}days")                      # ∈ [1=monday … 5=friday]

  cat <<-ENDOFTEXT
BEGIN:VCALENDAR
VERSION:2.0
PRODID:yalis.fr/epsi2ical v1.1
ENDOFTEXT

  while [ $offset -lt $offsetMax ]; do
    mon=$(date +%Y%m%dT%z -d "$(($offset+1-$dayOfWeek))days")
    tue=$(date +%Y%m%dT%z -d "$(($offset+2-$dayOfWeek))days")
    wed=$(date +%Y%m%dT%z -d "$(($offset+3-$dayOfWeek))days")
    thu=$(date +%Y%m%dT%z -d "$(($offset+4-$dayOfWeek))days")
    fri=$(date +%Y%m%dT%z -d "$(($offset+5-$dayOfWeek))days")

    for ((i=1; i<5; i=i*2)); do
      week="$(curl -s "https://edtmobiliteng.wigorservices.net/WebPsDyn.aspx?action=posEDTBEECOME&serverid=C&Tel=${1}&date=$(date +%m/%d/%Y -d "${offset}days")")" \
      && { echo "$week"; break; }
      sleep ${i}s
    done \
    | tr '\r\n' ' ' \
    | sed -r 's/[[:blank:]]+/ /g' \
    | grep -oE '<DIV [^>]*class="Case" [^>]*style="[^"]*left *:[^"]*"|DIV [^>]*style="[^"]*left *:[^"]*" [^>]*class="Case"|<td [^>]*class="TC(ase|Prof|hdeb|Salle)"([^<]|<[^/]|</[^t]|</t[^d])*</td>' \
    | awk -vmon=$mon -vtue=$tue -vwed=$wed -vthu=$thu -vfri=$fri -vid="epsi2ics/${1}@${HOSTNAME}" -vdtstamp=$dtstamp -F$'\t' '
      function out() {
        if (from!="" && to!="" && ase!="") printf( \
          "BEGIN:VEVENT\nUID:%s/%s/%s\nDTSTAMP:%s\nDTSTART:%s\nDTEND:%s\nSUMMARY:%s\nLOCATION:%s\nDESCRIPTION:🗣 %s 👥 %s\nEND:VEVENT\n", \
                          from, id, prof,      dtstamp,    from,     to,         ase,         where,             prof, who)
        from=""
        to=""
        ase=""
        where=""
        prof=""
        who=""
        day=""
        zoneH=0
        zoneM=0
      }
      function toZtime(localH, localM) {
        localM-=zoneM
        if (localM<0) {
          localM+=60
          localH-=1
        } else if (localM>59) {
          localM-=60
          localH+=1
        }
        localH-=zoneH
        return sprintf("%s%02d%02d00Z", day, localH, localM)
      }
      /class="Case"/ {
        out()
        pc=gensub(".*left *: *([0-9]+)[%.].*", "\\1", 1)
        if      (pc < 115) tmpd=mon
        else if (pc < 135) tmpd=tue
        else if (pc < 155) tmpd=wed
        else if (pc < 175) tmpd=thu
        else               tmpd=fri
        day=substr(tmpd, 1, 9)
        zoneH=substr(tmpd, 10, 3)+0
        zoneM=(substr(tmpd, 10, 1) substr(tmpd, 13, 2))+0
      }
      /class="TCase"/ {
        ase=gensub(".*</div>(.*)</.*", "\\1", 1)
      }
      /class="TCProf"/ {
        split(gensub(".*>(.*)<br/?>(.*)</.*", "\\1\t\\2", 1), tmp)
        prof=tmp[1]
        who=tmp[2]
      }
      /class="TChdeb"/ {
        split(gensub(".*> *0?([0-9]+):0?([0-9]+) *- *0?([0-9]+):0?([0-9]+) *</.*", "\\1\t\\2\t\\3\t\\4", 1), tmp)
        from=toZtime(tmp[1], tmp[2])
        to=toZtime(tmp[3], tmp[4])
      }
      /class="TCSalle"/ {
        where=gensub(".*>(Salle:)?(.*)</.*", "\\2", 1)
      }
      END {
        out()
      }'
    offset=$(($offset+7))
    sleep 0.3s
  done

  cat <<-ENDOFTEXT
END:VCALENDAR
ENDOFTEXT
) \
| env LANG=fr_FR@euro sed -r 's/(.{73})(.)/\1\n \2/g' \
| sed 's/$/\r/'