#!/bin/sh

. $_EXEC/cgilite/cgilite.sh
. $_EXEC/cgilite/session.sh

_(){ printf %s\\n "$*"; }
[ "${LANGUAGE}" -a -r "${_EXEC}/l10n/${LANGUAGE}.sh" ] && . "${_EXEC}/l10n/${LANGUAGE}.sh"

start_date= start_time= end_date= end_time=
rec_freq= rec_int= error_msg= rec_end=
title=
start= end= nstart= nend=

isdate(){
  local date="$1" y m d

  if   printf %s "$date" \
    | grep -xEq '[0-9]{4}-((01|03|05|07|08|10|12)-(0[1-9]|[12][0-9]|3[01])|(04|06|09|11)-(0[1-9]|[12][0-9]|30)|02-(0[1-9]|[12][0-9]))'
  then  # y-m-d (ISO Date)
    y="${date%%-*}" d="${date##*-}" m="${date%-*}" m="${m#*-}"
  elif printf %s "$date" \
    | grep -xEq '((0?1|0?3|0?5|0?7|0?8|10|12)/(0?[1-9]|[12][0-9]|3[01])|(0?4|0?6|0?9|11)/(0?[1-9]|[12][0-9]|30)|0?2-(0[1-9]|[12][0-9]))/([0-9]{2}|[0-9]{4})'
  then  # m/d/y (US Date)
    y="${date##*/}" m="${date%%/*}" d="${date%/*}" d="${d#*/}"
  elif printf %s "$date" \
    | grep -xEq '((0?[1-9]|[12][0-9]|3[01])[\./](0?1|0?3|0?5|0?7|0?8|10|12)|(0?[1-9]|[12][0-9]|30)[\./](0?4|0?6|0?9|11)|(0[1-9]|[12][0-9])[\./]0?2)[\./]([0-9]{2}|[0-9]{4})'
  then  # d/m/y or d.m.y (European Date / German Date)
    y="${date##*.}" d="${date%%.*}" m="${date%.*}" m="${m#*.}"
  else
    return 1
  fi
  [ $y -lt 100 -a $y -gt 50 ] && y=$((y + 1900))
  [ $y -lt 100 -a $y -le 50 ] && y=$((y + 2000))
  date="$(printf "%04i-%02i-%02i" $y ${m#0} ${d#0})"

  # leap year
  if [ "$m" -eq 2 -a "$d" -eq 29 ]; then
    if   [ "$((y % 400))" -eq 0 ]; then
      :
    elif [ "$((y % 100))" -eq 0 ]; then
      return 1
    elif [ "$((y % 4))" -eq 0 ]; then
      :
    else
      return 1
    fi
  fi

  printf '%04i-%02i-%02i\n' "$y" "${m#0}" "${d#0}"
  return 0
}

istime(){
  time="$1" h= m=

  if   printf %s "$time" | grep -xEq '(0?[1-9]|1[012])(:[0-5][0-9])? ?(am|AM)\.?'; then
    time="${time%?[aA][mM]}" h="${time%:*}" h="$(h % 12)"
    [ "$h" != "$time" ] && m="${time#*:}" || m=0
  elif printf %s "$time" | grep -xEq '(0?[1-9]|1[012])(:[0-5][0-9])? ?(pm|PM)\.?'; then
    time="${time%?[aA][mM]}" h="${time%:*}" h="$(h % 12 + 12)"
    [ "$h" != "$time" ] && m="${time#*:}" || m=0
  elif printf %s "$time" | grep -xEq '(0?[0-9]|1[0-9]|2[0-3]):[0-5][0-9]'; then
    time="${time%?[aA][mM]}" h="${time%:*}" m="${time#*:}"
  else
    return 1
  fi

  printf '%02i:%02i\n' "${h#0}" "${m#0}"
  return 0
}

while [ $# -gt 0 ]; do case $1 in
  --from|from|--start|start)
    if   isdate "$2" && istime "$3" ; then
      start_date="$(isdate "$2" )" start_time="$(istime "$3")"
      shift 3
    elif isdate "${2%% *}" && istime "${2#* }" ; then
      start_date="$(isdate "${2%% *}" )" start_time="$(istime "${2#* }")"
      shift 2
    elif isdate "$2" ; then
      start_date="$(isdate "$2")" start_time="00:00"
      shift 2
    else
      error_msg="Event start should be \"YYYY-MM-DD\" or \"YYYY-MM-DD hh:mm\""
      shift 1
    fi >/dev/null
    ;;
  --to|to|--end|end)
    if   isdate "$2" && istime "$3"; then
      end_date="$(isdate "$2")" end_time="$(istime "$3")"
      shift 3
    elif isdate "${2%% *}" && istime "${2#* }"; then
      end_date="$(isdate "${2%% *}")" end_time="$(istime "${2#* }")"
      shift 2
    elif isdate "$2"; then
      end_date="$(isdate "$2")" end_time="23:59"
      shift 2
    elif istime "$2"; then
      end_time="$(istime "$2")"
      shift 2
    else
      error_msg="Event end should be \"YYYY-MM-DD\" or \"YYYY-MM-DD hh:mm\" or \"hh:mm\""
      shift 1
    fi >/dev/null
    ;;
  --repeat|--recur|--recurrence|--every|every)
    if expr "$2" : '^[0-9]\+$' &&
       expr "$3" : '^\(days\|nights\|weeks\|months\|years\|weekday\)$'; then
      rec_freq="$2" rec_int="$3"
      shift 3
    elif expr "$2" : '^[0-9]\+ \+\(days\|nights\|weeks\|months\|years\|weekday\)$'; then
      rec_freq="${2%% *}" rec_int="${2##* }"
      shift 2
    elif expr "$2" : '^\(day\|daily\|night\|nightly\|week\|weekly\|month\|monthly\|year\|yearly\|annually\)$'; then
      rec_freq="1" rec_int="$2"
      shift 2
    elif expr "$2" : '^last weekday$'; then
      rec_freq="-1" rec_int="weekday"
      shift 2
    elif expr "$2 $3" : '^last weekday$'; then
      rec_freq="-1" rec_int="weekday"
      shift 3
    elif expr "$2" : '^\(biweekly\|bimonthly\)$'; then
      rec_freq="2" rec_int="$2"
      shift 2
    else
      error_msg="Recurrence should be \"N days|weeks|months|years\" or \"N|last weekday\""
      shift 1
    fi >/dev/null
    ;;
  --until|until)
    if isdate $2; then
      rec_end="$(isdate "$2")"
      shift 2
    else
      error_msg="Recurrence end should be \"YYYY-MM-DD\""
      shift 1
    fi >/dev/null
    ;;
  --title)
    title="$2"
    shift 2
    ;;
  *) shift 1;;
esac; done

if [ ! "$end_time" ]; then
  end_time="23:59"
fi

if [ ! "$end_date" -a "$end_time" -a "$start_time" ]; then
  if [ "$((${end_time%:*} * 60 + ${end_time#*:}))" -gt "$((${start_time%:*} * 60 + ${start_time#*:}))" ]; then
    end_date="$start_date"
  else
    end_date="$(date -d "@$(($(date -d "$start_date" +%s) + 86400))" +%F)"
  fi
fi

if [ ! "$start_date" ]; then
  error_msg="Event needs start date, e.g. --start \"YYYY-MM-DD\""
fi

if [ ! "$title" ]; then
  error_msg="Event needs title, e.g. --title \"Event Name\""
fi

if [ "$error_msg" ]; then
  _ "$error_msg"
  exit 1
fi

case $rec_int in
  day|daily|days|night|nightly|nights)
    rec_int="day";;
  week|weeks|weekly|biweekly)
    rec_int="week";;
  month|monthly|months|bimonthly)
    rec_int="month";;
  year|yearly|years|annually)
    rec_int="year";;
esac

if [ "$rec_end" ]; then
  rec_end="$(date -d "$rec_end" +%s)"
fi

if [ -s './#events' ]; then
  t1="$(stat -c %Y './#page.md')"
  read t2 junk <"./#events"
  if [ "$t1" -ge "$t2" ]; then
    truncate -s 0 "./#events"
  fi
fi

printf '%i	%i	%i	%i	%s	%i\n' \
  "$_DATE" "$(date -d "$start_date $start_time" +%s)" "$(date -d "$end_date $end_time" +%s)" \
  "${rec_freq:-0}" "${rec_int:-\\}" "${rec_end:--1}" \
  >>'./#events'

start="$(date -d "$start_date $start_time" +%s)"
  end="$(date -d "$end_date $end_time" +%s)"

if [ $_DATE -le $end ]; then
  nstart="$start" nend="$end"
fi

[ $_DATE -gt $end ] && case $rec_int in
  day)
    nend=$(( rec_freq * 86400 - (_DATE - end) % (rec_freq * 86400) + _DATE ))
    nstart=$(( start - end + nend))
    ;;
  week)
    nend=$(( rec_freq * 604800 - (_DATE - end) % (rec_freq * 604800) + _DATE ))
    nstart=$(( start - end + nend))
    ;;
  month)
    { read _y _m _d; read y m d; } <<-EOF
	$(date -d @$_DATE +"%Y %_m %_d"
	  date -d @$start +"%Y %_m %_d"
	)
	EOF
    _m=$((_y * 12 + _m)) m=$((y * 12 + m))
    while :; do
      mod=$(( (_m - m) % rec_freq )); [ $mod -eq 0 ] && mod="$rec_freq";
      m=$(( rec_freq - mod + _m ))
      y=$((m / 12)) m=$((m % 12)); [ $m -eq 0 ] && y=$((y - 1)) m=12;
      nstart="$(printf '%04i-%02i-%02i' "$y" "$m" "$d")"
      isdate "$nstart" >/dev/null && [ $(date -d "$nstart" +%s) -ge $_DATE ] && break
      debug loop
      m=$((y * 12 + m)) _m="$((_m + rec_freq))"
    done
    nstart="$(date -d "$nstart $start_time" +%s)"
      nend="$((end - start + nstart))"
    ;;
  year)
    ;;
  '')
    nstart="$start" nend="$end"
    ;;
esac

"$_EXEC/cgilite/html-sh.sed" <<-EOF
  [div .macro .event
    [label . $(HTML "$title")]
    [dl
      [dt $(_ Start:)][dd $(date -d @$nstart +"%F %T")]
      [dt   $(_ End:)][dd $(date -d @$nend +"%F %T")]
    ]
  ]
EOF

# uid="$(timeid)"
# tzid="$(cat /etc/timezone || printf 'UTC')"
# 
# cat >>"#events.ics" <<-EOF
# BEGIN:VCALENDAR
# VERSION:2.0
# PRODID:ShellWiki Event Macro
# BEGIN:VEVENT
# UID:$uid@$(HEADER Host)
# DTSTAMP:TZID=${tzid}:$(date +%Y%m%dT%H%M%S)
# DTSTART:TZID=${tzid}:$(date +%Y%m%dT%H%M%S -d "$start_date $start_time")
# DURATION:
# RRULE:FREQ=$ec_freq;INTERVAL=$rec_int;UNTIL=$(date +%Y%m%dT000000Z -d "$rec_end")
# SUMMARY:
# COMMENT:
# END:VEVENT
# END:VCARD
# EOF