#!/usr/bin/env bash
# rice-cal - data and actions for the calendar panel. Events live in khal,
# synced with the CalDAV server by vdirsyncer; reminders come from rice-reminder.
#
#   rice-cal month                month grid JSON (ISO weeks, Monday first); marks days with events
#   rice-cal agenda               events and reminders for the selected day
#   rice-cal select <YYYY-MM-DD>  pick a day
#   rice-cal shift <-1|1>         previous / next month
#   rice-cal today
#   rice-cal add                  new event on the selected day, typed in rofi:
#                                   "15:00 dentist"  "15:00-16:30 review"  "holiday" (all day)
#                                   timed events remind you 10 minutes before; end with !30m or !no
#   rice-cal sync                 sync with the server in the background
#   rice-cal setup                connect a CalDAV server (asks for URL, user, password; run in a terminal)
set -uo pipefail

e()   { eww -c "$HOME/.config/eww" "$@"; }
var() { e get "$1" 2>/dev/null; }
have_khal() { command -v khal >/dev/null && [[ -f ${XDG_CONFIG_HOME:-$HOME/.config}/khal/config ]]; }
isodate() { [[ ${1:-} =~ ^[0-9]{4}-[0-9]{2}-[0-9]{2}$ ]] && date -d "$1" +%F >/dev/null 2>&1; }

selected() { local d; d=$(var cal_day); isodate "$d" && echo "$d" || date +%F; }
offset()   { local o; o=$(var cal_offset); [[ $o =~ ^-?[0-9]+$ ]] && echo "$o" || echo 0; }

reminders() { rice-reminder json 2>/dev/null || echo '[]'; }

month() {
  local off="${1:-$(offset)}" sel="${2:-$(selected)}" first start end counts="{}"
  first=$(date -d "$(date +%Y-%m-01) $off month" +%F)
  start=$(date -d "$first -$(( $(date -d "$first" +%u) - 1 )) days" +%F)
  end=$(date -d "$start +42 days" +%F)

  if have_khal; then
    counts=$(khal list --once --day-format "" --format "{start-date}" "$start" "$end" 2>/dev/null |
      grep -E '^[0-9]{4}-[0-9]{2}-[0-9]{2}$' | sort | uniq -c |
      jq -R -s -c 'split("\n") | map(select(length > 0) | ltrimstr(" ") | capture("^ *(?<n>[0-9]+) (?<d>.+)$") | {(.d): (.n | tonumber)}) | add // {}')
  fi

  for i in $(seq 0 41); do date -d "$start +$i days" '+%F %-d %m %u %V'; done |
    jq -R -s -c --arg title "$(date -d "$first" '+%B %Y')" --arg today "$(date +%F)" --arg sel "$sel" \
       --arg month "$(date -d "$first" +%m)" --argjson counts "$counts" --argjson rem "$(reminders)" '
      ($rem | group_by(.date) | map({(.[0].date): length}) | add // {}) as $rc |
      split("\n") | map(select(length > 0) | split(" ")) as $days |
      {
        title: $title,
        dow: ["Mo", "Tu", "We", "Th", "Fr", "Sa", "Su"],
        weeks: [ range(0; 6) as $w | $days[$w * 7:($w + 1) * 7] | {
          wk: (.[0][4] | tonumber | tostring),
          days: map({
            date: .[0], d: .[1],
            other: (.[2] != $month),
            weekend: ((.[3] | tonumber) >= 6),
            today: (.[0] == $today),
            selected: (.[0] == $sel and .[0] != $today),
            events: (($counts[.[0]] // 0) + ($rc[.[0]] // 0))
          })
        } ]
      }'
}

agenda() {
  local day="${1:-$(selected)}" heading items="[]" status="" sep=$'\x1f'
  heading=$(date -d "$day" '+%A %-d %B')
  [[ $day == "$(date +%F)" ]] && heading="Today · $heading"

  if have_khal; then
    items=$(khal list --day-format "" --format "{start-time}${sep}{end-time}${sep}{title}${sep}{location}" "$day" 1d 2>/dev/null |
      jq -R -s -c --arg sep "$sep" '
        split("\n") | map(select(length > 0) | split($sep) | {
          kind: "event", id: "",
          time: (if .[0] == "" then "all day" else .[0] end),
          title: .[2],
          sub: ([(if .[0] != "" and .[1] != "" then "until " + .[1] else empty end),
                 (if (.[3] // "") != "" then .[3] else empty end)] | join(" · "))
        })')
  else
    status="Events need khal set up (run install.sh)"
  fi

  jq -cn --arg heading "$heading" --arg status "$status" --arg day "$day" \
    --argjson items "${items:-[]}" --argjson rem "$(reminders)" '
    {heading: $heading, status: $status,
     items: ($items + [ $rem[] | select(.date == $day) | {kind: "reminder", id: .id, time: .time, title: .text, sub: "reminder"} ]
             | sort_by(if .time == "all day" then "00:00" else .time end))}'
}

# Push new data straight into eww so clicks feel instant.
refresh() {
  local off="$1" day="$2"
  e update cal_offset="$off" cal_day="$day"
  e update month="$(month "$off" "$day")" agenda="$(agenda "$day")"
}

add() {
  have_khal || { rice-notify send "Calendar" "Events need khal set up (run install.sh)"; exit 1; }
  local day input remind=10m start="" end="" title
  day=$(selected)
  input=$(rofi -dmenu -theme "$HOME/.config/rofi/prompt.rasi" -p "$(date -d "$day" '+%a %-d %b')" \
    -mesg "15:00 dentist   ·   15:00-16:30 review   ·   holiday   ·   end with !30m or !no") || exit 0
  [[ -n $input ]] || exit 0

  if [[ $input =~ ^(.*[^[:space:]])[[:space:]]+!(no|[0-9]+[mhd])$ ]]; then
    input="${BASH_REMATCH[1]}"; remind="${BASH_REMATCH[2]}"
  fi

  if [[ $input =~ ^([0-9]{1,2}:[0-9]{2})(-([0-9]{1,2}:[0-9]{2}))?[[:space:]]+(.+)$ ]]; then
    start="${BASH_REMATCH[1]}"; end="${BASH_REMATCH[3]}"; title="${BASH_REMATCH[4]}"
    khal new "$day" "$start" "${end:-1h}" "$title" >/dev/null 2>&1 || { rice-notify send "Calendar" "khal could not add that"; exit 1; }
    if [[ $remind != no ]]; then
      local amount="${remind%?}" unit
      case "${remind: -1}" in m) unit=minutes ;; h) unit=hours ;; d) unit=days ;; esac
      at=$(date -d "$day $start $amount $unit ago" '+%F %H:%M' 2>/dev/null) &&
        rice-reminder add "$at" "$title at $start" >/dev/null 2>&1
    fi
  else
    title="$input"
    khal new "$day" "$title" >/dev/null 2>&1 || { rice-notify send "Calendar" "khal could not add that"; exit 1; }
  fi

  rice-notify send "Event added" "$title · $(date -d "$day" '+%a %-d %b') ${start:-all day}"
  setsid -f vdirsyncer sync >/dev/null 2>&1
  refresh "$(offset)" "$day"
}

setup() {
  local conf="${XDG_CONFIG_HOME:-$HOME/.config}" share="${XDG_DATA_HOME:-$HOME/.local/share}"
  local secrets="$conf/rice/secrets" data="$share/calendars" url user pass first
  command -v vdirsyncer >/dev/null && command -v khal >/dev/null ||
    { echo "rice-cal: install khal and vdirsyncer first"; return 1; }

  read -rp "CalDAV URL [https://dav.srtk.in/dav.php/]: " url </dev/tty
  url="${url:-https://dav.srtk.in/dav.php/}"
  [[ $url =~ ^https://[^\"[:space:]]+$ ]] || { echo "rice-cal: use an https:// URL"; return 1; }
  read -rp "Username: " user </dev/tty
  [[ $user =~ ^[A-Za-z0-9._@+-]+$ ]] || { echo "rice-cal: that username has characters vdirsyncer can't take"; return 1; }
  read -rsp "Password: " pass </dev/tty; echo

  # The password stays in a private file; the configs only point at it.
  mkdir -p "$secrets" && chmod 700 "$secrets"
  (umask 077; printf '%s' "$pass" > "$secrets/caldav")
  unset pass
  mkdir -p "$conf/vdirsyncer" "$conf/khal" "$data" "$share/vdirsyncer/status"

  cat > "$conf/vdirsyncer/config" <<EOF
# Written by rice-cal setup. The password is read from $secrets/caldav.
[general]
status_path = "$share/vdirsyncer/status/"

[pair calendar]
a = "calendar_local"
b = "calendar_remote"
collections = ["from a", "from b"]
metadata = ["displayname", "color"]
conflict_resolution = "b wins"

[storage calendar_local]
type = "filesystem"
path = "$data/"
fileext = ".ics"

[storage calendar_remote]
type = "caldav"
url = "$url"
username = "$user"
password.fetch = ["command", "cat", "$secrets/caldav"]
EOF

  echo "Connecting to $url ..."
  yes | vdirsyncer discover calendar >/dev/null || { echo "rice-cal: could not sign in to $url with those details"; return 1; }
  vdirsyncer metasync >/dev/null 2>&1
  vdirsyncer sync || { echo "rice-cal: first sync failed"; return 1; }

  first=$(find "$data" -mindepth 1 -maxdepth 1 -type d -printf '%f\n' | sort | head -n1)
  [[ -n $first ]] || { first=personal; mkdir -p "$data/$first"; }

  cat > "$conf/khal/config" <<EOF
# Written by rice-cal setup.
[calendars]
  [[synced]]
    path = $data/*
    type = discover

[locale]
timeformat = %H:%M
dateformat = %Y-%m-%d
longdateformat = %Y-%m-%d
datetimeformat = %Y-%m-%d %H:%M
longdatetimeformat = %Y-%m-%d %H:%M
firstweekday = 0

[default]
default_calendar = $first
highlight_event_days = True
EOF

  systemctl --user enable --now vdirsyncer.timer >/dev/null 2>&1
  echo "Calendar ready: new events go to '$first', and it syncs every 15 minutes."
}

case "${1:-}" in
  setup)  setup ;;
  month)  month ;;
  agenda) agenda ;;
  select)
    isodate "${2:-}" || { echo "rice-cal: select takes YYYY-MM-DD" >&2; exit 2; }
    now=$(date +%Y*12+%-m | sed 's/^0*//'); then=$(date -d "$2" +%Y*12+%-m)
    refresh "$(( then - now ))" "$2"
    ;;
  shift)
    [[ ${2:-} =~ ^-?[0-9]+$ ]] || { echo "rice-cal: shift takes a number" >&2; exit 2; }
    off=$(( $(offset) + $2 ))
    if (( off == 0 )); then day=$(date +%F); else day=$(date -d "$(date +%Y-%m-01) $off month" +%F); fi
    refresh "$off" "$day"
    ;;
  today) refresh 0 "$(date +%F)" ;;
  add)   add ;;
  sync)  setsid -f vdirsyncer sync >/dev/null 2>&1 ;;
  *) sed -n '2,15p' "$0" | sed 's/^# \{0,1\}//'; exit 2 ;;
esac