calcurse: sync with Google Calendar via calcurse-caldav

Hourly timer started from xmonad, plus UI hooks that sync before load and after exit. calcurse-sync notifies once when the OAuth login expires and restarts the daemon after imports, since it never re-reads its files.

.config/calcurse/hooks/post-save

@@ -0,0 +1,6 @@
+#!/bin/sh
+# Sync the UI's saved changes once it exits (syncing while it runs would change files under it).
+[ "$(ps -o args= -p "$PPID")" = calcurse ] && [ "$(ps -o tty= -p "$PPID" | tr -d ' ')" != '?' ] || exit 0
+# shellcheck disable=SC2016 # $1 expands in the inner shell
+setsid -f sh -c 'while kill -0 "$1" 2>/dev/null; do sleep 1; done; systemctl --user start calcurse-sync.service' \
+    sh "$PPID" >/dev/null 2>&1

.config/calcurse/hooks/pre-load

@@ -0,0 +1,5 @@
+#!/bin/sh
+# Sync with Google before the UI loads. Non-interactive calls (-Q, -d, -i, calcurse-caldav's own) run this hook
+# too, so act only for the UI: a bare "calcurse" with a terminal (the daemon is bare too, but has none).
+[ "$(ps -o args= -p "$PPID")" = calcurse ] && [ "$(ps -o tty= -p "$PPID" | tr -d ' ')" != '?' ] || exit 0
+calcurse-sync --now 2>&1 | systemd-cat -t calcurse-sync

.config/systemd/user/calcurse-sync.service

@@ -0,0 +1,6 @@
+[Unit]
+Description=Sync calcurse with Google Calendar
+
+[Service]
+Type=oneshot
+ExecStart=%h/.local/bin/calcurse-sync

.config/systemd/user/calcurse-sync.timer

@@ -0,0 +1,7 @@
+[Unit]
+Description=Sync calcurse with Google Calendar hourly
+
+[Timer]
+OnActiveSec=1min
+OnCalendar=hourly
+Persistent=true

.config/systemd/user/calcurse-today.service

@@ -1,5 +1,6 @@
 [Unit]
 Description=Notify today's calcurse events
+After=calcurse-sync.service
 
 [Service]
 Type=oneshot

.config/xmonad/xmonad.hs

@@ -359,6 +359,7 @@ myStartupHook = do
   spawnOnce "arch-audit-gtk"
   spawnOnce "calcurse --daemon"
   spawnOnce "systemctl --user start calcurse-today.timer"
+  spawnOnce "systemctl --user start calcurse-sync.timer"
   spawnOnce "systemctl --user start dunst"
   spawnOnce "lxpolkit"
   spawnOnce "numlockx"

.local/bin/calcurse-sync

@@ -0,0 +1,52 @@
+#!/bin/bash
+# Sync calcurse with Google Calendar via calcurse-caldav; notify once when the weekly OAuth login expires.
+# --now: called from the UI's pre-load hook (skip the UI check, shorter timeout, no daemon restart).
+set -uo pipefail
+
+data=${XDG_DATA_HOME:-$HOME/.local/share}/calcurse
+state=${XDG_STATE_HOME:-$HOME/.local/state}/calcurse-sync
+expired_flag=$state/login-expired
+now=false
+[[ ${1:-} == --now ]] && now=true
+
+# The UI keeps the data in memory, so syncing under it would lose changes; its post-save hook syncs after it exits.
+ui_running() {
+    # shellcheck disable=SC2009 # pgrep can't match "has any terminal"
+    ps -C calcurse -o tty= | grep -qv '?'
+}
+
+if ! $now && ui_running; then
+    echo "calcurse UI is running, skipping"
+    exit 0
+fi
+
+mkdir -p "$state"
+# BROWSER=true: an expired login must not open browser tabs on its own.
+out=$(BROWSER=true timeout "$($now && echo 15 || echo 60)" calcurse-caldav 2>&1)
+rc=$?
+printf '%s\n' "$out"
+
+if ((rc != 0)); then
+    if grep -q 'Access token is missing or refresh token is expired' <<<"$out"; then
+        if [[ ! -e $expired_flag ]]; then
+            notify-send -a calcurse -u critical -i x-office-calendar "Google Calendar login expired" \
+                "Run calcurse-caldav in a terminal, allow access in the browser, then calcurse-caldav --authcode '<code>'."
+            touch "$expired_flag"
+        fi
+    elif grep -q 'Another synchronization instance' <<<"$out"; then
+        exit 0
+    fi
+    exit "$rc"
+fi
+rm -f "$expired_flag"
+
+# A running daemon never re-reads the data files: restart it so imported appointments get alerts.
+if ! $now && ! grep -q '^0 items imported, 0 items removed locally' <<<"$out"; then
+    pidfile=$data/.daemon.pid
+    if [[ -s $pidfile ]] && pid=$(<"$pidfile") && kill "$pid" 2>/dev/null; then
+        timeout 5 tail --pid="$pid" -f /dev/null
+        # Own scope, so the daemon outlives this oneshot service.
+        systemd-run --user --scope -q calcurse --daemon
+        echo "restarted calcurse daemon"
+    fi
+fi