pim: personal information management, starting with a calendar

A calendar as a file tree, and tools that only know the tree:

	events/date/yyyy/mm/dd/hhmm-summary	as lived
	events/uuid/<uid>/			as stored
	ctl query alarm changed

lib/cal owns all of that. A backend supplies events and, where its
protocol allows, takes changes back -- six methods. cmd/icalfs is the
first: it reads .ics files from a directory and nothing else, because
fetching is rc/fetch's job and hget already exists. That keeps
net/http out of the binary and makes a subscribed calendar and a local
one the same thing.

The tools are rc on purpose. If the tree needs a compiled program to be
useful, the tree is the wrong shape. Three things were added to the
tree because the rc port needed them: a path from an occurrence to its
event, epoch seconds beside RFC3339, and a numeric slot for all-day
events so test(1) can compare it.

ctl reports caps, so a tool can say "read only" instead of trying and
failing. A published .ics is read only: nowhere to PUT, and no
METHOD:REQUEST to reply to. CalDAV would be read write rsvp schedule,
and that is the next backend.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 56 insertions, 0 deletions

diff --git a/pim/rc/fetch b/pim/rc/fetch
new file mode 100755
index 0000000..2208cc7
--- /dev/null
+++ b/pim/rc/fetch
@@ -0,0 +1,56 @@
+#!/bin/rc
+# pim/fetch -- refresh a subscribed calendar from its url.
+#
+#	pim/fetch $home/lib/cal/work.url $home/lib/cal/work.ics \
+#		/mnt/pim/calendars/work/ctl
+#
+# ical/fs does not fetch: a subscribed calendar is a file somebody else
+# wrote. This is that somebody. It writes the file only when the content
+# actually changed, then pokes ctl so the server reloads at once instead
+# of waiting to notice.
+#
+# The url of a private calendar is a secret, so it is read from a file
+# rather than passed as an argument where ps(1) would show it.
+rfork e
+
+if(! ~ $#* 2 && ! ~ $#* 3){
+	echo 'usage: fetch urlfile dest.ics [ctl]' >[1=2]
+	exit usage
+}
+urlfile=$1
+dest=$2
+ctl=$3
+
+if(! test -r $urlfile){
+	echo 'pim/fetch: cannot read '^$urlfile >[1=2]
+	exit nourl
+}
+url=`{sed -n '/^#/d; /^$/d; s/["'']//g; p; q' $urlfile}
+if(~ $#url 0){
+	echo 'pim/fetch: no url in '^$urlfile >[1=2]
+	exit nourl
+}
+
+tmp=$dest.new
+if(! hget $"url > $tmp){
+	rm -f $tmp
+	echo 'pim/fetch: fetch failed' >[1=2]
+	exit fetch
+}
+if(! test -s $tmp){
+	rm -f $tmp
+	echo 'pim/fetch: empty response' >[1=2]
+	exit empty
+}
+
+# a fetch that changes nothing must not rebuild the tree or wake watchers
+if(test -f $dest)
+	if(cmp -s $tmp $dest){
+		rm -f $tmp
+		exit 0
+	}
+mv $tmp $dest
+if(! ~ $#ctl 0)
+	if(test -f $ctl)
+		echo refresh >$ctl
+exit 0