23764: allow hidden continuations in calendar entries

allow UIDs to help with updates

4 files changed, 68 insertions, 13 deletions

diff --git a/ChangeLog b/ChangeLog
index c0ba169de..031da9e4d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2007-08-16  Peter Stephenson  <pws@csr.com>
 
+	* 23764: Doc/Zsh/calsys.yo, Functions/Calendar/calendar,
+	Functions/Calendar/calendar_add: allow hidden continuation
+	lines in calendar entry and use UID to help with updates.
+
 	* Roy Marples: 23762: configure.ac: need to suppress [...] quoting
 	for use of [...] in case.
 
diff --git a/Doc/Zsh/calsys.yo b/Doc/Zsh/calsys.yo
index 3b6551b07..d020a59ef 100644
--- a/Doc/Zsh/calsys.yo
+++ b/Doc/Zsh/calsys.yo
@@ -50,6 +50,12 @@ that continues the description of the event from the preceeding line
 (note the date may not be continued in this way).  An initial ampersand
 (tt(&)) is ignored for compatibility.
 
+An indented line on which the first non-whitespace character is tt(#)
+is not displayed with the calendar entry, but is still scanned for
+information.  This can be used to hide information useful to the
+calendar system but not to the user, such as the unique identifier
+used by tt(calendar_add).
+
 The Emacs extension that a date with no description may refer to a number
 of succeeding events at different times is not supported.
 
@@ -289,13 +295,18 @@ as recommended above.
 example(Feb 1, 2006 14:30 Pointless bureaucratic meeting
 Mar 27, 2006 11:00 Mutual recrimination and finger pointing
   Bring water pistol and waterproofs
+Mar 31, 2006 14:00 Very serious managerial pontification
+  # UID 12C7878A9A50
 Apr 10, 2006 13:30 Even more pointless blame assignment exercise WARN 30 mins
 May 18, 2006 16:00 Regular moaning session RPT monthly, 3rd Thursday)
 
-The second entry has a continuation line.  The third entry will produce
-a warning 30 minutes before the event (to allow you to equip yourself
-appropriately).  The fourth entry repeats after a month on the 3rd
-Thursday, i.e. June 15, 2006, at the same time.
+The second entry has a continuation line.  The third entry has a
+continuation line that will not be shown when the entry is displayed, but
+the unique identifier will be used by the tt(calendar_add) function when
+updating the event.  The fourth entry will produce a warning 30 minutes
+before the event (to allow you to equip yourself appropriately).  The fifth
+entry repeats after a month on the 3rd Thursday, i.e. June 15, 2006, at the
+same time.
 
 texinode(Calendar System User Functions)(Calendar Styles)(Calendar File and Date Formats)(Calendar Function System)
 sect(User Functions)
@@ -415,16 +426,32 @@ enditem()
 findex(calendar_add)
 item(tt(calendar_add) [ tt(-BL) ] var(event ...))(
 Adds a single event to the calendar in the appropriate location.
+The event can contain multiple lines, as described in
+ifnzman(noderef(Calendar File and Date Formats))\
+ifzman(the section Calendar File Format above).
 Using this function ensures that the calendar file is sorted in date
 and time order.  It also makes special arrangments for locking
-the file will it is altered.  The old calendar is left in a file
+the file while it is altered.  The old calendar is left in a file
 with the suffix tt(.old).
 
 The option tt(-B) indicates that backing up the calendar file will be
 handled by the caller and should not be performed by tt(calendar_add).  The
 option tt(-L) indicates that tt(calendar_add) does not need to lock the
-calendar file up the old one as it is already locked.  These options will
-not usually be needed by users.
+calendar file as it is already locked.  These options will not usually be
+needed by users.
+
+The function can use a unique identifier stored with each event to ensure
+that updates to existing events are treated correctly.  The entry
+should contain the word tt(UID), followed by whitespace, followed by
+a word consisting entirely of hexadecimal digits of arbitrary length
+(all digits are significant, including leading zeroes).  As the UID
+is not directly useful to the user, it is convenient to hide it on
+an indented continuation line starting with a tt(#), for example:
+
+example(Aug 31, 2007 09:30  Celebrate the end of the holidays
+  # UID 045B78A0)
+
+The second line will not be shown by the tt(calendar) function.
 )
 findex(calendar_edit)
 item(tt(calendar_edit))(
diff --git a/Functions/Calendar/calendar b/Functions/Calendar/calendar
index 328da853c..b5df2ca72 100644
--- a/Functions/Calendar/calendar
+++ b/Functions/Calendar/calendar
@@ -293,6 +293,13 @@ fi
       showline=${line%%$'\n'*}
     else
       showline=$line
+      match=()
+      # Strip continuation lines starting " #".
+      while [[ $showline = (#b)(*$'\n')[[:space:]]##\#[^$'\n']##(|$'\n'(*)) ]]; do
+	showline="$match[1]$match[3]"
+      done
+      # Strip trailing empty lines
+      showline=${showline%%[[:space:]]#}
     fi
     if (( showall || (t >= start && (remaining || t <= stop || icount < showcount)) ))
     then
diff --git a/Functions/Calendar/calendar_add b/Functions/Calendar/calendar_add
index 8e6eca8b6..dc9f50c2b 100644
--- a/Functions/Calendar/calendar_add
+++ b/Functions/Calendar/calendar_add
@@ -12,7 +12,7 @@ setopt extendedglob
 
 local calendar newfile REPLY lastline opt
 local -a calendar_entries lockfiles
-integer newdate done rstat nolock nobackup
+integer my_date done rstat nolock nobackup
 
 autoload -U calendar_{read,lockfiles,scandate}
 
@@ -42,10 +42,20 @@ if ! calendar_scandate -a "$*"; then
   print "$0: failed to parse date/time" >&2
   return 1
 fi
-(( newdate = $REPLY ))
+(( my_date = $REPLY ))
 
 # $calendar doesn't necessarily exist yet.
 
+local -a match mbegin mend
+local my_uid their_uid
+
+# Match a UID, a unique identifier for the entry inherited from
+# text/calendar format.
+local uidpat='(|*[[:space:]])UID[[:space:]]##(#b)([[:xdigit:]]##)(|[[:space:]]*)'
+if [[ "$*" = ${~uidpat} ]]; then
+  my_uid=$match[1]
+fi
+
 # start of block for following always to clear up lockfiles.
 {
   (( nolock )) || calendar_lockfiles $calendar || return 1
@@ -55,15 +65,22 @@ fi
 
     {
       for line in $calendar_entries; do
-	if (( ! done )) && calendar_scandate -a $line && (( REPLY > newdate )); then
+	if (( ! done )) && calendar_scandate -a $line && (( REPLY > my_date )); then
 	  print -r -- "$*"
 	  (( done = 1 ))
-	elif [[ $REPLY -eq $newdate && $line = "$*" ]]; then
+	fi
+	# Don't save this entry if it has the same UID as the new one.
+	if [[ -n $my_uid && $line = ${~uidpat} ]]; then
+	  their_uid=$match[1]
+	  [[ ${(U)my_uid} = ${(U)their_uid} ]] && continue
+	fi
+	if [[ $REPLY -eq $my_date && $line = "$*" ]]; then
+	  (( done )) && continue # paranoia: shouldn't happen
 	  (( done = 1 ))
 	fi
 	print -r -- $line
-	done
-	(( done )) || print -r -- "$*"
+      done
+      (( done )) || print -r -- "$*"
     } >$newfile
     if (( ! nobackup )); then
       if ! mv $calendar $calendar.old; then