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+;;; org-e-icalendar.el --- iCalendar Back-End for Org Export Engine
+
+;; Copyright (C) 2004-2012 Free Software Foundation, Inc.
+
+;; Author: Carsten Dominik <carsten at orgmode dot org>
+;;      Nicolas Goaziou <n dot goaziou at gmail dot com>
+;; Keywords: outlines, hypermedia, calendar, wp
+;; Homepage: http://orgmode.org
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+;;
+;; This library implements an iCalendar back-end for Org generic
+;; exporter.
+;;
+;; It provides three commands for export, depending on the chosen
+;; source and desired output: `org-e-icalendar-export-to-ics' (current
+;; file), `org-e-icalendar-export-agenda-files' (agenda files into
+;; separate calendars) and `org-e-icalendar-combined-agenda-file'
+;; (agenda files into one combined calendar).
+;;
+;; It also provides the `org-e-icalendar-export-current-agenda'
+;; function, which will create a calendar file from current agenda
+;; view.  It is meant to be called through `org-agenda-write'.
+;;
+;; This back-end introduces a new keyword, ICALENDAR_EXCLUDE_TAGS,
+;; which allows to specify a different set of exclude tags from other
+;; back-ends.
+;;
+;; It should follow RFC 5545 specifications.
+
+;;; Code:
+
+(require 'org-e-ascii)
+(declare-function org-bbdb-anniv-export-ical "org-bbdb" nil)
+
+
+
+;;; User-Configurable Variables
+
+(defgroup org-export-e-icalendar nil
+  "Options specific for iCalendar export back-end."
+  :tag "Org iCalendar"
+  :group 'org-export)
+
+(defcustom org-e-icalendar-combined-agenda-file "~/org.ics"
+  "The file name for the iCalendar file covering all agenda files.
+This file is created with the command \\[org-e-icalendar-combine-agenda-files].
+The file name should be absolute.  It will be overwritten without warning."
+  :group 'org-export-e-icalendar
+  :type 'file)
+
+(defcustom org-e-icalendar-alarm-time 0
+  "Number of minutes for triggering an alarm for exported timed events.
+
+A zero value (the default) turns off the definition of an alarm trigger
+for timed events.  If non-zero, alarms are created.
+
+- a single alarm per entry is defined
+- The alarm will go off N minutes before the event
+- only a DISPLAY action is defined."
+  :group 'org-export-e-icalendar
+  :version "24.1"
+  :type 'integer)
+
+(defcustom org-e-icalendar-combined-name "OrgMode"
+  "Calendar name for the combined iCalendar representing all agenda files."
+  :group 'org-export-e-icalendar
+  :type 'string)
+
+(defcustom org-e-icalendar-combined-description ""
+  "Calendar description for the combined iCalendar (all agenda files)."
+  :group 'org-export-e-icalendar
+  :type 'string)
+
+(defcustom org-e-icalendar-exclude-tags nil
+  "Tags that exclude a tree from export.
+This variable allows to specify different exclude tags from other
+back-ends.  It can also be set with the ICAL_EXCLUDE_TAGS
+keyword."
+  :group 'org-export-e-icalendar
+  :type '(repeat (string :tag "Tag")))
+
+(defcustom org-e-icalendar-use-deadline '(event-if-not-todo todo-due)
+  "Contexts where iCalendar export should use a deadline time stamp.
+
+This is a list with several symbols in it.  Valid symbol are:
+`event-if-todo'       Deadlines in TODO entries become calendar events.
+`event-if-not-todo'   Deadlines in non-TODO entries become calendar events.
+`todo-due'            Use deadlines in TODO entries as due-dates"
+  :group 'org-export-e-icalendar
+  :type '(set :greedy t
+	      (const :tag "Deadlines in non-TODO entries become events"
+		     event-if-not-todo)
+	      (const :tag "Deadline in TODO entries become events"
+		     event-if-todo)
+	      (const :tag "Deadlines in TODO entries become due-dates"
+		     todo-due)))
+
+(defcustom org-e-icalendar-use-scheduled '(todo-start)
+  "Contexts where iCalendar export should use a scheduling time stamp.
+
+This is a list with several symbols in it.  Valid symbol are:
+`event-if-todo'       Scheduling time stamps in TODO entries become an event.
+`event-if-not-todo'   Scheduling time stamps in non-TODO entries become an event.
+`todo-start'          Scheduling time stamps in TODO entries become start date.
+                      Some calendar applications show TODO entries only after
+                      that date."
+  :group 'org-export-e-icalendar
+  :type '(set :greedy t
+	      (const :tag
+		     "SCHEDULED timestamps in non-TODO entries become events"
+		     event-if-not-todo)
+	      (const :tag "SCHEDULED timestamps in TODO entries become events"
+		     event-if-todo)
+	      (const :tag "SCHEDULED in TODO entries become start date"
+		     todo-start)))
+
+(defcustom org-e-icalendar-categories '(local-tags category)
+  "Items that should be entered into the \"categories\" field.
+
+This is a list of symbols, the following are valid:
+`category'    The Org mode category of the current file or tree
+`todo-state'  The todo state, if any
+`local-tags'  The tags, defined in the current line
+`all-tags'    All tags, including inherited ones."
+  :group 'org-export-e-icalendar
+  :type '(repeat
+	  (choice
+	   (const :tag "The file or tree category" category)
+	   (const :tag "The TODO state" todo-state)
+	   (const :tag "Tags defined in current line" local-tags)
+	   (const :tag "All tags, including inherited ones" all-tags))))
+
+(defcustom org-e-icalendar-with-tasks nil
+  "Non-nil means export to iCalendar files should also cover TODO items.
+
+Valid values are:
+t                    include tasks independent of state.
+`todo'               include only tasks that are not yet done.
+`done'               include only tasks that are already done.
+nil                  ignore all tasks.
+list of keywords     include tasks with these keywords.
+`unblocked'          include all TODO items that are not blocked.
+
+This variable has precedence over `org-export-with-tasks'.  It
+can also be set with the #+OPTIONS line,
+e.g. \"tasks:unblocked\"."
+  :group 'org-export-e-icalendar
+  :type '(choice
+	  (const :tag "None" nil)
+	  (const :tag "Unfinished" t)
+	  (const :tag "Unblocked" unblocked)
+	  (const :tag "All" all)))
+
+(defcustom org-e-icalendar-with-timestamps 'active
+  "Non-nil means make an event from plain time stamps.
+
+It can be set to `active', `inactive', t or nil, in order to make
+an event from, respectively, only active timestamps, only
+inactive ones, all of them or none.
+
+This variable has precedence over `org-export-with-timestamps'.
+It can also be set with the #+OPTIONS line, e.g. \"<:t\"."
+  :group 'org-export-e-icalendar
+  :type '(choice
+	  (const :tag "All timestamps" t)
+	  (const :tag "Only active timestamps" active)
+	  (const :tag "Only inactive timestamps" inactive)
+	  (const :tag "No timestamp" nil)))
+
+(defcustom org-e-icalendar-include-bbdb-anniversaries nil
+  "Non-nil means a combined iCalendar file should include anniversaries.
+The anniversaries are defined in the BBDB database."
+  :group 'org-export-e-icalendar
+  :type 'boolean)
+
+(defcustom org-e-icalendar-include-sexps t
+  "Non-nil means export to iCalendar files should also cover sexp entries.
+These are entries like in the diary, but directly in an Org mode
+file."
+  :group 'org-export-e-icalendar
+  :type 'boolean)
+
+(defcustom org-e-icalendar-include-body t
+  "Amount of text below headline to be included in iCalendar export.
+This is a number of characters that should maximally be included.
+Properties, scheduling and clocking lines will always be removed.
+The text will be inserted into the DESCRIPTION field."
+  :group 'org-export-e-icalendar
+  :type '(choice
+	  (const :tag "Nothing" nil)
+	  (const :tag "Everything" t)
+	  (integer :tag "Max characters")))
+
+(defcustom org-e-icalendar-store-UID nil
+  "Non-nil means store any created UIDs in properties.
+
+The iCalendar standard requires that all entries have a unique identifier.
+Org will create these identifiers as needed.  When this variable is non-nil,
+the created UIDs will be stored in the ID property of the entry.  Then the
+next time this entry is exported, it will be exported with the same UID,
+superseding the previous form of it.  This is essential for
+synchronization services.
+
+This variable is not turned on by default because we want to avoid creating
+a property drawer in every entry if people are only playing with this feature,
+or if they are only using it locally."
+  :group 'org-export-e-icalendar
+  :type 'boolean)
+
+(defcustom org-e-icalendar-timezone (getenv "TZ")
+  "The time zone string for iCalendar export.
+When nil or the empty string, use output
+from (current-time-zone)."
+  :group 'org-export-e-icalendar
+  :type '(choice
+	  (const :tag "Unspecified" nil)
+	  (string :tag "Time zone")))
+
+(defcustom org-e-icalendar-date-time-format ":%Y%m%dT%H%M%S"
+  "Format-string for exporting icalendar DATE-TIME.
+
+See `format-time-string' for a full documentation.  The only
+difference is that `org-e-icalendar-timezone' is used for %Z.
+
+Interesting value are:
+ - \":%Y%m%dT%H%M%S\" for local time
+ - \";TZID=%Z:%Y%m%dT%H%M%S\" for local time with explicit timezone
+ - \":%Y%m%dT%H%M%SZ\" for time expressed in Universal Time"
+  :group 'org-export-e-icalendar
+  :version "24.1"
+  :type '(choice
+	  (const :tag "Local time" ":%Y%m%dT%H%M%S")
+	  (const :tag "Explicit local time" ";TZID=%Z:%Y%m%dT%H%M%S")
+	  (const :tag "Universal time" ":%Y%m%dT%H%M%SZ")
+	  (string :tag "Explicit format")))
+
+(defvar org-e-icalendar-after-save-hook nil
+  "Hook run after an iCalendar file has been saved.
+This hook is run with the name of the file as argument.  A good
+way to use this is to tell a desktop calendar application to
+re-read the iCalendar file.")
+
+
+
+;;; Define Back-End
+
+(org-export-define-derived-backend e-icalendar e-ascii
+  :translate-alist ((clock . ignore)
+		    (headline . org-e-icalendar-entry)
+		    (inlinetask . ignore)
+		    (planning . ignore)
+		    (section . ignore)
+		    (template . org-e-icalendar-template))
+  :options-alist
+  ((:exclude-tags
+    "ICALENDAR_EXCLUDE_TAGS" nil org-e-icalendar-exclude-tags split)
+   (:with-tasks nil "tasks" org-e-icalendar-with-tasks)
+   (:with-timestamps nil "<" org-e-icalendar-with-timestamps)
+   ;; The following property will be non-nil when export has been
+   ;; started from org-agenda-mode.  In this case, any entry without
+   ;; a non-nil "ICALENDAR_MARK" property will be ignored.
+   (:icalendar-agenda-view nil nil nil))
+  :filters-alist
+  ((:filter-headline . org-e-icalendar-clear-blank-lines))
+  :menu-entry
+  (?c "Export to iCalendar"
+      ((?f "Current file"
+	   (lambda (s v b) (org-e-icalendar-export-to-ics s v b)))
+       (?a "All agenda files"
+	   (lambda (s v b) (org-e-icalendar-export-agenda-files)))
+       (?c "Combine all agenda files"
+	   (lambda (s v b) (org-e-icalendar-combine-agenda-files))))))
+
+
+
+;;; Internal Functions
+
+(defun org-e-icalendar-create-uid (file &optional bell)
+  "Set ID property on headlines missing it in FILE.
+When optional argument BELL is non-nil, inform the user with
+a message if the file was modified."
+  (let (modified-flag)
+    (org-map-entries
+     (lambda ()
+       (let ((entry (org-element-at-point)))
+	 (unless (org-element-property :id entry)
+	   (org-id-get-create)
+	   (setq modified-flag t)
+	   (forward-line))
+	 (when (eq (org-element-type entry) 'inlinetask)
+	   (setq org-map-continue-from (org-element-property :end entry)))))
+     nil nil 'comment)
+    (when (and bell modified-flag)
+      (message "ID properties created in file \"%s\"" file)
+      (sit-for 2))))
+
+(defun org-e-icalendar-blocked-headline-p (headline info)
+  "Non-nil when HEADLINE is considered to be blocked.
+
+INFO is a plist used as a communication channel.
+
+An headline is blocked when either:
+
+  - It has children which are not all in a completed state.
+
+  - It has a parent with the property :ORDERED:, and there are
+    siblings prior to it with incomplete status.
+
+  - Its parent is blocked because it has siblings that should be
+    done first or is a child of a blocked grandparent entry."
+  (or
+   ;; Check if any child is not done.
+   (org-element-map
+    headline 'headline
+    (lambda (hl) (eq (org-element-property :todo-type hl) 'todo))
+    info 'first-match)
+   ;; Check :ORDERED: node property.
+   (catch 'blockedp
+     (let ((current headline))
+       (mapc (lambda (parent)
+	       (cond
+		((not (org-element-property :todo-keyword parent))
+		 (throw 'blockedp nil))
+		((org-not-nil (org-element-property :ordered parent))
+		 (let ((sibling current))
+		   (while (setq sibling (org-export-get-previous-element
+					 sibling info))
+		     (when (eq (org-element-property :todo-type sibling) 'todo)
+		       (throw 'blockedp t)))))
+		(t (setq current parent))))
+	     (org-export-get-genealogy headline))
+       nil))))
+
+(defun org-e-icalendar-use-UTC-date-time-p ()
+  "Non-nil when `org-e-icalendar-date-time-format' requires UTC time."
+  (char-equal (elt org-e-icalendar-date-time-format
+		   (1- (length org-e-icalendar-date-time-format))) ?Z))
+
+(defvar org-agenda-default-appointment-duration) ; From org-agenda.el.
+(defun org-e-icalendar-convert-timestamp (timestamp keyword &optional end utc)
+  "Convert TIMESTAMP to iCalendar format.
+
+TIMESTAMP is a timestamp object.  KEYWORD is added in front of
+it, in order to make a complete line (e.g. \"DTSTART\").
+
+When optional argument END is non-nil, use end of time range.
+Also increase the hour by two (if time string contains a time),
+or the day by one (if it does not contain a time).
+
+When optional argument UTC is non-nil, time will be expressed in
+Universal Time, ignoring `org-e-icalendar-date-time-format'.
+This is mandatory for \"DTSTAMP\" property."
+  (let* ((with-time-p (org-element-property :minute-start timestamp))
+	 (mi (cond ((not with-time-p) 0)
+		   ((not end) (org-element-property :minute-start timestamp))
+		   (org-agenda-default-appointment-duration
+		    (+ (org-element-property :minute-end timestamp)
+		       org-agenda-default-appointment-duration))
+		   (t (org-element-property :minute-end timestamp))))
+	 (h (cond ((not with-time-p) 0)
+		  ((not end) (org-element-property :hour-start timestamp))
+		  (org-agenda-default-appointment-duration
+		   (org-element-property :hour-end timestamp))
+		  (t (+ (org-element-property :hour-end timestamp) 2))))
+	 (d (cond ((not end) (org-element-property :day-start timestamp))
+		  ((not with-time-p)
+		   (1+ (org-element-property :day-end timestamp)))
+		  (t (org-element-property :day-end timestamp))))
+	 (m (org-element-property (if end :month-end :month-start) timestamp))
+	 (y (org-element-property (if end :year-end :year-start) timestamp)))
+    (concat
+     keyword
+     (format-time-string
+      (cond (utc ":%Y%m%dT%H%M%SZ")
+	    ((not with-time-p) ";VALUE=DATE:%Y%m%d")
+	    (t (replace-regexp-in-string "%Z"
+					 org-e-icalendar-timezone
+					 org-e-icalendar-date-time-format)))
+      ;; Convert timestamp into internal time in order to use
+      ;; `format-time-string' and fix any mistake (i.e. MI >= 60).
+      (encode-time 0 mi h d m y)
+      (or utc (and with-time-p (org-e-icalendar-use-UTC-date-time-p)))))))
+
+(defun org-e-icalendar-get-categories (entry info)
+  "Return categories according to `org-e-icalendar-categories'.
+ENTRY is an headline or an inlinetask element.  INFO is a plist
+used as a communication channel."
+  (mapconcat
+   'identity
+   (org-uniquify
+    (let (categories)
+      (mapc (lambda (type)
+	      (case type
+		(category
+		 (push (org-export-get-category entry info) categories))
+		(todo-state
+		 (let ((todo (org-element-property :todo-keyword entry)))
+		   (and todo (push todo categories))))
+		(local-tags
+		 (setq categories
+		       (append (nreverse (org-export-get-tags entry info))
+			       categories)))
+		(all-tags
+		 (setq categories
+		       (append (nreverse (org-export-get-tags entry info nil t))
+			       categories)))))
+	    org-e-icalendar-categories)
+      ;; Return list of categories, following specified order.
+      (nreverse categories))) ","))
+
+(defun org-e-icalendar-transcode-diary-sexp (sexp uid summary)
+  "Transcode a diary sexp into iCalendar format.
+SEXP is the diary sexp being transcoded, as a string.  UID is the
+unique identifier for the entry.  SUMMARY defines a short summary
+or subject for the event."
+  (when (require 'icalendar nil t)
+    (org-element-normalize-string
+     (with-temp-buffer
+       (let ((sexp (if (not (string-match "\\`<%%" sexp)) sexp
+		     (concat (substring sexp 1 -1) " " summary))))
+	 (put-text-property 0 1 'uid uid sexp)
+	 (insert sexp "\n"))
+       (org-diary-to-ical-string (current-buffer))))))
+
+(defun org-e-icalendar-cleanup-string (s)
+  "Cleanup string S according to RFC 5545."
+  (when s
+    ;; Protect "\", "," and ";" characters. and replace newline
+    ;; characters with literal \n.
+    (replace-regexp-in-string
+     "[ \t]*\n" "\\n"
+     (replace-regexp-in-string "[\\,;]" "\\\&" s)
+     nil t)))
+
+(defun org-e-icalendar-fold-string (s)
+  "Fold string S according to RFC 5545."
+  (org-element-normalize-string
+   (mapconcat
+    (lambda (line)
+      ;; Limit each line to a maximum of 75 characters.  If it is
+      ;; longer, fold it by using "\n " as a continuation marker.
+      (let ((len (length line)))
+	(if (<= len 75) line
+	  (let ((folded-line (substring line 0 75))
+		(chunk-start 75)
+		chunk-end)
+	    ;; Since continuation marker takes up one character on the
+	    ;; line, real contents must be split at 74 chars.
+	    (while (< (setq chunk-end (+ chunk-start 74)) len)
+	      (setq folded-line
+		    (concat folded-line "\n "
+			    (substring line chunk-start chunk-end))
+		    chunk-start chunk-end))
+	    (concat folded-line "\n " (substring line chunk-start))))))
+    (org-split-string s "\n") "\n")))
+
+
+
+;;; Filters
+
+(defun org-e-icalendar-clear-blank-lines (headline back-end info)
+  "Remove trailing blank lines in HEADLINE export.
+HEADLINE is a string representing a transcoded headline.
+BACK-END and INFO are ignored."
+  (replace-regexp-in-string "^\\(?:[ \t]*\n\\)*" "" headline))
+
+
+
+;;; Transcode Functions
+
+;;;; Headline and Inlinetasks
+
+;; The main function is `org-e-icalendar-entry', which extracts
+;; information from an headline or an inlinetask (summary,
+;; description...) and then delegates code generation to
+;; `org-e-icalendar--vtodo' and `org-e-icalendar--vevent', depending
+;; on the component needed.
+
+;; Obviously, `org-e-icalendar--valarm' handles alarms, which can
+;; happen within a VTODO component.
+
+(defun org-e-icalendar-entry (entry contents info)
+  "Transcode ENTRY element into iCalendar format.
+
+ENTRY is either an headline or an inlinetask.  CONTENTS is
+ignored.  INFO is a plist used as a communication channel.
+
+This function is called on every headline, the section below
+it (minus inlinetasks) being its contents.  It tries to create
+VEVENT and VTODO components out of scheduled date, deadline date,
+plain timestamps, diary sexps.  It also calls itself on every
+inlinetask within the section."
+  (unless (org-element-property :footnote-section-p entry)
+    (let* ((type (org-element-type entry))
+	   ;; Determine contents really associated to the entry.  For
+	   ;; an headline, limit them to section, if any.  For an
+	   ;; inlinetask, this is every element within the task.
+	   (inside
+	    (if (eq type 'inlinetask)
+		(cons 'org-data (cons nil (org-element-contents entry)))
+	      (let ((first (car (org-element-contents entry))))
+		(and (eq (org-element-type first) 'section)
+		     (cons 'org-data
+			   (cons nil (org-element-contents first))))))))
+      (concat
+       (unless (and (plist-get info :icalendar-agenda-view)
+		    (not (org-element-property :icalendar-mark entry)))
+	 (let ((todo-type (org-element-property :todo-type entry))
+	       (uid (or (org-element-property :id entry) (org-id-new)))
+	       (summary (org-e-icalendar-cleanup-string
+			 (or (org-element-property :summary entry)
+			     (org-export-data
+			      (org-element-property :title entry) info))))
+	       (loc (org-e-icalendar-cleanup-string
+		     (org-element-property :location entry)))
+	       ;; Build description of the entry from associated
+	       ;; section (headline) or contents (inlinetask).
+	       (desc
+		(org-e-icalendar-cleanup-string
+		 (or (org-element-property :description entry)
+		     (let ((contents (org-export-data inside info)))
+		       (cond
+			((not (org-string-nw-p contents)) nil)
+			((wholenump org-e-icalendar-include-body)
+			 (let ((contents (org-trim contents)))
+			   (substring
+			    contents 0 (min (length contents)
+					    org-e-icalendar-include-body))))
+			(org-e-icalendar-include-body (org-trim contents)))))))
+	       (cat (org-e-icalendar-get-categories entry info)))
+	   (concat
+	    ;; Events: Delegate to `org-e-icalendar--vevent' to
+	    ;; generate "VEVENT" component from scheduled, deadline,
+	    ;; or any timestamp in the entry.
+	    (let ((deadline (org-element-property :deadline entry)))
+	      (and deadline
+		   (memq (if todo-type 'event-if-todo 'event-if-not-todo)
+			 org-e-icalendar-use-deadline)
+		   (org-e-icalendar--vevent
+		    entry deadline (concat "DL-" uid)
+		    (concat "DL: " summary) loc desc cat)))
+	    (let ((scheduled (org-element-property :scheduled entry)))
+	      (and scheduled
+		   (memq (if todo-type 'event-if-todo 'event-if-not-todo)
+			 org-e-icalendar-use-scheduled)
+		   (org-e-icalendar--vevent
+		    entry scheduled (concat "SC-" uid)
+		    (concat "S: " summary) loc desc cat)))
+	    ;; When collecting plain timestamps from an headline, skip
+	    ;; inlinetasks since collection will happen once ENTRY is
+	    ;; one of them.
+	    (let ((counter 0))
+	      (mapconcat
+	       'identity
+	       (org-element-map
+		inside 'timestamp
+		(lambda (ts)
+		  (let ((uid (format "TS%d-%s" (incf counter) uid)))
+		    (org-e-icalendar--vevent entry ts uid summary loc desc cat)))
+		info nil (and (eq type 'headline) 'inlinetask))
+	       ""))
+	    ;; Task: First check if it is appropriate to export it.
+	    ;; If so, call `org-e-icalendar--vtodo' to transcode it
+	    ;; into a "VTODO" component.
+	    (when (and todo-type
+		       (not (and (eq (plist-get info :with-tasks) 'unblocked)
+				 (eq (org-element-type entry) 'headline)
+				 (org-e-icalendar-blocked-headline-p
+				  entry info))))
+	      (org-e-icalendar--vtodo entry uid summary loc desc cat))
+	    ;; Diary-sexp: Collect every diary-sexp element within
+	    ;; ENTRY and transcode them.  If ENTRY is an headline,
+	    ;; skip inlinetasks: they will be handled separately.
+	    (when org-e-icalendar-include-sexps
+	      (let ((counter 0))
+		(mapconcat 'identity
+			   (org-element-map
+			    inside 'diary-sexp
+			    (lambda (sexp)
+			      (org-e-icalendar-transcode-diary-sexp
+			       (org-element-property :value sexp)
+			       (format "DS%d-%s" (incf counter) uid)
+			       summary))
+			    info nil (and (eq type 'headline) 'inlinetask))
+			   ""))))))
+       ;; If ENTRY is an headline, call current function on every
+       ;; inlinetask within it.  In agenda export, this is independent
+       ;; from the mark (or lack thereof) on the entry.
+       (when (eq type 'headline)
+	 (mapconcat 'identity
+		    (org-element-map
+		     inside 'inlinetask
+		     (lambda (task) (org-e-icalendar-entry task nil info))
+		     info) ""))
+       ;; Don't forget components from inner entries.
+       contents))))
+
+(defun org-e-icalendar--vevent
+  (entry timestamp uid summary location description categories)
+  "Create a VEVENT component.
+
+ENTRY is either an headline or an inlinetask element.  TIMESTAMP
+is a timestamp object defining the date-time of the event.  UID
+is the unique identifier for the event.  SUMMARY defines a short
+summary or subject for the event.  LOCATION defines the intended
+venue for the event.  DESCRIPTION provides the complete
+description of the event.  CATEGORIES defines the categories the
+event belongs to.
+
+Return VEVENT component as a string."
+  (org-e-icalendar-fold-string
+   (if (eq (org-element-property :type timestamp) 'diary)
+       (org-e-icalendar-transcode-diary-sexp
+	(org-element-property :raw-value timestamp) uid summary)
+     (concat "BEGIN:VEVENT\n"
+	     (org-e-icalendar-convert-timestamp timestamp "DTSTAMP" nil t) "\n"
+	     "UID:" uid "\n"
+	     (org-e-icalendar-convert-timestamp timestamp "DTSTART") "\n"
+	     (org-e-icalendar-convert-timestamp timestamp "DTEND" t) "\n"
+	     ;; RRULE.
+	     (when (org-element-property :repeater-type timestamp)
+	       (format "RRULE:FREQ=%s;INTERVAL=%d\n"
+		       (case (org-element-property :repeater-unit timestamp)
+			 (hour "HOURLY") (day "DAILY") (week "WEEKLY")
+			 (month "MONTHLY") (year "YEARLY"))
+		       (org-element-property :repeater-value timestamp)))
+	     "SUMMARY:" summary "\n"
+	     (and (org-string-nw-p location) (format "LOCATION:%s\n" location))
+	     (and (org-string-nw-p description)
+		  (format "DESCRIPTION:%s\n" description))
+	     "CATEGORIES:" categories "\n"
+	     ;; VALARM.
+	     (org-e-icalendar--valarm entry timestamp summary)
+	     "END:VEVENT"))))
+
+(defun org-e-icalendar--vtodo
+  (entry uid summary location description categories)
+  "Create a VTODO component.
+
+ENTRY is either an headline or an inlinetask element.  UID is the
+unique identifier for the task.  SUMMARY defines a short summary
+or subject for the task.  LOCATION defines the intended venue for
+the task.  DESCRIPTION provides the complete description of the
+task.  CATEGORIES defines the categories the task belongs to.
+
+Return VTODO component as a string."
+  (let ((start (or (and (memq 'todo-start org-e-icalendar-use-scheduled)
+			(org-element-property :scheduled entry))
+		   ;; If we can't use a scheduled time for some
+		   ;; reason, start task now.
+		   (let ((now (decode-time (current-time))))
+		     (list 'timestamp
+			   (list :type 'active
+				 :minute-start (nth 1 now)
+				 :hour-start (nth 2 now)
+				 :day-start (nth 3 now)
+				 :month-start (nth 4 now)
+				 :year-start (nth 5 now)))))))
+    (org-e-icalendar-fold-string
+     (concat "BEGIN:VTODO\n"
+	     "UID:TODO-" uid "\n"
+	     (org-e-icalendar-convert-timestamp start "DTSTAMP" nil t) "\n"
+	     (org-e-icalendar-convert-timestamp start "DTSTART") "\n"
+	     (and (memq 'todo-due org-e-icalendar-use-deadline)
+		  (org-element-property :deadline entry)
+		  (concat (org-e-icalendar-convert-timestamp
+			   (org-element-property :deadline entry) "DUE")
+			  "\n"))
+	     "SUMMARY:" summary "\n"
+	     (and (org-string-nw-p location) (format "LOCATION:%s\n" location))
+	     (and (org-string-nw-p description)
+		  (format "DESCRIPTION:%s\n" description))
+	     "CATEGORIES:" categories "\n"
+	     "SEQUENCE:1\n"
+	     (format "PRIORITY:%d\n"
+		     (let ((pri (or (org-element-property :priority entry)
+				    org-default-priority)))
+		       (floor (- 9 (* 8. (/ (float (- org-lowest-priority pri))
+					    (- org-lowest-priority
+					       org-highest-priority)))))))
+	     (format "STATUS:%s\n"
+		     (if (eq (org-element-property :todo-type entry) 'todo)
+			 "NEEDS-ACTION"
+		       "COMPLETED"))
+	     "END:VTODO"))))
+
+(defun org-e-icalendar--valarm (entry timestamp summary)
+  "Create a VALARM component.
+
+ENTRY is the calendar entry triggering the alarm.  TIMESTAMP is
+the start date-time of the entry.  SUMMARY defines a short
+summary or subject for the task.
+
+Return VALARM component as a string, or nil if it isn't allowed."
+  ;; Create a VALARM entry if the entry is timed.  This is not very
+  ;; general in that:
+  ;; (a) only one alarm per entry is defined,
+  ;; (b) only minutes are allowed for the trigger period ahead of the
+  ;;     start time,
+  ;; (c) only a DISPLAY action is defined.                       [ESF]
+  (let ((alarm-time
+	 (let ((warntime
+		(org-element-property :appt-warntime entry)))
+	   (if warntime (string-to-number warntime) 0))))
+    (and (or (> alarm-time 0) (> org-e-icalendar-alarm-time 0))
+	 (org-element-property :hour-start timestamp)
+	 (format "BEGIN:VALARM
+ACTION:DISPLAY
+DESCRIPTION:%s
+TRIGGER:-P0DT0H%dM0S
+END:VALARM\n"
+		 summary
+		 (if (zerop alarm-time) org-e-icalendar-alarm-time alarm-time)))))
+
+
+;;;; Template
+
+(defun org-e-icalendar-template (contents info)
+  "Return complete document string after iCalendar conversion.
+CONTENTS is the transcoded contents string.  INFO is a plist used
+as a communication channel."
+  (org-e-icalendar--vcalendar
+   ;; Name.
+   (if (not (plist-get info :input-file)) (buffer-name (buffer-base-buffer))
+     (file-name-nondirectory
+      (file-name-sans-extension (plist-get info :input-file))))
+   ;; Owner.
+   (if (not (plist-get info :with-author)) ""
+     (org-export-data (plist-get info :author) info))
+   ;; Timezone.
+   (if (org-string-nw-p org-e-icalendar-timezone) org-e-icalendar-timezone
+     (cadr (current-time-zone)))
+   ;; Description.
+   (org-export-data (plist-get info :title) info)
+   contents))
+
+(defun org-e-icalendar--vcalendar (name owner tz description contents)
+  "Create a VCALENDAR component.
+NAME, OWNER, TZ, DESCRIPTION and CONTENTS are all strings giving,
+respectively, the name of the calendar, its owner, the timezone
+used, a short description and the other components included."
+  (concat (format "BEGIN:VCALENDAR
+VERSION:2.0
+X-WR-CALNAME:%s
+PRODID:-//%s//Emacs with Org mode//EN
+X-WR-TIMEZONE:%s
+X-WR-CALDESC:%s
+CALSCALE:GREGORIAN\n"
+		  (org-e-icalendar-cleanup-string name)
+		  (org-e-icalendar-cleanup-string owner)
+		  (org-e-icalendar-cleanup-string tz)
+		  (org-e-icalendar-cleanup-string description))
+	  contents
+	  "END:VCALENDAR\n"))
+
+
+
+;;; Interactive Functions
+
+;;;###autoload
+(defun org-e-icalendar-export-to-ics (&optional subtreep visible-only body-only)
+  "Export current buffer to an iCalendar file.
+
+If narrowing is active in the current buffer, only export its
+narrowed part.
+
+If a region is active, export that region.
+
+When optional argument SUBTREEP is non-nil, export the sub-tree
+at point, extracting information from the headline properties
+first.
+
+When optional argument VISIBLE-ONLY is non-nil, don't export
+contents of hidden elements.
+
+When optional argument BODY-ONLY is non-nil, only write code
+between \"BEGIN:VCALENDAR\" and \"END:VCALENDAR\".
+
+Return ICS file name."
+  (interactive)
+  (let ((file (buffer-file-name (buffer-base-buffer))))
+    (when (and file org-e-icalendar-store-UID)
+      (org-e-icalendar-create-uid file 'warn-user)))
+  ;; Export part.  Since this back-end is backed up by `e-ascii',
+  ;; ensure links will not be collected at the end of sections.
+  (let ((outfile (org-export-output-file-name ".ics" subtreep))
+	(org-e-ascii-links-to-notes nil))
+    (org-export-to-file 'e-icalendar outfile subtreep visible-only body-only
+			'(:ascii-charset utf-8))
+    (run-hook-with-args 'org-e-icalendar-after-save-hook outfile)
+    outfile))
+
+;;;###autoload
+(defun org-e-icalendar-export-agenda-files ()
+  "Export all agenda files to iCalendar files."
+  (interactive)
+  (let ((files (org-agenda-files t)))
+    (org-agenda-prepare-buffers files)
+    (unwind-protect
+	(mapc (lambda (file)
+		(catch 'nextfile
+		  (org-check-agenda-file file)
+		  (with-current-buffer (org-get-agenda-file-buffer file)
+		    (org-e-icalendar-export-to-ics))))
+	      files)
+      (org-release-buffers org-agenda-new-buffers))))
+
+;;;###autoload
+(defun org-e-icalendar-combine-agenda-files ()
+  "Combine all agenda files into a single iCalendar file.
+The file is stored under the name
+`org-e-icalendar-combined-agenda-file'."
+  (interactive)
+  (apply 'org-e-icalendar--combine-files nil (org-agenda-files t)))
+
+(defun org-e-icalendar-export-current-agenda ()
+  "Export current agenda view to an iCalendar file.
+The file is stored under the name
+`org-e-icalendar-combined-agenda-file'.  This function assumes
+major mode for current buffer is `org-agenda-mode'."
+  (apply 'org-e-icalendar--combine-files
+	 (org-create-marker-find-array (org-agenda-collect-markers))
+	 (org-agenda-files nil 'ifmode)))
+
+(defun org-e-icalendar--combine-files (restriction &rest files)
+  "Combine entries from multiple files into an iCalendar file.
+RESTRICTION, when non-nil, is an alist where key is a file name
+and value a list of buffer positions pointing to entries that
+should appear in the calendar.  It only makes sense if the
+function was called from an agenda buffer.  FILES is a list of
+files to build the calendar from."
+  (org-agenda-prepare-buffers files)
+  (unwind-protect
+      (progn
+	(with-temp-file org-e-icalendar-combined-agenda-file
+	  (insert
+	   (org-e-icalendar--vcalendar
+	    ;; Name.
+	    org-e-icalendar-combined-name
+	    ;; Owner.
+	    user-full-name
+	    ;; Timezone.
+	    (if (org-string-nw-p org-e-icalendar-timezone)
+		org-e-icalendar-timezone
+	      (cadr (current-time-zone)))
+	    ;; Description.
+	    org-e-icalendar-combined-description
+	    ;; Contents.
+	    (concat
+	     ;; Agenda contents.
+	     (mapconcat
+	      (lambda (file)
+		(catch 'nextfile
+		  (org-check-agenda-file file)
+		  (with-current-buffer (org-get-agenda-file-buffer file)
+		    ;; Create ID if necessary.
+		    (when org-e-icalendar-store-UID
+		      (org-e-icalendar-create-uid file))
+		    (let ((marks (cdr (assoc (expand-file-name file)
+					     restriction))))
+		      (unless (and restriction (not marks))
+			;; Add a hook adding :ICALENDAR_MARK: property
+			;; to each entry appearing in agenda view.
+			;; Use `apply-partially' because the function
+			;; still has to accept one argument.
+			(let ((org-export-before-processing-hook
+			       (cons (apply-partially
+				      (lambda (m-list dummy)
+					(mapc (lambda (m)
+						(org-entry-put
+						 m "ICALENDAR_MARK" "t"))
+					      m-list))
+				      (sort marks '>))
+				     org-export-before-processing-hook)))
+			  (org-export-as
+			   'e-icalendar nil nil t
+			   (list :ascii-charset 'utf-8
+				 :icalendar-agenda-view restriction))))))))
+	      files "")
+	     ;; BBDB anniversaries.
+	     (when (and org-e-icalendar-include-bbdb-anniversaries
+			(require 'org-bbdb nil t))
+	       (with-temp-buffer
+		 (org-bbdb-anniv-export-ical)
+		 (buffer-string)))))))
+	(run-hook-with-args 'org-e-icalendar-after-save-hook
+			    org-e-icalendar-combined-agenda-file))
+    (org-release-buffers org-agenda-new-buffers)))
+
+
+(provide 'org-e-icalendar)
+
+;;; org-e-icalendar.el ends here