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;;; crm.el --- read multiple strings with completion

;; Copyright (C) 1985, 1986, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
;;   2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.

;; Author: Sen Nagata <sen@eccosys.com>
;; Keywords: completion, minibuffer, multiple elements

;; This file is part of GNU Emacs.

;; GNU Emacs 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.

;; GNU Emacs 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 GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; This code defines a function, `completing-read-multiple', which
;; provides the ability to read multiple strings in the minibuffer,
;; with completion.

;; By using this functionality, a user may specify multiple strings at
;; a single prompt, optionally using completion.

;; Multiple strings are specified by separating each of the strings
;; with a prespecified separator character.  For example, if the
;; separator character is a comma, the strings 'alice', 'bob', and
;; 'eve' would be specified as 'alice,bob,eve'.

;; The default value for the separator character is the value of
;; `crm-default-separator' (comma).  The separator character may be
;; changed by modifying the value of `crm-separator'.

;; Contiguous strings of non-separator-characters are referred to as
;; 'elements'.  In the aforementioned example, the elements are:
;; 'alice', 'bob', and 'eve'.

;; Completion is available on a per-element basis.  For example, if
;; the contents of the minibuffer are 'alice,bob,eve' and point is
;; between 'l' and 'i', pressing TAB operates on the element 'alice'.

;; For the moment, I have decided to not bind any special behavior to
;; the separator key.  In the future, the separator key might be used
;; to provide completion in certain circumstances.  One of the reasons
;; why this functionality is not yet provided is that it is unclear to
;; the author what the precise circumstances are, under which
;; separator-invoked completion should be provided.

;; Design note: `completing-read-multiple' is modeled after
;; `completing-read'.  They should be similar -- it was intentional.

;; Some of this code started out as translation from C code in
;; src/minibuf.c to Emacs Lisp code.  After this code was rewritten in Elisp
;; and made to operate on any field, this file was completely rewritten to
;; just reuse that code.

;; Thanks to Sen Nagata <sen@eccosys.com> for the original version of the
;; code, and sorry for throwing it all out.  --Stef

;; Thanks to Richard Stallman for all of his help (many of the good
;; ideas in here are from him), Gerd Moellmann for his attention,
;; Stefan Monnier for responding with a code sample and comments very
;; early on, and Kai Grossjohann & Soren Dayton for valuable feedback.

;;; Questions and Thoughts:

;; -should `completing-read-multiple' allow a trailing separator in
;; a return value when REQUIRE-MATCH is t?  if not, should beep when a user
;; tries to exit the minibuffer via RET?

;; -tip: use M-f and M-b for ease of navigation among elements.

;; - the difference between minibuffer-completion-table and
;;   crm-completion-table is just crm--collection-fn.  In most cases it
;;   shouldn't make any difference.  But if a non-CRM completion function
;;   happens to be used, it will use minibuffer-completion-table and
;;   crm--collection-fn will try to make it do "more or less the right
;;   thing" by making it complete on the last element, which is about as
;;   good as we can hope for right now.
;;   I'm not sure if it's important or not.  Maybe we could just throw away
;;   crm-completion-table and crm--collection-fn, but there doesn't seem to
;;   be a pressing need for it, and since Sen did bother to write it, we may
;;   as well keep it, in case it helps.

;;; History:
;;
;; 2000-04-10:
;;
;;   first revamped version

;;; Code:
(defconst crm-default-separator ","
  "Default separator for `completing-read-multiple'.")

(defvar crm-separator crm-default-separator
  "Separator used for separating strings in `completing-read-multiple'.
It should be a single character string that doesn't appear in the list of
completion candidates.  Modify this value to make `completing-read-multiple'
use a separator other than `crm-default-separator'.")

(defvar crm-local-completion-map
  (let ((map (make-sparse-keymap)))
    (set-keymap-parent map minibuffer-local-completion-map)
    (define-key map [remap minibuffer-complete] #'crm-complete)
    (define-key map [remap minibuffer-complete-word] #'crm-complete-word)
    (define-key map [remap minibuffer-completion-help] #'crm-completion-help)
    map)
  "Local keymap for minibuffer multiple input with completion.
Analog of `minibuffer-local-completion-map'.")

(defvar crm-local-must-match-map
  (let ((map (make-sparse-keymap)))
    ;; We'd want to have multiple inheritance here.
    (set-keymap-parent map minibuffer-local-must-match-map)
    (define-key map [remap minibuffer-complete] #'crm-complete)
    (define-key map [remap minibuffer-complete-word] #'crm-complete-word)
    (define-key map [remap minibuffer-completion-help] #'crm-completion-help)
    (define-key map [remap minibuffer-complete-and-exit]
      #'crm-complete-and-exit)
    map)
  "Local keymap for minibuffer multiple input with exact match completion.
Analog of `minibuffer-local-must-match-map' for crm.")

(defvar crm-completion-table nil
  "An alist whose elements' cars are strings, or an obarray.
This is a table used for completion by `completing-read-multiple' and its
supporting functions.")

;; this function evolved from a posting by Stefan Monnier
(defun crm--collection-fn (string predicate flag)
  "Function used by `completing-read-multiple' to compute completion values.
The value of STRING is the string to be completed.

The value of PREDICATE is a function to filter possible matches, or
nil if none.

The value of FLAG is used to specify the type of completion operation.
A value of nil specifies `try-completion'.  A value of t specifies
`all-completions'.  A value of lambda specifes a test for an exact match.

For more information on STRING, PREDICATE, and FLAG, see the Elisp
Reference sections on 'Programmed Completion' and 'Basic Completion
Functions'."
  (let ((beg 0))
    (while (string-match crm-separator string beg)
      (setq beg (match-end 0)))
    (completion-table-with-context (substring string 0 beg)
                                   crm-completion-table
                                   (substring string beg)
                                   predicate
                                   flag)))

(defun crm--select-current-element ()
  "Parse the minibuffer to find the current element.
Place an overlay on the element, with a `field' property, and return it."
  (let* ((bob (minibuffer-prompt-end))
         (start (save-excursion
                  (if (re-search-backward crm-separator bob t)
                      (match-end 0)
                    bob)))
         (end (save-excursion
                (if (re-search-forward crm-separator nil t)
                    (match-beginning 0)
                  (point-max))))
         (ol (make-overlay start end nil nil t)))
    (overlay-put ol 'field (make-symbol "crm"))
    ol))

(defun crm-completion-help ()
  "Display a list of possible completions of the current minibuffer element."
  (interactive)
  (let ((ol (crm--select-current-element)))
    (unwind-protect
        (minibuffer-completion-help)
      (delete-overlay ol)))
  nil)

(defun crm-complete ()
  "Complete the current element.
If no characters can be completed, display a list of possible completions.

Return t if the current element is now a valid match; otherwise return nil."
  (interactive)
  (let ((ol (crm--select-current-element)))
    (unwind-protect
        (minibuffer-complete)
      (delete-overlay ol))))

(defun crm-complete-word ()
  "Complete the current element at most a single word.
Like `minibuffer-complete-word' but for `completing-read-multiple'."
  (interactive)
  (let ((ol (crm--select-current-element)))
    (unwind-protect
        (minibuffer-complete-word)
      (delete-overlay ol))))

(defun crm-complete-and-exit ()
  "If all of the minibuffer elements are valid completions then exit.
All elements in the minibuffer must match.  If there is a mismatch, move point
to the location of mismatch and do not exit.

This function is modeled after `minibuffer-complete-and-exit'."
  (interactive)
  (let ((doexit t))
    (goto-char (minibuffer-prompt-end))
    (while
        (and doexit
             (let ((ol (crm--select-current-element)))
               (goto-char (overlay-end ol))
               (unwind-protect
                   (catch 'exit
                     (minibuffer-complete-and-exit)
                     ;; This did not throw `exit', so there was a problem.
                     (setq doexit nil))
                 (goto-char (overlay-end ol))
                 (delete-overlay ol))
               (not (eobp))))
      ;; Skip to the next element.
      (forward-char 1))
    (if doexit (exit-minibuffer))))

(defun crm--choose-completion-string (choice buffer base-position
                                             &rest ignored)
  "Completion string chooser for `completing-read-multiple'.
This is called from `choose-completion-string-functions'.
It replaces the string that is currently being completed, without
exiting the minibuffer."
  (let ((completion-no-auto-exit t)
        (choose-completion-string-functions nil))
    (choose-completion-string choice buffer base-position)
    t))

;; superemulates behavior of completing_read in src/minibuf.c
;;;###autoload
(defun completing-read-multiple
  (prompt table &optional predicate require-match initial-input
          hist def inherit-input-method)
  "Read multiple strings in the minibuffer, with completion.
By using this functionality, a user may specify multiple strings at a
single prompt, optionally using completion.

Multiple strings are specified by separating each of the strings with
a prespecified separator character.  For example, if the separator
character is a comma, the strings 'alice', 'bob', and 'eve' would be
specified as 'alice,bob,eve'.

The default value for the separator character is the value of
`crm-default-separator' (comma).  The separator character may be
changed by modifying the value of `crm-separator'.

Contiguous strings of non-separator-characters are referred to as
'elements'.  In the aforementioned example, the elements are: 'alice',
'bob', and 'eve'.

Completion is available on a per-element basis.  For example, if the
contents of the minibuffer are 'alice,bob,eve' and point is between
'l' and 'i', pressing TAB operates on the element 'alice'.

The return value of this function is a list of the read strings.

See the documentation for `completing-read' for details on the arguments:
PROMPT, TABLE, PREDICATE, REQUIRE-MATCH, INITIAL-INPUT, HIST, DEF, and
INHERIT-INPUT-METHOD."
  (unwind-protect
      (progn
        (add-hook 'choose-completion-string-functions
                  'crm--choose-completion-string)
        (let* ((minibuffer-completion-table #'crm--collection-fn)
               (minibuffer-completion-predicate predicate)
               ;; see completing_read in src/minibuf.c
               (minibuffer-completion-confirm
                (unless (eq require-match t) require-match))
               (crm-completion-table table)
               (map (if require-match
                        crm-local-must-match-map
                      crm-local-completion-map))
               ;; If the user enters empty input, read-from-minibuffer returns
               ;; the empty string, not DEF.
               (input (read-from-minibuffer
                       prompt initial-input map
                       nil hist def inherit-input-method)))
          (and def (string-equal input "") (setq input def))
          (split-string input crm-separator)))
    (remove-hook 'choose-completion-string-functions
                 'crm--choose-completion-string)))

(define-obsolete-function-alias 'crm-minibuffer-complete 'crm-complete "23.1")
(define-obsolete-function-alias
  'crm-minibuffer-completion-help 'crm-completion-help "23.1")
(define-obsolete-function-alias
  'crm-minibuffer-complete-and-exit 'crm-complete-and-exit "23.1")

;; testing and debugging
;; (defun crm-init-test-environ ()
;;   "Set up some variables for testing."
;;   (interactive)
;;   (setq my-prompt "Prompt: ")
;;   (setq my-table
;;      '(("hi") ("there") ("man") ("may") ("mouth") ("ma")
;;        ("a") ("ab") ("abc") ("abd") ("abf") ("zab") ("acb")
;;        ("da") ("dab") ("dabc") ("dabd") ("dabf") ("dzab") ("dacb")
;;        ("fda") ("fdab") ("fdabc") ("fdabd") ("fdabf") ("fdzab") ("fdacb")
;;        ("gda") ("gdab") ("gdabc") ("gdabd") ("gdabf") ("gdzab") ("gdacb")
;;        ))
;;   (setq my-separator ","))

;(completing-read-multiple my-prompt my-table)
;(completing-read-multiple my-prompt my-table nil t)
;(completing-read-multiple my-prompt my-table nil "match")
;(completing-read my-prompt my-table nil t)
;(completing-read my-prompt my-table nil "match")

(provide 'crm)

;;; crm.el ends here