;;; notmuch-address.el --- address completion with notmuch  -*- lexical-binding: t -*-
;;
;; Copyright © David Edmondson
;;
;; This file is part of Notmuch.
;;
;; Notmuch 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.
;;
;; Notmuch 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 Notmuch.  If not, see <https://www.gnu.org/licenses/>.
;;
;; Authors: David Edmondson <dme@dme.org>

;;; Code:

(require 'message)
(require 'notmuch-parser)
(require 'notmuch-lib)
(require 'notmuch-company)

(declare-function company-manual-begin "company")

;;; Cache internals

(defvar notmuch-address-last-harvest 0
  "Time of last address harvest.")

(defvar notmuch-address-completions (make-hash-table :test 'equal)
  "Hash of email addresses for completion during email composition.
This variable is set by calling `notmuch-address-harvest'.")

(defvar notmuch-address-full-harvest-finished nil
  "Whether full completion address harvesting has finished.
Use `notmuch-address--harvest-ready' to access as that will load
a saved hash if necessary (and available).")

(defun notmuch-address--harvest-ready ()
  "Return t if there is a full address hash available.

If the hash is not present it attempts to load a saved hash."
  (or notmuch-address-full-harvest-finished
      (notmuch-address--load-address-hash)))

;;; Options

(defcustom notmuch-address-command 'internal
  "Determines how address completion candidates are generated.

If this is a string, then that string should be an external
program, which must take a single argument (searched string)
and output a list of completion candidates, one per line.

If this is the symbol `internal', then an implementation is used
that relies on the \"notmuch address\" command, but does not use
any third-party (i.e. \"external\") programs.

If this is the symbol `as-is', then Notmuch does not modify the
value of `message-completion-alist'. This option has to be set to
this value before `notmuch' is loaded, otherwise the modification
to `message-completion-alist' may already have taken place. This
setting obviously does not prevent `message-completion-alist'
from being modified at all; the user or some third-party package
may still modify it.

Finally, if this is nil, then address completion is disabled."
  :type '(radio
	  (const  :tag "Use internal address completion" internal)
	  (string :tag "Use external completion command")
	  (const  :tag "Disable address completion" nil)
	  (const  :tag "Use default or third-party mechanism" as-is))
  :group 'notmuch-send
  :group 'notmuch-address
  :group 'notmuch-external)

(defcustom notmuch-address-internal-completion '(sent nil)
  "Determines how internal address completion generates candidates.

This should be a list of the form (DIRECTION FILTER), where
DIRECTION is either sent or received and specifies whether the
candidates are searched in messages sent by the user or received
by the user (note received by is much faster), and FILTER is
either nil or a filter-string, such as \"date:1y..\" to append to
the query."
  :type '(list :tag "Use internal address completion"
	       (radio
		:tag "Base completion on messages you have"
		:value sent
		(const :tag "sent (more accurate)" sent)
		(const :tag "received (faster)" received))
	       (radio :tag "Filter messages used for completion"
		      (const :tag "Use all messages" nil)
		      (string :tag "Filter query")))
  ;; We override set so that we can clear the cache when this changes
  :set (lambda (symbol value)
	 (set-default symbol value)
	 (setq notmuch-address-last-harvest 0)
	 (setq notmuch-address-completions (clrhash notmuch-address-completions))
	 (setq notmuch-address-full-harvest-finished nil))
  :group 'notmuch-send
  :group 'notmuch-address
  :group 'notmuch-external)

(defcustom notmuch-address-save-filename nil
  "Filename to save the cached completion addresses.

All the addresses notmuch uses for address completion will be
cached in this file.  This has obvious privacy implications so
you should make sure it is not somewhere publicly readable."
  :type '(choice (const :tag "Off" nil)
		 (file :tag "Filename"))
  :group 'notmuch-send
  :group 'notmuch-address
  :group 'notmuch-external)

(defcustom notmuch-address-selection-function 'notmuch-address-selection-function
  "The function to select address from given list.

The function is called with PROMPT, COLLECTION, and INITIAL-INPUT
as arguments (subset of what `completing-read' can be called
with).  While executed the value of `completion-ignore-case'
is t.  See documentation of function
`notmuch-address-selection-function' to know how address
selection is made by default."
  :type 'function
  :group 'notmuch-send
  :group 'notmuch-address
  :group 'notmuch-external)

(defcustom notmuch-address-post-completion-functions nil
  "Functions called after completing address.

The completed address is passed as an argument to each function.
Note that this hook will be invoked for completion in headers
matching `notmuch-address-completion-headers-regexp'."
  :type 'hook
  :group 'notmuch-address
  :group 'notmuch-hooks)

(defcustom notmuch-address-use-company t
  "If available, use company mode for address completion."
  :type 'boolean
  :group 'notmuch-send
  :group 'notmuch-address)

;;; Setup

(defun notmuch-address-selection-function (prompt collection initial-input)
  "Default address selection function: delegate to completing read."
  (completing-read
   prompt collection nil nil initial-input 'notmuch-address-history))

(defvar notmuch-address-completion-headers-regexp
  "^\\(Resent-\\)?\\(To\\|B?Cc\\|Reply-To\\|From\\|Mail-Followup-To\\|Mail-Copies-To\\):")

(defvar notmuch-address-history nil)

(defun notmuch-address-message-insinuate ()
  (message "calling notmuch-address-message-insinuate is no longer needed"))

(defun notmuch-address-setup ()
  (unless (eq notmuch-address-command 'as-is)
    (when (and notmuch-address-use-company
	       (require 'company nil t))
      (notmuch-company-setup))
    (cl-pushnew (cons notmuch-address-completion-headers-regexp
		      #'notmuch-address-expand-name)
		message-completion-alist :test #'equal)))

(defun notmuch-address-toggle-internal-completion ()
  "Toggle use of internal completion for current buffer.

This overrides the global setting for address completion and
toggles the setting in this buffer."
  (interactive)
  (if (local-variable-p 'notmuch-address-command)
      (kill-local-variable 'notmuch-address-command)
    (setq-local notmuch-address-command 'internal))
  (when (boundp 'company-idle-delay)
    (if (local-variable-p 'company-idle-delay)
	(kill-local-variable 'company-idle-delay)
      (setq-local company-idle-delay nil))))

;;; Completion

(defun notmuch-address-matching (substring)
  "Returns a list of completion candidates matching SUBSTRING.
The candidates are taken from `notmuch-address-completions'."
  (let ((candidates)
	(re (regexp-quote substring)))
    (maphash (lambda (key _val)
	       (when (string-match re key)
		 (push key candidates)))
	     notmuch-address-completions)
    candidates))

(defun notmuch-address-options (original)
  "Return a list of completion candidates.
Use either elisp-based implementation or older implementation
requiring external commands."
  (cond
   ((eq notmuch-address-command 'internal)
    (unless (notmuch-address--harvest-ready)
      ;; First, run quick synchronous harvest based on what the user
      ;; entered so far.
      (notmuch-address-harvest original t))
    (prog1 (notmuch-address-matching original)
      ;; Then start the (potentially long-running) full asynchronous
      ;; harvest if necessary.
      (notmuch-address-harvest-trigger)))
   (t
    (notmuch--process-lines notmuch-address-command original))))

(defun notmuch-address-expand-name ()
  (cond
   ((and (eq notmuch-address-command 'internal)
	 notmuch-address-use-company
	 (bound-and-true-p company-mode))
    (company-manual-begin))
   (notmuch-address-command
    (let* ((end (point))
	   (beg (save-excursion
		  (re-search-backward "\\(\\`\\|[\n:,]\\)[ \t]*")
		  (goto-char (match-end 0))
		  (point)))
	   (orig (buffer-substring-no-properties beg end))
	   (completion-ignore-case t)
	   (options (with-temp-message "Looking for completion candidates..."
		      (notmuch-address-options orig)))
	   (num-options (length options))
	   (chosen (cond
		    ((eq num-options 0)
		     nil)
		    ((eq num-options 1)
		     (car options))
		    (t
		     (funcall notmuch-address-selection-function
			      (format "Address (%s matches): " num-options)
			      options
			      orig)))))
      (if chosen
	  (progn
	    (push chosen notmuch-address-history)
	    (delete-region beg end)
	    (insert chosen)
	    (run-hook-with-args 'notmuch-address-post-completion-functions
				chosen))
	(message "No matches.")
	(ding))))
   (t nil)))

;;; Harvest

(defun notmuch-address-harvest-addr (result)
  (puthash (plist-get result :name-addr)
	   t notmuch-address-completions))

(defun notmuch-address-harvest-filter (proc string)
  (when (buffer-live-p (process-buffer proc))
    (with-current-buffer (process-buffer proc)
      (save-excursion
	(goto-char (point-max))
	(insert string))
      (notmuch-sexp-parse-partial-list
       'notmuch-address-harvest-addr (process-buffer proc)))))

(defvar notmuch-address-harvest-procs '(nil . nil)
  "The currently running harvests.

The car is a partial harvest, and the cdr is a full harvest.")

(defun notmuch-address-harvest (&optional addr-prefix synchronous callback)
  "Collect addresses completion candidates.

It queries the notmuch database for messages sent/received (as
configured with `notmuch-address-command') by the user, collects
destination/source addresses from those messages and stores them
in `notmuch-address-completions'.

If ADDR-PREFIX is not nil, only messages with to/from addresses
matching ADDR-PREFIX*' are queried.

Address harvesting may take some time so the address collection runs
asynchronously unless SYNCHRONOUS is t. In case of asynchronous
execution, CALLBACK is called when harvesting finishes."
  (let* ((sent (eq (car notmuch-address-internal-completion) 'sent))
	 (config-query (cadr notmuch-address-internal-completion))
	 (prefix-query (and addr-prefix
			    (format "%s:%s*"
				    (if sent "to" "from")
				    addr-prefix)))
	 (from-or-to-me-query
	  (mapconcat (lambda (x)
		       (concat (if sent "from:" "to:") x))
		     (notmuch-user-emails) " or "))
	 (query (if (or prefix-query config-query)
		    (concat (format "(%s)" from-or-to-me-query)
			    (and prefix-query
				 (format " and (%s)" prefix-query))
			    (and config-query
				 (format " and (%s)" config-query)))
		  from-or-to-me-query))
	 (args `("address" "--format=sexp" "--format-version=5"
		 ,(if sent "--output=recipients" "--output=sender")
		 "--deduplicate=address"
		 ,query)))
    (if synchronous
	(mapc #'notmuch-address-harvest-addr
	      (apply 'notmuch-call-notmuch-sexp args))
      ;; Asynchronous
      (let* ((current-proc (if addr-prefix
			       (car notmuch-address-harvest-procs)
			     (cdr notmuch-address-harvest-procs)))
	     (proc-name (format "notmuch-address-%s-harvest"
				(if addr-prefix "partial" "full")))
	     (proc-buf (concat " *" proc-name "*")))
	;; Kill any existing process
	(when current-proc
	  (kill-buffer (process-buffer current-proc))) ; this also kills the process
	(setq current-proc
	      (apply 'notmuch-start-notmuch proc-name proc-buf
		     callback				; process sentinel
		     args))
	(set-process-filter current-proc 'notmuch-address-harvest-filter)
	(set-process-query-on-exit-flag current-proc nil)
	(if addr-prefix
	    (setcar notmuch-address-harvest-procs current-proc)
	  (setcdr notmuch-address-harvest-procs current-proc)))))
  ;; return value
  nil)

(defvar notmuch-address--save-hash-version 1
  "Version format of the save hash.")

(defun notmuch-address--get-address-hash ()
  "Return the saved address hash as a plist.

Returns nil if the save file does not exist, or it does not seem
to be a saved address hash."
  (and notmuch-address-save-filename
       (condition-case nil
	   (with-temp-buffer
	     (insert-file-contents notmuch-address-save-filename)
	     (let ((name (read (current-buffer)))
		   (plist (read (current-buffer))))
	       ;; We do two simple sanity checks on the loaded file.
	       ;; We just check a version is specified, not that
	       ;; it is the current version, as we are allowed to
	       ;; over-write and a save-file with an older version.
	       (and (string= name "notmuch-address-hash")
		    (plist-get plist :version)
		    plist)))
	 ;; The error case catches any of the reads failing.
	 (error nil))))

(defun notmuch-address--load-address-hash ()
  "Read the saved address hash and set the corresponding variables."
  (let ((load-plist (notmuch-address--get-address-hash)))
    (when (and load-plist
	       ;; If the user's setting have changed, or the version
	       ;; has changed, return nil to make sure the new settings
	       ;; take effect.
	       (equal (plist-get load-plist :completion-settings)
		      notmuch-address-internal-completion)
	       (equal (plist-get load-plist :version)
		      notmuch-address--save-hash-version))
      (setq notmuch-address-last-harvest (plist-get load-plist :last-harvest))
      (setq notmuch-address-completions (plist-get load-plist :completions))
      (setq notmuch-address-full-harvest-finished t)
      ;; Return t to say load was successful.
      t)))

(defun notmuch-address--save-address-hash ()
  (when notmuch-address-save-filename
    (if (or (not (file-exists-p notmuch-address-save-filename))
	    ;; The file exists, check it is a file we saved.
	    (notmuch-address--get-address-hash))
	(with-temp-file notmuch-address-save-filename
	  (let ((save-plist
		 (list :version notmuch-address--save-hash-version
		       :completion-settings notmuch-address-internal-completion
		       :last-harvest notmuch-address-last-harvest
		       :completions notmuch-address-completions)))
	    (print "notmuch-address-hash" (current-buffer))
	    (print save-plist (current-buffer))))
      (message "\
Warning: notmuch-address-save-filename %s exists but doesn't
appear to be an address savefile.  Not overwriting."
	       notmuch-address-save-filename))))

(defun notmuch-address-harvest-trigger ()
  (let ((now (float-time)))
    (when (> (- now notmuch-address-last-harvest) 86400)
      (setq notmuch-address-last-harvest now)
      (notmuch-address-harvest
       nil nil
       (lambda (_proc event)
	 ;; If harvest fails, we want to try
	 ;; again when the trigger is next called.
	 (if (string= event "finished\n")
	     (progn
	       (notmuch-address--save-address-hash)
	       (setq notmuch-address-full-harvest-finished t))
	   (setq notmuch-address-last-harvest 0)))))))

;;; Standalone completion

(defun notmuch-address-from-minibuffer (prompt)
  (if (not notmuch-address-command)
      (read-string prompt)
    (let ((rmap (copy-keymap minibuffer-local-map))
	  (omap minibuffer-local-map))
      ;; Configure TAB to start completion when executing read-string.
      ;; "Original" minibuffer keymap is restored just before calling
      ;; notmuch-address-expand-name as it may also use minibuffer-local-map
      ;; (completing-read probably does not but if something else is used there).
      (define-key rmap (kbd "TAB") (lambda ()
				     (interactive)
				     (let ((enable-recursive-minibuffers t)
					   (minibuffer-local-map omap))
				       (notmuch-address-expand-name))))
      (let ((minibuffer-local-map rmap))
	(read-string prompt)))))

;;; _

(provide 'notmuch-address)

;;; notmuch-address.el ends here