;;; notmuch-company.el --- Mail address completion for notmuch via company-mode  -*- lexical-binding: t -*-
;;
;; Copyright © Trevor Jim
;; Copyright © Michal Sojka
;;
;; 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: Trevor Jim <tjim@mac.com>
;; 	    Michal Sojka <sojkam1@fel.cvut.cz>
;; Keywords: mail, completion

;;; Commentary:

;; Mail address completion for notmuch via company-mode.  To enable
;; this, install company mode from <https://company-mode.github.io/>.
;;
;; NB company-minimum-prefix-length defaults to 3 so you don't get
;; completion unless you type 3 characters.

;;; Code:

(require 'notmuch-lib)

(defvar-local notmuch-company-last-prefix nil)

(declare-function company-begin-backend "company")
(declare-function company-grab "company")
(declare-function company-mode "company")
(declare-function company-manual-begin "company")
(defvar company-backends)
(defvar company-idle-delay)

(declare-function notmuch-address-harvest "notmuch-address")
(declare-function notmuch-address-harvest-trigger "notmuch-address")
(declare-function notmuch-address-matching "notmuch-address")
(declare-function notmuch-address--harvest-ready "notmuch-address")
(defvar notmuch-address-completion-headers-regexp)
(defvar notmuch-address-command)

;;;###autoload
(defun notmuch-company-setup ()
  (company-mode)
  (setq-local company-backends '(notmuch-company))
  ;; Disable automatic company completion unless an internal
  ;; completion method is configured. Company completion (using
  ;; internal completion) can still be accessed via standard company
  ;; functions, e.g., company-complete.
  (unless (eq notmuch-address-command 'internal)
    (setq-local company-idle-delay nil)))

;;;###autoload
(defun notmuch-company (command &optional arg &rest _ignore)
  "`company-mode' completion back-end for `notmuch'."
  (interactive (list 'interactive))
  (require 'company)
  (let ((case-fold-search t)
	(completion-ignore-case t))
    (cl-case command
      (interactive (company-begin-backend 'notmuch-company))
      (prefix (and (derived-mode-p 'message-mode)
		   (looking-back
		    (concat notmuch-address-completion-headers-regexp ".*")
		    (line-beginning-position))
		   (setq notmuch-company-last-prefix
			 (company-grab "[:,][ \t]*\\(.*\\)" 1 (point-at-bol)))))
      (candidates (cond
		   ((notmuch-address--harvest-ready)
		    ;; Update harvested addressed from time to time
		    (notmuch-address-harvest-trigger)
		    (notmuch-address-matching arg))
		   (t
		    (cons :async
			  (lambda (callback)
			    ;; First run quick asynchronous harvest
			    ;; based on what the user entered so far
			    (notmuch-address-harvest
			     arg nil
			     (lambda (_proc _event)
			       (funcall callback (notmuch-address-matching arg))
			       ;; Then start the (potentially long-running)
			       ;; full asynchronous harvest if necessary
			       (notmuch-address-harvest-trigger))))))))
      (match (if (string-match notmuch-company-last-prefix arg)
		 (match-end 0)
	       0))
      (post-completion
       (run-hook-with-args 'notmuch-address-post-completion-functions arg))
      (no-cache t))))

(provide 'notmuch-company)

;;; notmuch-company.el ends here