;;; company-clang.el --- company-mode completion back-end for Clang  -*- lexical-binding: t -*-

;; Copyright (C) 2009, 2011, 2013-2014  Free Software Foundation, Inc.

;; Author: Nikolaj Schumacher

;; 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:
;;

;;; Code:

(require 'company)
(require 'company-template)
(eval-when-compile (require 'cl))

(defgroup company-clang nil
  "Completion back-end for Clang."
  :group 'company)

(defcustom company-clang-executable
  (executable-find "clang")
  "Location of clang executable."
  :type 'file)

(defcustom company-clang-begin-after-member-access t
  "When non-nil, automatic completion will start whenever the current
symbol is preceded by \".\", \"->\" or \"::\", ignoring
`company-minimum-prefix-length'.

If `company-begin-commands' is a list, it should include `c-electric-lt-gt'
and `c-electric-colon', for automatic completion right after \">\" and
\":\".")

(defcustom company-clang-arguments nil
  "Additional arguments to pass to clang when completing.
Prefix files (-include ...) can be selected with `company-clang-set-prefix'
or automatically through a custom `company-clang-prefix-guesser'."
  :type '(repeat (string :tag "Argument" nil)))

(defcustom company-clang-prefix-guesser 'company-clang-guess-prefix
  "A function to determine the prefix file for the current buffer."
  :type '(function :tag "Guesser function" nil))

(defvar company-clang-modes '(c-mode c++-mode objc-mode)
  "Major modes which clang may complete.")

;; prefix ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(defvar company-clang--prefix nil)

(defsubst company-clang--guess-pch-file (file)
  (let ((dir (directory-file-name (file-name-directory file))))
    (when (equal (file-name-nondirectory dir) "Classes")
      (setq dir (file-name-directory dir)))
    (car (directory-files dir t "\\([^.]h\\|[^h]\\).pch\\'" t))))

(defsubst company-clang--file-substring (file beg end)
  (with-temp-buffer
    (insert-file-contents-literally file nil beg end)
    (buffer-string)))

(defun company-clang-guess-prefix ()
  "Try to guess the prefix file for the current buffer."
  ;; Prefixes seem to be called .pch.  Pre-compiled headers do, too.
  ;; So we look at the magic number to rule them out.
  (let* ((file (company-clang--guess-pch-file buffer-file-name))
         (magic-number (and file (company-clang--file-substring file 0 4))))
    (unless (member magic-number '("CPCH" "gpch"))
      file)))

(defun company-clang-set-prefix (&optional prefix)
  "Use PREFIX as a prefix (-include ...) file for clang completion."
  (interactive (let ((def (funcall company-clang-prefix-guesser)))
     (unless (stringp def)
       (setq def default-directory))
     (list (read-file-name "Prefix file: "
                           (when def (file-name-directory def))
                           def t (when def (file-name-nondirectory def))))))
  ;; TODO: pre-compile?
  (setq company-clang--prefix (and (stringp prefix)
                                   (file-regular-p prefix)
                                   prefix)))

;; Clean-up on exit.
(add-hook 'kill-emacs-hook 'company-clang-set-prefix)

;; parsing ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;; TODO: Handle Pattern (syntactic hints would be neat).
;; Do we ever see OVERLOAD (or OVERRIDE)?
(defconst company-clang--completion-pattern
  "^COMPLETION: \\_<\\(%s[a-zA-Z0-9_:]*\\)\\(?: : \\(.*\\)$\\)?$")

(defconst company-clang--error-buffer-name "*clang-error*")

(defun company-clang--lang-option ()
     (if (eq major-mode 'objc-mode)
         (if (string= "m" (file-name-extension buffer-file-name))
             "objective-c" "objective-c++")
       (substring (symbol-name major-mode) 0 -5)))

(defun company-clang--parse-output (prefix objc)
  (goto-char (point-min))
  (let ((pattern (format company-clang--completion-pattern
                         (regexp-quote prefix)))
        (case-fold-search nil)
        lines match)
    (while (re-search-forward pattern nil t)
      (setq match (match-string-no-properties 1))
      (unless (equal match "Pattern")
        (save-match-data
          (when (string-match ":" match)
            (setq match (substring match 0 (match-beginning 0)))))
        (let ((meta (match-string-no-properties 2)))
          (when (and meta (not (string= match meta)))
            (put-text-property 0 1 'meta
                               (company-clang--strip-formatting meta)
                               match)))
        (push match lines)))
    lines))

(defun company-clang--meta (candidate)
  (get-text-property 0 'meta candidate))

(defun company-clang--annotation (candidate)
  (let ((meta (company-clang--meta candidate)))
    (cond
     ((null meta) nil)
     ((string-match ":" meta)
      (substring meta (match-beginning 0)))
     ((string-match "\\((.*)\\'\\)" meta)
      (match-string 1 meta)))))

(defun company-clang--strip-formatting (text)
  (replace-regexp-in-string
   "#]" " "
   (replace-regexp-in-string "[<{[]#\\|#[>}]" "" text t)
   t))

(defun company-clang--handle-error (res args)
  (goto-char (point-min))
  (let* ((buf (get-buffer-create company-clang--error-buffer-name))
         (cmd (concat company-clang-executable " " (mapconcat 'identity args " ")))
         (pattern (format company-clang--completion-pattern ""))
         (err (if (re-search-forward pattern nil t)
                  (buffer-substring-no-properties (point-min)
                                                  (1- (match-beginning 0)))
                ;; Warn the user more aggressively if no match was found.
                (message "clang failed with error %d:\n%s" res cmd)
                (buffer-string))))

    (with-current-buffer buf
      (let ((inhibit-read-only t))
        (erase-buffer)
        (insert (current-time-string)
                (format "\nclang failed with error %d:\n" res)
                cmd "\n\n")
        (insert err)
        (setq buffer-read-only t)
        (goto-char (point-min))))))

(defun company-clang--start-process (prefix callback &rest args)
  (let ((objc (derived-mode-p 'objc-mode))
        (buf (get-buffer-create "*clang-output*")))
    (with-current-buffer buf (erase-buffer))
    (if (get-buffer-process buf)
        (funcall callback nil)
      (let ((process (apply #'start-process "company-clang" buf
                            company-clang-executable args)))
        (set-process-sentinel
         process
         (lambda (proc status)
           (unless (string-match-p "hangup" status)
             (funcall
              callback
              (let ((res (process-exit-status proc)))
                (with-current-buffer buf
                  (unless (eq 0 res)
                    (company-clang--handle-error res args))
                  ;; Still try to get any useful input.
                  (company-clang--parse-output prefix objc)))))))
        (unless (company-clang--auto-save-p)
          (send-region process (point-min) (point-max))
          (send-string process "\n")
          (process-send-eof process))))))

(defsubst company-clang--build-location (pos)
  (save-excursion
    (goto-char pos)
    (format "%s:%d:%d"
            (if (company-clang--auto-save-p) buffer-file-name "-")
            (line-number-at-pos)
            (1+ (length
                 (encode-coding-region
                  (line-beginning-position)
                  (point)
                  'utf-8
                  t))))))

(defsubst company-clang--build-complete-args (pos)
  (append '("-cc1" "-fsyntax-only" "-code-completion-macros")
          (unless (company-clang--auto-save-p)
            (list "-x" (company-clang--lang-option)))
          company-clang-arguments
          (when (stringp company-clang--prefix)
            (list "-include" (expand-file-name company-clang--prefix)))
          '("-code-completion-at")
          (list (company-clang--build-location pos))
          (list (if (company-clang--auto-save-p) buffer-file-name "-"))))

(defun company-clang--candidates (prefix callback)
  (and (company-clang--auto-save-p)
       (buffer-modified-p)
       (basic-save-buffer))
  (when (null company-clang--prefix)
    (company-clang-set-prefix (or (funcall company-clang-prefix-guesser)
                                  'none)))
  (apply 'company-clang--start-process
         prefix
         callback
         (company-clang--build-complete-args (- (point) (length prefix)))))

(defun company-clang--prefix ()
  (let ((symbol (company-grab-symbol)))
    (if symbol
        (if (and company-clang-begin-after-member-access
                 (save-excursion
                   (forward-char (- (length symbol)))
                   (looking-back "\\.\\|->\\|::" (- (point) 2))))
            (cons symbol t)
          symbol)
      'stop)))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(defconst company-clang-required-version 1.1)

(defvar company-clang--version nil)

(defun company-clang--auto-save-p ()
  (< company-clang--version 2.9))

(defsubst company-clang-version ()
  "Return the version of `company-clang-executable'."
  (with-temp-buffer
    (call-process company-clang-executable nil t nil "--version")
    (goto-char (point-min))
    (if (re-search-forward "clang\\(?: version \\|-\\)\\([0-9.]+\\)" nil t)
        (let ((ver (string-to-number (match-string-no-properties 1))))
          (if (> ver 100)
              (/ ver 100)
            ver))
      0)))

(defun company-clang-objc-templatify (selector)
  (let* ((end (point-marker))
         (beg (- (point) (length selector) 1))
         (templ (company-template-declare-template beg end))
         (cnt 0))
    (save-excursion
      (goto-char beg)
      (catch 'stop
        (while (search-forward ":" end t)
          (when (looking-at "([^)]*) ?")
            (delete-region (match-beginning 0) (match-end 0)))
          (company-template-add-field templ (point) (format "arg%d" cnt))
          (if (< (point) end)
              (insert " ")
            (throw 'stop t))
          (incf cnt))))
    (company-template-move-to-first templ)))

(defun company-clang (command &optional arg &rest ignored)
  "`company-mode' completion back-end for Clang.
Clang is a parser for C and ObjC.  Clang version 1.1 or newer is required.

Additional command line arguments can be specified in
`company-clang-arguments'.  Prefix files (-include ...) can be selected
with `company-clang-set-prefix' or automatically through a custom
`company-clang-prefix-guesser'.

With Clang versions before 2.9, we have to save the buffer before
performing completion.  With Clang 2.9 and later, buffer contents are
passed via standard input."
  (interactive (list 'interactive))
  (case command
    (interactive (company-begin-backend 'company-clang))
    (init (when (memq major-mode company-clang-modes)
            (unless company-clang-executable
              (error "Company found no clang executable"))
            (setq company-clang--version (company-clang-version))
            (when (< company-clang--version company-clang-required-version)
              (error "Company requires clang version 1.1"))))
    (prefix (and (memq major-mode company-clang-modes)
                 buffer-file-name
                 company-clang-executable
                 (not (company-in-string-or-comment))
                 (company-clang--prefix)))
    (candidates (cons :async
                      (lambda (cb) (company-clang--candidates arg cb))))
    (meta       (company-clang--meta arg))
    (annotation (company-clang--annotation arg))
    (post-completion (let ((anno (company-clang--annotation arg)))
                       (when anno
                         (insert anno)
                         (if (string-match ":" anno)
                             (company-clang-objc-templatify anno)
                          (company-template-c-like-templatify anno)))))))

(provide 'company-clang)
;;; company-clang.el ends here