;;; ninja-mode.el --- Major mode for editing .ninja files -*- lexical-binding: t -*-

;; Package-Requires: ((emacs "24"))

;; Copyright 2011 Google Inc. All Rights Reserved.
;;
;; Licensed under the Apache License, Version 2.0 (the "License");
;; you may not use this file except in compliance with the License.
;; You may obtain a copy of the License at
;;
;;     http://www.apache.org/licenses/LICENSE-2.0
;;
;; Unless required by applicable law or agreed to in writing, software
;; distributed under the License is distributed on an "AS IS" BASIS,
;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
;; See the License for the specific language governing permissions and
;; limitations under the License.

;;; Commentary:

;; Simple emacs mode for editing .ninja files.

;;; Code:

(defcustom ninja-indent-offset 2
  "*Amount of offset per level of indentation."
  :type 'integer
  :safe 'natnump
  :group 'ninja)

(defconst ninja-keywords-re
  (concat "^" (regexp-opt '("rule" "build" "subninja" "include" "pool" "default")
                          'words)))

(defvar ninja-keywords
  `((,ninja-keywords-re . font-lock-keyword-face)
    ("^[[:space:]]*\\([[:alnum:]_]+\\)[[:space:]]*=" 1 font-lock-variable-name-face)
    ;; Variable expansion.
    ("$[[:alnum:]_]+" . font-lock-variable-name-face)
    ("${[[:alnum:]._]+}" . font-lock-variable-name-face)
    ;; Rule names
    ("rule +\\([[:alnum:]_.-]+\\)" 1 font-lock-function-name-face)
    ;; Build Statement - highlight the rule used,
    ;; allow for escaped $,: in outputs.
    ("build +\\(?:[^:$\n]\\|$[:$]\\)+ *: *\\([[:alnum:]_.-]+\\)"
     1 font-lock-function-name-face)))

(defvar ninja-mode-syntax-table
  (let ((table (make-syntax-table)))
    (modify-syntax-entry ?\" "." table)
    table)
  "Syntax table used in `ninja-mode'.")

(defun ninja-syntax-propertize (start end)
  (save-match-data
    (goto-char start)
    (while (search-forward "#" end t)
      (let ((match-pos (match-beginning 0)))
        (when (and
               ;; Is it the first non-white character on the line?
               (eq match-pos (save-excursion (back-to-indentation) (point)))
               (save-excursion
                 (goto-char (line-end-position 0))
                 (or
                  ;; If we're continuing the previous line, it's not a
                  ;; comment.
                  (not (eq ?$ (char-before)))
                  ;; Except if the previous line is a comment as well, as the
                  ;; continuation dollar is ignored then.
                  (nth 4 (syntax-ppss)))))
          (put-text-property match-pos (1+ match-pos) 'syntax-table '(11))
          (let ((line-end (line-end-position)))
            ;; Avoid putting properties past the end of the buffer.
            ;; Otherwise we get an `args-out-of-range' error.
            (unless (= line-end (1+ (buffer-size)))
              (put-text-property line-end (1+ line-end) 'syntax-table '(12)))))))))

(defun ninja-compute-indentation ()
  "Calculate indentation for the current line."
  (save-excursion
    (beginning-of-line)
    (if (or (looking-at ninja-keywords-re)
            (= (line-number-at-pos) 1))
        0
      (forward-line -1)
      (if (looking-at ninja-keywords-re)
          ninja-indent-offset
        (current-indentation)))))

(defun ninja-indent-line ()
  "Indent the current line.  Uses previous indentation level if
 available or `ninja-indent-offset'"
  (interactive "*")
  (indent-line-to (ninja-compute-indentation)))

;;;###autoload
(define-derived-mode ninja-mode prog-mode "ninja"
  (set (make-local-variable 'comment-start) "#")
  (set (make-local-variable 'parse-sexp-lookup-properties) t)
  (set (make-local-variable 'syntax-propertize-function) #'ninja-syntax-propertize)
  (set (make-local-variable 'indent-line-function) 'ninja-indent-line)
  (setq font-lock-defaults '(ninja-keywords)))

;; Run ninja-mode for files ending in .ninja.
;;;###autoload
(add-to-list 'auto-mode-alist '("\\.ninja$" . ninja-mode))

(provide 'ninja-mode)

;;; ninja-mode.el ends here