;;; A major mode for editing IRSIM netlists. Public domain. Created by

;;; Peter Scott <pjscott@iastate.edu> in 2008. To install, put

;;; irsim-mode.el somewhere that emacs will see it like you site-lisp/

;;; sirectory and stick something like this in your .emacs file:

;;;

;;; (autoload 'irsim-mode "irsim-mode" nil t)

;;; (setq auto-mode-alist

;;;       (cons '("\\.sim$" . irsim-mode) auto-mode-alist))

;;;

;;; Note that this will override the default behavior for opening .sim

;;; files, which is to go into simula-mode. This might be a problem if

;;; you use both.

;;;

;;; Note also that this mode is opinionated. It has a very specific

;;; idea of how IRSIM code ought to be indented, and if you don't like

;;; it then just set irsim-use-fancy-indent to nil. I think that the

;;; default indentation method leads to very pretty files and easy

;;; typing, but YMMV.

(require 'font-lock)

(require 'cl)

;; Customizable variables:

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

(defvar irsim-use-fancy-indent t

  "Specifies whether irsim-mode should use fancy indentation or

  plain. Default is fancy, but set it to nil for plan.")

(defvar irsim-tab-stops '(0 3 16 32 48 51)

  "The starting column positions for each entry in a transistor

  line using the fancy indent function. Change if you like.")

;; Some global variables

(defvar irsim-mode-version "0.1"

  "The current version number of irsim-mode.")

(defvar irsim-mode-hook nil)

(defconst irsim-font-lock-keywords

  (list

   '("^[\t ]*[np]" . font-lock-builtin-face)

   '("[a-zA-Z_][_-a-zA-Z0-9.]*" . font-lock-variable-name-face))

  "Minimal highlighting expressions for IRSIM mode")

;; Define comment behavior and make underscores act as normal

;; characters for forward-word and backward-word behavior. This makes

;; a lot more sense than the default.

(defvar irsim-mode-syntax-table

  (let ((irsim-mode-syntax-table (make-syntax-table)))

    (modify-syntax-entry ?| "<   " irsim-mode-syntax-table)

    (modify-syntax-entry ?\n ">   " irsim-mode-syntax-table)

    (modify-syntax-entry ?\^m ">   " irsim-mode-syntax-table)

    (modify-syntax-entry ?_ "w" irsim-mode-syntax-table)

    irsim-mode-syntax-table))

;; Indentation

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

(defun irsim-line-type ()

  "Returns the type of line in IRSIM code that the point is

  on. Valid return values are 'transistor-line, 'comment-line, or

  nil"

  (save-excursion

    (move-beginning-of-line nil)

    (if (looking-at "^[\t ]*[np]")

	'transistor-line

	(if (looking-at "^[\t ]*\\|")

	    'comment-line))))

;; To indent a transistor line, just move the columns into place and

;; put the cursor at the last empty column. Or don't move it if there

;; are no more empty columns. Comment lines should not be indented.

(defun irsim-indent-line ()

  "Indent the current line of IRSIM code properly"

  (interactive)

  (let ((at-end nil))

    (if (looking-at "[\t ]*$")

	(setq at-end t))

    (if (eql (irsim-line-type) 'transistor-line)

	(progn

	  (save-excursion

	    (save-restriction

	      ;; Narrow to just this line

	      (narrow-to-region (line-beginning-position) (line-end-position))

	      (beginning-of-line)

	      (indent-line-to 0)

	      (let ((tab-stops (copy-seq irsim-tab-stops)))

		(while (and tab-stops (not (looking-at "[\t ]*$")))

		  (while (looking-at "[\t ]")

		    (delete-char 1))

		  (indent-to-column (car tab-stops))

		  (setq tab-stops (cdr tab-stops))

		  (forward-word))

		(when (and at-end tab-stops)

		  (message "yarr")

		  (end-of-line)

		  (indent-to-column (car tab-stops))))))

	  (if at-end (end-of-line)))

	(if (eql (irsim-line-type) 'comment-line)

	    (save-excursion

	      (beginning-of-line)

	      (indent-line-to 0))))))

(defun irsim-mode ()

  "Major mode for editing IRSIM netlists."

  (interactive)

  (kill-all-local-variables)

  (make-local-variable 'font-lock-defaults)

  (setq font-lock-defaults '(irsim-font-lock-keywords))

  (set-syntax-table irsim-mode-syntax-table)

  (set (make-local-variable 'comment-start) "| ")

  (when irsim-use-fancy-indent

    (set (make-local-variable 'indent-line-function) 'irsim-indent-line))

  (setq mode-name "IRSIM"

	major-mode 'irsim-mode)

  (run-hooks 'irsim-mode-hook))

(provide 'irsim-mode)