;;; Haskell mode for emacs (c) Simon Marlow 11/1/92

;;; To: partain@dcs.gla.ac.uk
;;; Subject: Haskell mode for emacs
;;; Date: Mon, 14 Dec 92 17:41:56 +0000
;;; From: Simon Marlow <simonm@dcs.gla.ac.uk>
;;; 
;;; ...	 What it buys you: very little actually, but the nice things are
;;; 
;;; (i)    Pressing line feed indents the next line according to the
;;;	   previous one,
;;; (ii)   Pressing Meta-; gives you a comment on the current line,
;;; (iii)  For literate scripts, pressing line feed gives you a bird
;;;	   track on the next line if there was one on the previous
;;;	   line, and does the indentation
;;; (iv)   For literate scripts, pressing Meta-Tab toggles a bird track
;;;	   on or off at the beginning of the current line,
;;; (v)    There's a function for toggling bird tracks on all lines in a
;;;	   region.
;;;  (vi)  Emacs says "Haskell" or "Literate Haskell" in the mode line :-)
;;; 
;;; You'll have to make the necessary changes in .emacs to load in the
;;; library automatically (you probably know what to do). ...

(defvar haskell-mode-map ()
  "Keymap used in Haskell mode.")

(defvar haskell-literate-mode-map ()
  "Keymap used in Haskell literate script mode.")

(defvar haskell-mode-syntax-table ()
  "Syntax table for haskell mode.")

(if haskell-mode-map
    ()
  (setq haskell-mode-map (make-sparse-keymap))
  (define-key haskell-mode-map "\C-j" 'haskell-newline-and-indent))

(if haskell-literate-mode-map
    ()
  (setq haskell-literate-mode-map (make-sparse-keymap))
  (define-key haskell-literate-mode-map "\C-j" 'haskell-literate-newline-and-indent)
  (define-key haskell-literate-mode-map "\M-\C-i" 'haskell-literate-toggle-bird-track-line))

(if haskell-mode-syntax-table
    ()
  (let ((i 0))
    (setq haskell-mode-syntax-table (make-syntax-table))
    (while (< i ?0)
      (modify-syntax-entry i "." haskell-mode-syntax-table)
      (setq i (1+ i)))
    (while (< i (1+ ?9))
      (modify-syntax-entry i "_" haskell-mode-syntax-table)
      (setq i (1+ i)))
    (while (< i ?A)
      (modify-syntax-entry i "." haskell-mode-syntax-table)
      (setq i (1+ i)))
    (while (< i (1+ ?Z))
      (modify-syntax-entry i "w" haskell-mode-syntax-table)
      (setq i (1+ i)))
    (while (< i ?a)
      (modify-syntax-entry i "." haskell-mode-syntax-table)
      (setq i (1+ i)))
    (while (< i (1+ ?z))
      (modify-syntax-entry i "w" haskell-mode-syntax-table)
      (setq i (1+ i)))
    (while (< i 128)
      (modify-syntax-entry i "." haskell-mode-syntax-table)
      (setq i (1+ i)))
    (modify-syntax-entry ?   " " haskell-mode-syntax-table)
    (modify-syntax-entry ?\t " " haskell-mode-syntax-table)
    (modify-syntax-entry ?\n ">" haskell-mode-syntax-table)
    (modify-syntax-entry ?\f ">" haskell-mode-syntax-table)
    (modify-syntax-entry ?\" "\"" haskell-mode-syntax-table)
    (modify-syntax-entry ?\' "w" haskell-mode-syntax-table)
    (modify-syntax-entry ?_  "w" haskell-mode-syntax-table)
    (modify-syntax-entry ?\\ "." haskell-mode-syntax-table)
    (modify-syntax-entry ?\( "()" haskell-mode-syntax-table)
    (modify-syntax-entry ?\) ")(" haskell-mode-syntax-table)
    (modify-syntax-entry ?\[ "(]" haskell-mode-syntax-table)
    (modify-syntax-entry ?\] ")[" haskell-mode-syntax-table)
    (modify-syntax-entry ?{  "(}1" haskell-mode-syntax-table)
    (modify-syntax-entry ?}  "){4" haskell-mode-syntax-table)
    (modify-syntax-entry ?-  "_ 123" haskell-mode-syntax-table)
    ))

(defun haskell-vars ()
  (kill-all-local-variables)
  (make-local-variable 'paragraph-start)
  (setq paragraph-start (concat "^$\\|" page-delimiter))
  (make-local-variable 'paragraph-separate)
  (setq paragraph-separate paragraph-start)
  (make-local-variable 'comment-start)
  (setq comment-start "--")
  (make-local-variable 'comment-start-skip)
  (setq comment-start-skip "--[^a-zA-Z0-9]*")
  (make-local-variable 'comment-column)
  (setq comment-column 40)
  (make-local-variable 'comment-indent-hook)
  (setq comment-indent-hook 'haskell-comment-indent))

(defun haskell-mode ()
  "Major mode for editing Haskell programs.
Blank lines separate paragraphs, Comments start with '--'. 
Use Linefeed to do a newline and indent to the level of the previous line.
Tab simply inserts a TAB character.
Entry to this mode calls the value of haskell-mode-hook if non-nil."
  (interactive)
  (haskell-vars)
  (setq major-mode 'haskell-mode)
  (setq mode-name "Haskell")
  (use-local-map haskell-mode-map)
  (set-syntax-table haskell-mode-syntax-table)
  (run-hooks 'haskell-mode-hook))

(defun haskell-literate-mode ()
  "Major mode for editing haskell programs in literate script form.
Linefeed produces a newline, indented maybe with a bird track on it.
M-TAB toggles the state of the bird track on the current-line.
Entry to this mode calls haskell-mode-hook and haskell-literate-mode-hook."
  (interactive)
  (haskell-vars)
  (setq major-mode 'haskell-literate-mode)
  (setq mode-name "Literate Haskell")
  (use-local-map haskell-literate-mode-map)
  (set-syntax-table haskell-mode-syntax-table)
  (run-hooks 'haskell-mode-hook)
  (run-hooks 'haskell-literate-mode-hook))

;; Find the indentation level for a comment..
(defun haskell-comment-indent ()
  (skip-chars-backward " \t")
  ;; if the line is blank, put the comment at the beginning,
  ;; else at comment-column
  (if (bolp) 0 (max (1+ (current-column)) comment-column)))

;; Newline, and indent according to the previous line's indentation.
;; Don't forget to use 'indent-tabs-mode' if you require tabs to be used
;; for indentation.
(defun haskell-newline-and-indent ()
  (interactive)
  (newline)
  (let ((c 0))
    (save-excursion
      (forward-line -1)
      (back-to-indentation)
      (setq c (if (eolp) 0 (current-column))))
    (indent-to c)))			;ident new line to this level

;;; Functions for literate scripts

;; Newline and maybe add a bird track, indent
(defun haskell-literate-newline-and-indent ()
  (interactive)
  (newline)
  (let ((bird-track nil) (indent-column 0))
    (save-excursion
      (forward-line -1)
      (if (= (following-char) ?>) (setq bird-track t))
      (skip-chars-forward "^ \t")
      (skip-chars-forward " \t")
      (setq indent-column (if (eolp) 0 (current-column))))
    (if bird-track (insert-char ?> 1))
    (indent-to indent-column)))

;; Toggle bird-track ][ 
(defun haskell-literate-toggle-bird-track-line ()
  (interactive)
  (save-excursion
    (beginning-of-line)
    (if (= (following-char) ? )
 	(progn (delete-char 1) (insert-char ?> 1))
      (if (= (following-char) ?>)
 	  (progn (delete-char 1) (insert-char ?  1))
  	(progn (insert-char ?> 1) (insert-char ?  1))))))

(defun haskell-literate-toggle-bird-track-region (start end)
  (interactive "r") 
  (save-excursion 
    (goto-char start) 
    (while (<= (point) end) 
      (beginning-of-line)
      (haskell-literate-toggle-bird-track-line)
      (forward-line 1))))