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;;;
;;; ghc-flymake.el
;;;

;; Author:  Kazu Yamamoto <Kazu@Mew.org>
;; Created: Mar 12, 2010

;;; Code:

(require 'flymake)

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(defvar ghc-hlint-options nil "*Hlint options")

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(defconst ghc-error-buffer-name "*GHC Errors*")

(defconst ghc-flymake-allowed-file-name-masks
  '("\\.l?hs$" ghc-flymake-init flymake-simple-cleanup flymake-get-real-file-name))

(defconst ghc-flymake-err-line-patterns
  '("^\\(.*\\.l?hs\\):\\([0-9]+\\):\\([0-9]+\\):[ ]*\\(.+\\)" 1 2 3 4))

(add-to-list 'flymake-allowed-file-name-masks
	     ghc-flymake-allowed-file-name-masks)

(add-to-list 'flymake-err-line-patterns
	     ghc-flymake-err-line-patterns)

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(defun ghc-flymake-init ()
  (let ((after-save-hook nil))
    (save-buffer))
  (let ((file (file-name-nondirectory (buffer-file-name))))
    (list ghc-module-command (ghc-flymake-command file ghc-hlint-options))))

(defvar ghc-flymake-command nil) ;; nil: check, t: lint

(defun ghc-flymake-command (file opts)
   (if ghc-flymake-command
       (let ((hopts (ghc-mapconcat (lambda (x) (list "-h" x)) opts)))
	 `(,@hopts "lint" ,file))
     (list "check" file)))

(defun ghc-flymake-toggle-command ()
  (interactive)
  (setq ghc-flymake-command (not ghc-flymake-command))
  (if ghc-flymake-command
      (message "Syntax check with hlint")
    (message "Syntax check with GHC")))

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(defun ghc-flymake-display-errors ()
  (interactive)
  (if (not (ghc-flymake-have-errs-p))
      (message "No errors or warnings")
    (let ((buf (get-buffer-create ghc-error-buffer-name))
	  (title (ghc-flymake-err-title))
	  (errs (ghc-flymake-err-list)))
      (with-current-buffer buf
	(erase-buffer)
	(ghc-flymake-insert-errors title errs))
      (display-buffer buf))))

(defun ghc-flymake-insert-errors (title errs)
  (save-excursion
    (insert title "\n\n")
    (mapc (lambda (x) (insert (ghc-replace-character x ghc-null ghc-newline) "\n")) errs)))

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(defun ghc-extract-type (str)
  (with-temp-buffer
    (insert str)
    (goto-char (point-min))
    (when (re-search-forward "Inferred type: " nil t)
      (delete-region (point-min) (point)))
    (when (re-search-forward " forall [^.]+\\." nil t)
      (replace-match ""))
    (while (re-search-forward "\0 +" nil t)
      (replace-match " "))
    (goto-char (point-min))
    (while (re-search-forward "\\[Char\\]" nil t)
      (replace-match "String"))
    (re-search-forward "\0" nil t)
    (buffer-substring-no-properties (point-min) (1- (point)))))

(defun ghc-flymake-insert-from-warning ()
  (interactive)
  (dolist (data (ghc-flymake-err-list))
    (save-excursion
      (cond
       ((string-match "Inferred type: " data)
	(beginning-of-line)
	(insert (ghc-extract-type data) "\n"))
       ((string-match "lacks an accompanying binding" data)
	(beginning-of-line)
	(when (looking-at "^\\([^ ]+\\) *::")
	  (save-match-data
	    (forward-line)
	    (if (eobp) (insert "\n")))
	  (insert (match-string 1) " = undefined\n")))
       ((string-match "Not in scope: `\\([^']+\\)'" data)
	(save-match-data
	  (unless (re-search-forward "^$" nil t)
	    (goto-char (point-max))
	    (insert "\n")))
	(insert "\n" (match-string 1 data) " = undefined\n"))
       ((string-match "Found:\0[ ]*\\([^\0]+\\)\0Why not:\0[ ]*\\([^\0]+\\)" data)
	(let ((old (match-string 1 data))
	      (new (match-string 2 data)))
	  (beginning-of-line)
	  (when (search-forward old nil t)
	    (let ((end (point)))
	      (search-backward old nil t)
	      (delete-region (point) end))
	    (insert new))))))))

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(defun ghc-flymake-err-get-title (x) (nth 0 x))
(defun ghc-flymake-err-get-errs (x) (nth 1 x))

(defalias 'ghc-flymake-have-errs-p 'ghc-flymake-data)

(defun ghc-flymake-data ()
  (let* ((line-no (flymake-current-line-no))
         (info (nth 0 (flymake-find-err-info flymake-err-info line-no))))
    (flymake-make-err-menu-data line-no info)))

(defun ghc-flymake-err-title ()
  (ghc-flymake-err-get-title (ghc-flymake-data)))

(defun ghc-flymake-err-list ()
  (mapcar 'car (ghc-flymake-err-get-errs (ghc-flymake-data))))

(provide 'ghc-flymake)