;;; ert-buffer.el --- Support functions for running ert tests on buffers

;; Copyright (C) 2010-2012  Free Software Foundation, Inc.

;; Author: Stefan Merten <address@hidden>,

;; 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:
;; 
;; Some functions need a buffer to run on.  They may use the buffer content as
;; well as the point and the mark as input and may modify all of them.  Here are
;; some support functions to test such functions using `ert'.
;;
;; Use `ert-equal-buffer' and/or `ert-equal-buffer-return' for your `should'
;; forms.
;;
;; You may use the constants `ert-Buf-point-char' and `ert-Buf-mark-char' in
;; constructing comparison strings.

;;; Code:

(require 'cl)
(require 'ert)

;; ****************************************************************************
;; `ert-Buf' and related functions

(defconst ert-Buf-point-char "\^@"
  "Special character used to mark the position of point in a `ert-Buf'.")

(defconst ert-Buf-mark-char "\^?"
  "Special character used to mark the position of mark in a `ert-Buf'.")

(defstruct (ert-Buf
	    (:constructor string-to-ert-Buf
			  (string
			   &aux
			   (analysis (ert-Buf-parse-string string))
			   (content (car analysis))
			   (point (cadr analysis))
			   (mark (caddr analysis))))
	    (:constructor buffer-to-ert-Buf
			  (&aux
			   (content (buffer-substring-no-properties
				     (point-min) (point-max)))
			   (point (point))
			   (mark (mark t))
			   (string
			    (ert-Buf-create-string content point mark)))))
  "Structure to hold comparable information about a buffer."
  (content nil :read-only t)
  (point nil :read-only t)
  (mark nil :read-only t)
  (string nil :read-only t)
  )

(defun ert-Buf-parse-string (string)
  "Parse STRING and return clean results.
Return a list consisting of the cleaned content, the position of
point if `ert-Buf-point-char' was found and the the position of mark
if `ert-Buf-mark-char' was found."
  (with-temp-buffer
    (let ((case-fold-search nil)
	  fnd point-fnd mark-fnd)
      (insert string)
      (goto-char (point-min))
      (while (re-search-forward
	      (concat "[" ert-Buf-point-char ert-Buf-mark-char "]") nil t)
	(setq fnd (match-string 0))
	(replace-match "")
	(cond
	 ((equal fnd ert-Buf-point-char)
	  (if point-fnd
	      (error "Duplicate point"))
	  (setq point-fnd (point)))
	 ((equal fnd ert-Buf-mark-char)
	  (if mark-fnd
	      (error "Duplicate mark"))
	  (setq mark-fnd (point)))
	 (t
	  (error "Unexpected marker found"))))
      (list (buffer-substring-no-properties (point-min) (point-max))
	    point-fnd mark-fnd))))

(defun ert-Buf-create-string (content point mark)
  "Create a string representation from CONTENT, POINT and MARK."
  (with-temp-buffer
    (insert content)
    (let (pnt-chs)
      (if point
	  (setq pnt-chs (nconc pnt-chs (list (cons point ert-Buf-point-char)))))
      (if mark
	  (setq pnt-chs (nconc pnt-chs (list (cons mark ert-Buf-mark-char)))))
      ;; Sort pairs so the highest position is last.
      (setq pnt-chs (sort pnt-chs (lambda (el1 el2) (> (car el1) (car el2)))))
      (while pnt-chs
	(goto-char (caar pnt-chs))
	(insert (cdar pnt-chs))
	(setq pnt-chs (cdr pnt-chs)))
      (buffer-substring-no-properties (point-min) (point-max)))))

(defun ert-Buf-to-buffer (buf)
  "Set current buffer according to BUF."
  (insert (ert-Buf-content buf))
  (if (ert-Buf-point buf)
      (goto-char (ert-Buf-point buf)))
  (if (ert-Buf-mark buf)
      (set-mark (ert-Buf-mark buf))))

;; ****************************************************************************
;; Runners

(defvar ert-inputs nil
  "Variable to hold the strings to give successively to `ert-completing-read'.")

(defadvice completing-read (around ert-completing-read first
				   (prompt collection &optional predicate
					   require-match initial-input hist
					   def inherit-input-method))
  "Advice `completing-read' to accept input from `ert-inputs'."
  (if (not ert-inputs)
      (error "No more input strings in `ert-inputs'"))
  (let* ((input (pop ert-inputs)))
    (setq ad-return-value
	  (cond
	   ((eq (try-completion input collection predicate) t) ;; Perfect match.
	    input)
	   ((not require-match) ;; Non-matching input allowed.
	    input)
	   ((and (equal input "")
		 (eq require-match t)) ;; Empty input and this is allowed.
	    input)
	   (t
	    (error
	     "Input '%s' is not allowed for `completing-read' expecting %s"
	     input collection))))))

(defadvice read-string (around ert-read-string first
			       (prompt &optional initial-input history
				       default-value inherit-input-method))
  "Advice `read-string' to accept input from `ert-inputs'."
  (if (not ert-inputs)
      (error "No more input strings in `ert-inputs'"))
  (let* ((input (pop ert-inputs)))
    (setq ad-return-value
	  (if (and (equal input "") default-value)
	      default-value
	    input))))

(defadvice read-number (around ert-read-number first
			       (prompt &optional default))
  "Advice `read-number' to accept input from `ert-inputs'."
  (if (not ert-inputs)
      (error "No more input strings in `ert-inputs'"))
  (let* ((input (pop ert-inputs)))
    (setq ad-return-value
	  (if (and (equal input "") default)
	      default
	    input))))

(defun ert-run-test-with-buffer (input funcall interactive)
  "With a buffer filled with INPUT run list FUNCALL.
Return a cons consisting of the return value and a `ert-Buf'.  If
INTERACTIVE is non-nil FUNCALL is called in an interactive
environment."
  (let ((buf (string-to-ert-Buf input)))
    (with-temp-buffer
      (ert-Buf-to-buffer buf)
      (let ((act-return
	     (cond
	      ((not interactive)
	       (apply (car funcall) (cdr funcall)))
	      ((eq interactive t)
	       (let ((current-prefix-arg (cadr funcall)))
		 (call-interactively (car funcall))))
	      ((listp interactive)
	       (setq ert-inputs interactive)
	       (ad-activate 'read-string)
	       (ad-activate 'read-number)
	       (ad-activate 'completing-read)
	       (unwind-protect
		   (let ((current-prefix-arg (cadr funcall)))
		     (call-interactively (car funcall)))
		 (progn
		   (ad-deactivate 'completing-read)
		   (ad-deactivate 'read-number)
		   (ad-deactivate 'read-string)))
	       (if ert-inputs
		   (error "%d input strings left over"
			  (length ert-inputs))))))
	    (act-buf (buffer-to-ert-Buf)))
	(cons act-return act-buf)))))

(defun ert-compare-test-with-buffer (result exp-output ignore-return exp-return)
  "Compare RESULT of test from `ert-run-test-with-buffer' with expected values.
Return a list of booleans where t stands for a successful test of this kind:

* Content of output buffer
* Point in output buffer
* Return value

EXP-OUTPUT, IGNORE-RETURN, EXP-RETURN are described in
`ert-equal-buffer-internal'."
  (let ((act-return (car result))
	(act-buf (cdr result))
	(exp-buf (and exp-output (string-to-ert-Buf exp-output))))
    (list
     (or (not exp-buf)
	 (equal (ert-Buf-content act-buf) (ert-Buf-content exp-buf)))
     (or
      (not exp-buf)
      (not (ert-Buf-point exp-buf))
      (equal (ert-Buf-point act-buf) (ert-Buf-point exp-buf)))
     (or ignore-return
	 (equal act-return exp-return)))))

(defun ert-equal-buffer-internal (funcall input exp-output ignore-return exp-return interactive)
  "Run list FUNCALL with a buffer filled with INPUT.
Compare the buffer content to EXP-OUTPUT if this is
non-nil.  Ignore return value if IGNORE-RETURN or compare the
return value to EXP-RETURN.  Return t if equal.

INPUT and EXP-OUTPUT are expected to be parsable by
`ert-Buf-parse-string'.

If INTERACTIVE is non-nil the FUNCALL is done interactively and
`current-prefix-arg' is set to the cadr of FUNCALL and thus must
comply to the format of `current-prefix-arg'.  If INTERACTIVE is t
only `call-interactively' is used.  If INTERACTIVE is a list of
strings the elements of the list are given to (advised forms of)
functions reading from the minibuffer as user input strings."
  (reduce (lambda (l r) (and l r))
	  (ert-compare-test-with-buffer
	   (ert-run-test-with-buffer input funcall interactive)
	   exp-output ignore-return exp-return)))

(defun ert-equal-buffer-return (funcall input exp-output exp-return &optional interactive)
  "Call `ert-equal-buffer-internal' caring for result of FUNCALL.
INPUT, EXP-OUTPUT, IGNORE-RETURN, EXP-RETURN, INTERACTIVE are
described in `ert-equal-buffer-internal'."
  (ert-equal-buffer-internal
   funcall input exp-output nil exp-return interactive))

(defun ert-equal-buffer (funcall input exp-output &optional interactive)
  "Call `ert-equal-buffer-internal' not caring for result of FUNCALL.
INPUT, EXP-OUTPUT, INTERACTIVE are described in
`ert-equal-buffer-internal'."
  (ert-equal-buffer-internal funcall input exp-output t nil interactive))

;; ****************************************************************************
;; Explainers

(defun ert-equal-buffer-internal-explain (funcall input exp-output ignore-return exp-return interactive)
  "Explain why `ert-equal-buffer-internal' failed with these parameters.
Return the explanation.  FUNCALL, INPUT, EXP-OUTPUT,
IGNORE-RETURN, EXP-RETURN, INTERACTIVE are described in
`ert-equal-buffer-internal'."
  (let ((test-result (ert-run-test-with-buffer input funcall interactive))
	(exp-buf (and exp-output (string-to-ert-Buf exp-output))))
    (destructuring-bind (ok-string ok-point ok-return)
	(ert-compare-test-with-buffer
	 test-result exp-output ignore-return exp-return)
      (let (result)
	(if (not ok-return)
	    (push (list 'different-return-values
			(ert--explain-not-equal (car test-result) exp-return))
		  result))
	(if (not ok-point)
	    (push (list 'different-points
			(ert-Buf-string (cdr test-result))
			(ert-Buf-string exp-buf))
		  result))
	(if (not ok-string)
	    (push (list 'different-buffer-contents
			(ert--explain-not-equal
			 (ert-Buf-content (cdr test-result))
			 (ert-Buf-content exp-buf)))
		  result))
	result))))

(defun ert-equal-buffer-return-explain (funcall input exp-output exp-return &optional interactive)
  "Explain why `ert-equal-buffer-return' failed with these parameters.
Return the explanation.  FUNCALL, INPUT, EXP-OUTPUT, EXP-RETURN,
INTERACTIVE are described in `ert-equal-buffer-internal'."
  (ert-equal-buffer-internal-explain
   funcall input exp-output nil exp-return interactive))

(put 'ert-equal-buffer-return 'ert-explainer 'ert-equal-buffer-return-explain)

(defun ert-equal-buffer-explain (funcall input exp-output &optional interactive)
  "Explain why `ert-equal-buffer' failed with these parameters.
Return the explanation.  FUNCALL, INPUT, EXP-OUTPUT, EXP-RETURN,
INTERACTIVE are described in `ert-equal-buffer-internal'."
  (ert-equal-buffer-internal-explain
   funcall input exp-output t nil interactive))

(put 'ert-equal-buffer 'ert-explainer 'ert-equal-buffer-explain)

;; Local Variables:
;;   sentence-end-double-space: t
;; End:

(provide 'ert-buffer)

;;; ert-buffer.el ends here