;;; pp.el --- pretty printer for Emacs Lisp  -*- lexical-binding: t -*-

;; Copyright (C) 1989, 1993, 2001-2017 Free Software Foundation, Inc.

;; Author: Randal Schwartz <merlyn@stonehenge.com>
;; Keywords: lisp

;; 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:

;;; Code:

(eval-when-compile (require 'cl-lib))
(require 'ring)

(defvar font-lock-verbose)

(defgroup pp nil
  "Pretty printer for Emacs Lisp."
  :prefix "pp-"
  :group 'lisp)

(defcustom pp-escape-newlines t
  "Value of `print-escape-newlines' used by pp-* functions."
  :type 'boolean
  :group 'pp)

;;;###autoload
(defun pp-to-string (object)
  "Return a string containing the pretty-printed representation of OBJECT.
OBJECT can be any Lisp object.  Quoting characters are used as needed
to make output that `read' can handle, whenever this is possible."
  (with-temp-buffer
    (lisp-mode-variables nil)
    (set-syntax-table emacs-lisp-mode-syntax-table)
    (let ((print-escape-newlines pp-escape-newlines)
          (print-quoted t))
      (prin1 object (current-buffer)))
    (pp-buffer)
    (buffer-string)))

;;;###autoload
(defun pp-buffer ()
  "Prettify the current buffer with printed representation of a Lisp object."
  (goto-char (point-min))
  (while (not (eobp))
    ;; (message "%06d" (- (point-max) (point)))
    (cond
     ((ignore-errors (down-list 1) t)
      (save-excursion
        (backward-char 1)
        (skip-chars-backward "'`#^")
        (when (and (not (bobp)) (memq (char-before) '(?\s ?\t ?\n)))
          (delete-region
           (point)
           (progn (skip-chars-backward " \t\n") (point)))
          (insert "\n"))))
     ((ignore-errors (up-list 1) t)
      (skip-syntax-forward ")")
      (delete-region
       (point)
       (progn (skip-chars-forward " \t\n") (point)))
      (insert ?\n))
     (t (goto-char (point-max)))))
  (goto-char (point-min))
  (indent-sexp))

;;;###autoload
(defun pp (object &optional stream)
  "Output the pretty-printed representation of OBJECT, any Lisp object.
Quoting characters are printed as needed to make output that `read'
can handle, whenever this is possible.
Output stream is STREAM, or value of `standard-output' (which see)."
  (princ (pp-to-string object) (or stream standard-output)))

(defun pp-display-expression (expression out-buffer-name)
  "Prettify and display EXPRESSION in an appropriate way, depending on length.
If a temporary buffer is needed for representation, it will be named
after OUT-BUFFER-NAME."
  (let* ((old-show-function temp-buffer-show-function)
	 ;; Use this function to display the buffer.
	 ;; This function either decides not to display it at all
	 ;; or displays it in the usual way.
	 (temp-buffer-show-function
	  (function
	   (lambda (buf)
	     (with-current-buffer buf
	       (goto-char (point-min))
	       (end-of-line 1)
	       (if (or (< (1+ (point)) (point-max))
		       (>= (- (point) (point-min)) (frame-width)))
		   (let ((temp-buffer-show-function old-show-function)
			 (old-selected (selected-window))
			 (window (display-buffer buf)))
		     (goto-char (point-min)) ; expected by some hooks ...
		     (make-frame-visible (window-frame window))
		     (unwind-protect
			 (progn
			   (select-window window)
			   (run-hooks 'temp-buffer-show-hook))
		       (when (window-live-p old-selected)
			 (select-window old-selected))
		       (message "See buffer %s." out-buffer-name)))
		 (message "%s" (buffer-substring (point-min) (point)))
		 ))))))
    (with-output-to-temp-buffer out-buffer-name
      (pp expression)
      (with-current-buffer standard-output
	(emacs-lisp-mode)
	(setq buffer-read-only nil)
	(set (make-local-variable 'font-lock-verbose) nil)))))


(cl-defstruct (pp-state (:constructor
                         make-pp-state
                         (stream
                          &aux
                          (right-margin fill-column)
                          (left-margin 0)
                          (indent '(0))
                          (scan-depth 0)
                          (print-depth 0)
                          (print-width 0)
                          (scan-width 0)
                          (block-mode (list nil))
                          (fifo (make-ring 30)))))
  stream
  right-margin ; how far we may go.
  left-margin  ; how far printer has gone
  print-width ; total width of tokens printed so far.
  indent ; left-margin, stack per depth.
  scan-width ; total width of tokens scanned so far.
  scan-depth
  print-depth
  block-widths
  block-mode ; `:vertical', `:horizontal', nil (undecided); stack per depth.
  fifo
  )

(defun pp--print (state)
  (cl-symbol-macrolet ((stream (pp-state-stream state))
                       (depth (pp-state-print-depth state))
                       (scan-depth (pp-state-scan-depth state))
                       (fifo (pp-state-fifo state))
                       (left-margin (pp-state-left-margin state))
                       (width (pp-state-print-width state))
                       (indent (pp-state-indent state))
                       (right-margin (pp-state-right-margin state))
                       (block-mode (pp-state-block-mode state)))
    (catch 'rescan
      (while (not (ring-empty-p fifo))
        (pcase (ring-remove fifo)
          ((and `(,len . :open-block) token)
           (if (<= len 0)
               ;; Not ready to print this yet!
               (progn (ring-insert-at-beginning fifo token)
                      (throw 'rescan nil))
             (cl-incf depth)
             (push left-margin indent)
             (push (if (> (+ left-margin len) right-margin)
                       :vertical :horizontal)
                   block-mode)))
          (:close-block (cl-decf depth) (pop indent) (pop block-mode))
          (:blank
           (pcase (car block-mode)
            (:vertical
             (terpri stream)
             (princ (make-string (car indent) ?\s) stream)
             (setf left-margin (car indent)))
            ((or :horizontal 'nil)
             (write-char ?\s stream)
             (cl-incf left-margin))
            (_ (error "oops")))
           (cl-incf width))
          (:eof nil)
          ((and (pred characterp) char)
           (write-char char stream)
           (cl-incf left-margin (char-width char))
           (cl-incf width (char-width char)))
          (string
           (princ string stream)
           (cl-incf left-margin (string-width string))
           (cl-incf width (string-width string))))))))

(defun pp--scan (token state)
  (cl-symbol-macrolet ((stream (pp-state-stream state))
                       (depth (pp-state-scan-depth state))
                       (print-depth (pp-state-print-depth state))
                       (fifo (pp-state-fifo state))
                       (width (pp-state-scan-width state))
                       (right-margin (pp-state-right-margin state))
                       (block-widths (pp-state-block-widths state)))
    (cl-flet ((scanlen (len) (cl-incf width len)))
      (cl-assert (> (ring-size fifo) (ring-length fifo)))
      (ring-insert fifo token)
      (pcase token
        (:open-block
         (cl-incf depth)
         (let ((block-token (cons (- width) (ring-remove fifo 0))))
           (push block-token block-widths)
           (ring-insert fifo block-token)))
        (:close-block
         (cl-incf (caar block-widths) width)
         (when (> (caar block-widths) right-margin)
           (pp--print state))
         (cl-decf depth)
         (pop block-widths))
        (:blank (scanlen 1))
        (:eof (pp--print state))
        ((pred characterp) (scanlen (char-width token)))
        (_ (scanlen (string-width token)))))
    (when block-widths
      (when (> (+ (caar block-widths) width) right-margin)
        (dolist (block-width block-widths)
          (setf (car block-width) (+ right-margin 1))))
      (when (> (caar block-widths) right-margin)
        (pp--print state)))))

(defvar cl-print-readably) ; cl-print.el

(defun pp-prin1 (object &optional stream)
  (let ((cl-print-readably nil)
        (stream (make-pp-state (or stream standard-output))))
    (pp--scan :open-block stream)
    (prog1 (cl-prin1 object (cons :pprint stream))
      (pp--scan :close-block stream)
      (pp--scan :eof stream))))

;; fallback to standard `cl-print-object'.
(cl-defmethod cl-print-object (object (stream (head :pprint)))
  (pp--scan (cl-prin1-to-string object) (cdr stream))
  object)

(cl-defmethod cl-print-object ((list cons) (stream (head :pprint)))
  (let ((state (cdr stream)))
    (pcase list
      (`(,head . ,tail)
       (pp--scan "(" state)
       (pp--scan :open-block state)
       (cl-print-object head stream)
       (while (consp tail)
         (pp--scan :blank state)
         (cl-print-object (pop tail) stream))
       (when tail
         (pp--scan :blank state)
         (pp--scan ?\. state)
         (pp--scan :blank state)
         (cl-print-object tail stream))
       (pp--scan :close-block state)
       (pp--scan ")" state))))
  list)

;;;###autoload
(defun pp-eval-expression (expression)
  "Evaluate EXPRESSION and pretty-print its value.
Also add the value to the front of the list in the variable `values'."
  (interactive
   (list (read--expression "Eval: ")))
  (message "Evaluating...")
  (push (eval expression lexical-binding) values)
  (pp-display-expression (car values) "*Pp Eval Output*"))

;;;###autoload
(defun pp-macroexpand-expression (expression)
  "Macroexpand EXPRESSION and pretty-print its value."
  (interactive
   (list (read--expression "Macroexpand: ")))
  (pp-display-expression (macroexpand-1 expression) "*Pp Macroexpand Output*"))

(defun pp-last-sexp ()
  "Read sexp before point.  Ignores leading comment characters."
  (with-syntax-table emacs-lisp-mode-syntax-table
    (let ((pt (point)))
      (save-excursion
        (forward-sexp -1)
        (read
         ;; If first line is commented, ignore all leading comments:
         (if (save-excursion (beginning-of-line) (looking-at-p "[ \t]*;"))
             (let ((exp (buffer-substring (point) pt))
                   (start nil))
               (while (string-match "\n[ \t]*;+" exp start)
                 (setq start (1+ (match-beginning 0))
                       exp (concat (substring exp 0 start)
                                   (substring exp (match-end 0)))))
               exp)
           (current-buffer)))))))

;;;###autoload
(defun pp-eval-last-sexp (arg)
  "Run `pp-eval-expression' on sexp before point.
With argument, pretty-print output into current buffer.
Ignores leading comment characters."
  (interactive "P")
  (if arg
      (insert (pp-to-string (eval (pp-last-sexp) lexical-binding)))
    (pp-eval-expression (pp-last-sexp))))

;;;###autoload
(defun pp-macroexpand-last-sexp (arg)
  "Run `pp-macroexpand-expression' on sexp before point.
With argument, pretty-print output into current buffer.
Ignores leading comment characters."
  (interactive "P")
  (if arg
      (insert (pp-to-string (macroexpand-1 (pp-last-sexp))))
    (pp-macroexpand-expression (pp-last-sexp))))

(provide 'pp)				; so (require 'pp) works

;;; pp.el ends here