;;; p4-browse.el --- minor mode for browsing revisions of a given file

;; Author: Paul Du Bois <dubois@geoworks.com>
;; Maintainer: dubois@infinite-machine.com
;; $Id: //depot/tools/lisp/p4-browse.el#2 $

;;; Commentary:

;; This is a minor mode for viewing revisions of a file.  It binds
;; keys that bring up diffs and changelist descriptions for the currently
;; viewed revision of the file.

;; diffs and changelist buffers automatically update themselves when
;; the user moves to a different revision.

;; The single user entry point is the command `p4-browse-file-revisions'.

;;; Code:

(require 'p4)

(defun p4-browse-file-revisions (&optional file)
  "Begin browsing revisions of FILE.
Interactively, browses the current buffer's file."
  (interactive)
  (or file (setq file buffer-file-name))
  (p4b-display-revision file "have"))

;;; ----------------------------------------------------------------------
;;; minor mode
;;; ----------------------------------------------------------------------

(defvar p4-browse-minor-mode nil
  "Minor mode for browsing through revisions of a file.")
(make-variable-buffer-local 'p4-browse-minor-mode)

;; just here for documentation string
(defun p4-browse-minor-mode ()
  "Minor mode for browsing through revisions of a file.

\\[p4b-revision-previous] \\[p4b-revision-next]	go back and forward one revision, respectively.
\\[p4b-revision-goto]	will jump to a given revision.

\\[p4b-describe-changelist]	displays the changelist that created the current revision.
\\[p4b-diff-with-previous]	displays the differences from that changelist.

\\[p4b-quit]	quits browse mode.")

(defvar p4-browse-map nil)
(if p4-browse-map nil
  (let ((map (make-keymap)))
    (suppress-keymap map 'nodigits)
    (define-key map "c" 'p4b-describe-changelist)
    (define-key map "d" 'p4b-diff-with-previous)
    (define-key map "g" 'p4b-revision-goto)
    (define-key map "q" 'p4b-quit)
    (define-key map "<" 'p4b-revision-previous)
    (define-key map ">" 'p4b-revision-next)
    (define-key map "?" 'p4b-help)
    (setq p4-browse-map map)
    (setq minor-mode-map-alist
	  (cons (cons 'p4-browse-minor-mode p4-browse-map)
		(delq 'p4-browse-minor-mode minor-mode-map-alist)))))

(or (assq 'p4-browse-minor-mode minor-mode-alist)
    (setq minor-mode-alist
	  (cons '(p4-browse-minor-mode " P4-Browse") minor-mode-alist)))

;; Name of buffer to use for "p4 describe" output
(defvar p4b-description-buffer "*P4 browse: describe*")
(defvar p4b-diff-buffer "*P4 browse: diff2*")

;;; ----------------------------------------------------------------------
;;; User-level commands
;;; ----------------------------------------------------------------------

(defun p4b-help ()
  "Display simple help for p4-browse minor mode.

\\{p4-browse-map}"
  (interactive)
  (message "< > g: Prev/next/goto revision   c d ?: Show changelist/diff/help   q: quit"))

(defun p4b-describe-changelist ()
  "View the changelist description associated with the current revision."
  (interactive)
  (let ((inhibit-read-only t)
	(change (nth 2 (p4b-parse-header))))
    (p4-exec-p4-fast p4b-description-buffer "describe" "-s" change)
    (save-excursion
      (set-buffer p4b-description-buffer)
      (set-buffer-modified-p nil)
      (toggle-read-only t)
      (view-mode-enter nil 'p4b-kill-buffer))
    ;; play nicely with auto-update
    (if (null (get-buffer-window p4b-description-buffer 'visible))
	(p4-display-output p4b-description-buffer))))

(defun p4b-kill-buffer (buffer-name)
  (let ((buffer (get-buffer buffer-name)))
    (if (null buffer) nil
      (delete-windows-on buffer)
      (kill-buffer buffer))))

(defun p4b-diff-with-previous ()
  "Show diff that lead to current revision."
  (interactive)
  (let* ((header (p4b-parse-header))
	 (file (nth 0 header))
	 (revision (string-to-number (nth 1 header)))
	 (buf p4b-diff-buffer))
    (p4-exec-p4-fast buf "diff2"
		     (format "%s#%d" file (1- revision))
		     (format "%s#%d" file revision))
    (save-excursion
      (set-buffer buf)
      (run-hooks 'p4-diff-hook)
      (goto-char (point-min)))
    ;; play nicely with auto-update
    (if (null (get-buffer-window buf 'visible))
	(p4-display-output buf "Diff"))))

(defun p4b-revision-goto (arg)
  "View the passed revision of the file.
Prefix argument is the revision to view."
  (interactive
   (list (if current-prefix-arg
	     (prefix-numeric-value current-prefix-arg)
	   ;; read string instead of number so user can ask for head/have
	   (read-string "Revision: "))))

  (let ((file (nth 0 (p4b-parse-header))))
    (p4b-display-revision file arg 'reuse-window)))

(defun p4b-revision-previous (arg)
  "View the previous revision of the file.
Prefix argument is the number of revisions to go back."
  (interactive "p")
  (p4b-revision-next (- arg)))

(defun p4b-revision-next (arg)
  "View the next revision of the file
Prefix argument is the number of revisions to go forward."
  (interactive "p")
  (let ((file (nth 0 (p4b-parse-header)))
	(revision (+ arg (string-to-number (nth 1 (p4b-parse-header))))))
    (p4b-display-revision file revision 'reuse-window)))

(defun p4b-quit ()
  "Quit and clean up any spare buffers"
  (interactive)
  (mapcar 'p4b-kill-buffer
	  (list (current-buffer)
		p4b-description-buffer
		p4b-diff-buffer)))

;;; ----------------------------------------------------------------------
;;; Internals
;;; ----------------------------------------------------------------------

(defun p4b-parse-header ()
  (save-excursion
    (goto-char (point-min))
    (if (not (looking-at "\\(.*\\)#\\(\\sw+\\).*change \\(\\sw+\\)"))
	(error "Can't find header")
      (list (match-string 1) (match-string 2) (match-string 3)))))

(defun p4b-display-revision (file revision &optional reuse-window)
  (catch 'abort
    (let* ((dir default-directory)
	   ;; FILE might be in //depot syntax
	   (file-path (concat dir "/" (file-name-nondirectory file)))
	   (buf (get-buffer-create "*tmp revision*"))
	   (buffer-name (concat (file-name-nondirectory file) "#" revision))

	   (context (p4-make-window-context (selected-window))))

      (message "Fetching revision %s..." revision)
      (p4-exec-p4-fast buf "print" (concat file "#" revision))
      (message "Fetching revision %s... done." revision)

      (save-excursion
	(set-buffer buf)
	(goto-char (point-min))

	;; If the header is not valid, it's probably an error from Perforce
	(condition-case nil
	    (p4b-parse-header)
	  (error (goto-char 1) (end-of-line)
		 (message "%s" (buffer-substring 1 (point)))
		 (throw 'abort nil)))

	;; normal-mode relies on the file name to choose a mode
	(set-visited-file-name file-path t)
	(normal-mode)
	(set-visited-file-name nil)

	;; set default-dir so p4 client can find P4CONFIG files
	(setq default-directory dir)
	(setq p4-browse-minor-mode t)
	(if (get-buffer buffer-name)
	    (kill-buffer buffer-name))
	(rename-buffer buffer-name)
	(set-buffer-modified-p nil)
	(toggle-read-only t))

      (if reuse-window
	  (progn
	    (kill-buffer (current-buffer))
	    (switch-to-buffer buf)
	    (p4-restore-window-context (selected-window) context)
	    (if (get-buffer-window p4b-description-buffer 'visible)
		(p4b-describe-changelist))
	    (if (get-buffer-window p4b-diff-buffer 'visible)
		(p4b-diff-with-previous)))
	(p4-display-output buf)
	(p4b-help)))))