;;; vcs.el --- Module file for version control configuration.
;;
;; Copyright (C) 2017-2019 Wojciech Kozlowski
;;
;; Author: Wojciech Kozlowski <wk@wojciechkozlowski.eu>
;; Created: 2017-08-25
;;
;; This file is not part of GNU Emacs.
;;
;;; Commentary:
;;
;; This module sets up configuration for version control.
;;
;;; License: GPLv3

;;; Required packages:

;;; Code:

(defvar emodule/vcs-packages

  '(diff-hl
    magit
    magit-todos)

  )

;;; Configuration:

(defun emodule/vcs-init ()
  "Initialise the `vcs' module."

  ;; -----------------------------------------------------------------------------------------------
  ;; `diff-hl'
  ;; -----------------------------------------------------------------------------------------------

  ;; The `magit-post-refresh-hook' doesn't work very well if it's not the first in the list of
  ;; hooks. Therefore, we guarantee that in a hacky way by loading it after 0 seconds of idle time.
  (use-package diff-hl
    :defer 0
    :config
    (global-diff-hl-mode)
    (add-hook 'dired-mode-hook 'diff-hl-dired-mode)
    (add-hook 'magit-post-refresh-hook 'diff-hl-magit-post-refresh))

  ;; -----------------------------------------------------------------------------------------------
  ;; `diff-mode'
  ;; -----------------------------------------------------------------------------------------------

  (use-package diff-mode
    :init

    ;; Diff mode hook - whitespace mode settings and set read-only mode.
    (add-hook 'diff-mode-hook (lambda ()
                                (setq-local whitespace-style
                                            '(face
                                              tabs
                                              tab-mark
                                              spaces
                                              space-mark
                                              trailing
                                              indentation::space
                                              indentation::tab
                                              newline
                                              newline-mark))
                                (read-only-mode 1)))

    :config

    ;; Extra functions -----------------------------------------------------------------------------

    ;; Display source in other window whilst keeping point in the diff file. Based on the code for
    ;; `diff-goto-source.
    (defun x-diff-display-source (&optional other-file event)
      "Display the corresponding source line in another window.
    `diff-jump-to-old-file' (or its opposite if the OTHER-FILE
    prefix arg is given) determines whether to jump to the old or
    the new file.  If the prefix arg is bigger than 8 (for
    example with \\[universal-argument] \\[universal-argument])
    then `diff-jump-to-old-file' is also set, for the next
    invocations."

      (interactive (list current-prefix-arg last-input-event))
      ;; When pointing at a removal line, we probably want to jump to the old location, and else to
      ;; the new (i.e. as if reverting). This is a convenient detail when using smerge-diff.
      (if event (posn-set-point (event-end event)))
      (let ((rev (not (save-excursion (beginning-of-line)
                                      (looking-at "[-<]")))))
        (pcase-let ((`(,buf ,line-offset ,pos ,src ,_dst ,switched)
                     (diff-find-source-location other-file rev)))
          (let ((window (display-buffer buf t)))
            (save-selected-window
              (select-window window)
              (goto-char (+ (car pos) (cdr src)))
              (diff-hunk-status-msg line-offset (diff-xor rev switched) t))))))

    ;; Key-bindings --------------------------------------------------------------------------------

    ;; This shadows new global key-binding for other-window.
    (define-key diff-mode-map (kbd "M-o") nil)

    ;; This copies behaviour from other modes where C-o displays the relevant
    ;; source in another window.
    (define-key diff-mode-map (kbd "C-o") 'x-diff-display-source))

  ;; -----------------------------------------------------------------------------------------------
  ;; `ediff'
  ;; -----------------------------------------------------------------------------------------------

  (setq ediff-diff-options "-w"
        ediff-split-window-function 'split-window-horizontally
        ediff-window-setup-function 'ediff-setup-windows-plain)

  ;; -----------------------------------------------------------------------------------------------
  ;; Load and configure `magit'.
  ;; -----------------------------------------------------------------------------------------------

  (use-package magit
    :bind
    ("C-x g l" . magit-log-head)
    ("C-x g f" . magit-log-buffer-file)
    ("C-x g b" . magit-blame)
    ("C-x g m" . magit-show-refs-popup)
    ("C-x g c" . magit-branch-and-checkout)
    ("C-x g s" . magit-status)
    ("C-x g r" . magit-reflog)
    ("C-x g t" . magit-tag)
    :config
    (add-hook 'magit-mode-hook 'magit-load-config-extensions)
    (setq magit-bury-buffer-function 'magit-mode-quit-window))

  (use-package magit-todos
    :hook (magit-mode . magit-todos-mode))

  )

(provide 'emodule/vcs)
;;; vcs.el ends here