;;; ui/vc-gutter/config.el -*- lexical-binding: t; -*-

(defvar +vc-gutter-in-margin nil
  "If non-nil, use the margin for diffs instead of the fringe.")

(defvar +vc-gutter-in-remote-files nil
  "If non-nil, enable the vc gutter in remote files (e.g. open through TRAMP).")

(defvar +vc-gutter-diff-unsaved-buffer nil
  "If non-nil, `diff-hl-flydiff-mode' will be activated. This allows on-the-fly
diffing, even for unsaved buffers.")

(defvar +vc-gutter-default-style t
  "If non-nil, enable the default look of the vc gutter. This means subtle thin
bitmaps on the left, an arrow bitmap for flycheck, and flycheck indicators moved
to the right fringe.")


;;
;; Packages

(use-package! git-gutter
  :commands git-gutter:revert-hunk git-gutter:stage-hunk
  :init
  (add-hook! 'find-file-hook
    (defun +vc-gutter-init-maybe-h ()
      "Enable `git-gutter-mode' in the current buffer.

If the buffer doesn't represent an existing file, `git-gutter-mode's activation
is deferred until the file is saved. Respects `git-gutter:disabled-modes'."
      (when (or +vc-gutter-in-remote-files
                (not (file-remote-p (or buffer-file-name default-directory))))
        (if (not buffer-file-name)
            (add-hook 'after-save-hook #'+vc-gutter-init-maybe-h nil 'local)
          (when (and (vc-backend buffer-file-name)
                     (progn
                       (require 'git-gutter)
                       (not (memq major-mode git-gutter:disabled-modes))))
            (if (and (display-graphic-p)
                     (require 'git-gutter-fringe nil t))
                (progn
                  (setq-local git-gutter:init-function      #'git-gutter-fr:init)
                  (setq-local git-gutter:view-diff-function #'git-gutter-fr:view-diff-infos)
                  (setq-local git-gutter:clear-function     #'git-gutter-fr:clear)
                  (setq-local git-gutter:window-width -1))
              (setq-local git-gutter:init-function      'nil)
              (setq-local git-gutter:view-diff-function #'git-gutter:view-diff-infos)
              (setq-local git-gutter:clear-function     #'git-gutter:clear-diff-infos)
              (setq-local git-gutter:window-width 1))
            (git-gutter-mode +1)
            (remove-hook 'after-save-hook #'+vc-gutter-init-maybe-h 'local))))))

  ;; Disable in Org mode, as per
  ;; <https://github.com/syl20bnr/spacemacs/issues/10555> and
  ;; <https://github.com/syohex/emacs-git-gutter/issues/24>. Apparently, the
  ;; mode-enabling function for global minor modes gets called for new buffers
  ;; while they are still in `fundamental-mode', before a major mode has been
  ;; assigned. I don't know why this is the case, but adding `fundamental-mode'
  ;; here fixes the issue.
  (setq git-gutter:disabled-modes '(fundamental-mode image-mode pdf-view-mode))

  ;; standardize default fringe width
  (if (fboundp 'fringe-mode) (fringe-mode '4))
  :config
  (set-popup-rule! "^\\*git-gutter" :select nil :size '+popup-shrink-to-fit)

  ;; Update git-gutter on focus (in case I was using git externally)
  (add-hook 'focus-in-hook #'git-gutter:update-all-windows)

  (add-hook! '(doom-escape-hook doom-switch-window-hook) :append
    (defun +vc-gutter-update-h (&rest _)
      "Refresh git-gutter on ESC. Return nil to prevent shadowing other
`doom-escape-hook' hooks."
      (when (and git-gutter-mode
                 (not (memq this-command '(git-gutter:stage-hunk
                                           git-gutter:revert-hunk))))
        (ignore (git-gutter)))))
  ;; update git-gutter when using magit commands
  (advice-add #'magit-stage-file   :after #'+vc-gutter-update-h)
  (advice-add #'magit-unstage-file :after #'+vc-gutter-update-h))


;; subtle diff indicators in the fringe
(when +vc-gutter-default-style
  (after! git-gutter-fringe
    ;; places the git gutter outside the margins.
    (setq-default fringes-outside-margins t)
    ;; thin fringe bitmaps
    (define-fringe-bitmap 'git-gutter-fr:added [224]
      nil nil '(center repeated))
    (define-fringe-bitmap 'git-gutter-fr:modified [224]
      nil nil '(center repeated))
    (define-fringe-bitmap 'git-gutter-fr:deleted [128 192 224 240]
      nil nil 'bottom)
    ;; let diff have left fringe, flycheck can have right fringe
    (after! flycheck
      (setq flycheck-indication-mode 'right-fringe)
      ;; A non-descript, left-pointing arrow
      (define-fringe-bitmap 'flycheck-fringe-bitmap-double-arrow
        [16 48 112 240 112 48 16] nil nil 'center))))