(defun my/ag-goto ()

  (interactive)

  (save-excursion

    (let ( lineno end )

      (forward-line 1)

      (backward-char 1)

      (setq end (point))

      (forward-line 0)

      (if (not (search-forward-regexp "^\\([1-9][0-9]*\\):" end t))

          (message "Not at line number...")

        (setq lineno (string-to-int (match-string 1)))

        (if (search-backward-regexp "^$" nil t)

            (forward-char)

          (goto-char (point-min)))

        (search-forward-regexp "^.*")

        (find-file-other-window (match-string 0))

        (goto-line lineno)))))

(defvar my/ag-mode-map (make-sparse-keymap))

(define-key my/ag-mode-map (kbd "RET") 'my/ag-goto)

(defface my/ag-lineno-face

  '((t :inherit warning))

  "Face for line number.")

(defface my/ag-path-face

  '((t :inherit success))

  "Face for line number.")

(defvar my/ag-keywords

  '(("[1-9][0-9]\\{0,3\\}:" . (0 'my/ag-lineno-face))

    ("^[^:]\\{4\\}.*" . (0 'my/ag-path-face))))

(defun my/ag-font-lock-extend-region ()

  (save-excursion

    (goto-char font-lock-beg)

    (forward-line 2)

    (setq font-lock-beg (point))))

(define-derived-mode my/ag-mode fundamental-mode "Ag"

  "Major mode for Ag parsing."

  (setq font-lock-defaults '(my/ag-keywords t nil nil)) ;  (font-lock-multiline . t)

  ;; (add-hook 'font-lock-extend-region-functions 'my/ag-font-lock-extend-region)

  (use-local-map my/ag-mode-map))

(defvar my/ag-buffer-name "*ag*")

(defvar my/ag-buffer nil)

(defun my/ag-filter (proc str)

  (when (buffer-live-p (process-buffer proc))

    (with-current-buffer (process-buffer proc)

      (save-excursion

        (goto-char (process-mark proc))

        (insert str)

        (set-marker (process-mark proc) (point)))

      )))

(defvar my/ag-regex-history nil)

(defun my/ag (regex)

  (interactive

   (let* ( (def (when my/ag-regex-history (car my/ag-regex-history)))

           (part (when def (if (< (length def) 20)

                               def

                             (concat (substring def 0 20) "...")))) )

     (list (read-string

            (if part (format "Regex [%s]: " part) "Regex: ")

            ""  'my/ag-regex-history  def  t))))

  (let ( proc (dir default-directory) )

    (setq my/ag-buffer (get-buffer-create my/ag-buffer-name))

    (with-current-buffer my/ag-buffer

      (setq default-directory dir)

      (erase-buffer)

      (my/ag-mode))

    (display-buffer my/ag-buffer)

    (setq proc (make-process

                :name "ag"

                :buffer my/ag-buffer

                :filter 'my/ag-filter

                :command (list "ag" "--group" "--nocolor" regex))) ))