;;; jao-eshell-here.el --- Easy opening of eshell buffers -*- lexical-binding: t; -*-

;; Copyright (C) 2021  jao

;; Author: jao <mail@jao.io>
;; Keywords: eshell

;; This program 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.

;; This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;;  Commands for toggling eshell buffers below the current one.

;;; Code:

(require 'eshell)

(defvar jao-eshell-here-display-buffer-alist
  '(("^\\*eshell"
     (display-buffer-reuse-window display-buffer-below-selected)
     (window-height . 0.5)))
  "Value to use for `display-buffer-alist' when displaying the eshell buffer.")

(defun jao-eshell-here--find-window (b)
  (when-let (w (seq-find (lambda (w) (eq (window-buffer w) b))
                         (window-list)))
    (select-window w)))

(defun jao-eshell-here--frame-buffer (&optional b)
  (let ((p 'jao-eshell-buffer))
    (if b (set-frame-parameter nil p b) (frame-parameter nil p))))

(defun jao-eshell--cd-here (&optional dir)
  (eshell-kill-input)
  (eshell/cd (or dir default-directory))
  (insert "\n")
  (eshell-send-input))

(defun jao-eshell-here (stay &optional force-new)
  "Open an eshell buffer below current buffer.
Buffers are reused (per frame) unless FORCE-NEW is t. With prefix
STAY (C-u), open at project's root, and with double prefix (C-u
C-u) open in the current's buffer default dir."
  (interactive "p")
  (let ((b (unless force-new (jao-eshell-here--frame-buffer)))
        (dir (cond ((> stay 4) default-directory)
                   ((> stay 1)
                    (project-root
                     (or (project-current)
                         `(transient . ,default-directory))))))
        (display-buffer-alist
         (append display-buffer-alist jao-eshell-here-display-buffer-alist)))
    (jao-with-attached-buffer "^\\*eshell" 0.5
      (if (buffer-live-p b)
          (progn (pop-to-buffer b nil t)
                 (eshell-save-some-history)
                 (when dir (jao-eshell--cd-here dir)))
        (let ((default-directory (or dir default-directory)))
          (eshell (when force-new 4)))
        (unless force-new (jao-eshell-here--frame-buffer (current-buffer)))))))

;;;###autoload
(defun eshell/x ()
  (when (derived-mode-p 'eshell-mode)
    (when (fboundp 'eshell-autojump-save)
      (eshell-autojump-save))
    (eshell-save-some-history)
    (if (> (frame-height) (window-height))
        (delete-window)
      (bury-buffer))))

;;;###autoload
(defun jao-eshell-here-toggle (stay &optional force-new)
  "Open or close an eshell buffer, using `jao-eshell-here'."
  (interactive "p")
  (if (or (and force-new (derived-mode-p 'eshell-mode))
          (eq (current-buffer) (jao-eshell-here--frame-buffer)))
      (eshell/x)
    (jao-eshell-here stay force-new)))

;;;###autoload
(defun jao-eshell-here-toggle-new (stay)
  "Open or close a new eshell buffer, using `jao-eshell-here'."
  (interactive "p")
  (jao-eshell-here-toggle stay t))

(provide 'jao-eshell-here)
;;; jao-eshell-here.el ends here