;;; esv.el --- read the Bible  -*- lexical-binding:t -*-

;; Copyright (C) 2024 Jeremy Baxter

;; Author: Jeremy Baxter <jeremy@baxters.nz>
;; Maintainer: Jeremy Baxter <jeremy@baxters.nz>
;; Created: May 2024
;; Keywords: bible

;; This file is not part of GNU Emacs.

;; esv.el 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.
;;
;; esv.el 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 esv.el.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; esv.el provides `esv', a command for fetching a given passage of
;; the ESV Bible.  The majority of the work is done by the esv command
;; line tool; esv.el just presents the text nicely in an Emacs buffer
;; for a pleasurable viewing experience.
;;
;; If you do not already have esv, find it on its website:
;;   https://sr.ht/~jeremy/esv

;;; Code:

(defgroup esv nil
  "Read the Bible."
  :prefix "esv-"
  :group 'applications)

(defcustom esv-close-existing-buffers nil
  "Whether to close an existing `esv' buffer if one already exists."
  :type 'boolean)

(defcustom esv-columns 72
  "Length of each line output by `esv'."
  :type 'natnum)

(defcustom esv-mode-hook nil
  "Hook run after entering `esv-mode'."
  :type 'hook)

(defcustom esv-process "esv"
  "Name of the process created by `esv'."
  :type 'string)

(defcustom esv-program "esv"
  "Path to or name of the program started by `esv'."
  :type 'string)

(defvar esv-arguments '()
  "List of additional arguments passed to `esv-program'.")

(define-derived-mode esv-mode text-mode "ESV-Bible"
  "Major mode used for reading the Bible with `esv'."
  :group 'esv

  (read-only-mode))

(defun esv (passage)
  "Fetch the Bible passage identified by BOOK and VERSES.
The result will be redirected to a buffer named after the passage.

Requires the esv command line tool to be in the system's PATH.
esv can be acquired at <https://sr.ht/~jeremy/esv>."
  (interactive "MPassage: ")
  (let*
      ((slices (split-string passage))
       (verses (car (last slices)))
       (book (mapconcat #'(lambda (e) e)
                        (take (1- (length slices)) slices) " "))
       (buffer (concat book " " verses))
       (arg-list (append esv-arguments
                         (list (format "-l%d" esv-columns))
                         (list book) (list verses))))
    (catch 'buffer-exists
      (when (get-buffer buffer)
        (unless esv-close-existing-buffers
          (message "Buffer `%s' already exists" buffer)
          (throw 'buffer-exists nil))
        (kill-buffer buffer)))
    (apply #'call-process esv-program nil buffer t arg-list)
    (display-buffer buffer)
    (with-current-buffer buffer
      (esv-mode)
      (goto-char (point-min)))
    (set-window-start (get-buffer-window buffer) (point-min)))
  t)

(provide 'esv)

;;; esv.el ends here