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

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

(defcustom esv-columns 72
  "Length of each line output by `esv'."
  :type 'natnum
  :group 'esv)
(defcustom esv-mode-hook nil
  "Hook run after entering `esv-mode'."
  :type 'hook
  :group 'esv)
(defcustom esv-process "esv"
  "Name of the process created by `esv'."
  :type 'string
  :group 'esv)
(defcustom esv-program "esv"
  "Path to or name of the program started by `esv'."
  :type 'string
  :group 'esv)

(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 (book verses)
  "Fetch the Bible passage identified by BOOK and VERSES.
The result will be redirected to a buffer specified by `esv-buffer'."
  (interactive "MBook: \nMVerses: ")
  (let ((buffer (concat book " " verses)))
    (catch 'buffer-exists
      (when (get-buffer buffer)
        (message "Buffer `%s' already exists" buffer)
        (throw 'buffer-exists nil))
      ;; execute esv
      (call-process esv-program nil buffer t
        ;; arguments
        (format "-l%d" esv-columns) book verses)
      ;; display buffer in another window
      (display-buffer buffer)
      ;; move point to the beginning of the buffer
      (with-current-buffer buffer
        (esv-mode)
        (goto-char (point-min)))
      (set-window-start (get-buffer-window buffer) (point-min))
      t)))

(provide 'esv)