Initial commit for the comint-ledger mode.

Used Mickey Petersen's example of the Cassandra comint mode as a
starting point.

https://www.masteringemacs.org/article/comint-writing-command-interpreter

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) <year> <copyright holders>
+Copyright (c) 2023 Bram Schoenmakers <me@bramschoenmakers.nl>
 
 Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 

comint-ledger.el

@@ -0,0 +1,96 @@
+;;; comint-ledger.el --- Command interpreter for the Ledger CLI  -*- lexical-binding: t; -*-
+
+;; Author: Bram Schoenmakers
+;; URL: https://apps.bram85.nl/git/bram/comint-ledger
+;; Version: 0.1
+;; Keywords: processes
+;; Package-Requires: ((emacs "28.2"))
+
+;;; This file is NOT part of GNU Emacs
+
+;;; Commentary:
+;;
+;; Command interpreter (comint) for the Ledger CLI tool.
+;; Starting point for this mode is Mickey Petersen's article on writing comint modes.
+;;
+;; https://www.masteringemacs.org/article/comint-writing-command-interpreter
+;;
+;;; Code:
+
+(require 'comint)
+
+(defvar ledger-cli-path (executable-find "ledger")
+  "Path to the program used by `run-ledger'.")
+
+(defvar ledger-file-path nil
+  "Path to the ledger data file.")
+
+(defvar ledger-cli-arguments '()
+  "Commandline arguments to pass to `ledger'.")
+
+(defvar ledger-mode-map
+  (let ((map (nconc (make-sparse-keymap) comint-mode-map)))
+    ;; example definition
+    (define-key map "\t" 'completion-at-point)
+    map)
+  "Basic mode map for `run-ledger'.")
+
+(defvar ledger-prompt-regexp (rx bol "] ")
+  "Prompt for `run-ledger'.")
+
+(defvar ledger-buffer-name "*Ledger*"
+  "Name of the buffer to use for the `run-ledger' comint instance.")
+
+(defun run-ledger ()
+  "Run an inferior instance of `ledger' inside Emacs."
+  (interactive)
+  (let* ((ledger-program ledger-cli-path)
+         (ledger-file-arguments (list "-f" ledger-file-path))
+         (ledger-arguments (append ledger-file-arguments ledger-cli-arguments))
+         (buffer (get-buffer-create ledger-buffer-name))
+         (proc-alive (comint-check-proc buffer)))
+    ;; if the process is dead then re-create the process and reset the
+    ;; mode.
+    (unless proc-alive
+      (with-current-buffer buffer
+        (apply 'make-comint-in-buffer "Ledger" buffer
+               ledger-program nil ledger-arguments)
+        (comint-ledger-mode)))
+    ;; Regardless, provided we have a valid buffer, we pop to it.
+    (when buffer
+      (pop-to-buffer buffer))))
+
+(defun ledger--initialize ()
+  "Helper function to initialize ledger."
+  (setq comint-process-echoes t)
+  (setq comint-use-prompt-regexp t))
+
+(define-derived-mode comint-ledger-mode comint-mode "comint-ledger"
+  "Major mode for `run-ledger'.
+
+\\<ledger-mode-map>"
+  ;; this sets up the prompt so it matches things like: [foo@bar]
+  (setq comint-prompt-regexp ledger-prompt-regexp)
+  ;; this makes it read only; a contentious subject as some prefer the
+  ;; buffer to be overwritable.
+  (setq comint-prompt-read-only t)
+  ;; this makes it so commands like M-{ and M-} work.
+  (set (make-local-variable 'paragraph-separate) "\\'")
+  (set (make-local-variable 'font-lock-defaults) '(ledger-font-lock-keywords t))
+  (set (make-local-variable 'paragraph-start) ledger-prompt-regexp))
+
+(add-hook 'ledger-mode-hook 'ledger--initialize)
+
+(defconst ledger-keywords
+  '()
+  "List of keywords to highlight in `ledger-font-lock-keywords'.")
+
+(defvar ledger-font-lock-keywords
+  (list
+   ;; highlight all the reserved commands.
+   `(,(concat "\\_<" (regexp-opt ledger-keywords) "\\_>") . font-lock-keyword-face))
+  "Additional expressions to highlight in `comint-ledger-mode'.")
+
+(provide 'comint-ledger)
+
+;;; comint-ledger.el ends here