align (indent) in bibtex file

Question

I have a bibtex file, and would like to have indentation as follows.

@book{moon70:trees,
       AUTHOR = {John W. Moon}, 
        TITLE = {Counting labelled trees},
         YEAR = 1970,
       SERIES = {Canadian Mathematical Monographs},
       NUMBER = 1,
    PUBLISHER = {Canadian Mathematical Congress}
}

I am thinking of creating a indent-bibtex-entry command, but I am stuck in steps 4 and 5.

1. Save current position, jump to the previous ocurrence of the regular expression ^[ \t]*@, then to the next { and then to the next ,.
2. While next nonblank is not }
3. Capture the next field with the regular expression [ \t\n]*\([^ \t=]+\)=.
4. Replace by \n \1 = where the number of spaces must make the total length of this expression equal to, say, 15.
5. Capture the entry's content (see caveats below), removing line-breaks and spaces before and after.
6. Goto 2.
7. Restore cursor's position.

Caveats

The content of an entry is somewhat tex-aware. The entries are text between quotes "like this" or between matching braces {like this}. However, you may have braces (as long as they're balanced) inside, and escaped quotes as well {na\"ive {example}}.

Simplier, but also nice

If that is too difficult, an alternative is to define a command indent-field, assuming that the line contains a single field. The problem is similar to the previous step 4 (but here it is step 3).

1. Save current position, jump to the beginning of the line.
2. Capture the next field with the regular expression [ \t\n]*\([^ \t=]+\)=[ \t\n*]*.
3. Replace by \n \1 = where the number of spaces must make the total length of this expression equal to, say, 15.
4. Restore cursor's position.

Any suggestions? I am still working on the code for the items I "know" how to do. This is my first time with elisp.

Answer 1

Here's a possible solution for you. I broke up the code so you might be able to learn a little elisp at the same time...

(defun indent-me ()
  "Indent a bibtext entry.
This assumes the entry starts with a non-white in column 0, and
ends with a } on a line by itself.  Invoke the function anywhere
inside the entry."
  (interactive)
  (save-excursion
    ;; go to col 0 and search upwards for the start of the entry
    (goto-char (line-beginning-position))
    (while (not (looking-at "^@book"))
      (forward-line -1))
    ;; now looking at the start of entry, eg. @book
    (forward-line 1)
    (while (not (looking-at "^}"))
      (indent-one-line)
      (forward-line 1))
    ))


(defun indent-one-line ()
  "Indent one line of the entry."
  (interactive)
  (let (tokens tag newline)
    (setq tokens (split-string (line-contents)))
    (setq tag (car tokens))
    (setq tag (string-pad-left tag 15))
    (setq newline (cdr tokens))
    (setq newline (push tag newline))
    (setq newline (mapconcat 'concat newline " "))
    (goto-char (line-beginning-position))
    (kill-line)
    (insert newline)
    ))


(defun line-contents ()
  "Return the contents of the current buffer line."
  (buffer-substring-no-properties
   (line-beginning-position) (line-end-position)))

(defun string-pad-left (string length)
  "Return STRING padded left to LENGTH."
  (let (result)
    (while (> length (length string))
      (setq string (concat " " string)))
    (setq result string)
    result))