#+title: org-tangle
#+author: Nicolas Girard
#+email: nicolas dot girard at gmail dot com
#+OPTIONS:   H:2 num:nil toc:nil


=org-tangle= takes one or several [[http://orgmode.org][Org]] files as arguments and produces programs

* Usage
#+name: usage
#+begin_src sh
  org-tangle [options] file1.org [file2.org ...]
#+end_src

Options:
#+tblname: toptions
| -E EMACS       | Specify the Emacs executable. Default value is 'emacs24-nox'        |
| -O OPTIONS     | Specify the options to pass to Emacs. Default value is '-Q --batch' |
| -q             | Enable quick expansion of noweb references                          |
|                | (see variable org-babel-use-quick-and-dirty-noweb-expansion).       |
| -L ORGDIR      | Specify an alternate directory for Org libs.                        |
| -l lang1,lang2 | List of languages which can be evaluated in Org buffers.            |
|                | By default, only emacs-lisp is loaded                               |
|                | (see variable org-babel-load-languages)                             |
| -V             | Show version and exit                                               |

* Source code
#+header: :shebang "#!/usr/bin/env bash"
#+begin_src sh :noweb tangle :tangle org-tangle :exports none
  <<src>>
#+end_src

** Shell code
:PROPERTIES:
:noweb-sep: "\n\n"
:END:
*** Initial variables
#+name: src
#+begin_src sh
  DIR=`pwd`
  FILES=""
  ORGDIR="/path/to/alternate/org-mode"
  QUICK_EXPANSION=nil
  EMACS=<<emacs>>
  EMACS_OPTS="-Q --batch"
  VERSION=0.1
#+end_src

=<<emacs>>= =
#+name: emacs
#+begin_src sh
  emacs
#+end_src

*** Help function
#+name: src
#+begin_src sh
  read -d '' help_string <<"EOF"
  Usage: <<usage>>
  
  <<format-options(toptions,fmt="%-15s %s")>>
  EOF

  help () {
    echo -ne "$help_string\n"
  }
#+end_src
*** Main part
Let's deal with command line options
#+name: src
#+begin_src sh
  while getopts "hE:O:L:l:qV" option "$@"; do
    case $option in
      h) help && exit 0 ;;
      E) EMACS="$OPTARG" ;;
      O) EMACS_OPTS="$OPTARG" ;;
      q) QUICK_EXPANSION=t ;;
      l) LANGUAGES="$OPTARG" ;;
      L) ORGDIR="$OPTARG" ;;
      V) echo "$(basename $0) $VERSION" && exit 0 ;;
    esac
  done ; shift $((OPTIND -1))
#+end_src

We need at least one file as an argument
#+name: src
#+begin_src sh
  [ "$1" ] || { help && exit 1; }
#+end_src

Wrap each argument in the code required to call tangle on it
#+name: src
#+begin_src sh
  for i in $@; do
        FILES="$FILES \"$i\""
  done
#+end_src

Create a temporary file
#+name: src
#+begin_src sh
  out=$(mktemp)
#+end_src

Now, execute emacs...
#+begin_src sh :noweb-ref src :noweb-sep " "
  $EMACS ${EMACS_OPTS} --eval "(progn
    <<escape-quotes(elisp-code)>>)"
#+end_src

...saving its output to a temporary file...
#+begin_src sh :noweb-ref src :noweb-sep "\n\n"
  >${out} 2>&1
#+end_src

...and its return value.
#+begin_src sh :noweb-ref src :noweb-sep "\n"
  ret=$?
#+end_src

If things went fine, display the number of tangled blocs
#+begin_src sh :noweb-ref src :noweb-sep "\n"
  if [ ${ret} -eq 0 ]; then
    grep -i tangled ${out}
#+end_src

Otherwise, display the whole output for the user to further investigate
#+name: src
#+begin_src sh
  else
    cat ${out}
  fi
#+end_src

Finally, exit with the same value as Emacs
#+name: src
#+begin_src sh
  exit ${ret}
#+end_src
** Elisp code
#+name: elisp-code
#+begin_src org :noweb yes :exports none
  <<elisp>>
#+end_src

When =ORGDIR= actually exists, load Org libraries from this directory. Otherwise, we'll use the ones that ship with Emacs or were installed using =package.el=

#+name: elisp
#+begin_src emacs-lisp
  (package-initialize)
  (when (file-accessible-directory-p "$ORGDIR")
     (add-to-list 'load-path (expand-file-name "$ORGDIR/lisp/"))
     (add-to-list 'load-path (expand-file-name "$ORGDIR/contrib/lisp/" t)))
#+end_src

Require Org libs
#+name: elisp
#+begin_src emacs-lisp
  (require 'org)
  (require 'ob)
  (require 'ob-tangle)
#+end_src

Set =org-babel-use-quick-and-dirty-noweb-expansion= to the value of =QUICK_EXPANSION=
#+name: elisp
#+begin_src emacs-lisp
  (setq org-babel-use-quick-and-dirty-noweb-expansion ${QUICK_EXPANSION})
#+end_src

Do not require confirmation before evaluating code blocks
#+name: elisp
#+begin_src emacs-lisp
  (setq org-confirm-babel-evaluate nil)
#+end_src

Load the languages specified via the =-l= option, if any
#+name: elisp
#+begin_src emacs-lisp
  (unless (equal "$LANGUAGES" "")
    (org-babel-do-load-languages
      'org-babel-load-languages
      (mapcar 
        (lambda (str) (cons (make-symbol str) t))
        (split-string "$LANGUAGES" ","))))
#+end_src

For each file in =FILES=...
#+name: elisp
#+begin_src emacs-lisp
  (mapc (lambda (file)
    <<elisp-func>>) '($FILES))
#+end_src

- open it within Emacs;
  #+name: elisp-func
  #+begin_src emacs-lisp
    (find-file (expand-file-name file "$DIR"))
  #+end_src
- tangle it;
  #+name: elisp-func
  #+begin_src emacs-lisp
    (org-babel-tangle)
  #+end_src
- then close it.
  #+name: elisp-func
  #+begin_src emacs-lisp
    (kill-buffer)
  #+end_src
** Utility functions 
=<<escape-quotes>>= =
#+name: escape-quotes
#+begin_src emacs-lisp :var str-val=""
  (save-match-data
    (replace-regexp-in-string "\"" "\\\\\"" str-val))
#+end_src
Used to escape the quotes within the elisp code before embedding it into the shell code, in order to preserve readability.

=<<format-options>>= =
#+name: format-options
#+begin_src emacs-lisp :var table="" :var fmt="%s%s" :results value
  (mapconcat 
    (lambda (row)
      (format fmt (car row) (cadr row))) table "\n")
#+end_src
Used to format the options table.