ob-jq.el

;;; ob-jq.el --- org-babel functions for jq scripts  -*- lexical-binding: t; -*-

;; Copyright (C) 2015 Bjarte Johansen

;; Author: Bjarte Johansen
;; Keywords: literate programming, reproducible research
;; Homepage: http://www.github.com/ljos/jq-mode
;; Version: 0.1.0

;;; License:

;; This program 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, or (at your option)
;; any later version.
;;
;; This program 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 jq-mode. If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; Provides a way to evaluate jq scripts in org-mode.

;;; Usage:

;; Add to your Emacs config:

;; (org-babel-do-load-languages
;;  'org-babel-load-languages
;;  '((jq . t)))

;;; Code:
(require 'ob)
(require 'jq-mode)
(require 'json)

(defvar org-babel-jq-command "jq"
  "Name of the jq executable command.")

(defvar org-babel-tangle-lang-exts)
(add-to-list 'org-babel-tangle-lang-exts '("jq" . "jq"))

(defconst org-babel-header-args:jq
  '(
    (:in-file  . :any)
    (:cmd-line . :any)
    (:compact  . ((yes no)))
    )
  "Jq specific header arguments.")

(defvar org-babel-default-header-args:jq '(
                                           (:results . "output")
                                           (:compact . "no")
                                           )
  "Default arguments for evaluating a jq source block.")

(defun org-babel-jq-table-to-json (data)
  "Convert org table to JSON.

First line specifies the keys."
  (let* ((header (car data))
         (data (cdr data)))
    (while (eq (car data) 'hline)
      (setq data (cdr data)))
    (json-encode
     (mapcar
      (lambda (row) (cl-mapcar 'cons header row))
      data))))

(defun org-babel-jq-args (params)
  "Return an --arg argument for each PARAMS :var"
  (let ((vars (org-babel--get-vars params)))
    (and vars
         (mapconcat
          (lambda (var)
            (format "--arg %s %S" (car var) (cdr var)))
          vars
          " "))))

(defun org-babel-execute:jq (body params)
  "Execute a block of jq code with org-babel.  This function is
called by `org-babel-execute-src-block'"
  (message "executing jq source code block")
  (let* ((result-params (cdr (assq :result-params params)))
         (compact (equal "yes" (cdr (assq :compact params))))
         (cmd-line (cdr (assq :cmd-line params)))
         (vars (org-babel-jq-args params))
         (in-file (cdr (assq :in-file params)))
         (code-file (let ((file (org-babel-temp-file "jq-")))
                      (with-temp-file file
                        (insert body)
                        file)))
         (stdin (let ((stdin (cdr (assq :stdin params))))
                  (when stdin
                    (let ((tmp (org-babel-temp-file "jq-stdin-"))
                          (res (org-babel-ref-resolve stdin)))
                      (with-temp-file tmp
                        (insert
                         (cond
                          ((listp res) (org-babel-jq-table-to-json res))
                          (t res)))
                        tmp)))))
         (cmd (mapconcat #'identity
                         (remq nil
                               (list org-babel-jq-command
                                     (format "--from-file \"%s\"" code-file)
                                     (when compact "--compact-output")
                                     cmd-line
                                     vars
                                     (when in-file (shell-quote-argument (expand-file-name in-file)))))
                         " ")))
    (org-babel-reassemble-table
     (let ((results
            (cond
             (stdin (with-temp-buffer
                      (call-process-shell-command cmd stdin (current-buffer))
                      (buffer-string)))
             (t (org-babel-eval cmd "")))))
       (when results
         (org-babel-result-cond result-params
           results
           (let ((data (json-read-from-string results)))
             ;; If we have an array we might have a table
             (if (and (vectorp data)
                      (> (length data) 0))
                 (cond
                  ;; If the first element is a vector then just "unpack"
                  ;; the vector of vectors
                  ((vectorp (aref data 0))
                   (mapcar (lambda (row) (append row nil)) data))
                  ;; If the first element is a list we will assume we
                  ;; have an array of objects, so generate the colnames
                  ;; accordingly
                  ((consp (aref data 0))
                   (let ((colnames (mapcar 'car (aref data 0))))
                     (unless (assq :colnames params)
                       (push `(:colnames . ,colnames) params))
                     (mapcar (lambda (row) (mapcar 'cdr row)) data)))
                  ;; For a vector of scalars just return it as an
                  ;; array, it will make a single-row table
                  (t (list (append data nil))))
               ;; If we have an object then just output it as string
               results)))))
     (org-babel-pick-name (cdr (assq :colname-names params))
                          (cdr (assq :colnames params)))
     (org-babel-pick-name (cdr (assq :rowname-names params))
                          (cdr (assq :rownames params))))))

(provide 'ob-jq)
;;; ob-jq.el ends here