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README.md

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+# ob-d2
+
+## Introduction
+`ob-go` enables [Org-Babel](http://orgmode.org/worg/org-contrib/babel/intro.html) support for evaluating [d2](https://d2lang.com/tour/intro/) code.
+It was created based on the usage of [ob-ditaa](https://orgmode.org/worg//org-contrib/babel/languages/ob-doc-ditaa.html).
+The d2 code is compiled via the `d2` command.
+
+```
+#+BEGIN_ d2 :file hello.png
+x -> y: hello world
+#+END_SRC
+```
+
+<div>
+  <img height="500px" alt="hello world" src="hello.png">
+</div>
+
+## Language Specific Header Arguments
+
+In addition to the normal header arguments for Babel, d2 uses the `:flags` header to pass additional flags to the `d2` command.
+`:file` is required since the output of d2 is an image.
+
+## Additional Examples
+All courtesy of Terrastruct, Inc. who published these in their d2 documentation.
+
+### Flags to specify theme and sketch format
+
+```
+#+BEGIN_SRC d2 :file flags.png :flags -t 101 -s
+High Mem Instance -> EC2 <- High CPU Instance: Hosted By
+#+END_SRC
+```
+
+<div>
+  <img height="500px" alt="flags" src="flags.png">
+</div>
+
+### Complex example
+
+```
+#+BEGIN_SRC d2 :file complex.png
+clouds: {
+  aws: {
+    load_balancer -> api
+    api -> db
+  }
+  gcloud: {
+    auth -> db
+  }
+
+  gcloud -> aws
+}
+#+END_SRC
+```
+
+<div>
+  <img height="700px" alt="complex" src="complex.png">
+</div>
+

ob-d2.el

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+;;; ob-d2.el --- org-babel functions for d2
+
+;; Copyright (C) 2022-2023 Xavier Capaldi
+
+;; Author: Xavier Capaldi
+;; Keywords: d2, literate programming, reproducible research
+;; Homepage: http://orgmode.org
+;; Version: 0.01
+
+;;; 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 GNU Emacs; see the file COPYING.  If not, write to the
+;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+;; Boston, MA 02110-1301, USA.
+
+;;; Commentary:
+
+;; Org-Babel support for evaluating d2 diagram scripting source code.
+;;
+;; d2 differs from most standard languages in that:
+;;
+;; 1) there is no such thing as a "session" in d2
+;;
+;; 2) we are only going to return results of type "file"
+;;
+;; 3) you can specify `:flags' headers to be passed to the `d2' command
+;;
+;; 4) there are no variables (at least for now)
+
+;;; Requirements:
+
+;; - You must have d2 installed and d2 should be in your `exec-path'. If not,
+;;   feel free to modify `org-babel-d2-command' to the location of your d2
+;;   command.
+;;
+;; - `d2-mode' is also recommended for syntax highlighting and formatting,
+;;   however it is not required.
+
+;;; TODO
+
+;; - Provide better error feedback.
+
+;;; Code:
+(require 'ob)
+(require 'org-compat)
+
+;; optionally define a file extension for this language
+(add-to-list 'org-babel-tangle-lang-exts '("d2" . "d2"))
+
+(defvar org-babel-default-header-args:d2
+  '((:results . "file")
+    (:exports . "results"))
+  "Default arguments for evaluating a d2 source block.")
+
+(defvar org-babel-d2-command "d2"
+  "The d2 command to use to compile and run the d2 code.")
+
+(defun org-babel-execute:d2 (body params)
+  "Execute a block of d2 code with org-babel.
+This function is called by `org-babel-execute-src-block'."
+  (let* ((out-file (or (cdr (assq :file params))
+		       (error
+			"d2 code block requires :file header argument")))
+	 (flags (cdr (assq :flags params)))
+	 (in-file (org-babel-temp-file "d2-src-" ".d2"))
+	 (cmd (concat org-babel-d2-command
+		          " " flags
+                  " " (org-babel-process-file-name in-file)
+                  " " (org-babel-process-file-name out-file))))
+
+    (with-temp-file in-file (insert body))
+    (message cmd)
+    (shell-command cmd)
+    nil))
+
+(defun org-babel-prep-session:d2 (session params)
+  "Return an error because d2 does not support sessions."
+  (error "d2 does not support sessions"))
+
+(provide 'ob-d2)
+
+;;; ob-d2.el ends here