From 1c22c76ff634882d7861d4ac1348a2c1de9d94aa Mon Sep 17 00:00:00 2001
From: Chris Hodapp <hodapp87@gmail.com>
Date: Fri, 17 Apr 2020 16:55:54 -0400
Subject: [PATCH] Add some elisp scratch code

---
 copy_log.sh |  2 +-
 export.el   |  9 ---------
 util.el     | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 59 insertions(+), 10 deletions(-)
 delete mode 100644 export.el
 create mode 100644 util.el

diff --git a/copy_log.sh b/copy_log.sh
index 7c9afdb..19b06c3 100755
--- a/copy_log.sh
+++ b/copy_log.sh
@@ -1,4 +1,4 @@
 #!/bin/sh
 
 ./org_fix_links.py < /mnt/share/syncthing/notes/log.org > log_tmp.org
-emacs -q --batch -l export.el -f export-run
+emacs -q --batch -l util.el -f export-run
diff --git a/export.el b/export.el
deleted file mode 100644
index ed4adfd..0000000
--- a/export.el
+++ /dev/null
@@ -1,9 +0,0 @@
-;; See still:
-;; command-line-args
-
-(require 'ox-hugo)
-(defun export-run ()
-  (progn
-    (find-file "./log_tmp.org")
-    (org-hugo-export-as-md)
-    (write-file "./log_tmp.md")))
diff --git a/util.el b/util.el
new file mode 100644
index 0000000..9a0189c
--- /dev/null
+++ b/util.el
@@ -0,0 +1,58 @@
+;; See still:
+;; command-line-args
+
+(require 'ox-hugo)
+(require 'cl)
+
+;; Predicate for if 'el' is a headline that has some tag.
+(defun element-has-tag-p (el tag)
+  (if (not (eq (org-element-type el) 'headline))
+      nil 
+    (let* ((tags     (org-element-property :tags el))
+           (match_fn (lambda (tag_test) (string= tag tag_test)))
+           (match    (mapcar match_fn tags)))
+      (some 'identity match))))
+
+;; Creates a new buffer of the given name, and write the contents of
+;; some org mode AST into it (e.g. from org-element-parse-buffer)
+(defun interpret-to-buffer (name tree)
+  (let ((buf (generate-new-buffer name)))
+    (with-current-buffer buf
+      (org-mode)
+      (mapc 'insert (org-element-interpret-data tree)))
+    buf))
+
+;; Modifies 'tree' destructively to remove any headline that contains
+;; 'tag'.
+(defun filter-out-tag (tree tag)
+  (if (let ((el-type (org-element-type tree)))
+        (not (or (eq el-type 'headline)
+                 (eq el-type 'org-data))))
+      tree
+    (if (element-has-tag-p tree tag)
+        ;; has tag - stop recursing here:
+        nil
+      ;; lacks tag - keep searching:
+      (org-element-set-contents
+       tree (mapcar (lambda (el) (filter-out-tag el tag))
+                    (org-element-contents tree))))))
+
+;; Produce a new buffer
+(defun filter-buffer (fname newbuf tag)
+  (let* ((buf (find-file-noselect fname))
+         (tree (with-current-buffer buf (org-element-parse-buffer)))
+         (tree (filter-out-tag tree tag)))
+    (interpret-to-buffer newbuf tree)))
+
+(defun filter-org-tag (tag src-name dst-name)
+  (with-current-buffer (filter-buffer src-name "tmp.org" tag)
+    (write-file dst-name)))
+
+;; (filter-out-tag-from-file "/Users/hodapp/log_tmp2.org" "tmp.org" "dream")
+;; (filter-org-tag "dream" "/Users/hodapp/log_tmp2.org" "/Users/hodapp/log_tmp_filter.org")
+
+(defun export-run ()
+  (progn
+    (find-file "./log_tmp.org")
+    (org-hugo-export-as-md)
+    (write-file "./log_tmp.md")))