From dcc56e2e0326c20e787244dfba9b06be37df8de9 Mon Sep 17 00:00:00 2001
From: Magnus Hagander <magnus@hagander.net>
Date: Wed, 20 Jun 2018 13:40:31 +0200
Subject: [PATCH] Add support for merging json data based on dropdown in admin
 forms

This makes it possible to have different default values for a json field
depending on what's picked in a different dropdown. Values are merged
with whatever is in the field already if the dropdown is changed, not
overwritten.
---
 postgresqleu/confreg/backendforms.py     |  4 ++++
 template/confreg/admin_backend_form.html | 21 +++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/postgresqleu/confreg/backendforms.py b/postgresqleu/confreg/backendforms.py
index d45c38d..ee800e8 100644
--- a/postgresqleu/confreg/backendforms.py
+++ b/postgresqleu/confreg/backendforms.py
@@ -97,6 +97,10 @@ class BackendForm(ConcurrentProtectedModelForm):
 	def fix_fields(self):
 		pass
 
+	@property
+	def get_json_merge_data(self):
+		pass
+
 	@classmethod
 	def get_initial(self):
 		return {}
diff --git a/template/confreg/admin_backend_form.html b/template/confreg/admin_backend_form.html
index f2c1cf9..f972a6a 100644
--- a/template/confreg/admin_backend_form.html
+++ b/template/confreg/admin_backend_form.html
@@ -29,12 +29,33 @@ $('#id_{{f}}').addClass('jsoneditor');
     editor.renderer.setShowGutter(textarea.data('gutter'));
     editor.getSession().setValue(textarea.val());
     editor.getSession().setMode("ace/mode/json");
+    textarea.data('jsoneditor', editor);
 
     textarea.closest('form').submit(function() {
       textarea.val(editor.getSession().getValue());
     })
   });
 
+{%if form.json_merge_data %}
+  var mergedata = {{form.json_merge_data|safe}};
+  $.each(mergedata, function(i,v) {
+    $('#'+v['source']).change(function(e) {
+       var val = e.target.value;
+       var mergewith = v['map'][val];
+       var editor = $('#'+v['target']).data('jsoneditor');
+       try {
+          current = JSON.parse(editor.getSession().getValue());
+       }
+       catch {
+         /* If current JSON is invalid, we can't merge. So just give up */
+         return;
+       }
+       var dest = $.extend({}, mergewith, current);
+       editor.setValue(JSON.stringify(dest, null, 2), -1);
+    });
+  });
+
+{%endif%}
 
    $('.backend-vat-field').each(function(i, e) {
       $(e).change(function(e) {
-- 
2.39.5