add WIP prototype of apply code

openshift/dynamic/apply.py

@@ -0,0 +1,79 @@
+import yaml
+
+from openshift.dynamic.exceptions import NotFoundError
+
+LAST_APPLIED_CONFIG_ANNOTATION = 'kubectl.kubernetes.io/last-applied-configuration'
+
+def apply(resource, definition):
+    definition['metadata']['annotations'][LAST_APPLIED_CONFIG_ANNOTATION] = definition
+    try:
+        current = resource.get(name=definition['metadata']['name'], namespace=definition['metadata']['namespace']).to_dict()
+    except NotFoundError:
+        return resource.create(body=definition)
+    last_applied = current['metadata']['annotations'].get(LAST_APPLIED_CONFIG_ANNOTATION)
+    if last_applied:
+        last_applied = yaml.load(last_applied)
+        del current['metadata']['annotations'][LAST_APPLIED_CONFIG_ANNOTATION]
+    else:
+        return resource.patch(body=definition, name=definition['metadata']['name'], namespace=definition['metadata']['namespace'])
+
+    patch = merge(last_applied, definition, current)
+    if patch:
+        return resource.patch(body=patch, name=definition['metadata']['name'], namespace=definition['metadata']['namespace'])
+    else:
+        return "No update necessary"
+
+
+# The patch is the difference from current to modified without deletions, plus deletions
+# from original to modified. To find it, we compute deletions, which are the deletions from
+# original to modified, and delta, which is the difference from current to modified without
+# deletions, and then apply delta to deletions as a patch, which should be strictly additive.
+def merge(original, modified, current):
+    base = {}
+    deletions = get_deletions(original, modified)
+    delta = get_delta(current, modified)
+    base.update(deletions)
+    base.update(delta)
+    return base
+
+
+def get_deletions(original, modified):
+    patch = {}
+    for k, original_value in original.items():
+        modified_value = modified.get(k)
+        if modified_value is None:
+            patch[k] = None
+            continue
+        if type(original_value) != type(modified_value):
+            continue
+        if isinstance(original_value, dict):
+            p = get_deletions(original_value, modified_value)
+            if p:
+                patch[k] = p
+        elif isinstance(original_value, (list, tuple)):
+            # I have no idea what to do here
+            pass
+    return patch
+
+
+def get_delta(current, modified):
+    patch = {}
+    for k, modified_value in modified.items():
+        current_value = current.get(k)
+        if current_value is None:
+            patch[k] = modified_value
+            continue
+        if modified_value == current_value:
+            continue
+        if type(modified_value) != type(current_value):
+            patch[k] = modified_value
+        elif isinstance(modified_value, dict):
+            p = get_delta(current_value, modified_value)
+            if p:
+                patch[k] = p
+        elif isinstance(current_value, (list, tuple)):
+            # I have no idea what to do here
+            patch[k] = modified_value
+        else:
+            patch[k] = modified_value
+    return patch