[Feature] Simple template extension mechanism (#361)

Co-authored-by: Tim Lorsbach <tim@lorsba.ch>
Reviewed-on: enviPath/enviPy#361

epdb/apps.py

@@ -16,6 +16,10 @@ class EPDBConfig(AppConfig):
         model_name = getattr(settings, "EPDB_PACKAGE_MODEL", "epdb.Package")
         logger.info(f"Using Package model: {model_name}")
 
+        from .autodiscovery import autodiscover
+
+        autodiscover()
+
         if settings.PLUGINS_ENABLED:
             from bridge.contracts import Property
             from utilities.plugin import discover_plugins

epdb/autodiscovery.py

@@ -0,0 +1,5 @@
+from django.utils.module_loading import autodiscover_modules
+
+
+def autodiscover():
+    autodiscover_modules("epdb_hooks")

epdb/template_registry.py

@@ -0,0 +1,17 @@
+from collections import defaultdict
+from threading import Lock
+
+_registry = defaultdict(list)
+_lock = Lock()
+
+
+def register_template(slot: str, template_name: str, *, order: int = 100):
+    item = (order, template_name)
+    with _lock:
+        if item not in _registry[slot]:
+            _registry[slot].append(item)
+            _registry[slot].sort(key=lambda x: x[0])
+
+
+def get_templates(slot: str):
+    return [template_name for _, template_name in _registry.get(slot, [])]

epdb/templatetags/envipytags.py

@@ -2,6 +2,8 @@ from django import template
 from pydantic import AnyHttpUrl, ValidationError
 from pydantic.type_adapter import TypeAdapter
 
+from epdb.template_registry import get_templates
+
 register = template.Library()
 
 url_adapter = TypeAdapter(AnyHttpUrl)
@@ -19,3 +21,8 @@ def is_url(value):
         return True
     except ValidationError:
         return False
+
+
+@register.simple_tag
+def epdb_slot_templates(slot):
+    return get_templates(slot)