Add for_each and template_if_empty

makesite.py

@@ -124,8 +124,40 @@ def read_content(filename):
 
 def render(template, **params):
     """Replace placeholders in template with values from params."""
-    return re.sub(r'{{\s*([^}\s]+)\s*}}',
+    def handle_variable(match):
-                  lambda match: str(params.get(match.group(1), match.group(0))),
+        var = match.group(1).strip()
+        if match.group(1).startswith("template "):
+            import_name = var[7:]
+            import_ = fread(import_name)
+            return render(import_, **params)
+        elif var.startswith("for_each "):
+            args = var.split(" ")[1:]
+            attribute_name = args[0]
+            template_name = args[1]
+
+            template_ = fread(template_name)
+            templates = []
+            for val in params.get(attribute_name, []):
+                templates.append(render(template_, **params, item=val))
+            return "\n".join(templates)
+        elif var.startswith("item."):
+            return str(params["item"].get(var[5:], match.group(0)))
+        elif var.startswith("template_if_empty "):
+            # {{ template_if_empty <param> <template if param is empty> <otherwise> }}
+            args = var[17:].split(" ")[1:]
+            value = params["item"].get(args[0][5:], "") if args[0].startswith("item.") else params.get(args[0], "")
+            template_name = args[1] if value == "" else args[2]
+            template_ = fread(template_name)
+            return render(template_, **params)
+        else:
+            if not var in params:
+                print("Did not find variable '%s'!" % var)
+                return match.group(0)
+            
+            return params[var]
+
+    return re.sub(r'{{\s*([^}]+)\s*}}',
+                  handle_variable,
                   template)
 
 
@@ -238,7 +270,7 @@ def main():
     if os.path.isfile(params_file):
         params.update(**json.loads(fread(params_file)))
 
-    for variable in options.variables:
+    for variable in (options.variables or []):
         key, val = variable.split('=')
         params[key] = val