Add error page generator

frontend/error-pages/build.py

@@ -0,0 +1,43 @@
+from typing import NamedTuple, Dict, List, Type
+from os import makedirs, path
+
+
+template_path = 'template.html'
+result_path = 'built'
+
+class Substitutions(NamedTuple):
+    title: str
+    description: str
+
+error_messages: Dict[str, Substitutions] = {
+    '403': Substitutions(
+        title='403 - Forbidden',
+        description='You are not allowed to view this resource.'
+    ), 
+    '404': Substitutions(
+        title='404 - Not found',
+        description='The requested resource cannot be found.'
+    ), 
+    '50x': Substitutions(
+        title='50x - Server error',
+        description='It\'s my fault.'
+    ), 
+}
+
+
+def substitute(source: str, substitutions: Substitutions) -> str:
+    for i, property_name in enumerate(Substitutions._fields):
+        source = source.replace(f'{{{property_name}}}', str(substitutions[i]))
+    return source
+
+
+if __name__ == '__main__':
+    with open(template_path) as f:
+        template = f.read()
+
+    makedirs(result_path, mode=0o440, exist_ok=True)
+
+    for name, substitutions in error_messages.items():
+        with open(path.join(result_path, f'{name}.html'), 'w') as f:
+            html = substitute(template, substitutions)
+            f.write(html)