[proxy] allow prompting the user when a package suitable for current site is found; add proxy's options page

This commit also causes uncached responses to be forced on all
HTTP request to external servers. This is needed to make sure
that changes Haketilo makes to HTTP response headers are always
picked up by the browser. The drawback is that this increases
network traffic causing a performance hit. We might optimize this
in the future.

2 files changed, 45 insertions, 22 deletions

diff --git a/src/hydrilla/proxy/policies/base.py b/src/hydrilla/proxy/policies/base.py
index bb95d29..8ffc45e 100644
--- a/src/hydrilla/proxy/policies/base.py
+++ b/src/hydrilla/proxy/policies/base.py
@@ -58,22 +58,21 @@ class Policy(ABC):
     """...."""
     process_request:  t.ClassVar[bool] = False
     process_response: t.ClassVar[bool] = False
+    anticache:        t.ClassVar[bool] = True
 
     priority: t.ClassVar[PolicyPriority]
 
-    @property
-    def anticache(self) -> bool:
-        return self.process_request or self.process_response
-
     def consume_request(self, request_info: http_messages.RequestInfo) \
         -> t.Optional[ProducedMessage]:
-        """...."""
-        return None
+        raise NotImplementedError(
+            'This kind of policy does not consume requests.'
+        )
 
     def consume_response(self, response_info: http_messages.ResponseInfo) \
         -> t.Optional[http_messages.ProducedResponse]:
-        """...."""
-        return None
+        raise NotImplementedError(
+            'This kind of policy does not consume responses.'
+        )
 
 
 # mypy needs to be corrected:
diff --git a/src/hydrilla/proxy/policies/payload.py b/src/hydrilla/proxy/policies/payload.py
index a063c7c..1069c41 100644
--- a/src/hydrilla/proxy/policies/payload.py
+++ b/src/hydrilla/proxy/policies/payload.py
@@ -60,6 +60,20 @@ class PayloadAwarePolicy(base.Policy):
 
         return f'{request_url.url_without_path}/{"/".join(base_path_segments)}/'
 
+    def _payload_details_to_signed_query_string(
+            self,
+            _salt:        str,
+            **extra_keys: str
+    ) -> str:
+        params: t.Mapping[str, str] = {
+            'payload_id': self.payload_data.ref.id,
+            **extra_keys
+        }
+
+        serializer = URLSafeSerializer(self.payload_data.global_secret, _salt)
+
+        return urlencode({'details': serializer.dumps(params)})
+
 
 @dc.dataclass(frozen=True) # type: ignore[misc]
 class PayloadAwarePolicyFactory(base.PolicyFactory):
@@ -283,20 +297,18 @@ class AutoPayloadInjectPolicy(PayloadInjectPolicy):
             return super().consume_response(response_info)
         except (state.RepoCommunicationError, state.FileInstallationError,
                 _PayloadHasProblemsError) as ex:
-            params = {
-                'next_url':   response_info.url.orig_url,
-                'payload_id': self.payload_data.ref.id
+            extra_params: dict[str, str] = {
+                'next_url': response_info.url.orig_url
             }
-
             if isinstance(ex, state.FileInstallationError):
-                params['repo_id']     = ex.repo_id
-                params['file_sha256'] = ex.sha256
+                extra_params['repo_id']     = ex.repo_id
+                extra_params['file_sha256'] = ex.sha256
 
-            serializer = URLSafeSerializer(
-                self.payload_data.global_secret,
-                salt = 'auto_install_error'
+            query = self._payload_details_to_signed_query_string(
+                _salt = 'auto_install_error',
+                **extra_params
             )
-            query = urlencode({'details': serializer.dumps(params)})
+
             redirect_url = 'https://hkt.mitm.it/auto_install_error?' + query
             msg = 'Error occured when installing payload. Redirecting.'
 
@@ -310,13 +322,25 @@ class AutoPayloadInjectPolicy(PayloadInjectPolicy):
 @dc.dataclass(frozen=True)
 class PayloadSuggestPolicy(PayloadAwarePolicy):
     """...."""
+    process_request: t.ClassVar[bool] = True
+
     priority: t.ClassVar[base.PolicyPriority] = base.PolicyPriority._ONE
 
-    def make_response(self, request_info: http_messages.RequestInfo) \
+    def consume_request(self, request_info: http_messages.RequestInfo) \
         -> http_messages.ProducedResponse:
-        """...."""
-        # TODO: implement
-        return http_messages.ProducedResponse(200, ((b'a', b'b'),), b'')
+        query = self._payload_details_to_signed_query_string(
+            _salt    = 'package_suggestion',
+            next_url = request_info.url.orig_url
+        )
+
+        redirect_url = 'https://hkt.mitm.it/package_suggestion?' + query
+        msg = 'A package was found that could be used on this site. Redirecting.'
+
+        return http_messages.ProducedResponse(
+            status_code = 303,
+            headers     = [(b'Location', redirect_url.encode())],
+            body        = msg.encode()
+        )
 
 
 @dc.dataclass(frozen=True, unsafe_hash=True)