1 files changed, 72 insertions, 0 deletions
diff --git a/synapse/streams/config.py b/synapse/streams/config.py
new file mode 100644
index 0000000000..b6ffbab1e7
--- /dev/null
+++ b/synapse/streams/config.py
@@ -0,0 +1,72 @@
+# -*- coding: utf-8 -*-
+# Copyright 2014 matrix.org
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from synapse.api.errors import SynapseError
+from synapse.types import StreamToken
+
+import logging
+
+
+logger = logging.getLogger(__name__)
+
+
+class PaginationConfig(object):
+
+    """A configuration object which stores pagination parameters."""
+
+    def __init__(self, from_tok=None, to_tok=None, direction='f', limit=0):
+        self.from_token = StreamToken.from_string(from_tok) if from_tok else None
+        self.to_token = StreamToken.from_string(to_tok) if to_tok else None
+        self.direction = 'f' if direction == 'f' else 'b'
+        self.limit = int(limit)
+
+    @classmethod
+    def from_request(cls, request, raise_invalid_params=True):
+        params = {
+            "direction": 'f',
+        }
+
+        query_param_mappings = [  # 3-tuple of qp_key, attribute, rules
+            ("from", "from_tok", lambda x: type(x) == str),
+            ("to", "to_tok", lambda x: type(x) == str),
+            ("limit", "limit", lambda x: x.isdigit()),
+            ("dir", "direction", lambda x: x == 'f' or x == 'b'),
+        ]
+
+        for qp, attr, is_valid in query_param_mappings:
+            if qp in request.args:
+                if is_valid(request.args[qp][0]):
+                    params[attr] = request.args[qp][0]
+                elif raise_invalid_params:
+                    raise SynapseError(400, "%s parameter is invalid." % qp)
+
+        if "from_tok" in params and params["from_tok"] == "END":
+            # TODO (erikj): This is for compatibility only.
+            del params["from_tok"]
+
+        try:
+            return PaginationConfig(**params)
+        except:
+            logger.exception("Failed to create pagination config")
+            raise SynapseError(400, "Invalid request.")
+
+    def __str__(self):
+        return (
+            "<PaginationConfig from_tok=%s, to_tok=%s, "
+            "direction=%s, limit=%s>"
+        ) % (self.from_tok, self.to_tok, self.direction, self.limit)
+
+
+