From 36fb761e12a00ca0d522920365e80946d54f3380 Mon Sep 17 00:00:00 2001
From: Neeraj Kashyap <nkashy1@gmail.com>
Date: Sat, 21 Aug 2021 11:26:52 -0700
Subject: [PATCH] Added stream boundary validator

(and tests)
---
 backend/moonstream/stream_boundaries.py      | 38 +++++++++++++
 backend/moonstream/test_stream_boundaries.py | 57 ++++++++++++++++++++
 2 files changed, 95 insertions(+)
 create mode 100644 backend/moonstream/stream_boundaries.py
 create mode 100644 backend/moonstream/test_stream_boundaries.py

diff --git a/backend/moonstream/stream_boundaries.py b/backend/moonstream/stream_boundaries.py
new file mode 100644
index 00000000..b285fd01
--- /dev/null
+++ b/backend/moonstream/stream_boundaries.py
@@ -0,0 +1,38 @@
+"""
+Utilities to work with stream boundaries.
+"""
+import time
+
+from .data import StreamBoundary
+
+
+class InvalidStreamBoundary(Exception):
+    """
+    Raised if a StreamBoundary object does not satisfy required constraints.
+    """
+
+
+def validate_stream_boundary(
+    stream_boundary: StreamBoundary,
+    time_difference_seconds: int,
+    raise_when_invalid: bool = False,
+) -> bool:
+    """
+    This function can be used by event providers to check if a stream boundary is valid according to their
+    requirements.
+    """
+    start_time = stream_boundary.start_time
+    max_end_time = start_time + time_difference_seconds
+    end_time = stream_boundary.end_time
+    if end_time is None:
+        end_time = int(time.time())
+
+    if end_time > max_end_time:
+        if raise_when_invalid:
+            raise InvalidStreamBoundary(
+                f"Stream boundary start and end times must not differ by more than {time_difference_seconds} seconds:\n{stream_boundary.json()}"
+            )
+        else:
+            return False
+
+    return True
diff --git a/backend/moonstream/test_stream_boundaries.py b/backend/moonstream/test_stream_boundaries.py
new file mode 100644
index 00000000..44a2ca09
--- /dev/null
+++ b/backend/moonstream/test_stream_boundaries.py
@@ -0,0 +1,57 @@
+"""
+Tests for stream boundary utilities.
+"""
+import unittest
+
+from .data import StreamBoundary
+from . import stream_boundaries
+
+
+class TestValidateStreamBoundary(unittest.TestCase):
+    def test_valid_stream_boundary(self):
+        stream_boundary = StreamBoundary(
+            start_time=1, end_time=5, include_start=True, include_end=True
+        )
+        self.assertTrue(
+            stream_boundaries.validate_stream_boundary(
+                stream_boundary, 10, raise_when_invalid=False
+            )
+        )
+
+    def test_invalid_stream_boundary(self):
+        stream_boundary = StreamBoundary(
+            start_time=1, end_time=5, include_start=True, include_end=True
+        )
+        self.assertFalse(
+            stream_boundaries.validate_stream_boundary(
+                stream_boundary, 1, raise_when_invalid=False
+            )
+        )
+
+    def test_invalid_stream_boundary_error(self):
+        stream_boundary = StreamBoundary(
+            start_time=1, end_time=5, include_start=True, include_end=True
+        )
+        with self.assertRaises(stream_boundaries.InvalidStreamBoundary):
+            stream_boundaries.validate_stream_boundary(
+                stream_boundary, 1, raise_when_invalid=True
+            )
+
+    def test_unconstrainted_invalid_stream_boundary(self):
+        stream_boundary = StreamBoundary()
+        self.assertFalse(
+            stream_boundaries.validate_stream_boundary(
+                stream_boundary, 1, raise_when_invalid=False
+            )
+        )
+
+    def test_unconstrained_invalid_stream_boundary_error(self):
+        stream_boundary = StreamBoundary()
+        with self.assertRaises(stream_boundaries.InvalidStreamBoundary):
+            stream_boundaries.validate_stream_boundary(
+                stream_boundary, 1, raise_when_invalid=True
+            )
+
+
+if __name__ == "__main__":
+    unittest.main()