add compression to GameplayDatabase and test if compression works with the sqlite_zstd extension

tests/test_ZstdCompression.py

@@ -0,0 +1,92 @@
+import unittest, sqlite3, os
+from pathlib import Path
+
+from server.database import GameplayDatabase
+
+EXT_PATH = Path(os.environ.get("SQLITE_ZSTD_EXT", "lib/libsqlite_zstd.so")).expanduser().resolve()
+
+def _open(db_path: str) -> sqlite3.Connection:
+  conn = sqlite3.connect(db_path)
+  conn.row_factory = sqlite3.Row
+  if EXT_PATH.exists():
+    conn.enable_load_extension(True)
+    conn.load_extension(str(EXT_PATH))
+    conn.enable_load_extension(False)
+  return conn
+
+@unittest.skipUnless(EXT_PATH.exists(), f"sqlite-zstd extension not found at {EXT_PATH}")
+class TestZstdCompression(unittest.TestCase):
+
+  def test_extension_loads(self):
+    conn = sqlite3.connect(":memory:")
+    conn.enable_load_extension(True)
+    conn.load_extension(str(EXT_PATH))
+    conn.enable_load_extension(False)
+    result = conn.execute("SELECT zstd_compress('hello world', 6)").fetchone()[0]
+    self.assertIsInstance(result, bytes)
+    self.assertGreater(len(result), 0)
+    conn.close()
+
+  def test_compress_decompress_roundtrip(self):
+    # Use a long repetitive string so compression actually reduces size
+    original = '{"board": {"width": 11, "height": 11, "snakes": []}, "turn": 42} ' * 20
+    conn = sqlite3.connect(":memory:")
+    conn.enable_load_extension(True)
+    conn.load_extension(str(EXT_PATH))
+    conn.enable_load_extension(False)
+    compressed = conn.execute("SELECT zstd_compress(?, 6)", (original,)).fetchone()[0]
+    self.assertIsInstance(compressed, bytes)
+    self.assertLess(len(compressed), len(original))
+    conn.close()
+
+  def test_transparent_compression_enabled(self):
+    db_path = os.environ.get("GAMEPLAY_DB_PATH", "data/database/gameplay.sqlite3")
+    if not Path(db_path).exists():
+      self.skipTest(f"Database not found at {db_path}")
+
+    conn = _open(db_path)
+    tables = {r[0] for r in conn.execute("SELECT name FROM sqlite_master").fetchall()}
+    self.assertIn("_zstd_configs", tables, "_zstd_configs table missing — compression not enabled")
+
+    configs = conn.execute("SELECT config FROM _zstd_configs").fetchall()
+    compressed_columns = [row["config"] for row in configs]
+    self.assertEqual(len(compressed_columns), 6)
+
+    expected = ["board_state_json", "snakes_json", "you_json", "food_json", "hazards_json", "body_json"]
+    for col in expected:
+      self.assertTrue(
+        any(col in cfg for cfg in compressed_columns),
+        f"{col} not found in _zstd_configs",
+      )
+    conn.close()
+
+  def test_turns_and_snake_turns_are_views(self):
+    db_path = os.environ.get("GAMEPLAY_DB_PATH", "data/database/gameplay.sqlite3")
+    if not Path(db_path).exists():
+      self.skipTest(f"Database not found at {db_path}")
+
+    conn = _open(db_path)
+    views = {r[0] for r in conn.execute("SELECT name FROM sqlite_master WHERE type='view'").fetchall()}
+    self.assertIn("turns", views)
+    self.assertIn("snake_turns", views)
+    conn.close()
+
+  def test_board_state_json_is_stored_compressed(self):
+    db_path = os.environ.get("GAMEPLAY_DB_PATH", "data/database/gameplay.sqlite3")
+    if not Path(db_path).exists():
+      self.skipTest(f"Database not found at {db_path}")
+
+    conn = _open(db_path)
+    tables = {r[0] for r in conn.execute("SELECT name FROM sqlite_master WHERE type='table'").fetchall()}
+    if "_turns_zstd" not in tables:
+      self.skipTest("_turns_zstd table not found")
+
+    row = conn.execute("SELECT board_state_json FROM _turns_zstd LIMIT 1").fetchone()
+    if row is None:
+      self.skipTest("No rows in _turns_zstd")
+
+    self.assertIsInstance(row[0], (bytes, bytearray), "board_state_json should be stored as compressed bytes")
+    conn.close()
+
+if __name__ == "__main__":
+  unittest.main()