Add fetch utility functions and tests

Author: VeckoTheGecko

src/virtualship/cli/_fetch.py

@@ -0,0 +1,37 @@
+import hashlib
+from datetime import datetime
+
+from pydantic import BaseModel
+
+
+def _hash(s: str, *, length: int) -> str:
+    """Create a hash of a string."""
+    assert length % 2 == 0, "Length must be even."
+    half_length = length // 2
+
+    return hashlib.shake_128(s.encode("utf-8")).hexdigest(half_length)
+
+
+def create_hash(s: str) -> str:
+    """Create an 8 digit hash of a string."""
+    return _hash(s, length=8)
+
+
+def hash_model(model: BaseModel) -> str:
+    """
+    Hash a Pydantic model.
+
+    :param region: The region to hash.
+    :returns: The hash.
+    """
+    return create_hash(model.model_dump_json())
+
+
+def filename_to_hash(filename: str) -> str:
+    """Extract hash from filename of the format YYYYMMDD_HHMMSS_{hash}."""
+    return filename.split("_")[-1]
+
+
+def hash_to_filename(hash: str) -> str:
+    """Return a filename of the format YYYYMMDD_HHMMSS_{hash}."""
+    return f"{datetime.now().strftime('%Y%m%d_%H%M%S')}_{hash}"

tests/cli/test_fetch.py

@@ -0,0 +1,27 @@
+from pydantic import BaseModel
+
+from virtualship.cli._fetch import (
+    create_hash,
+    filename_to_hash,
+    hash_model,
+    hash_to_filename,
+)
+
+
+def test_create_hash():
+    assert len(create_hash("correct-length")) == 8
+    assert create_hash("same") == create_hash("same")
+    assert create_hash("unique1") != create_hash("unique2")
+
+
+def test_hash_filename_roundtrip():
+    hash_ = create_hash("test")
+    assert filename_to_hash(hash_to_filename(hash_)) == hash_
+
+
+def test_hash_model():
+    class TestModel(BaseModel):
+        a: int
+        b: str
+
+    hash_model(TestModel(a=0, b="b"))