Automatically determine the package version

Use the HEAD commit's date as the package's version. Append the number
of commits made on the same date as HEAD to ensure multiple releases on
the same date still have unique versions.

3 files changed, 47 insertions, 3 deletions

diff --git a/pyproject.toml b/pyproject.toml
index ac28b6e..c839da5 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,10 +1,9 @@
 [build-system]
-requires = ["setuptools>=61"]
-build-backend = "setuptools.build_meta"
+requires = ["setuptools>=61", "setuptools-git-versioning>=1.8"]
+build-backend = "setuptools.build_meta:__legacy__"
 
 [project]
 name = "snekbox"
-version = "1.0.0"
 description = "HTTP REST API for sanboxed execution of arbitrary Python code."
 readme = "README.md"
 license = {text = "MIT"}
@@ -22,6 +21,7 @@ classifiers = [
     "Topic :: Security",
     "Topic :: Software Development :: Interpreters",
 ]
+dynamic = ["version"]
 
 requires-python = ">=3.10"
 dependencies = [
@@ -45,6 +45,10 @@ snekbox = "snekbox.__main__:main"
 [tool.setuptools]
 packages = ["snekbox"]
 
+[tool.setuptools-git-versioning]
+enabled = true
+version_callback = "scripts.version:get_version"
+
 [tool.coverage.report]
 exclude_lines = [
     "pragma: no cover",
diff --git a/scripts/version.py b/scripts/version.py
new file mode 100644
index 0000000..9076b93
--- /dev/null
+++ b/scripts/version.py
@@ -0,0 +1,34 @@
+import datetime
+import subprocess
+
+__all__ = ("get_version",)
+
+
+def get_version() -> str:
+    """
+    Return a version based on the HEAD commit's date.
+
+    The format is 'year.month.day.commits' and is compliant with PEP 440. 'commits' is the amount of
+    commits made on the same date as HEAD, excluding HEAD. This ensures versions are unique if
+    multiple release occur on the same date.
+    """
+    args = ["git", "show", "-s", "--format=%ct", "HEAD"]
+    stdout = subprocess.check_output(args, text=True)
+    timestamp = float(stdout.strip())
+    date = datetime.datetime.fromtimestamp(timestamp, datetime.timezone.utc)
+
+    commits = count_commits_on_date(date) - 1  # Exclude HEAD.
+
+    # Don't use strftime because it includes leading zeros, which are against PEP 440.
+    return f"{date.year}.{date.month}.{date.day}.{commits}"
+
+
+def count_commits_on_date(dt: datetime.datetime) -> int:
+    """Return the amount of commits made on the given UTC aware datetime."""
+    dt = dt.combine(dt - datetime.timedelta(days=1), dt.max.time(), dt.tzinfo)
+
+    # git log uses the committer date for this, not the author date.
+    args = ["git", "log", "--oneline", "--after", str(dt.timestamp())]
+    stdout = subprocess.check_output(args, text=True)
+
+    return stdout.strip().count("\n")
diff --git a/snekbox/__init__.py b/snekbox/__init__.py
index ccb8b11..a3a5f09 100644
--- a/snekbox/__init__.py
+++ b/snekbox/__init__.py
@@ -1,7 +1,13 @@
 import os
+from importlib import metadata
 
 DEBUG = os.environ.get("DEBUG", False)
 
+try:
+    __version__ = metadata.version("snekbox")
+except metadata.PackageNotFoundError:  # pragma: no cover
+    __version__ = "0.0.0.0+unknown"
+
 from snekbox.api import SnekAPI  # noqa: E402
 from snekbox.nsjail import NsJail  # noqa: E402
 from snekbox.utils.logging import init_logger, init_sentry  # noqa: E402