From ff1ba2c0c38b297f1f4451b6f667b1a56699767d Mon Sep 17 00:00:00 2001
From: Nicholas Karlson <nicholaskarlson@gmail.com>
Date: Mon, 19 Jan 2026 03:09:01 -0800
Subject: [PATCH] Chore: add Track D mini-library package skeleton

---
 src/pystatsv1/trackd/__init__.py | 19 +++++++++++++++++++
 src/pystatsv1/trackd/_errors.py  | 15 +++++++++++++++
 src/pystatsv1/trackd/_types.py   | 16 ++++++++++++++++
 tests/test_trackd_imports.py     |  8 ++++++++
 4 files changed, 58 insertions(+)
 create mode 100644 src/pystatsv1/trackd/__init__.py
 create mode 100644 src/pystatsv1/trackd/_errors.py
 create mode 100644 src/pystatsv1/trackd/_types.py
 create mode 100644 tests/test_trackd_imports.py

diff --git a/src/pystatsv1/trackd/__init__.py b/src/pystatsv1/trackd/__init__.py
new file mode 100644
index 0000000..b0fe20e
--- /dev/null
+++ b/src/pystatsv1/trackd/__init__.py
@@ -0,0 +1,19 @@
+"""Track D (Business): accounting-oriented statistics, forecasting, and data analysis.
+
+This subpackage will gradually grow from thin chapter-runner scripts into a reusable
+mini-library: data loading, schema checks, feature engineering helpers, forecasting
+baselines, and report builders.
+"""
+
+from __future__ import annotations
+
+from ._errors import TrackDDataError, TrackDSchemaError  # noqa: F401
+from ._types import DataFrame, DataFrames, PathLike  # noqa: F401
+
+__all__ = [
+    "DataFrame",
+    "DataFrames",
+    "PathLike",
+    "TrackDDataError",
+    "TrackDSchemaError",
+]
diff --git a/src/pystatsv1/trackd/_errors.py b/src/pystatsv1/trackd/_errors.py
new file mode 100644
index 0000000..9bca9a2
--- /dev/null
+++ b/src/pystatsv1/trackd/_errors.py
@@ -0,0 +1,15 @@
+"""Exceptions for Track D helpers."""
+
+from __future__ import annotations
+
+
+class TrackDError(Exception):
+    """Base exception for Track D helpers."""
+
+
+class TrackDDataError(TrackDError):
+    """Raised when Track D input data is missing or invalid."""
+
+
+class TrackDSchemaError(TrackDError):
+    """Raised when Track D input data fails schema/contract checks."""
diff --git a/src/pystatsv1/trackd/_types.py b/src/pystatsv1/trackd/_types.py
new file mode 100644
index 0000000..273c302
--- /dev/null
+++ b/src/pystatsv1/trackd/_types.py
@@ -0,0 +1,16 @@
+"""Shared types for Track D helpers.
+
+These are intentionally lightweight. Track D functions should accept common "path
+like" inputs and return pandas DataFrames.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+from typing import TypeAlias
+
+import pandas as pd
+
+PathLike: TypeAlias = str | Path
+DataFrame: TypeAlias = pd.DataFrame
+DataFrames: TypeAlias = dict[str, pd.DataFrame]
diff --git a/tests/test_trackd_imports.py b/tests/test_trackd_imports.py
new file mode 100644
index 0000000..4bbbbea
--- /dev/null
+++ b/tests/test_trackd_imports.py
@@ -0,0 +1,8 @@
+from __future__ import annotations
+
+import importlib
+
+
+def test_trackd_imports() -> None:
+    mod = importlib.import_module("pystatsv1.trackd")
+    assert mod is not None