US01-02: Establish Application and Database Foundation (#47)

photo_pipeline/config.py

@@ -0,0 +1,52 @@
+"""Typed application configuration.
+
+Values come from ``PHOTO_PIPELINE_*`` environment variables. Secrets use
+``SecretStr`` so they are masked in logs, reprs, and model dumps, and are never
+returned by the API. Only ``.get_secret_value()`` exposes them, and only where a
+real external call needs them.
+
+pydantic-settings would do this too, but a prefix-scan over the declared fields
+is a few lines and one fewer dependency.
+"""
+
+from __future__ import annotations
+
+import os
+from pathlib import Path
+from typing import Mapping
+
+from pydantic import BaseModel, ConfigDict, SecretStr
+
+ENV_PREFIX = "PHOTO_PIPELINE_"
+
+
+class Config(BaseModel):
+    model_config = ConfigDict(frozen=True)
+
+    data_dir: Path = Path("data")
+    db_path: Path | None = None  # defaults to data_dir/photo_pipeline.db
+    host: str = "127.0.0.1"
+    port: int = 8000
+    log_level: str = "INFO"
+    log_format: str = "json"  # "json" or "text"
+
+    vision_api_key: SecretStr | None = None
+    immich_api_key: SecretStr | None = None
+
+    @property
+    def database_path(self) -> Path:
+        return self.db_path or (self.data_dir / "photo_pipeline.db")
+
+    @property
+    def database_url(self) -> str:
+        return f"sqlite:///{self.database_path}"
+
+    @classmethod
+    def from_env(cls, environ: Mapping[str, str] | None = None) -> "Config":
+        env = os.environ if environ is None else environ
+        data = {
+            name: env[ENV_PREFIX + name.upper()]
+            for name in cls.model_fields
+            if env.get(ENV_PREFIX + name.upper())
+        }
+        return cls(**data)