Create initial framework for configuration files

stlt/config.py

@@ -0,0 +1,79 @@
+"""Reading and writing user configuration and secrets."""
+from __future__ import annotations
+
+from pathlib import Path
+import typing as t
+
+import attr
+import toml
+
+from stlt.errors import ConfigError
+
+
+EMPTY_CONFIG_FILE = {
+    "oauth": {
+        "client_id": "CLIENT_ID",
+        "client_secret": "CLIENT_SECRET",
+        "redirect_uri": "REDIRECT_URI",
+        "scope": "SCOPE",
+    }
+}
+
+
+@attr.s(slots=True)
+class OAuthConfig:
+    """Configuration data class for `SpotifyOAuth`."""
+
+    client_id: str = attr.ib()
+    client_secret: str = attr.ib()
+    redirect_uri: str = attr.ib()
+    scope: str = attr.ib()
+
+    @classmethod
+    def from_dict(cls, data: t.Mapping) -> OAuthConfig:
+        """Create an `OAuthConfig` from a `toml`-based mapping."""
+        fields = {}
+        for field in attr.fields(cls):
+            name = field.name
+            try:
+                fields[name] = data[name]
+            except KeyError:
+                raise ConfigError(f"Missing required key '{name}'") from None
+        return cls(**fields)
+
+
+@attr.s(slots=True)
+class Config:
+    """Configuration data class for the project."""
+
+    oauth: OAuthConfig = attr.ib()
+
+    @classmethod
+    def from_dict(cls, data: t.Mapping) -> Config:
+        """Create a `Config` from a `toml`-based mapping."""
+        builders = {
+            "oauth": OAuthConfig.from_dict,
+        }
+        fields = {}
+        for field in attr.fields(cls):
+            name = field.name
+            try:
+                fields[name] = builders[name](data[name])
+            except KeyError:
+                raise ConfigError(f"Missing required section '{name}'") from None
+        return cls(**fields)
+
+
+def ensure_config(config: Path) -> None:
+    """Ensure that the `config` file exists and is valid."""
+    config.parent.mkdir(parents=True, exist_ok=True)
+    config.touch(exist_ok=True)
+
+    with config.open("w") as f:
+        toml.dump(EMPTY_CONFIG_FILE, f)
+
+
+def load_config(config: Path) -> t.Mapping:
+    """Deserialize the `config` file into a `Mapping`."""
+    ensure_config(config)
+    return toml.load(config)

stlt/errors.py

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+"""Error types that appear within the library."""
+
+
+class StltError(Exception):
+    """Base error type for the library."""
+
+
+class ConfigError(Exception):
+    """Error type raised on configuration."""

tests/test_config.py

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+import pytest
+import toml
+
+from stlt.config import (
+    Config,
+    EMPTY_CONFIG_FILE,
+    OAuthConfig,
+    ensure_config,
+    load_config,
+)
+from stlt.errors import ConfigError
+
+
+@pytest.fixture
+def path(tmp_path):
+    return tmp_path / ".config" / "config.toml"
+
+
+class TestEnsureConfig:
+    def test_creates_a_placeholder_configuration_file(self, path):
+        ensure_config(path)
+
+        assert toml.load(path) == EMPTY_CONFIG_FILE
+
+    def test_creates_parent_folders(self, path):
+        ensure_config(path)
+
+        assert path.parent.exists()
+
+
+class TestLoadConfig:
+    def test_loads_a_placeholder_configuration_file(self, path):
+        assert load_config(path) == EMPTY_CONFIG_FILE
+
+
+class TestOAuthConfig:
+    def test_from_dict_parses_a_valid_mapping(self, path):
+        expected = OAuthConfig(**EMPTY_CONFIG_FILE["oauth"])
+
+        assert OAuthConfig.from_dict(EMPTY_CONFIG_FILE["oauth"]) == expected
+
+    def test_from_dict_fails_on_missing_keys(self, path):
+        with pytest.raises(ConfigError, match="Missing required key"):
+            OAuthConfig.from_dict({})
+
+
+class TestConfig:
+    def test_from_dict_parses_a_valid_mapping(self, path):
+        expected = Config(oauth=OAuthConfig.from_dict(EMPTY_CONFIG_FILE["oauth"]))
+
+        assert Config.from_dict(EMPTY_CONFIG_FILE) == expected
+
+    def test_from_dict_fails_on_missing_sections(self, path):
+        with pytest.raises(ConfigError, match="Missing required section"):
+            Config.from_dict({})