2 files changed, 74 insertions, 0 deletions
diff --git a/waterspout_radar/__init__.py b/waterspout_radar/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/waterspout_radar/__init__.py
diff --git a/waterspout_radar/_config.py b/waterspout_radar/_config.py
new file mode 100644
index 0000000..5f946cf
--- /dev/null
+++ b/waterspout_radar/_config.py
@@ -0,0 +1,74 @@
+"""
+Implements loading and providing the configuration of the radar instance. Usage should be straight-forward:
+
+	>>> from . import _config
+	>>> config = _config.load()
+	>>> config.locations
+	['New York City', 'Jersey City']
+
+An example configuration file looks like this:
+
+	[Storage]
+	db = .waterspout/db.json
+	staging = .waterspout/staging.json
+
+	[Locations]
+	New York City
+	Jersey City
+
+	[Windy]
+	key = <secret key>
+
+	[Web]
+	port = 80
+"""
+
+import configparser
+import dataclasses
+import typing
+
+
+@dataclasses.dataclass
+class Config:
+	key: str
+	locations: typing.List[str]
+	db: str
+	staging: str
+	port: int
+
+
+class ConfigError(Exception):
+	"Raised when configuration could not be loaded or was malformed."
+
+
+def load(pathname: str="radar.conf") -> Config:
+	"Loads configuration from a file at *pathname*. May raise ConfigError when content does not meet expectations."
+	config = configparser.ConfigParser(allow_no_value=True)
+	config.read(pathname)
+	raw = {}
+	errors = []
+
+	def _load_key(section, name, target=None, type=None, default=None, required=False):
+		target = target or name
+		try:
+			value = config[section][name]
+			if type:
+				value = type(value)
+			raw[target] = value
+		except (KeyError, ValueError):
+			if default:
+				raw[target] = default
+			if required:
+				errors.append(f"Config is missing required field: {pathname}: {section}: {name}")
+
+	_load_key("Storage", "db", default="radar.json")
+	_load_key("Storage", "staging", default=raw["db"] + ".staging")
+	_load_key("Windy", "key", required=True)
+	_load_key("Web", "port", type=int)
+	try:
+		raw["locations"] = list(config["Locations"])
+	except KeyError:
+		errors.append(f"Config is missing Locations: {pathname}")
+	if errors:
+		raise ConfigError(*errors)
+	return Config(**raw)