Add config

1 files changed, 133 insertions, 0 deletions

diff --git a/metricity/config.py b/metricity/config.py
new file mode 100644
index 0000000..8b043f5
--- /dev/null
+++ b/metricity/config.py
@@ -0,0 +1,133 @@
+"""Configuration reader for Metricity."""
+import logging
+from os import environ
+from pathlib import Path
+from typing import Any, Dict, List, Optional, Tuple, Union
+
+import toml
+from deepmerge import Merger
+from dotenv import load_dotenv
+
+load_dotenv()
+
+log = logging.getLogger(__name__)
+
+
+class MetricityConfigurationError(Exception):
+    """Exception signifying something has gone awry whilst parsing Metricity config."""
+
+
+def get_section(section: str) -> Dict[str, Any]:
+    """
+    Load the section config from config-default.toml and config.toml.
+
+    Use deepmerge.Merger to merge the configuration from config.toml
+    and override that of config-default.toml.
+    """
+    # Load default configuration
+    if not Path("config-default.toml").exists():
+        raise MetricityConfigurationError("config-default.toml is missing")
+
+    with open("config-default.toml", "r") as default_config_file:
+        default_config = toml.load(default_config_file)
+
+    # Load user configuration
+    user_config = {}
+
+    if Path("config.toml").exists():
+        with open("config.toml", "r") as default_config_file:
+            user_config = toml.load(default_config_file)
+
+    # Merge the configuration
+    merger = Merger(
+        [
+            (dict, "merge")
+        ],
+        ["override"],
+        ["override"]
+    )
+
+    conf = merger.merge(default_config, user_config)
+
+    # Check whether we are missing the requested section
+    if not conf.get(section):
+        raise MetricityConfigurationError(
+            f"Config is missing section '{section}'"
+        )
+
+    return conf[section]
+
+
+class ConfigSection(type):
+    """Metaclass for loading TOML configuration into the relevant class."""
+
+    def __new__(
+        cls: type,
+        name: str,
+        bases: Tuple[type],
+        dictionary: Dict[str, Any]
+    ) -> type:
+        """Use the section attr in the subclass to fill in the values from the TOML."""
+        config = get_section(dictionary["section"])
+
+        log.info(f"Loading configuration section {dictionary['section']}")
+
+        for key, value in config.items():
+            if isinstance(value, dict):
+                if env_var := value.get("env"):
+                    if env_value := environ.get(env_var):
+                        config[key] = env_value
+                    else:
+                        if not value.get("optional"):
+                            raise MetricityConfigurationError(
+                                f"Required config option '{key}' in"
+                                f" '{dictionary['section']}' is missing, either set"
+                                f" the environment variable {env_var} or override "
+                                "it in your config.toml file"
+                            )
+                        else:
+                            config[key] = None
+
+        dictionary.update(config)
+
+        config_section = super().__new__(cls, name, bases, dictionary)
+
+        return config_section
+
+
+class PythonConfig(metaclass=ConfigSection):
+    """Settings relating to the Python environment the application runs in."""
+
+    section = "python"
+
+    log_level: str
+    discord_log_level: str
+
+
+class BotConfig(metaclass=ConfigSection):
+    """Configuration for the Metricity bot."""
+
+    section = "bot"
+
+    command_prefix: Union[List[str], str]
+    token: str
+
+    guild_id: int
+    staff_role_id: int
+
+    staff_categories: List[int]
+    ignore_categories: List[int]
+
+
+class DatabaseConfig(metaclass=ConfigSection):
+    """Configuration about the database Metricity will use."""
+
+    section = "database"
+
+    uri: Optional[str]
+
+    host: Optional[str]
+    port: Optional[int]
+    database: Optional[str]
+    username: Optional[str]
+    password: Optional[str]