feat: Refactor log-alert application into modular structure

- Introduced alerters package with base Alerter class and implementations for LogAlerter and GotifyAlerter.
- Created fetchers package with abstract LogFetcher class and implementations for FileLogFetcher, LokiLogFetcher, and ParseableLogFetcher.
- Added filters package with base Filter class and implementations for RegexpFilter and GeolocationFilter.
- Implemented rules package with base AlertRule class and SimpleAlertRule for alerting logic.
- Enhanced configuration handling with utilities for loading and validating JSON configuration.
- Updated logging setup for better logging management.
- Modified main application logic to utilize the new modular structure, improving maintainability and readability.
- Updated config.json and config.schema.json to reflect changes in alerting and fetching configurations.
- Added python-dateutil to requirements for date parsing functionality.

log-alert/utils/config.py

@@ -0,0 +1,62 @@
+"""Configuration loading and validation utilities."""
+
+import json
+import jsonschema
+import logging
+import os
+import sys
+from typing import Dict, Any
+
+logger = logging.getLogger("log-alert")
+
+
+def load_config(config_path: str) -> Dict[str, Any]:
+    """Load the configuration from a JSON file and validate it with JSON Schema."""
+    try:
+        with open(config_path, 'r') as config_file:
+            # read JSON first
+            config = json.load(config_file)
+            # Perform schema validation if jsonschema is available
+            validate_config_with_schema(config)
+            # Update config to load env variable where required
+            return update_config_from_env(config)
+    except FileNotFoundError:
+        logger.error(f"Error: Configuration file '{config_path}' not found.")
+        sys.exit(1)
+    except json.JSONDecodeError:
+        logger.error(f"Error: Invalid JSON in configuration file '{config_path}'.")
+        sys.exit(1)
+
+
+def validate_config_with_schema(config: Dict[str, Any]) -> None:
+    """Validate a loaded config dict against config.schema.json if jsonschema is installed."""
+    # Find the schema file relative to the log-alert.py location
+    schema_path = os.path.join(os.path.dirname(os.path.dirname(__file__)), 'config.schema.json')
+    try:
+        with open(schema_path, 'r') as sf:
+            schema = json.load(sf)
+        jsonschema.validate(instance=config, schema=schema)
+    except FileNotFoundError:
+        logger.error(f"Schema file '{schema_path}' not found")
+    except jsonschema.exceptions.ValidationError as e:
+        logger.error(f"Configuration validation error: {e.message}")
+        logger.error("Detailed error:", e)
+        sys.exit(1)
+    except Exception as e:
+        logger.error(f"Unexpected error while validating configuration: {e}")
+        sys.exit(1)
+
+
+def update_config_from_env(config: Dict[str, Any]) -> Dict[str, Any]:
+    """Update config values from environment variables if specified."""
+    for key, value in list(config.items()):
+        if isinstance(value, dict):
+            config[key] = update_config_from_env(value)
+        elif isinstance(value, list):
+            config[key] = [update_config_from_env(item) for item in value]
+        elif isinstance(value, str) and key.endswith("-from-env"):
+            new_key = key[:-9]  # Remove '-from-env'
+            config[new_key] = value.format_map(os.environ)
+            del config[key]
+            return update_config_from_env(config) # re-evaluate in case of nested env vars
+    return config