Enhancement: Add configuration module for constants

[knowlen]

Description

As identified in PR #32 review, magic numbers and constants like TOKEN_EXPIRY_BUFFER = 60 could be made configurable to allow users to adjust behavior for their specific needs.

Current Constants to Make Configurable

OAuth2 Module

• TOKEN_EXPIRY_BUFFER = 60 - seconds before token expiry to refresh
• STATE_LENGTH = 32 - length of CSRF state parameter
• DEFAULT_TIMEOUT = 30 - HTTP request timeout
• CALLBACK_PORT = 8765 - default OAuth2 callback port

Client Module

• DEFAULT_RETRY_COUNT = 3 - number of retries for failed requests
• DEFAULT_RETRY_DELAY = 1.0 - delay between retries
• CONNECTION_POOL_SIZE = 10 - HTTP connection pool size

Proposed Configuration System

1. Environment Variables

import os

TOKEN_EXPIRY_BUFFER = int(os.getenv('ESOLOGS_TOKEN_EXPIRY_BUFFER', '60'))
DEFAULT_TIMEOUT = float(os.getenv('ESOLOGS_DEFAULT_TIMEOUT', '30'))

2. Configuration Class

from dataclasses import dataclass
from typing import Optional

@dataclass
class ESOLogsConfig:
    token_expiry_buffer: int = 60
    state_length: int = 32
    default_timeout: float = 30.0
    callback_port: int = 8765
    retry_count: int = 3
    retry_delay: float = 1.0
    connection_pool_size: int = 10
    
    @classmethod
    def from_env(cls) -> 'ESOLogsConfig':
        '''Load configuration from environment variables'''
        # Implementation
    
    @classmethod
    def from_file(cls, path: str) -> 'ESOLogsConfig':
        '''Load configuration from JSON/YAML file'''
        # Implementation

# Global config instance
config = ESOLogsConfig.from_env()

3. Usage Pattern

from esologs.config import config

# Use in code
if token.expires_in <= config.token_expiry_buffer:
    # Refresh token

Benefits

• Users can tune behavior for their environment
• Easier testing with different configurations
• Better documentation of tunable parameters
• Follows 12-factor app principles

Implementation Notes

• Maintain backward compatibility
• Document all configuration options
• Validate configuration values
• Consider using pydantic for validation

References

• PR Release v0.2.0b1 - First Beta Release #32 review feedback
• 12-factor app configuration principles