#!/usr/bin/env python3
"""
Author Whitelist Module — Security Fix for Issue #132

Validates task authors against an authorized whitelist before processing.
Prevents unauthorized command execution from untrusted Gitea users.

Configuration (in order of precedence):
1. Environment variable: TIMMY_AUTHOR_WHITELIST (comma-separated)
2. Config file: security.author_whitelist (list)
3. Default: empty list (deny all - secure by default)

Security Events:
- All authorization failures are logged with full context
- Logs include: timestamp, author, issue, IP (if available), action taken
"""

import os
import json
import logging
from pathlib import Path
from typing import List, Optional, Dict, Any
from dataclasses import dataclass, asdict
from datetime import datetime


@dataclass
class AuthorizationResult:
    """Result of an authorization check"""
    authorized: bool
    author: str
    reason: str
    timestamp: str
    issue_number: Optional[int] = None
    
    def to_dict(self) -> Dict[str, Any]:
        return asdict(self)


class SecurityLogger:
    """Dedicated security event logging"""
    
    def __init__(self, log_dir: Optional[Path] = None):
        self.log_dir = log_dir or Path.home() / "timmy" / "logs" / "security"
        self.log_dir.mkdir(parents=True, exist_ok=True)
        self.security_log = self.log_dir / "auth_events.jsonl"
        
        # Also set up Python logger for immediate console/file output
        self.logger = logging.getLogger("timmy.security")
        self.logger.setLevel(logging.WARNING)
        
        if not self.logger.handlers:
            handler = logging.StreamHandler()
            formatter = logging.Formatter(
                '%(asctime)s - SECURITY - %(levelname)s - %(message)s'
            )
            handler.setFormatter(formatter)
            self.logger.addHandler(handler)
    
    def log_authorization(self, result: AuthorizationResult, context: Optional[Dict] = None):
        """Log authorization attempt with full context"""
        entry = {
            "timestamp": result.timestamp,
            "event_type": "authorization",
            "authorized": result.authorized,
            "author": result.author,
            "reason": result.reason,
            "issue_number": result.issue_number,
            "context": context or {}
        }
        
        # Write to structured log file
        with open(self.security_log, 'a') as f:
            f.write(json.dumps(entry) + '\n')
        
        # Log to Python logger for immediate visibility
        if result.authorized:
            self.logger.info(f"AUTHORIZED: '{result.author}' - {result.reason}")
        else:
            self.logger.warning(
                f"UNAUTHORIZED ACCESS ATTEMPT: '{result.author}' - {result.reason}"
            )
    
    def log_security_event(self, event_type: str, details: Dict[str, Any]):
        """Log general security event"""
        entry = {
            "timestamp": datetime.utcnow().isoformat(),
            "event_type": event_type,
            **details
        }
        
        with open(self.security_log, 'a') as f:
            f.write(json.dumps(entry) + '\n')
        
        self.logger.warning(f"SECURITY EVENT [{event_type}]: {details}")


class AuthorWhitelist:
    """
    Author whitelist validator for task router security.
    
    Usage:
        whitelist = AuthorWhitelist()
        result = whitelist.validate_author("username", issue_number=123)
        if not result.authorized:
            # Return 403, do not process task
    """
    
    # Default deny all (secure by default)
    DEFAULT_WHITELIST: List[str] = []
    
    def __init__(
        self,
        whitelist: Optional[List[str]] = None,
        config_path: Optional[Path] = None,
        log_dir: Optional[Path] = None
    ):
        """
        Initialize whitelist from provided list, env var, or config file.
        
        Priority:
        1. Explicit whitelist parameter
        2. TIMMY_AUTHOR_WHITELIST environment variable
        3. Config file security.author_whitelist
        4. Default empty list (secure by default)
        """
        self.security_logger = SecurityLogger(log_dir)
        self._whitelist: List[str] = []
        self._config_path = config_path or Path("/tmp/timmy-home/config.yaml")
        
        # Load whitelist from available sources
        if whitelist is not None:
            self._whitelist = [u.strip().lower() for u in whitelist if u.strip()]
        else:
            self._whitelist = self._load_whitelist()
        
        # Log initialization (without exposing full whitelist in production)
        self.security_logger.log_security_event(
            "whitelist_initialized",
            {
                "whitelist_size": len(self._whitelist),
                "whitelist_empty": len(self._whitelist) == 0,
                "source": self._get_whitelist_source()
            }
        )
    
    def _get_whitelist_source(self) -> str:
        """Determine which source the whitelist came from"""
        if os.environ.get("TIMMY_AUTHOR_WHITELIST"):
            return "environment"
        if self._config_path.exists():
            try:
                import yaml
                with open(self._config_path) as f:
                    config = yaml.safe_load(f)
                if config and config.get("security", {}).get("author_whitelist"):
                    return "config_file"
            except Exception:
                pass
        return "default"
    
    def _load_whitelist(self) -> List[str]:
        """Load whitelist from environment or config"""
        # 1. Check environment variable
        env_whitelist = os.environ.get("TIMMY_AUTHOR_WHITELIST", "").strip()
        if env_whitelist:
            return [u.strip().lower() for u in env_whitelist.split(",") if u.strip()]
        
        # 2. Check config file
        if self._config_path.exists():
            try:
                import yaml
                with open(self._config_path) as f:
                    config = yaml.safe_load(f)
                
                if config:
                    security_config = config.get("security", {})
                    config_whitelist = security_config.get("author_whitelist", [])
                    if config_whitelist:
                        return [u.strip().lower() for u in config_whitelist if u.strip()]
            except Exception as e:
                self.security_logger.log_security_event(
                    "config_load_error",
                    {"error": str(e), "path": str(self._config_path)}
                )
        
        # 3. Default: empty list (secure by default - deny all)
        return list(self.DEFAULT_WHITELIST)
    
    def validate_author(
        self,
        author: str,
        issue_number: Optional[int] = None,
        context: Optional[Dict[str, Any]] = None
    ) -> AuthorizationResult:
        """
        Validate if an author is authorized to submit tasks.
        
        Args:
            author: The username to validate
            issue_number: Optional issue number for logging context
            context: Additional context (IP, user agent, etc.)
            
        Returns:
            AuthorizationResult with authorized status and reason
        """
        timestamp = datetime.utcnow().isoformat()
        author_clean = author.strip().lower() if author else ""
        
        # Check for empty author
        if not author_clean:
            result = AuthorizationResult(
                authorized=False,
                author=author or "<empty>",
                reason="Empty author provided",
                timestamp=timestamp,
                issue_number=issue_number
            )
            self.security_logger.log_authorization(result, context)
            return result
        
        # Check whitelist
        if author_clean in self._whitelist:
            result = AuthorizationResult(
                authorized=True,
                author=author,
                reason="Author found in whitelist",
                timestamp=timestamp,
                issue_number=issue_number
            )
            self.security_logger.log_authorization(result, context)
            return result
        
        # Not authorized
        result = AuthorizationResult(
            authorized=False,
            author=author,
            reason="Author not in whitelist",
            timestamp=timestamp,
            issue_number=issue_number
        )
        self.security_logger.log_authorization(result, context)
        return result
    
    def is_authorized(self, author: str) -> bool:
        """Quick check if author is authorized (without logging)"""
        if not author:
            return False
        return author.strip().lower() in self._whitelist
    
    def get_whitelist(self) -> List[str]:
        """Get current whitelist (for admin/debug purposes)"""
        return list(self._whitelist)
    
    def add_author(self, author: str) -> None:
        """Add an author to the whitelist (runtime only)"""
        author_clean = author.strip().lower()
        if author_clean and author_clean not in self._whitelist:
            self._whitelist.append(author_clean)
            self.security_logger.log_security_event(
                "whitelist_modified",
                {"action": "add", "author": author, "new_size": len(self._whitelist)}
            )
    
    def remove_author(self, author: str) -> None:
        """Remove an author from the whitelist (runtime only)"""
        author_clean = author.strip().lower()
        if author_clean in self._whitelist:
            self._whitelist.remove(author_clean)
            self.security_logger.log_security_event(
                "whitelist_modified",
                {"action": "remove", "author": author, "new_size": len(self._whitelist)}
            )


# HTTP-style response helpers for integration with web frameworks
def create_403_response(result: AuthorizationResult) -> Dict[str, Any]:
    """Create a 403 Forbidden response for unauthorized authors"""
    return {
        "status_code": 403,
        "error": "Forbidden",
        "message": "Author not authorized to submit tasks",
        "details": {
            "author": result.author,
            "reason": result.reason,
            "timestamp": result.timestamp
        }
    }


def create_200_response(result: AuthorizationResult) -> Dict[str, Any]:
    """Create a 200 OK response for authorized authors"""
    return {
        "status_code": 200,
        "authorized": True,
        "author": result.author,
        "timestamp": result.timestamp
    }


if __name__ == "__main__":
    # Demo usage
    print("=" * 60)
    print("AUTHOR WHITELIST MODULE — Security Demo")
    print("=" * 60)
    
    # Example with explicit whitelist
    whitelist = AuthorWhitelist(whitelist=["admin", "timmy", "ezra"])
    
    print("\nTest Cases:")
    print("-" * 60)
    
    test_cases = [
        ("timmy", 123),
        ("hacker", 456),
        ("", 789),
        ("ADMIN", 100),  # Case insensitive
    ]
    
    for author, issue in test_cases:
        result = whitelist.validate_author(author, issue_number=issue)
        status = "✅ AUTHORIZED" if result.authorized else "❌ DENIED"
        print(f"\n{status} '{author}' on issue #{issue}")
        print(f"   Reason: {result.reason}")
    
    print("\n" + "=" * 60)
    print("Current whitelist:", whitelist.get_whitelist())