"""
Vulnerability Checker Module - Security scanning and vulnerability detection.

This module handles:
- Bandit security scanning for Python code
- Safety checks for dependency vulnerabilities
- Custom security rule validation
"""

import os
import subprocess
import logging
import json
from pathlib import Path
from typing import List, Dict, Any

logger = logging.getLogger(__name__)


class VulnerabilityChecker:
    """Security vulnerability scanning and detection."""
    
    def __init__(self, config: Dict[str, Any], project_root: str):
        """
        Initialize the vulnerability checker.
        
        Args:
            config: Configuration dictionary for vulnerability checker
            project_root: Root directory of the project
        """
        self.config = config
        self.project_root = Path(project_root)
        self.results = {
            "bandit_issues": [],
            "safety_vulnerabilities": [],
            "custom_checks": [],
            "total_issues": 0,
            "severity_counts": {
                "CRITICAL": 0,
                "HIGH": 0,
                "MEDIUM": 0,
                "LOW": 0
            },
            "errors": []
        }
    
    def run(self) -> Dict[str, Any]:
        """
        Run all vulnerability checks.
        
        Returns:
            Dictionary containing results of vulnerability checks
        """
        logger.info("Starting vulnerability checks...")
        
        if not self.config.get("enabled", True):
            logger.info("Vulnerability checker is disabled in configuration")
            return self.results
        
        # Run Bandit security scanner
        if self.config.get("run_bandit", True):
            self._run_bandit()
        
        # Run Safety dependency checker
        if self.config.get("run_safety", True):
            self._run_safety()
        
        # Run custom security checks
        if self.config.get("custom_security_checks", True):
            self._run_custom_checks()
        
        # Calculate total issues
        self.results["total_issues"] = (
            len(self.results["bandit_issues"]) +
            len(self.results["safety_vulnerabilities"]) +
            len(self.results["custom_checks"])
        )
        
        logger.info(f"Vulnerability checks completed. Found {self.results['total_issues']} issues")
        return self.results
    
    def _run_bandit(self):
        """Run Bandit security scanner."""
        logger.info("Running Bandit security scanner...")
        
        try:
            exclude_dirs = ",".join(self.config.get("exclude_dirs", []))
            
            cmd = [
                "bandit",
                "-r", str(self.project_root),
                "-f", "json",
                "-ll"  # Only report low severity and above
            ]
            
            if exclude_dirs:
                cmd.extend(["-x", exclude_dirs])
            
            result = subprocess.run(
                cmd,
                capture_output=True,
                text=True,
                cwd=self.project_root
            )
            
            # Bandit returns non-zero if issues found, which is expected
            if result.stdout:
                try:
                    bandit_output = json.loads(result.stdout)
                    issues = bandit_output.get("results", [])
                    
                    for issue in issues:
                        severity = issue.get("issue_severity", "LOW")
                        self.results["bandit_issues"].append({
                            "file": issue.get("filename", ""),
                            "line": issue.get("line_number", 0),
                            "severity": severity,
                            "confidence": issue.get("issue_confidence", ""),
                            "issue": issue.get("issue_text", ""),
                            "code": issue.get("code", "")
                        })
                        
                        # Update severity counts
                        if severity in self.results["severity_counts"]:
                            self.results["severity_counts"][severity] += 1
                    
                    logger.info(f"Bandit found {len(issues)} security issues")
                    
                except json.JSONDecodeError:
                    logger.error("Failed to parse Bandit output")
                    self.results["errors"].append("Failed to parse Bandit output")
                    
        except FileNotFoundError:
            error_msg = "Bandit is not installed. Install with: pip install bandit"
            logger.error(error_msg)
            self.results["errors"].append(error_msg)
        except Exception as e:
            logger.error(f"Error running Bandit: {str(e)}")
            self.results["errors"].append(f"Bandit error: {str(e)}")
    
    def _run_safety(self):
        """Run Safety to check for vulnerable dependencies."""
        logger.info("Running Safety dependency checker...")
        
        try:
            # Check if requirements.txt exists
            req_files = list(self.project_root.glob("**/requirements*.txt"))
            
            if not req_files:
                logger.warning("No requirements.txt files found")
                return
            
            for req_file in req_files:
                cmd = [
                    "safety",
                    "check",
                    "--file", str(req_file),
                    "--json"
                ]
                
                result = subprocess.run(
                    cmd,
                    capture_output=True,
                    text=True,
                    cwd=self.project_root
                )
                
                # Safety returns non-zero if vulnerabilities found
                if result.stdout:
                    try:
                        safety_output = json.loads(result.stdout)
                        
                        for vuln in safety_output:
                            self.results["safety_vulnerabilities"].append({
                                "package": vuln[0],
                                "installed_version": vuln[2],
                                "affected_versions": vuln[1],
                                "vulnerability": vuln[3],
                                "severity": "HIGH",  # Safety doesn't provide severity, assume HIGH
                                "file": str(req_file)
                            })
                            self.results["severity_counts"]["HIGH"] += 1
                        
                        logger.info(f"Safety found {len(safety_output)} vulnerable dependencies in {req_file.name}")
                        
                    except json.JSONDecodeError:
                        logger.warning(f"Could not parse Safety output for {req_file.name}")
                        
        except FileNotFoundError:
            error_msg = "Safety is not installed. Install with: pip install safety"
            logger.error(error_msg)
            self.results["errors"].append(error_msg)
        except Exception as e:
            logger.error(f"Error running Safety: {str(e)}")
            self.results["errors"].append(f"Safety error: {str(e)}")
    
    def _run_custom_checks(self):
        """Run custom security checks specific to the project."""
        logger.info("Running custom security checks...")
        
        # Check 1: Look for exposed secrets in .env files
        self._check_env_files()
        
        # Check 2: Verify CORS configuration
        self._check_cors_config()
        
        # Check 3: Check for DEBUG mode in production
        self._check_debug_mode()
        
        # Check 4: Validate JWT secret key strength
        self._check_jwt_secret()
    
    def _check_env_files(self):
        """Check for potential exposed secrets in .env files."""
        env_files = list(self.project_root.glob("**/.env"))
        
        for env_file in env_files:
            if env_file.name == ".env.example":
                continue
                
            try:
                with open(env_file, 'r') as f:
                    content = f.read()
                    
                    # Check for weak or default secrets
                    if "SECRET_KEY=changeme" in content or "SECRET_KEY=secret" in content:
                        self.results["custom_checks"].append({
                            "file": str(env_file),
                            "severity": "CRITICAL",
                            "issue": "Weak or default SECRET_KEY detected",
                            "recommendation": "Use a strong, randomly generated secret key"
                        })
                        self.results["severity_counts"]["CRITICAL"] += 1
                        
            except Exception as e:
                logger.warning(f"Could not read {env_file}: {str(e)}")
    
    def _check_cors_config(self):
        """Check for overly permissive CORS configuration."""
        config_files = list(self.project_root.glob("**/config.py"))
        
        for config_file in config_files:
            try:
                with open(config_file, 'r') as f:
                    content = f.read()
                    
                    # Check for allow all origins in production
                    if 'BACKEND_CORS_ORIGINS' in content and '"*"' in content:
                        self.results["custom_checks"].append({
                            "file": str(config_file),
                            "severity": "MEDIUM",
                            "issue": "CORS allows all origins (*)",
                            "recommendation": "Restrict CORS origins in production to specific domains"
                        })
                        self.results["severity_counts"]["MEDIUM"] += 1
                        
            except Exception as e:
                logger.warning(f"Could not read {config_file}: {str(e)}")
    
    def _check_debug_mode(self):
        """Check if DEBUG mode is enabled."""
        config_files = list(self.project_root.glob("**/config.py"))
        
        for config_file in config_files:
            try:
                with open(config_file, 'r') as f:
                    content = f.read()
                    
                    if 'DEBUG: bool = True' in content or 'DEBUG = True' in content:
                        self.results["custom_checks"].append({
                            "file": str(config_file),
                            "severity": "MEDIUM",
                            "issue": "DEBUG mode is enabled",
                            "recommendation": "Disable DEBUG mode in production environments"
                        })
                        self.results["severity_counts"]["MEDIUM"] += 1
                        
            except Exception as e:
                logger.warning(f"Could not read {config_file}: {str(e)}")
    
    def _check_jwt_secret(self):
        """Check JWT secret key strength."""
        env_files = list(self.project_root.glob("**/.env"))
        
        for env_file in env_files:
            if env_file.name == ".env.example":
                continue
                
            try:
                with open(env_file, 'r') as f:
                    for line in f:
                        if line.startswith("SECRET_KEY="):
                            secret = line.split("=", 1)[1].strip()
                            
                            # Check secret key length
                            if len(secret) < 32:
                                self.results["custom_checks"].append({
                                    "file": str(env_file),
                                    "severity": "HIGH",
                                    "issue": "JWT SECRET_KEY is too short (< 32 characters)",
                                    "recommendation": "Use a secret key of at least 32 characters"
                                })
                                self.results["severity_counts"]["HIGH"] += 1
                                
            except Exception as e:
                logger.warning(f"Could not read {env_file}: {str(e)}")
    
    def get_summary(self) -> str:
        """Get a summary of vulnerability check results."""
        summary = f"""
Vulnerability Check Summary:
- Total issues found: {self.results['total_issues']}
- Bandit security issues: {len(self.results['bandit_issues'])}
- Vulnerable dependencies: {len(self.results['safety_vulnerabilities'])}
- Custom check issues: {len(self.results['custom_checks'])}

Severity Breakdown:
- CRITICAL: {self.results['severity_counts']['CRITICAL']}
- HIGH: {self.results['severity_counts']['HIGH']}
- MEDIUM: {self.results['severity_counts']['MEDIUM']}
- LOW: {self.results['severity_counts']['LOW']}
"""
        return summary