// zero-trust-gateway.js
const jwt = require('jsonwebtoken');
const axios = require('axios');

class ZeroTrustGateway {
  constructor() {
    this.identityProvider = process.env.IDENTITY_PROVIDER_URL;
    this.deviceRegistry = new Map();
    this.sessionContext = new Map();
  }

  /**
   * Verify identity - Who are you?
   */
  async verifyIdentity(token) {
    try {
      // Verify JWT token
      const decoded = jwt.verify(token, process.env.JWT_PUBLIC_KEY, {
        algorithms: ['RS256']
      });

      // Check token hasn't been revoked
      const revoked = await this.checkTokenRevocation(decoded.jti);
      if (revoked) {
        throw new Error('Token has been revoked');
      }

      return {
        valid: true,
        userId: decoded.sub,
        roles: decoded.roles,
        permissions: decoded.permissions
      };
    } catch (error) {
      return { valid: false, error: error.message };
    }
  }

  /**
   * Verify device - What device are you using?
   */
  async verifyDevice(deviceId, deviceFingerprint) {
    const registered = this.deviceRegistry.get(deviceId);

    if (!registered) {
      return {
        trusted: false,
        reason: 'Device not registered'
      };
    }

    // Check device fingerprint matches
    if (registered.fingerprint !== deviceFingerprint) {
      return {
        trusted: false,
        reason: 'Device fingerprint mismatch'
      };
    }

    // Check device compliance
    const compliance = await this.checkDeviceCompliance(deviceId);

    return {
      trusted: compliance.compliant,
      reason: compliance.reason,
      riskScore: compliance.riskScore
    };
  }

  /**
   * Verify location - Where are you?
   */
  async verifyLocation(ip, expectedCountry) {
    try {
      // Get geolocation data
      const geoData = await this.getGeoLocation(ip);

      // Check for impossible travel
      const lastLocation = this.getLastKnownLocation(ip);
      if (lastLocation) {
        const impossibleTravel = this.detectImpossibleTravel(
          lastLocation,
          geoData,
          Date.now() - lastLocation.timestamp
        );

        if (impossibleTravel) {
          return {
            valid: false,
            reason: 'Impossible travel detected',
            riskScore: 9
          };
        }
      }

      // Check against allowed locations
      if (expectedCountry && geoData.country !== expectedCountry) {
        return {
          valid: false,
          reason: 'Unexpected location',
          riskScore: 7
        };
      }

      return {
        valid: true,
        location: geoData,
        riskScore: 1
      };
    } catch (error) {
      return {
        valid: false,
        reason: 'Location verification failed',
        riskScore: 5
      };
    }
  }

  /**
   * Verify authorization - What can you access?
   */
  async verifyAuthorization(userId, resource, action, context) {
    // Get user permissions
    const user = await this.getUserPermissions(userId);

    // Check direct permissions
    if (this.hasPermission(user, resource, action)) {
      return { authorized: true, reason: 'Direct permission' };
    }

    // Check role-based permissions
    for (const role of user.roles) {
      if (this.hasRolePermission(role, resource, action)) {
        return { authorized: true, reason: `Role: ${role}` };
      }
    }

    // Check attribute-based policies
    const abacResult = await this.evaluateABAC(user, resource, action, context);
    if (abacResult.allowed) {
      return { authorized: true, reason: 'ABAC policy' };
    }

    return {
      authorized: false,
      reason: 'Insufficient permissions'
    };
  }

  /**
   * Calculate risk score
   */
  calculateRiskScore(factors) {
    let score = 0;

    // Identity factors
    if (!factors.mfaUsed) score += 3;
    if (factors.newDevice) score += 2;

    // Location factors
    if (factors.unusualLocation) score += 3;
    if (factors.vpnDetected) score += 1;

    // Behavior factors
    if (factors.unusualTime) score += 2;
    if (factors.rapidRequests) score += 2;

    // Device factors
    if (!factors.deviceCompliant) score += 4;
    if (factors.jailbroken) score += 5;

    return Math.min(score, 10);
  }

  /**
   * Continuous verification middleware
   */
  middleware() {
    return async (req, res, next) => {
      const startTime = Date.now();

      try {
        // Extract authentication token
        const token = req.headers.authorization?.replace('Bearer ', '');
        if (!token) {
          return res.status(401).json({
            error: 'unauthorized',
            message: 'No authentication token provided'
          });
        }

        // Step 1: Verify identity
        const identity = await this.verifyIdentity(token);
        if (!identity.valid) {
          return res.status(401).json({
            error: 'unauthorized',
            message: 'Invalid identity'
          });
        }

        // Step 2: Verify device
        const deviceId = req.headers['x-device-id'];
        const deviceFingerprint = req.headers['x-device-fingerprint'];

        if (deviceId && deviceFingerprint) {
          const device = await this.verifyDevice(deviceId, deviceFingerprint);
          if (!device.trusted) {
            return res.status(403).json({
              error: 'forbidden',
              message: device.reason
            });
          }
        }

        // Step 3: Verify location
        const location = await this.verifyLocation(req.ip);
        if (!location.valid) {
          // Require step-up authentication
          return res.status(403).json({
            error: 'forbidden',
            message: 'Additional authentication required',
            requiresStepUp: true
          });
        }

        // Step 4: Calculate risk score
        const riskScore = this.calculateRiskScore({
          mfaUsed: identity.mfaUsed,
          newDevice: !deviceId,
          unusualLocation: location.riskScore > 5,
          deviceCompliant: true
        });

        // Step 5: Verify authorization
        const authorization = await this.verifyAuthorization(
          identity.userId,
          req.path,
          req.method,
          {
            ip: req.ip,
            riskScore,
            time: new Date()
          }
        );

        if (!authorization.authorized) {
          return res.status(403).json({
            error: 'forbidden',
            message: authorization.reason
          });
        }

        // Add context to request
        req.zeroTrust = {
          userId: identity.userId,
          roles: identity.roles,
          riskScore,
          verificationTime: Date.now() - startTime
        };

        // Log access
        this.logAccess(req, identity, riskScore);

        next();
      } catch (error) {
        console.error('Zero Trust verification failed:', error);
        return res.status(500).json({
          error: 'internal_error',
          message: 'Security verification failed'
        });
      }
    };
  }

  async checkTokenRevocation(jti) {
    // Check against revocation list
    return false;
  }

  async checkDeviceCompliance(deviceId) {
    // Check device meets security requirements
    return {
      compliant: true,
      reason: 'Device meets requirements',
      riskScore: 1
    };
  }

  async getGeoLocation(ip) {
    // Get geolocation from IP
    return {
      country: 'US',
      city: 'San Francisco',
      lat: 37.7749,
      lon: -122.4194
    };
  }

  getLastKnownLocation(ip) {
    return null;
  }

  detectImpossibleTravel(lastLocation, currentLocation, timeDiff) {
    // Calculate if travel is physically possible
    return false;
  }

  async getUserPermissions(userId) {
    // Fetch user permissions
    return {
      roles: ['user'],
      permissions: []
    };
  }

  hasPermission(user, resource, action) {
    return false;
  }

  hasRolePermission(role, resource, action) {
    return false;
  }

  async evaluateABAC(user, resource, action, context) {
    return { allowed: false };
  }

  logAccess(req, identity, riskScore) {
    console.log({
      timestamp: new Date().toISOString(),
      userId: identity.userId,
      resource: req.path,
      method: req.method,
      riskScore,
      ip: req.ip
    });
  }
}

// Express setup
const express = require('express');
const app = express();

const ztGateway = new ZeroTrustGateway();

// Apply Zero Trust middleware
app.use(ztGateway.middleware());

// Protected endpoint
app.get('/api/sensitive-data', (req, res) => {
  res.json({
    message: 'Access granted',
    riskScore: req.zeroTrust.riskScore
  });
});

module.exports = ZeroTrustGateway;

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def load_policies(self) -> List[Dict]:
    """Load Zero Trust policies"""
    return [
        {
            'name': 'high_risk_block',
            'condition': lambda ctx: ctx.risk_score >= 8,
            'action': 'deny',
            'reason': 'High risk score'
        },
        {
            'name': 'require_mfa',
            'condition': lambda ctx: ctx.risk_score >= 5,
            'action': 'step_up_auth',
            'reason': 'Elevated risk requires MFA'
        },
        {
            'name': 'untrusted_device',
            'condition': lambda ctx: not self.is_device_trusted(ctx.device_id),
            'action': 'deny',
            'reason': 'Untrusted device'
        },
        {
            'name': 'unusual_location',
            'condition': lambda ctx: self.is_unusual_location(ctx),
            'action': 'step_up_auth',
            'reason': 'Unusual location detected'
        }
    ]

def evaluate(self, context: ZeroTrustContext, resource: str, action: str) -> Dict:
    """Evaluate Zero Trust policies"""
    for policy in self.policies:
        if policy['condition'](context):
            return {
                'allowed': policy['action'] != 'deny',
                'action': policy['action'],
                'reason': policy['reason'],
                'policy': policy['name']
            }

    # Check resource-specific permissions
    if self.has_permission(context.user_id, resource, action):
        return {
            'allowed': True,
            'action': 'allow',
            'reason': 'User has required permissions'
        }

    return {
        'allowed': False,
        'action': 'deny',
        'reason': 'No matching policy allows access'
    }

def is_device_trusted(self, device_id: str) -> bool:
    # Check device trust status
    return True

def is_unusual_location(self, context: ZeroTrustContext) -> bool:
    # Check if location is unusual for user
    return False

def has_permission(self, user_id: str, resource: str, action: str) -> bool:
    # Check user permissions
    return False

    # Evaluate policies
    result = zt_policy.evaluate(
        context,
        request.path,
        request.method
    )

    if not result['allowed']:
        return jsonify({
            'error': 'forbidden',
            'reason': result['reason'],
            'action_required': result['action']
        }), 403

    return f(*args, **kwargs)

return decorated_function

# Check for suspicious patterns
if not request.headers.get('X-Device-ID'):
    score += 2

# Add more risk factors
return min(score, 10)

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