script.js

// DOM Elements
const uploadArea = document.getElementById('uploadArea');
const fileInput = document.getElementById('fileInput');
const fileInfo = document.getElementById('fileInfo');
const fileName = document.getElementById('fileName');
const removeFile = document.getElementById('removeFile');
const scanButton = document.getElementById('scanButton');
const resultsSection = document.getElementById('resultsSection');

// Mock data for demo purposes
const mockScenarios = [
    {
        appName: "PhonePe Pro",
        imitatedBrand: "PhonePe",
        uiSimilarity: 94,
        permissionRisk: "high",
        riskScore: 8.7,
        decision: "blocked",
        explanation: "This application exhibits extremely high UI similarity (94%) to the legitimate PhonePe app, suggesting a sophisticated phishing attempt. The app requests dangerous permissions including SMS access, contact list access, and device admin privileges that are unnecessary for a payment app. The certificate signature does not match the official PhonePe developer. Our AI model detected pixel-perfect cloning of login screens and payment interfaces designed to harvest user credentials and financial information."
    },
    {
        appName: "Google Pay Lite",
        imitatedBrand: "Google Pay",
        uiSimilarity: 87,
        permissionRisk: "high",
        riskScore: 8.2,
        decision: "blocked",
        explanation: "This fraudulent application mimics Google Pay's interface with 87% similarity. Analysis reveals unauthorized use of Google's brand assets and color schemes. The app requests excessive permissions including camera, microphone, and location tracking that exceed normal payment app requirements. The package name 'com.gpaylite.unofficial' and mismatched developer certificate are red flags. Our deep learning model identified cloned UPI transaction screens designed to intercept payment credentials."
    },
    {
        appName: "Paytm Cashback",
        imitatedBrand: "Paytm",
        uiSimilarity: 91,
        permissionRisk: "high",
        riskScore: 9.1,
        decision: "blocked",
        explanation: "Critical threat detected. This malicious app shows 91% UI similarity to official Paytm, using identical color schemes, logos, and interface elements. It requests dangerous permissions including SMS interception, call logs, and storage access to steal OTPs and personal data. The developer certificate is fraudulent and the app contains obfuscated code designed to evade detection. Our AI identified cloned wallet screens and fake cashback offers designed to trick users into entering banking credentials."
    },
    {
        appName: "BHIM UPI Fast",
        imitatedBrand: "BHIM",
        uiSimilarity: 78,
        permissionRisk: "medium",
        riskScore: 6.8,
        decision: "blocked",
        explanation: "This application attempts to impersonate BHIM UPI with 78% interface similarity. While not a perfect clone, it uses similar branding elements and color schemes to deceive users. The app requests medium-risk permissions including contacts and SMS access. The developer signature doesn't match NPCI (National Payments Corporation of India), the official BHIM developer. Our model detected suspicious network activity patterns and cloned UPI PIN entry screens that could compromise user security."
    },
    {
        appName: "Calculator Pro",
        imitatedBrand: "None",
        uiSimilarity: 12,
        permissionRisk: "low",
        riskScore: 1.8,
        decision: "safe",
        explanation: "This application passed all security checks. It shows minimal similarity to known banking or payment apps and does not attempt brand impersonation. The requested permissions (basic storage and display) are appropriate for a calculator application. The developer certificate is valid and the app's behavior matches its stated functionality. Our AI model found no suspicious UI patterns, no hidden payment screens, and no malicious code. The app is safe to install."
    },
    {
        appName: "Fitness Tracker",
        imitatedBrand: "None",
        uiSimilarity: 8,
        permissionRisk: "low",
        riskScore: 2.1,
        decision: "safe",
        explanation: "Security analysis complete: This fitness tracking application is legitimate. It shows no similarity to financial apps and doesn't mimic any known banking brands. The requested permissions (location, activity recognition, sensors) are standard for fitness apps. The developer has a verified certificate and the app's code is transparent with no obfuscation. Our AI detected no fraudulent UI patterns or hidden functionality. The app poses no security risk and is safe for installation."
    }
];

let selectedFile = null;

// Event Listeners
uploadArea.addEventListener('click', () => fileInput.click());
fileInput.addEventListener('change', handleFileSelect);
removeFile.addEventListener('click', handleFileRemove);
scanButton.addEventListener('click', handleScan);

// Drag and Drop
uploadArea.addEventListener('dragover', (e) => {
    e.preventDefault();
    uploadArea.classList.add('drag-over');
});

uploadArea.addEventListener('dragleave', () => {
    uploadArea.classList.remove('drag-over');
});

uploadArea.addEventListener('drop', (e) => {
    e.preventDefault();
    uploadArea.classList.remove('drag-over');

    const files = e.dataTransfer.files;
    if (files.length > 0) {
        const file = files[0];
        if (file.name.endsWith('.apk') || file.name.endsWith('.json')) {
            selectedFile = file;
            displayFileInfo(file);
        }
    }
});

// Demo Mode Functionality
const demoModeToggle = document.getElementById('demoModeToggle');
const demoButtons = document.getElementById('demoButtons');
const demoBlockedBtn = document.getElementById('demoBlocked');
const demoSafeBtn = document.getElementById('demoSafe');

// Predefined test cases
const DEMO_TEST_CASES = {
    blocked: {
        app_name: "PhonePe Pro",
        package_name: "com.phonepe.unofficial",
        permissions: ["READ_SMS", "RECEIVE_SMS", "READ_CONTACTS", "ACCESSIBILITY_SERVICE"],
        declared_brand: "PhonePe",
        app_icon_image: null
    },
    safe: {
        app_name: "Simple Calculator",
        package_name: "com.calculator.simple",
        permissions: ["INTERNET"],
        declared_brand: null,
        app_icon_image: null
    }
};

// Toggle demo mode
demoModeToggle.addEventListener('change', (e) => {
    if (e.target.checked) {
        demoButtons.style.display = 'flex';
    } else {
        demoButtons.style.display = 'none';
    }
});

// Demo: Fake PhonePe (BLOCKED)
demoBlockedBtn.addEventListener('click', async () => {
    await runDemoTest(DEMO_TEST_CASES.blocked, 'Fake PhonePe App');
});

// Demo: Safe App (SAFE)
demoSafeBtn.addEventListener('click', async () => {
    await runDemoTest(DEMO_TEST_CASES.safe, 'Simple Calculator');
});

// Run demo test
async function runDemoTest(metadata, displayName) {
    // Show loading state
    const buttonText = scanButton.querySelector('.button-text');
    const buttonLoader = scanButton.querySelector('.button-loader');
    buttonText.style.display = 'none';
    buttonLoader.style.display = 'flex';
    scanButton.disabled = true;

    try {
        // Simulate analysis delay
        await new Promise(resolve => setTimeout(resolve, 1500));

        // Analyze metadata
        const analysis = analyzeMetadata(metadata);

        // Display results
        displayResults(analysis);

        // Show results section
        resultsSection.style.display = 'block';
        resultsSection.scrollIntoView({ behavior: 'smooth', block: 'nearest' });

        console.log(`Demo Test: ${displayName}`, analysis);
    } catch (error) {
        alert('Error running demo: ' + error.message);
        console.error('Demo error:', error);
    } finally {
        // Reset button
        buttonText.style.display = 'block';
        buttonLoader.style.display = 'none';
        scanButton.disabled = false;
    }
}


// File Handling
function handleFileSelect(e) {
    const file = e.target.files[0];
    if (file) {
        selectedFile = file;
        displayFileInfo(file);
    }
}

function displayFileInfo(file) {
    fileName.textContent = file.name;
    uploadArea.style.display = 'none';
    fileInfo.style.display = 'flex';
    scanButton.disabled = false;
}

function handleFileRemove(e) {
    e.stopPropagation();
    selectedFile = null;
    fileInput.value = '';
    uploadArea.style.display = 'flex';
    fileInfo.style.display = 'none';
    scanButton.disabled = true;
    resultsSection.style.display = 'none';
}

// Metadata Extraction
async function extractMetadata(file) {
    const fileName = file.name.toLowerCase();

    if (fileName.endsWith('.json')) {
        // Read JSON file directly
        return await readJSONMetadata(file);
    } else if (fileName.endsWith('.apk')) {
        // Simulate APK metadata extraction
        return await simulateAPKMetadata(file);
    }

    throw new Error('Unsupported file type');
}

async function readJSONMetadata(file) {
    return new Promise((resolve, reject) => {
        const reader = new FileReader();

        reader.onload = (e) => {
            try {
                const metadata = JSON.parse(e.target.result);

                // Validate required fields
                if (!metadata.app_name || !metadata.package_name) {
                    reject(new Error('Invalid JSON: missing required fields (app_name, package_name)'));
                    return;
                }

                // Ensure permissions is an array
                if (!Array.isArray(metadata.permissions)) {
                    metadata.permissions = [];
                }

                resolve(metadata);
            } catch (error) {
                reject(new Error('Invalid JSON file: ' + error.message));
            }
        };

        reader.onerror = () => reject(new Error('Failed to read file'));
        reader.readAsText(file);
    });
}

async function simulateAPKMetadata(file) {
    // Simulate APK parsing delay
    await new Promise(resolve => setTimeout(resolve, 1000));

    // Generate simulated metadata based on file name
    const fileName = file.name.replace('.apk', '');

    // Simulate different app scenarios based on filename patterns
    const metadata = {
        app_name: fileName,
        package_name: `com.${fileName.toLowerCase().replace(/\s+/g, '.')}.app`,
        permissions: [],
        app_icon_image: null,
        declared_brand: null
    };

    // Detect potential fraud patterns in filename
    if (fileName.toLowerCase().includes('phonepe')) {
        metadata.app_name = 'PhonePe Pro';
        metadata.package_name = 'com.phonepe.unofficial';
        metadata.permissions = ['READ_SMS', 'RECEIVE_SMS', 'READ_CONTACTS', 'CAMERA', 'ACCESS_FINE_LOCATION'];
        metadata.declared_brand = 'PhonePe';
    } else if (fileName.toLowerCase().includes('googlepay') || fileName.toLowerCase().includes('gpay')) {
        metadata.app_name = 'Google Pay Lite';
        metadata.package_name = 'com.gpaylite.unofficial';
        metadata.permissions = ['READ_SMS', 'CAMERA', 'RECORD_AUDIO', 'ACCESS_FINE_LOCATION'];
        metadata.declared_brand = 'Google Pay';
    } else if (fileName.toLowerCase().includes('paytm')) {
        metadata.app_name = 'Paytm Cashback';
        metadata.package_name = 'com.paytm.cashback.fake';
        metadata.permissions = ['READ_SMS', 'RECEIVE_SMS', 'READ_CALL_LOG', 'READ_CONTACTS', 'WRITE_EXTERNAL_STORAGE'];
        metadata.declared_brand = 'Paytm';
    } else if (fileName.toLowerCase().includes('bhim') || fileName.toLowerCase().includes('upi')) {
        metadata.app_name = 'BHIM UPI Fast';
        metadata.package_name = 'com.bhim.upi.fast';
        metadata.permissions = ['READ_SMS', 'READ_CONTACTS', 'CAMERA'];
        metadata.declared_brand = 'BHIM';
    } else {
        // Safe app scenario
        metadata.permissions = ['INTERNET', 'ACCESS_NETWORK_STATE'];
    }

    return metadata;
}

// AI Analysis Workflow
function analyzeMetadata(metadata) {
    const analysis = {
        appName: metadata.app_name,
        imitatedBrand: 'None',
        uiSimilarity: 0,
        permissionRisk: 'low',
        permissionRiskScore: 0,
        riskScore: 0,
        finalRiskScore: 0,
        decision: 'safe',
        explanation: '',
        permissionAnalysis: null,
        visualAnalysis: null
    };

    // Analyze permissions with Indian financial fraud focus
    const permissionAnalysis = analyzePermissions(metadata.permissions);
    analysis.permissionAnalysis = permissionAnalysis;
    analysis.permissionRisk = permissionAnalysis.permission_risk_level.toLowerCase();
    analysis.permissionRiskScore = permissionAnalysis.permission_risk_score;

    // Perform visual similarity analysis
    const visualAnalysis = analyzeVisualSimilarity(metadata);
    analysis.visualAnalysis = visualAnalysis;
    analysis.imitatedBrand = visualAnalysis.matched_brand;
    analysis.uiSimilarity = visualAnalysis.ui_similarity_percentage;

    // Check for brand impersonation based on visual analysis
    const isBrandImpersonation = visualAnalysis.impersonation_flag;

    // Calculate Final Risk Score using weighted formula
    // Final Risk = (0.6 × Permission Risk Score) + (0.4 × UI Similarity Percentage)
    const finalRiskScore = (0.6 * analysis.permissionRiskScore) + (0.4 * analysis.uiSimilarity);
    analysis.finalRiskScore = Math.round(finalRiskScore * 10) / 10; // Round to 1 decimal place

    // Make decision based on threshold
    // If Final Risk ≥ 70 → BLOCK, Else → ALLOW
    if (analysis.finalRiskScore >= 70) {
        analysis.decision = 'blocked';
    } else {
        analysis.decision = 'safe';
    }

    // Legacy risk score (0-10) for UI display compatibility
    analysis.riskScore = (analysis.finalRiskScore / 10).toFixed(1);

    // Generate explanation
    analysis.explanation = generateExplanation(metadata, analysis, permissionAnalysis, visualAnalysis);

    // Log final risk calculation for debugging
    console.log('Final Risk Calculation:', {
        permission_risk_score: analysis.permissionRiskScore,
        ui_similarity_percentage: analysis.uiSimilarity,
        final_risk_score: analysis.finalRiskScore,
        final_decision: analysis.decision.toUpperCase()
    });

    return analysis;
}

// Permission Analysis for Indian Financial Fraud Detection
function analyzePermissions(permissions) {
    // High-risk permissions commonly used in Indian financial fraud
    const highRiskPermissions = [
        'READ_SMS',
        'RECEIVE_SMS',
        'READ_CONTACTS',
        'ACCESSIBILITY_SERVICE',
        'REQUEST_INSTALL_PACKAGES',
        'DEVICE_ADMIN',
        'READ_CALL_LOG'
    ];

    // Additional dangerous permissions
    const additionalDangerousPermissions = [
        'SEND_SMS',
        'WRITE_CALL_LOG',
        'WRITE_CONTACTS',
        'CAMERA',
        'RECORD_AUDIO',
        'ACCESS_FINE_LOCATION',
        'ACCESS_COARSE_LOCATION',
        'WRITE_EXTERNAL_STORAGE',
        'READ_EXTERNAL_STORAGE',
        'GET_ACCOUNTS',
        'USE_CREDENTIALS',
        'BIND_DEVICE_ADMIN',
        'SYSTEM_ALERT_WINDOW'
    ];

    // Count high-risk permissions
    const highRiskFound = permissions.filter(p => highRiskPermissions.includes(p));
    const additionalDangerousFound = permissions.filter(p =>
        additionalDangerousPermissions.includes(p) && !highRiskPermissions.includes(p)
    );

    // Only count high-risk permissions as per requirement
    const dangerousPermissionCount = highRiskFound.length;

    // Calculate permission risk score (0-100)
    let permissionRiskScore = 0;

    // High-risk permissions: 20 points each (max 140, capped at 100)
    permissionRiskScore += highRiskFound.length * 20;

    // Additional dangerous permissions: 5 points each
    permissionRiskScore += additionalDangerousFound.length * 5;

    // Cap at 100
    permissionRiskScore = Math.min(100, permissionRiskScore);

    // Determine risk level
    let permissionRiskLevel;
    if (permissionRiskScore >= 60) {
        permissionRiskLevel = 'HIGH';
    } else if (permissionRiskScore >= 30) {
        permissionRiskLevel = 'MEDIUM';
    } else {
        permissionRiskLevel = 'LOW';
    }

    // Return JSON structure
    const analysis = {
        dangerous_permission_count: dangerousPermissionCount,
        permission_risk_score: permissionRiskScore,
        permission_risk_level: permissionRiskLevel,
        high_risk_permissions_found: highRiskFound,
        additional_dangerous_permissions: additionalDangerousFound
    };

    // Log the analysis for debugging
    console.log('Permission Analysis:', JSON.stringify(analysis, null, 2));

    return analysis;
}

function generateExplanation(metadata, analysis, permissionAnalysis, visualAnalysis) {
    const highRiskPerms = permissionAnalysis.high_risk_permissions_found;
    const allDangerousPerms = [...permissionAnalysis.high_risk_permissions_found, ...permissionAnalysis.additional_dangerous_permissions];

    if (analysis.decision === 'blocked') {
        // BLOCKED - Simple explanation for non-technical users
        let explanation = '⚠️ यह ऐप खतरनाक है। ';

        // Explain impersonation in simple terms
        if (visualAnalysis.impersonation_flag) {
            explanation += `यह ${visualAnalysis.matched_brand} की नकल करके आपको धोखा देने की कोशिश कर रहा है। `;
        }

        // Explain dangerous permissions
        if (highRiskPerms.length > 0) {
            explanation += `यह आपके SMS, contacts और अन्य निजी जानकारी को चुरा सकता है। `;
        } else if (allDangerousPerms.length > 0) {
            explanation += `यह आपकी निजी जानकारी को access कर सकता है। `;
        }

        // What could happen
        explanation += `अगर आप इसे install करते हैं तो आपके बैंक account से पैसे चोरी हो सकते हैं या आपकी OTP और password चोरी हो सकते हैं।`;

        return explanation;

    } else {
        // SAFE - Simple reassurance for users
        let explanation = '✅ यह ऐप सुरक्षित है। ';

        // Explain why it's safe
        if (visualAnalysis.matched_brand === 'None') {
            explanation += 'यह किसी बैंक या payment app की नकल नहीं कर रहा है। ';
        }

        if (allDangerousPerms.length === 0) {
            explanation += 'इसमें कोई खतरनाक permissions नहीं हैं। ';
        } else {
            explanation += 'इसके permissions सामान्य हैं और इसके काम के लिए जरूरी हैं। ';
        }

        explanation += 'आप इसे बिना किसी चिंता के install कर सकते हैं।';

        return explanation;
    }
}

// Scan Functionality
async function handleScan() {
    if (!selectedFile) return;

    // Show loading state
    const buttonText = scanButton.querySelector('.button-text');
    const buttonLoader = scanButton.querySelector('.button-loader');
    buttonText.style.display = 'none';
    buttonLoader.style.display = 'flex';
    scanButton.disabled = true;

    try {
        // Extract metadata from file
        const metadata = await extractMetadata(selectedFile);

        // Simulate AI analysis delay
        await new Promise(resolve => setTimeout(resolve, 1500));

        // Analyze metadata with AI workflow
        const analysis = analyzeMetadata(metadata);

        // Display results
        displayResults(analysis);

        // Scroll to results
        resultsSection.scrollIntoView({ behavior: 'smooth', block: 'nearest' });

    } catch (error) {
        alert('Error scanning file: ' + error.message);
        console.error('Scan error:', error);
    } finally {
        // Reset button
        buttonText.style.display = 'block';
        buttonLoader.style.display = 'none';
        scanButton.disabled = false;
    }
}

function displayResults(data) {
    // Show results section
    resultsSection.style.display = 'block';

    // Populate data
    document.getElementById('appName').textContent = data.appName;
    document.getElementById('imitatedBrand').textContent = data.imitatedBrand;

    // UI Similarity with animation
    const similarityFill = document.getElementById('similarityFill');
    const similarityText = document.getElementById('similarityText');
    setTimeout(() => {
        similarityFill.style.width = data.uiSimilarity + '%';
        similarityText.textContent = data.uiSimilarity + '%';
    }, 100);

    // Permission Risk with score
    const permissionRisk = document.getElementById('permissionRisk');
    permissionRisk.textContent = `${data.permissionRisk.toUpperCase()} (${data.permissionRiskScore}/100)`;
    permissionRisk.className = 'risk-badge ' + data.permissionRisk;

    // Final Risk Score (0-100 scale)
    const riskScoreElement = document.getElementById('riskScore');
    if (data.finalRiskScore !== undefined) {
        riskScoreElement.textContent = `${data.finalRiskScore} / 100`;
    } else {
        // Fallback to legacy score
        riskScoreElement.textContent = data.riskScore + ' / 10';
    }

    // Decision Badge
    const decisionBadge = document.getElementById('decisionBadge');
    decisionBadge.textContent = data.decision === 'blocked' ? '🚫 BLOCKED' : '✓ SAFE';
    decisionBadge.className = 'decision-badge ' + data.decision;

    // Explanation
    document.getElementById('explanationText').textContent = data.explanation;
}

// Initialize
document.addEventListener('DOMContentLoaded', () => {
    console.log('AppShield AI - Fraud App Detector initialized');
});