graph TD
    A[Identify Migration Need] --> B[Pre-Migration Preparation]
    B --> C[Create Snapshot]
    C --> D[Analyze Dependencies]
    D --> E[Plan Rollback]
    E --> F[Execute Migration]
    F --> G[Verify in Staging]
    G --> H{Verified?}
    H -->|No| I[Fix Issues]
    I --> G
    H -->|Yes| J[Deploy to Production]
    J --> K[Monitor]
    K --> L{Issues?}
    L -->|Yes| M[Execute Rollback]
    L -->|No| N[Migration Complete]
    M --> N

## Pre-Migration Checklist

### Planning
- [ ] Migration scope defined
- [ ] Target version identified
- [ ] Breaking changes documented
- [ ] Migration timeline established
- [ ] Stakeholders notified

### Environment
- [ ] Development environment ready
- [ ] Staging environment ready
- [ ] Production backup scheduled
- [ ] Rollback plan documented

### Resources
- [ ] Team members assigned
- [ ] Documentation reviewed
- [ ] Migration tools prepared
- [ ] Support resources available

### Testing
- [ ] Test cases identified
- [ ] Regression tests prepared
- [ ] Performance baselines recorded
- [ ] Monitoring configured

// Example: Analyzing library upgrade
const breakingChanges = {
    // API changes
    removedMethods: ['oldMethod', 'deprecatedFunction'],
    renamedMethods: {
        'oldName': 'newName'
    },
    signatureChanges: {
        'method1': 'parameters changed from (a, b) to (options)'
    },

    // Behavior changes
    asyncChanges: {
        'method2': 'now returns Promise instead of callback'
    },
    defaultChanges: {
        'config': 'default value changed from true to false'
    },

    // Deprecations
    deprecatedFeatures: ['featureX', 'optionY']
};

console.log('Breaking Changes:', breakingChanges);

## Migration Scope

### What's Migrating
- **Library/Framework:** [Name]
- **From Version:** [X.Y.Z]
- **To Version:** [A.B.C]
- **Breaking Changes:** [List]

### What's Affected
- **Modules:** [List of affected modules]
- **Features:** [List of affected features]
- **Integrations:** [List of affected integrations]

### What's NOT Migrating
- **Unaffected Modules:** [List]
- **Optional Features:** [List]
- **Third-party Code:** [List]

### Success Criteria
- [ ] All tests pass
- [ ] No regressions
- [ ] Performance within baseline
- [ ] No critical errors

#!/bin/bash
# scripts/create-snapshot.sh - Create system snapshot

SNAPSHOT_DIR="snapshots/$(date +%Y%m%d_%H%M%S)"
mkdir -p "$SNAPSHOT_DIR"

echo "Creating snapshot in $SNAPSHOT_DIR..."

# Capture package versions
npm list --depth=0 > "$SNAPSHOT_DIR/npm-packages.txt"
pip list > "$SNAPSHOT_DIR/python-packages.txt"

# Capture configuration
cp -r .env "$SNAPSHOT_DIR/"
cp package.json "$SNAPSHOT_DIR/"
cp requirements.txt "$SNAPSHOT_DIR/" 2>/dev/null || true

# Capture database schema
if [ -f "schema.sql" ]; then
    cp schema.sql "$SNAPSHOT_DIR/"
fi

# Run tests and capture results
npm test 2>&1 | tee "$SNAPSHOT_DIR/test-results-before.txt"

# Capture performance baseline
npm run benchmark 2>&1 | tee "$SNAPSHOT_DIR/performance-baseline.txt"

echo "Snapshot created: $SNAPSHOT_DIR"

# Check snapshot contents
ls -lh snapshots/$(date +%Y%m%d_%H%M%S)

# Verify critical files
for file in npm-packages.txt package.json .env; do
    if [ ! -f "snapshots/$(date +%Y%m%d_%H%M%S)/$file" ]; then
        echo "❌ Missing critical file: $file"
        exit 1
    fi
done

echo "✅ Snapshot verified"

#!/bin/bash
# scripts/run-baseline-tests.sh

echo "Running baseline tests..."

# Run all tests
npm test -- --coverage

# Capture results
mkdir -p baseline-results
cp coverage/coverage-final.json baseline-results/

# Run performance tests
npm run benchmark

# Capture performance
cp benchmark-results.json baseline-results/

echo "✅ Baseline tests complete"

// scripts/analyze-dependencies.js - Dependency impact analysis

const { execSync } = require('child_process');

function analyzeDependencies() {
    // Get current dependencies
    const currentDeps = JSON.parse(execSync('npm ls --json', { encoding: 'utf-8' }));

    // Get target version dependencies
    const targetDeps = JSON.parse(execSync('npm view package-name@version --json', { encoding: 'utf-8' }));

    // Compare dependencies
    const analysis = {
        current: currentDeps.dependencies,
        target: targetDeps.dependencies,
        changes: compareDependencies(currentDeps.dependencies, targetDeps.dependencies),
        impact: assessImpact(currentDeps.dependencies, targetDeps.dependencies)
    };

    return analysis;
}

function compareDependencies(current, target) {
    const changes = {
        added: [],
        removed: [],
        updated: []
    };

    // Check for added dependencies
    for (const dep in target) {
        if (!(dep in current)) {
            changes.added.push(dep);
        }
    }

    // Check for removed dependencies
    for (const dep in current) {
        if (!(dep in target)) {
            changes.removed.push(dep);
        }
    }

    // Check for updated dependencies
    for (const dep in target) {
        if (dep in current && current[dep] !== target[dep]) {
            changes.updated.push({
                name: dep,
                from: current[dep],
                to: target[dep]
            });
        }
    }

    return changes;
}

function assessImpact(current, target) {
    const impact = {
        high: [],
        medium: [],
        low: []
    };

    // Assess impact of each change
    for (const change of Object.keys(target)) {
        if (change in current && current[change] !== target[change]) {
            // Major version bump = high impact
            const [currentMajor, targetMajor] = [current[change], target[change]].map(v => parseInt(v.split('.')[0]));
            
            if (targetMajor > currentMajor) {
                impact.high.push(change);
            } else if (targetMajor === currentMajor) {
                impact.medium.push(change);
            } else {
                impact.low.push(change);
            }
        }
    }

    return impact;
}

const analysis = analyzeDependencies();
console.log('Dependency Analysis:', JSON.stringify(analysis, null, 2));

#!/bin/bash
# scripts/check-dependency-conflicts.sh

echo "Checking for dependency conflicts..."

# Check for peer dependency conflicts
npm ls

# Check for circular dependencies
npm ls --json | jq '.dependencies | to_entries | map(select(.value.dependencies | contains(.key)) | .key)'

# Check for incompatible versions
npm outdated

echo "✅ Dependency check complete"

## Phase 1: Development Migration

### 1.1 Update Dependencies
\`\`\`bash
npm install package-name@new-version
\`\`\`

### 1.2 Update Code
- Update import statements
- Replace deprecated APIs
- Update method signatures
- Handle breaking changes

### 1.3 Run Tests
\`\`\`bash
npm test
\`\`\`

### 1.4 Fix Issues
- Address test failures
- Update documentation
- Commit changes

### 1.5 Verification
- [ ] All tests pass
- [ ] No warnings
- [ ] Code compiles
- [ ] Linting passes

## Phase 2: Staging Migration

### 2.1 Deploy to Staging
\`\`\`bash
npm run deploy:staging
\`\`\`

### 2.2 Run Full Test Suite
\`\`\`bash
npm test -- --coverage
\`\`\`

### 2.3 Integration Testing
- Test all integrations
- Verify API compatibility
- Check data migrations

### 2.4 Performance Testing
- Run performance benchmarks
- Compare to baseline
- Verify no regression

### 2.4 Verification
- [ ] All tests pass
- [ ] Performance within 10% of baseline
- [ ] No critical errors
- [ ] Stakeholder approval

## Phase 3: Production Migration

### 3.1 Schedule Migration
- Choose low-traffic period
- Notify all stakeholders
- Prepare rollback plan

### 3.2 Pre-Migration Checks
- Verify rollback plan is ready
- Confirm monitoring is active
- Verify backup is current

### 3.3 Execute Migration
\`\`\`bash
npm run deploy:production
\`\`\`

### 3.4 Immediate Verification
- Check health endpoints
- Verify key functionality
- Monitor error rates

### 3.5 Post-Migration Monitoring
- Monitor for 1 hour
- Check performance metrics
- Review error logs

### 3.6 Verification
- [ ] Health checks pass
- [ ] Error rates normal
- [ ] Performance acceptable
- [ ] No critical issues

#!/bin/bash
# scripts/migrate.sh - Automated migration script

set -e

# Configuration
PACKAGE_NAME="package-name"
NEW_VERSION="new-version"
OLD_VERSION=$(npm view $PACKAGE_NAME version)

echo "=== Migration Script ==="
echo "Migrating $PACKAGE_NAME from $OLD_VERSION to $NEW_VERSION"

# Pre-migration checks
echo "Running pre-migration checks..."
./scripts/create-snapshot.sh
./scripts/analyze-dependencies.js

# Backup current state
echo "Creating backup..."
cp -r node_modules node_modules.backup
cp package.json package.json.backup

# Update dependencies
echo "Updating dependencies..."
npm install $PACKAGE_NAME@$NEW_VERSION

# Update code if needed
echo "Updating code..."
# Add code transformation commands here

# Run tests
echo "Running tests..."
npm test

if [ $? -ne 0 ]; then
    echo "❌ Tests failed. Rolling back..."
    ./scripts/rollback.sh
    exit 1
fi

echo "✅ Migration complete"

## Rollback Plan

### Rollback Triggers
- [ ] Critical errors (>5% error rate)
- [ ] Performance degradation (>50% slower)
- [ ] Data corruption
- [ ] Security vulnerability
- [ ] Stakeholder request

### Rollback Steps
1. Stop new version deployment
2. Restore previous version
3. Restore database from backup
4. Restart services
5. Verify functionality
6. Notify stakeholders

### Rollback Time Estimate
- **Detection:** 5 minutes
- **Decision:** 10 minutes
- **Execution:** 15 minutes
- **Verification:** 10 minutes
- **Total:** 40 minutes

### Rollback Verification
- [ ] All services running
- [ ] Health checks pass
- [ ] Error rates normal
- [ ] Performance restored

#!/bin/bash
# scripts/rollback.sh - Automated rollback

set -e

echo "=== Rollback Script ==="

# Stop current version
echo "Stopping current version..."
npm run stop

# Restore previous version
echo "Restoring previous version..."
if [ -f "package.json.backup" ]; then
    mv package.json.backup package.json
fi

if [ -d "node_modules.backup" ]; then
    rm -rf node_modules
    mv node_modules.backup node_modules
fi

# Reinstall dependencies
echo "Reinstalling dependencies..."
npm install

# Restore database if needed
if [ -f "snapshots/latest/schema.sql" ]; then
    echo "Restoring database..."
    mysql -u user -p database < snapshots/latest/schema.sql
fi

# Restart services
echo "Restarting services..."
npm run start

# Verify
echo "Verifying rollback..."
sleep 5
npm run health-check

if [ $? -eq 0 ]; then
    echo "✅ Rollback successful"
else
    echo "❌ Rollback failed. Manual intervention required."
    exit 1
fi

## Post-Migration Verification Checklist

### Functional Verification
- [ ] All core features work
- [ ] No broken integrations
- [ ] Data integrity maintained
- [ ] User workflows unaffected

### Performance Verification
- [ ] Response times within baseline
- [ ] Throughput maintained
- [ ] No memory leaks
- [ ] CPU usage normal

### Security Verification
- [ ] Authentication works
- [ ] Authorization maintained
- [ ] No new vulnerabilities
- [ ] Secrets properly configured

### Monitoring Verification
- [ ] Error rates normal
- [ ] No critical alerts
- [ ] Metrics within thresholds
- [ ] Logs clean

#!/bin/bash
# scripts/verify-migration.sh - Post-migration verification

echo "=== Migration Verification ==="

# Health check
echo "Checking health..."
HEALTH_STATUS=$(curl -s -o /dev/null -w "%{http_code}" http://localhost:3000/health)

if [ "$HEALTH_STATUS" -ne "200" ]; then
    echo "❌ Health check failed"
    exit 1
fi

echo "✅ Health check passed"

# Run tests
echo "Running tests..."
npm test

if [ $? -ne 0 ]; then
    echo "❌ Tests failed"
    exit 1
fi

echo "✅ Tests passed"

# Performance check
echo "Checking performance..."
PERFORMANCE=$(npm run benchmark | grep "avg" | awk '{print $2}')

BASELINE=$(cat baseline-results/performance-baseline.txt | grep "avg" | awk '{print $2}')

# Allow 10% degradation
THRESHOLD=$(echo "$BASELINE * 1.1" | bc)

if (( $(echo "$PERFORMANCE > $THRESHOLD" | bc -l) )); then
    echo "⚠️  Performance degraded: $PERFORMANCE vs baseline $BASELINE"
else
    echo "✅ Performance acceptable"
fi

echo "=== Verification Complete ==="

# Simple version upgrade
npm install package@latest
npm test
npm run deploy

// Run both old and new versions side by side
const oldVersion = require('package-name');
const newVersion = require('package-name-new');

// Feature flag to switch between versions
const useNewVersion = process.env.USE_NEW_VERSION === 'true';

const api = useNewVersion ? newVersion : oldVersion;

// Gradually migrate traffic
if (useNewVersion) {
    // Use new version
} else {
    // Use old version
}

// Gradually replace old system with new system
class LegacyService {
    process(data) {
        // Old implementation
    }
}

class NewService {
    process(data) {
        // New implementation
    }
}

class ServiceFacade {
    constructor(legacy, modern) {
        this.legacy = legacy;
        this.modern = modern;
        this.useModern = false;
    }

    process(data) {
        if (this.useModern) {
            return this.modern.process(data);
        }
        return this.legacy.process(data);
    }

    migrateToModern() {
        this.useModern = true;
    }
}

// Start with legacy, gradually migrate to modern
const facade = new ServiceFacade(new LegacyService(), new NewService());

// Mark features as deprecated
function oldFeature() {
    console.warn('DEPRECATED: oldFeature is deprecated and will be removed in v2.0');
    // Old implementation
}

function newFeature() {
    // New implementation
}

// Gradually remove old code
if (process.env.ENABLE_NEW_FEATURE === 'true') {
    newFeature();
} else {
    oldFeature();
}

## Complete Migration Checklist

### Pre-Migration
- [ ] Migration scope defined
- [ ] Breaking changes documented
- [ ] Snapshot created
- [ ] Dependencies analyzed
- [ ] Rollback plan ready
- [ ] Tests passing on baseline

### During Migration
- [ ] Development migration complete
- [ ] Staging migration verified
- [ ] Performance tested
- [ ] Stakeholder approval received
- [ ] Production deployment scheduled

### Post-Migration
- [ ] Health checks passing
- [ ] Tests passing
- [ ] Performance acceptable
- [ ] No critical errors
- [ ] Monitoring stable
- [ ] Documentation updated

# Version checks
npm view package version
npm outdated
npm ls

# Dependency management
npm install package@version
npm update package
npm uninstall package

# Testing
npm test
npm run test:watch
npm run test:coverage

# Deployment
npm run deploy:staging
npm run deploy:production
npm run rollback

# Quick rollback
git revert HEAD
npm install
npm run deploy

# Restore from backup
cp package.json.backup package.json
npm install
npm run start

# Database rollback
mysql -u user -p database < backup.sql
pg_restore -d database -f backup.dump