How to seed databases in Node.js

const { Sequelize, DataTypes } = require('sequelize')
const bcrypt = require('bcrypt')

// Database connection
const sequelize = new Sequelize(process.env.DATABASE_URL || 'postgres://localhost:5432/myapp', {
    logging: false
})

// User model
const User = sequelize.define('User', {
    email: { type: DataTypes.STRING, unique: true, allowNull: false },
    name: { type: DataTypes.STRING, allowNull: false },
    password: { type: DataTypes.STRING, allowNull: false },
    role: { type: DataTypes.ENUM('admin', 'user', 'moderator'), defaultValue: 'user' },
    isActive: { type: DataTypes.BOOLEAN, defaultValue: true }
})

// Post model
const Post = sequelize.define('Post', {
    title: { type: DataTypes.STRING, allowNull: false },
    content: { type: DataTypes.TEXT, allowNull: false },
    published: { type: DataTypes.BOOLEAN, defaultValue: false },
    publishedAt: { type: DataTypes.DATE }
})

// Define associations
User.hasMany(Post, { foreignKey: 'authorId' })
Post.belongsTo(User, { foreignKey: 'authorId', as: 'author' })

// Seed data
const seedUsers = [
    {
        email: '[email protected]',
        name: 'Admin User',
        password: 'admin123',
        role: 'admin'
    },
    {
        email: '[email protected]',
        name: 'John Doe',
        password: 'password123',
        role: 'user'
    },
    {
        email: '[email protected]',
        name: 'Jane Smith',
        password: 'password123',
        role: 'moderator'
    }
]

const seedPosts = [
    {
        title: 'Getting Started with Node.js',
        content: 'Node.js is a powerful JavaScript runtime for building server-side applications...',
        published: true,
        publishedAt: new Date('2025-01-01')
    },
    {
        title: 'Database Best Practices',
        content: 'When working with databases, it\'s important to follow best practices...',
        published: true,
        publishedAt: new Date('2025-01-15')
    },
    {
        title: 'Draft Post',
        content: 'This is a draft post that hasn\'t been published yet.',
        published: false
    }
]

// Seeding functions
async function seedDatabase() {
    try {
        console.log('Starting database seeding...')

        // Sync database (create tables)
        await sequelize.sync({ force: true })
        console.log('Database synced')

        // Seed users
        const createdUsers = []
        for (const userData of seedUsers) {
            const hashedPassword = await bcrypt.hash(userData.password, 10)
            const user = await User.create({
                ...userData,
                password: hashedPassword
            })
            createdUsers.push(user)
            console.log(`Created user: ${user.email}`)
        }

        // Seed posts
        for (let i = 0; i < seedPosts.length; i++) {
            const postData = seedPosts[i]
            const author = createdUsers[i % createdUsers.length]

            const post = await Post.create({
                ...postData,
                authorId: author.id
            })
            console.log(`Created post: ${post.title} by ${author.name}`)
        }

        console.log('Database seeding completed successfully')
    } catch (error) {
        console.error('Error seeding database:', error)
        throw error
    }
}

// Clean database function
async function cleanDatabase() {
    try {
        console.log('Cleaning database...')
        await Post.destroy({ where: {} })
        await User.destroy({ where: {} })
        console.log('Database cleaned')
    } catch (error) {
        console.error('Error cleaning database:', error)
        throw error
    }
}

// Development seed with more sample data
async function seedDevelopmentData() {
    try {
        await cleanDatabase()
        await seedDatabase()

        // Add additional development data
        const users = await User.findAll()
        const sampleTitles = [
            'Advanced JavaScript Patterns',
            'React Best Practices',
            'Vue.js Components Guide',
            'Node.js Performance Tips'
        ]

        for (const title of sampleTitles) {
            await Post.create({
                title,
                content: `This is sample content for ${title}. Lorem ipsum dolor sit amet...`,
                published: Math.random() > 0.3,
                publishedAt: new Date(),
                authorId: users[Math.floor(Math.random() * users.length)].id
            })
        }

        console.log('Development data seeded')
    } catch (error) {
        console.error('Error seeding development data:', error)
    }
}

// Command line interface
async function runSeeder() {
    const command = process.argv[2]

    try {
        switch (command) {
            case 'seed':
                await seedDatabase()
                break
            case 'clean':
                await cleanDatabase()
                break
            case 'dev':
                await seedDevelopmentData()
                break
            default:
                console.log('Available commands: seed, clean, dev')
        }
    } catch (error) {
        console.error('Seeding failed:', error)
        process.exit(1)
    } finally {
        await sequelize.close()
    }
}

// Export functions for use in other modules
module.exports = {
    seedDatabase,
    cleanDatabase,
    seedDevelopmentData
}

// Run if called directly
if (require.main === module) {
    runSeeder()
}