MongoDB

// MongoDB 연결 및 CRUD - Node.js + mongodb
const { MongoClient, ObjectId } = require('mongodb');

// 연결 설정
const uri = 'mongodb://localhost:27017';
const client = new MongoClient(uri, {
    maxPoolSize: 50,
    wtimeoutMS: 2500,
});

let db, products;

async function connect() {
    await client.connect();
    db = client.db('myapp');
    products = db.collection('products');
    console.log('✅ MongoDB 연결됨');
}

// 문서 삽입
async function createProduct(productData) {
    const product = {
        ...productData,
        createdAt: new Date(),
        updatedAt: new Date(),
    };

    const result = await products.insertOne(product);
    console.log(`삽입됨: ${result.insertedId}`);
    return result.insertedId;
}

// 배치 삽입
async function bulkInsert(items) {
    const operations = items.map(item => ({
        updateOne: {
            filter: { sku: item.sku },
            update: { $set: item, $setOnInsert: { createdAt: new Date() } },
            upsert: true
        }
    }));

    const result = await products.bulkWrite(operations);
    console.log(`삽입: ${result.upsertedCount}, 수정: ${result.modifiedCount}`);
}

// 문서 조회
async function findProducts(filters = {}) {
    const cursor = products.find(filters)
        .sort({ createdAt: -1 })
        .limit(20)
        .project({ name: 1, price: 1, category: 1 });

    return await cursor.toArray();
}

// Aggregation Pipeline
async function getCategoryStats() {
    const pipeline = [
        { $match: { price: { $gt: 0 } } },
        {
            $group: {
                _id: '$category',
                count: { $sum: 1 },
                avgPrice: { $avg: '$price' },
                maxPrice: { $max: '$price' },
                products: { $push: '$name' }
            }
        },
        { $sort: { count: -1 } },
        {
            $project: {
                category: '$_id',
                count: 1,
                avgPrice: { $round: ['$avgPrice', 2] },
                top3: { $slice: ['$products', 3] },
                _id: 0
            }
        }
    ];

    return await products.aggregate(pipeline).toArray();
}

// $lookup (JOIN)
async function getProductsWithReviews() {
    const pipeline = [
        {
            $lookup: {
                from: 'reviews',
                localField: '_id',
                foreignField: 'productId',
                as: 'reviews'
            }
        },
        {
            $addFields: {
                reviewCount: { $size: '$reviews' },
                avgRating: { $avg: '$reviews.rating' }
            }
        },
        {
            $project: { reviews: 0 }
        }
    ];

    return await products.aggregate(pipeline).toArray();
}

// 트랜잭션 (MongoDB 4.0+)
async function transferWithTransaction(fromId, toId, amount) {
    const session = client.startSession();
    const accounts = db.collection('accounts');

    try {
        session.startTransaction();

        // 출금
        const fromResult = await accounts.updateOne(
            { _id: fromId, balance: { $gte: amount } },
            { $inc: { balance: -amount } },
            { session }
        );

        if (fromResult.modifiedCount === 0) {
            throw new Error('잔액 부족');
        }

        // 입금
        await accounts.updateOne(
            { _id: toId },
            { $inc: { balance: amount } },
            { session }
        );

        await session.commitTransaction();
        console.log(`✅ 이체 완료: ${fromId} → ${toId}, ${amount}`);

    } catch (error) {
        await session.abortTransaction();
        console.error(`❌ 이체 실패: ${error.message}`);
        throw error;

    } finally {
        session.endSession();
    }
}

// Change Streams (실시간 변경 감지)
async function watchChanges() {
    const changeStream = products.watch([
        { $match: { operationType: { $in: ['insert', 'update'] } } }
    ]);

    changeStream.on('change', (change) => {
        console.log('변경 감지:', change.operationType, change.documentKey);
    });
}

// 인덱스 생성
async function createIndexes() {
    await products.createIndex({ name: 1 });
    await products.createIndex({ category: 1, price: -1 });
    await products.createIndex({ name: 'text', description: 'text' });
    console.log('✅ 인덱스 생성 완료');
}

// 실행
(async () => {
    try {
        await connect();
        await createIndexes();

        const stats = await getCategoryStats();
        console.log('카테고리 통계:', stats);

    } finally {
        await client.close();
    }
})();

// MongoDB Shell (mongosh) 명령어

// ============================================
// 1. 기본 CRUD
// ============================================
// 데이터베이스 선택
use myapp

// 문서 삽입
db.products.insertOne({
    name: "iPhone 15 Pro",
    price: 1299,
    category: "smartphone",
    specs: { brand: "Apple", storage: "256GB" },
    tags: ["flagship", "5G"],
    createdAt: new Date()
})

// 여러 문서 삽입
db.products.insertMany([
    { name: "Galaxy S24", price: 999, category: "smartphone" },
    { name: "Pixel 8", price: 699, category: "smartphone" }
])

// 조회
db.products.find({ category: "smartphone" })
db.products.findOne({ name: "iPhone 15 Pro" })

// 조건 연산자
db.products.find({ price: { $gte: 500, $lte: 1000 } })
db.products.find({ tags: { $in: ["flagship", "premium"] } })
db.products.find({ "specs.brand": "Apple" })

// 프로젝션
db.products.find({}, { name: 1, price: 1, _id: 0 })

// 정렬, 제한
db.products.find().sort({ price: -1 }).limit(5)


// ============================================
// 2. 업데이트
// ============================================
// 단일 문서 업데이트
db.products.updateOne(
    { name: "iPhone 15 Pro" },
    {
        $set: { price: 1199 },
        $push: { tags: "sale" },
        $inc: { viewCount: 1 }
    }
)

// 여러 문서 업데이트
db.products.updateMany(
    { category: "smartphone" },
    { $set: { inStock: true } }
)

// Upsert (없으면 삽입)
db.products.updateOne(
    { sku: "IPHONE15PRO" },
    { $set: { name: "iPhone 15 Pro", price: 1299 } },
    { upsert: true }
)


// ============================================
// 3. Aggregation Pipeline
// ============================================
// 카테고리별 통계
db.products.aggregate([
    { $match: { price: { $gt: 0 } } },
    { $group: {
        _id: "$category",
        count: { $sum: 1 },
        avgPrice: { $avg: "$price" },
        maxPrice: { $max: "$price" }
    }},
    { $sort: { count: -1 } }
])

// $lookup (JOIN)
db.products.aggregate([
    { $lookup: {
        from: "reviews",
        localField: "_id",
        foreignField: "productId",
        as: "reviews"
    }},
    { $addFields: {
        reviewCount: { $size: "$reviews" },
        avgRating: { $avg: "$reviews.rating" }
    }}
])

// $facet (다중 파이프라인)
db.products.aggregate([
    { $facet: {
        byCategory: [
            { $group: { _id: "$category", count: { $sum: 1 } } }
        ],
        priceRanges: [
            { $bucket: {
                groupBy: "$price",
                boundaries: [0, 500, 1000, 2000, Infinity],
                output: { count: { $sum: 1 } }
            }}
        ],
        totalCount: [
            { $count: "total" }
        ]
    }}
])


// ============================================
// 4. 인덱스
// ============================================
// 인덱스 생성
db.products.createIndex({ name: 1 })
db.products.createIndex({ category: 1, price: -1 })
db.products.createIndex({ name: "text", description: "text" })

// 고유 인덱스
db.products.createIndex({ sku: 1 }, { unique: true })

// 인덱스 확인
db.products.getIndexes()

// 쿼리 실행 계획
db.products.find({ category: "smartphone" }).explain("executionStats")


// ============================================
// 5. 관리 명령어
// ============================================
// 컬렉션 통계
db.products.stats()

// 현재 작업
db.currentOp()

// 레플리카셋 상태
rs.status()

// 샤딩 상태
sh.status()

// 사용자 생성
db.createUser({
    user: "appUser",
    pwd: "securePassword",
    roles: [{ role: "readWrite", db: "myapp" }]
})