Dalia-assignment-w4

Week4/homework/ex1-aggregation/aggregation.js

@@ -0,0 +1,110 @@
+const { MongoClient, ServerApiVersion } = require("mongodb");
+require("dotenv").config(); 
+const uri = process.env.MONGODB_URL; 
+
+
+const client = new MongoClient(uri, {
+  serverApi: {
+    version: ServerApiVersion.v1,
+    strict: true,
+    deprecationErrors: true,
+  },
+});
+
+async function run() {
+  try {
+    await client.connect();
+    console.log("Connected to MongoDB successfully!");
+
+    const db = client.db("databaseWeek4");
+    const collection = db.collection("population"); 
+    // =====================
+    // 1️⃣ Get population per country (example: Netherlands)
+    // =====================
+    const populationNetherlands = await getPopulationPerCountry(
+      collection,
+      "Netherlands"
+    );
+    console.log("\nPopulation per year for Netherlands:");
+    console.table(populationNetherlands);
+
+    // =====================
+    // 2️ Get population per continent for year & age
+    // =====================
+    const continentInfo2020 = await getContinentInfo(collection, 2020, "100+");
+    console.log("\nPopulation for continents in 2020 (age 100+):");
+    console.table(continentInfo2020);
+  } catch (err) {
+    console.error(err);
+  } finally {
+    await client.close();
+    console.log("MongoDB connection closed.");
+  }
+}
+run();
+
+// =====================
+// D1: Total population per country
+// =====================
+const getPopulationPerCountry = async (collection, country) => {
+  const pipeline = [
+    { $match: { Country: country } }, 
+    {
+      $group: {
+        _id: "$Year",
+        countPopulation: { $sum: { $add: ["$M", "$F"] } },
+      },
+    },
+    {
+      $project: {
+        _id: 0,
+        Year: "$_id",
+        countPopulation: 1,
+      },
+    },
+    { $sort: { Year: 1 } }, 
+  ];
+
+  return await collection.aggregate(pipeline).toArray();
+};
+
+// D2: Total population per continent/year/age
+
+const getContinentInfo = async (collection, year, age) => {
+  const pipeline = [
+    {
+      $match: {
+        Country: {
+          $in: [
+            "AFRICA",
+            "ASIA",
+            "EUROPE",
+            "LATIN AMERICA AND THE CARIBBEAN",
+            "NORTHERN AMERICA",
+            "OCEANIA",
+          ],
+        },
+        Year: year,
+        Age: age,
+      },
+    },
+    {
+      $addFields: {
+        TotalPopulation: { $add: ["$M", "$F"] }, 
+      },
+    },
+    {
+      $project: {
+        _id: 0,
+        Country: 1,
+        Year: 1,
+        Age: 1,
+        M: 1,
+        F: 1,
+        TotalPopulation: 1,
+      },
+    },
+  ];
+
+  return await collection.aggregate(pipeline).toArray();
+};

Week4/homework/ex2-transactions/index.js

@@ -0,0 +1,13 @@
+const { setupAccounts } = require("./setup");
+const { transferMoney } = require("./transfer");
+
+async function main() {
+
+  await setupAccounts();
+
+  await transferMoney(101, 102, 1000, "Homework test");
+
+  console.log("All operations completed!");
+}
+
+main();

Week4/homework/ex2-transactions/setup.js

@@ -0,0 +1,39 @@
+const { MongoClient, ServerApiVersion } = require("mongodb");
+require("dotenv").config();
+
+const uri = process.env.MONGODB_URL;
+const client = new MongoClient(uri, {
+  serverApi: {
+    version: ServerApiVersion.v1,
+    strict: true,
+    deprecationErrors: true,
+  },
+});
+
+async function setupAccounts() {
+  try {
+    await client.connect();
+    const db = client.db("databaseWeek4");
+    const collection = db.collection("accounts");
+
+    await collection.deleteMany({});
+
+    const accounts = [
+      { account_number: 101, balance: 5000, account_changes: [] },
+      { account_number: 102, balance: 3000, account_changes: [] }
+    ];
+
+    await collection.insertMany(accounts);
+    console.log("Accounts setup completed!");
+  } catch (err) {
+    console.error(err);
+  } finally {
+    await client.close();
+  }
+}
+
+module.exports = { setupAccounts };
+
+if (require.main === module) {
+  setupAccounts();
+}

Week4/homework/ex2-transactions/transfer.js

@@ -0,0 +1,75 @@
+const { MongoClient, ServerApiVersion } = require("mongodb");
+require("dotenv").config();
+
+const uri = process.env.MONGODB_URL;
+const client = new MongoClient(uri, {
+  serverApi: {
+    version: ServerApiVersion.v1,
+    strict: true,
+    deprecationErrors: true,
+  },
+});
+
+async function transferMoney(fromAccount, toAccount, amount, remark) {
+  const session = client.startSession();
+  try {
+    await client.connect();
+    const db = client.db("databaseWeek4");
+    const collection = db.collection("accounts");
+
+    await session.withTransaction(async () => {
+
+      const from = await collection.findOne({ account_number: fromAccount }, { session });
+      const to = await collection.findOne({ account_number: toAccount }, { session });
+
+      if (!from || !to) throw new Error("Account not found");
+      if (from.balance < amount) throw new Error("Insufficient funds");
+
+      await collection.updateOne(
+        { account_number: fromAccount },
+        {
+          $inc: { balance: -amount },
+          $push: {
+            account_changes: {
+              change_number: from.account_changes.length + 1,
+              amount: -amount,
+              changed_date: new Date(),
+              remark: remark
+            }
+          }
+        },
+        { session }
+      );
+
+      await collection.updateOne(
+        { account_number: toAccount },
+        {
+          $inc: { balance: amount },
+          $push: {
+            account_changes: {
+              change_number: to.account_changes.length + 1,
+              amount: amount,
+              changed_date: new Date(),
+              remark: remark
+            }
+          }
+        },
+        { session }
+      );
+    });
+
+    console.log(`Transferred ${amount} from ${fromAccount} to ${toAccount}`);
+  } catch (err) {
+    console.error("Transaction failed:", err.message);
+  } finally {
+    await session.endSession();
+    await client.close();
+  }
+}
+
+module.exports = { transferMoney };
+
+
+if (require.main === module) {
+  transferMoney(101, 102, 1000, "Test transfer");
+}