From 5070d3d1062b7b3bb7be2980eec857732b725014 Mon Sep 17 00:00:00 2001
From: Sergeyu <sergeyu@kmslh.com>
Date: Sun, 26 Oct 2025 15:13:11 +0200
Subject: [PATCH 1/8] feat: add solutions for fs

---
 src/fs/copy.js                 | 33 ++++++++++++++++++++++++++++++++-
 src/fs/create.js               | 23 ++++++++++++++++++++++-
 src/fs/delete.js               | 20 +++++++++++++++++++-
 src/fs/files/fileToRemove.txt  |  1 -
 src/fs/files/wrongFilename.txt |  3 ---
 src/fs/list.js                 | 21 ++++++++++++++++++++-
 src/fs/read.js                 | 21 ++++++++++++++++++++-
 src/fs/rename.js               | 31 ++++++++++++++++++++++++++++++-
 8 files changed, 143 insertions(+), 10 deletions(-)
 delete mode 100644 src/fs/files/fileToRemove.txt
 delete mode 100644 src/fs/files/wrongFilename.txt

diff --git a/src/fs/copy.js b/src/fs/copy.js
index e226075b4c..a26a3498f5 100644
--- a/src/fs/copy.js
+++ b/src/fs/copy.js
@@ -1,5 +1,36 @@
+import { promises as fs } from 'fs';
+import path from 'path';
+import { fileURLToPath } from 'url';
+
 const copy = async () => {
-  // Write your code here
+  const __filename = fileURLToPath(import.meta.url);
+  const __dirname = path.dirname(__filename);
+  const srcDir = path.join(__dirname, 'files');
+  const destDir = path.join(__dirname, 'files_copy');
+
+  try {
+    // Validate source directory exists
+    await fs.access(srcDir);
+  } catch {
+    throw new Error('FS operation failed');
+  }
+
+  // Fail if destination already exists
+  try {
+    await fs.access(destDir);
+    // If access succeeds, destination exists
+    throw new Error('FS operation failed');
+  } catch (err) {
+    // If error is because it doesn't exist, proceed; else rethrow custom error already thrown
+    if (err?.message === 'FS operation failed') throw err; // dest exists case above
+  }
+
+  try {
+    // Use recursive copy
+    await fs.cp(srcDir, destDir, { recursive: true });
+  } catch {
+    throw new Error('FS operation failed');
+  }
 };
 
 await copy();
diff --git a/src/fs/create.js b/src/fs/create.js
index 6ede285599..2f5574afd0 100644
--- a/src/fs/create.js
+++ b/src/fs/create.js
@@ -1,5 +1,26 @@
+import { promises as fs } from 'fs';
+import path from 'path';
+import { fileURLToPath } from 'url';
+
 const create = async () => {
-  // Write your code here
+  const __filename = fileURLToPath(import.meta.url);
+  const __dirname = path.dirname(__filename);
+  const dir = path.join(__dirname, 'files');
+  const filePath = path.join(dir, 'fresh.txt');
+  const content = 'I am fresh and young inside of the files folder';
+
+  try {
+    await fs.access(filePath);
+    throw new Error('FS operation failed');
+  } catch (err) {
+    if (err?.message === 'FS operation failed') throw err;
+  }
+
+  try {
+    await fs.writeFile(filePath, content, 'utf8');
+  } catch {
+    throw new Error('FS operation failed');
+  }
 };
 
 await create();
diff --git a/src/fs/delete.js b/src/fs/delete.js
index a70b13766c..6f00f9fb1e 100644
--- a/src/fs/delete.js
+++ b/src/fs/delete.js
@@ -1,5 +1,23 @@
+import { promises as fs } from 'fs';
+import path from 'path';
+import { fileURLToPath } from 'url';
+
 const remove = async () => {
-  // Write your code here
+  const __filename = fileURLToPath(import.meta.url);
+  const __dirname = path.dirname(__filename);
+  const filePath = path.join(__dirname, 'files', 'fileToRemove.txt');
+
+  try {
+    await fs.access(filePath);
+  } catch {
+    throw new Error('FS operation failed');
+  }
+
+  try {
+    await fs.unlink(filePath);
+  } catch {
+    throw new Error('FS operation failed');
+  }
 };
 
 await remove();
diff --git a/src/fs/files/fileToRemove.txt b/src/fs/files/fileToRemove.txt
deleted file mode 100644
index 43e64cd45c..0000000000
--- a/src/fs/files/fileToRemove.txt
+++ /dev/null
@@ -1 +0,0 @@
-How dare you!
\ No newline at end of file
diff --git a/src/fs/files/wrongFilename.txt b/src/fs/files/wrongFilename.txt
deleted file mode 100644
index 38cca5db19..0000000000
--- a/src/fs/files/wrongFilename.txt
+++ /dev/null
@@ -1,3 +0,0 @@
-# This is a file with a wrong filename
-
-Hello from **markdown**!
\ No newline at end of file
diff --git a/src/fs/list.js b/src/fs/list.js
index 0c0fa21f7e..4cedbf4332 100644
--- a/src/fs/list.js
+++ b/src/fs/list.js
@@ -1,5 +1,24 @@
+import { promises as fs } from 'fs';
+import path from 'path';
+import { fileURLToPath } from 'url';
+
 const list = async () => {
-  // Write your code here
+  const __filename = fileURLToPath(import.meta.url);
+  const __dirname = path.dirname(__filename);
+  const dir = path.join(__dirname, 'files');
+
+  try {
+    await fs.access(dir);
+  } catch {
+    throw new Error('FS operation failed');
+  }
+
+  try {
+    const entries = await fs.readdir(dir);
+    console.log(entries);
+  } catch {
+    throw new Error('FS operation failed');
+  }
 };
 
 await list();
diff --git a/src/fs/read.js b/src/fs/read.js
index e3938be563..6a75ee497e 100644
--- a/src/fs/read.js
+++ b/src/fs/read.js
@@ -1,5 +1,24 @@
+import { promises as fs } from 'fs';
+import path from 'path';
+import { fileURLToPath } from 'url';
+
 const read = async () => {
-  // Write your code here
+  const __filename = fileURLToPath(import.meta.url);
+  const __dirname = path.dirname(__filename);
+  const filePath = path.join(__dirname, 'files', 'fileToRead.txt');
+
+  try {
+    await fs.access(filePath);
+  } catch {
+    throw new Error('FS operation failed');
+  }
+
+  try {
+    const data = await fs.readFile(filePath, 'utf8');
+    console.log(data);
+  } catch {
+    throw new Error('FS operation failed');
+  }
 };
 
 await read();
diff --git a/src/fs/rename.js b/src/fs/rename.js
index b1d65b0c86..472a4ee7ba 100644
--- a/src/fs/rename.js
+++ b/src/fs/rename.js
@@ -1,5 +1,34 @@
+import { promises as fs } from 'fs';
+import path from 'path';
+import { fileURLToPath } from 'url';
+
 const rename = async () => {
-  // Write your code here
+  const __filename = fileURLToPath(import.meta.url);
+  const __dirname = path.dirname(__filename);
+  const dir = path.join(__dirname, 'files');
+  const oldPath = path.join(dir, 'wrongFilename.txt');
+  const newPath = path.join(dir, 'properFilename.md');
+
+  // Check old exists
+  try {
+    await fs.access(oldPath);
+  } catch {
+    throw new Error('FS operation failed');
+  }
+
+  // Fail if new already exists
+  try {
+    await fs.access(newPath);
+    throw new Error('FS operation failed');
+  } catch (err) {
+    if (err?.message === 'FS operation failed') throw err;
+  }
+
+  try {
+    await fs.rename(oldPath, newPath);
+  } catch {
+    throw new Error('FS operation failed');
+  }
 };
 
 await rename();

From 49143e1b783b25cc7e9de8009b59b0404687b6eb Mon Sep 17 00:00:00 2001
From: Sergeyu <sergeyu@kmslh.com>
Date: Mon, 27 Oct 2025 12:10:17 +0200
Subject: [PATCH 2/8] feat: add solutions for cli

---
 src/cli/args.js | 15 ++++++++++++++-
 src/cli/env.js  |  7 ++++++-
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/cli/args.js b/src/cli/args.js
index 9e3622f791..275b8f49ff 100644
--- a/src/cli/args.js
+++ b/src/cli/args.js
@@ -1,5 +1,18 @@
 const parseArgs = () => {
-  // Write your code here
+  const args = process.argv.slice(2);
+  const result = [];
+  for (let i = 0; i < args.length; i++) {
+    const token = args[i];
+    if (token.startsWith('--')) {
+      const name = token.slice(2);
+      const value = args[i + 1];
+      if (value && !value.startsWith('--')) {
+        result.push(`${name} is ${value}`);
+        i++; // skip value
+      }
+    }
+  }
+  if (result.length) console.log(result.join(', '));
 };
 
 parseArgs();
diff --git a/src/cli/env.js b/src/cli/env.js
index e3616dc8e7..332a4a3523 100644
--- a/src/cli/env.js
+++ b/src/cli/env.js
@@ -1,5 +1,10 @@
 const parseEnv = () => {
-  // Write your code here
+  const prefix = 'RSS_';
+  const result = Object.keys(process.env)
+    .filter((key) => key.startsWith(prefix))
+    .map((key) => `${key}=${process.env[key]}`)
+    .join('; ');
+  if (result) console.log(result);
 };
 
 parseEnv();

From 4620acea3670836b8a9707f0329e93c0e12c528d Mon Sep 17 00:00:00 2001
From: Sergeyu <sergeyu@kmslh.com>
Date: Mon, 27 Oct 2025 12:28:31 +0200
Subject: [PATCH 3/8] refactor: rewrite cjsToEsm.cjs to it's equivalent in
 ECMAScript notation

---
 src/modules/esm.mjs | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100644 src/modules/esm.mjs

diff --git a/src/modules/esm.mjs b/src/modules/esm.mjs
new file mode 100644
index 0000000000..95c3e9ca6b
--- /dev/null
+++ b/src/modules/esm.mjs
@@ -0,0 +1,40 @@
+import path from 'node:path';
+import { release, version } from 'node:os';
+import { createServer as createServerHttp } from 'node:http';
+import { fileURLToPath } from 'node:url';
+
+// Load side-effect CommonJS module
+import './files/c.cjs';
+
+// Emulate __filename and __dirname in ESM
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+
+const random = Math.random();
+
+// Conditional JSON module import using top-level await
+const unknownObject = (
+  await import(random > 0.5 ? './files/a.json' : './files/b.json', { assert: { type: 'json' } })
+).default;
+
+console.log(`Release ${release()}`);
+console.log(`Version ${version()}`);
+console.log(`Path segment separator is "${path.sep}"`);
+
+console.log(`Path to current file is ${__filename}`);
+console.log(`Path to current directory is ${__dirname}`);
+
+const myServer = createServerHttp((_, res) => {
+  res.end('Request accepted');
+});
+
+const PORT = 3000;
+
+console.log(unknownObject);
+
+myServer.listen(PORT, () => {
+  console.log(`Server is listening on port ${PORT}`);
+  console.log('To terminate it, use Ctrl+C combination');
+});
+
+export { unknownObject, myServer };

From cbb8e983018515f78acbcc14bc221d51c179db4e Mon Sep 17 00:00:00 2001
From: Sergeyu <sergeyu@kmslh.com>
Date: Mon, 27 Oct 2025 12:34:16 +0200
Subject: [PATCH 4/8] feat: implement function that calculates SHA256 hash

---
 src/hash/calcHash.js | 42 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 40 insertions(+), 2 deletions(-)

diff --git a/src/hash/calcHash.js b/src/hash/calcHash.js
index e37c17ed62..6da240d466 100644
--- a/src/hash/calcHash.js
+++ b/src/hash/calcHash.js
@@ -1,5 +1,43 @@
+import { createReadStream } from 'node:fs';
+import { createHash } from 'node:crypto';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+// filepath: c:\Users\Sergeyu\IdeaProjects\node-nodejs-basics\src\hash\calcHash.js
 const calculateHash = async () => {
-  // Write your code here
+  const __filename = fileURLToPath(import.meta.url);
+  const __dirname = path.dirname(__filename);
+  const filePath = path.join(__dirname, 'files', 'fileToCalculateHashFor.txt');
+
+  return new Promise((resolve, reject) => {
+    const hash = createHash('sha256');
+    const stream = createReadStream(filePath);
+
+    stream.on('error', (err) => {
+      console.error('Stream error while reading file:', err.message);
+      reject(err);
+    });
+
+    stream.on('data', (chunk) => {
+      hash.update(chunk);
+    });
+
+    stream.on('end', () => {
+      try {
+        const digest = hash.digest('hex');
+        console.log(digest);
+        resolve(digest);
+      } catch (err) {
+        console.error('Hash digest error:', err.message);
+        reject(err);
+      }
+    });
+  });
 };
 
-await calculateHash();
+try {
+  await calculateHash();
+} catch (err) {
+  // Already logged detailed error above; keep outer catch minimal
+  process.exitCode = 1;
+}

From d3e804fa35d636ad7d61fe764c02697f030e4440 Mon Sep 17 00:00:00 2001
From: Sergeyu <sergeyu@kmslh.com>
Date: Mon, 27 Oct 2025 12:38:18 +0200
Subject: [PATCH 5/8] feat: implement several functions in dedicated files
 read.js write.js transform.js

---
 src/streams/read.js      | 26 ++++++++++++++++++++++++--
 src/streams/transform.js | 24 ++++++++++++++++++++++--
 src/streams/write.js     | 26 ++++++++++++++++++++++++--
 3 files changed, 70 insertions(+), 6 deletions(-)

diff --git a/src/streams/read.js b/src/streams/read.js
index e3938be563..39b1d41f76 100644
--- a/src/streams/read.js
+++ b/src/streams/read.js
@@ -1,5 +1,27 @@
+import { createReadStream } from 'node:fs';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { pipeline } from 'node:stream';
+
 const read = async () => {
-  // Write your code here
+  const __filename = fileURLToPath(import.meta.url);
+  const __dirname = path.dirname(__filename);
+  const filePath = path.join(__dirname, 'files', 'fileToRead.txt');
+
+  await new Promise((resolve, reject) => {
+    pipeline(createReadStream(filePath), process.stdout, (err) => {
+      if (err) {
+        reject(err);
+      } else {
+        resolve();
+      }
+    });
+  });
 };
 
-await read();
+try {
+  await read();
+} catch (e) {
+  console.error('Stream read error:', e.message);
+  process.exitCode = 1;
+}
diff --git a/src/streams/transform.js b/src/streams/transform.js
index 9e6c15fe84..8954e79ec3 100644
--- a/src/streams/transform.js
+++ b/src/streams/transform.js
@@ -1,5 +1,25 @@
+import { Transform, pipeline } from 'node:stream';
+
+const reverseTransform = new Transform({
+  transform(chunk, _enc, callback) {
+    // Reverse the chunk string and push
+    const reversed = chunk.toString().split('').reverse().join('');
+    this.push(reversed);
+    callback();
+  }
+});
+
 const transform = async () => {
-  // Write your code here
+  await new Promise((resolve, reject) => {
+    pipeline(process.stdin, reverseTransform, process.stdout, (err) => {
+      if (err) reject(err); else resolve();
+    });
+  });
 };
 
-await transform();
+try {
+  await transform();
+} catch (e) {
+    console.error('Stream transform error:', e.message);
+    process.exitCode = 1;
+}
diff --git a/src/streams/write.js b/src/streams/write.js
index 84aa11e7cb..86dd586d96 100644
--- a/src/streams/write.js
+++ b/src/streams/write.js
@@ -1,5 +1,27 @@
+import { createWriteStream } from 'node:fs';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { pipeline } from 'node:stream';
+
 const write = async () => {
-  // Write your code here
+  const __filename = fileURLToPath(import.meta.url);
+  const __dirname = path.dirname(__filename);
+  const filePath = path.join(__dirname, 'files', 'fileToWrite.txt');
+
+  await new Promise((resolve, reject) => {
+    pipeline(process.stdin, createWriteStream(filePath, { flags: 'w' }), (err) => {
+      if (err) {
+        reject(err);
+      } else {
+        resolve();
+      }
+    });
+  });
 };
 
-await write();
+try {
+  await write();
+} catch (e) {
+  console.error('Stream write error:', e.message);
+  process.exitCode = 1;
+}

From 13cc4a5469ebc74cf683b4c3b0c0fcd2630757c8 Mon Sep 17 00:00:00 2001
From: Sergeyu <sergeyu@kmslh.com>
Date: Mon, 27 Oct 2025 12:48:52 +0200
Subject: [PATCH 6/8] feat: implement several functions in dedicated files that
  compresses and decompresses using zlib

---
 src/zip/compress.js   | 31 +++++++++++++++++++++++++++++--
 src/zip/decompress.js | 31 +++++++++++++++++++++++++++++--
 2 files changed, 58 insertions(+), 4 deletions(-)

diff --git a/src/zip/compress.js b/src/zip/compress.js
index d55209587e..36ef16139d 100644
--- a/src/zip/compress.js
+++ b/src/zip/compress.js
@@ -1,5 +1,32 @@
+import { createReadStream, createWriteStream } from 'node:fs';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { pipeline } from 'node:stream';
+import { createGzip } from 'node:zlib';
+
 const compress = async () => {
-  // Write your code here
+  const __filename = fileURLToPath(import.meta.url);
+  const __dirname = path.dirname(__filename);
+  const sourcePath = path.join(__dirname, 'files', 'fileToCompress.txt');
+  const destPath = path.join(__dirname, 'files', 'archive.gz');
+
+  const gzip = createGzip();
+
+  await new Promise((resolve, reject) => {
+    pipeline(
+      createReadStream(sourcePath),
+      gzip,
+      createWriteStream(destPath, { flags: 'w' }),
+      (err) => {
+        if (err) reject(err); else resolve();
+      }
+    );
+  });
 };
 
-await compress();
+try {
+  await compress();
+} catch (e) {
+  console.error('Compression error:', e.message);
+  process.exitCode = 1;
+}
diff --git a/src/zip/decompress.js b/src/zip/decompress.js
index 8aaf26c8a4..537d55063b 100644
--- a/src/zip/decompress.js
+++ b/src/zip/decompress.js
@@ -1,5 +1,32 @@
+import { createReadStream, createWriteStream } from 'node:fs';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { pipeline } from 'node:stream';
+import { createGunzip } from 'node:zlib';
+
 const decompress = async () => {
-  // Write your code here
+  const __filename = fileURLToPath(import.meta.url);
+  const __dirname = path.dirname(__filename);
+  const sourcePath = path.join(__dirname, 'files', 'archive.gz');
+  const destPath = path.join(__dirname, 'files', 'fileToCompress.txt');
+
+  const gunzip = createGunzip();
+
+  await new Promise((resolve, reject) => {
+    pipeline(
+      createReadStream(sourcePath),
+      gunzip,
+      createWriteStream(destPath, { flags: 'w' }),
+      (err) => {
+        if (err) reject(err); else resolve();
+      }
+    );
+  });
 };
 
-await decompress();
+try {
+  await decompress();
+} catch (e) {
+  console.error('Decompression error:', e.message);
+  process.exitCode = 1;
+}

From 2db08fcf54c7fbfa9fecc345e9c1173c5de023fb Mon Sep 17 00:00:00 2001
From: Sergeyu <sergeyu@kmslh.com>
Date: Mon, 27 Oct 2025 12:55:43 +0200
Subject: [PATCH 7/8] feat: implement several functions with worker threads

---
 src/wt/main.js   | 44 +++++++++++++++++++++++++++++++++++++++++++-
 src/wt/worker.js |  7 +++++++
 2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/src/wt/main.js b/src/wt/main.js
index e2ef054d41..86314fbb25 100644
--- a/src/wt/main.js
+++ b/src/wt/main.js
@@ -1,5 +1,47 @@
+import { cpus } from 'node:os';
+import { Worker } from 'node:worker_threads';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
 const performCalculations = async () => {
-  // Write your code here
+  const __filename = fileURLToPath(import.meta.url);
+  const __dirname = path.dirname(__filename);
+  const workerFile = path.join(__dirname, 'worker.js');
+
+  const coreCount = Math.max(1, cpus().length);
+
+  const promises = [];
+  for (let i = 0; i < coreCount; i++) {
+    const n = 10 + i;
+    promises.push(new Promise((resolve) => {
+      let settled = false;
+      const worker = new Worker(workerFile, { workerData: n });
+
+      worker.on('message', (value) => {
+        if (!settled) {
+          settled = true;
+          resolve({ status: 'resolved', data: value });
+        }
+      });
+
+      worker.on('error', () => {
+        if (!settled) {
+          settled = true;
+          resolve({ status: 'error', data: null });
+        }
+      });
+
+      worker.on('exit', (code) => {
+        if (!settled && code !== 0) {
+          settled = true;
+          resolve({ status: 'error', data: null });
+        }
+      });
+    }));
+  }
+
+  const results = await Promise.all(promises);
+  console.log(results);
 };
 
 await performCalculations();
diff --git a/src/wt/worker.js b/src/wt/worker.js
index 405595394d..66e1ca32b8 100644
--- a/src/wt/worker.js
+++ b/src/wt/worker.js
@@ -1,8 +1,15 @@
 // n should be received from main thread
+import { parentPort, workerData } from 'node:worker_threads';
+
 const nthFibonacci = (n) => n < 2 ? n : nthFibonacci(n - 1) + nthFibonacci(n - 2);
 
 const sendResult = () => {
   // This function sends result of nthFibonacci computations to main thread
+  if (typeof workerData !== 'number' || Number.isNaN(workerData)) {
+    throw new Error('Invalid workerData: expected a number');
+  }
+  const result = nthFibonacci(workerData);
+  parentPort.postMessage(result);
 };
 
 sendResult();

From c73e249c29e55453c0ddfc86338fd2c7ff608e9e Mon Sep 17 00:00:00 2001
From: Sergeyu <sergeyu@kmslh.com>
Date: Mon, 27 Oct 2025 13:10:21 +0200
Subject: [PATCH 8/8] feat: implement function spawnChildProcess

---
 src/cp/cp.js | 38 +++++++++++++++++++++++++++++++++++---
 1 file changed, 35 insertions(+), 3 deletions(-)

diff --git a/src/cp/cp.js b/src/cp/cp.js
index 72c6addc9c..ab5a6eecaf 100644
--- a/src/cp/cp.js
+++ b/src/cp/cp.js
@@ -1,6 +1,38 @@
-const spawnChildProcess = async (args) => {
-  // Write your code here
+import { spawn } from 'node:child_process';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+
+const spawnChildProcess = async (args = []) => {
+  // Resolve path to the script we want to run
+  const scriptPath = path.join(__dirname, 'files', 'script.js');
+
+  // Ensure args is an array
+  const normalizedArgs = Array.isArray(args) ? args.map(String) : [];
+
+  // Spawn a new Node.js process executing the script with provided arguments
+  const child = spawn(process.execPath, [scriptPath, ...normalizedArgs], {
+    stdio: ['pipe', 'pipe', 'inherit'], // pipe stdin & stdout, inherit stderr
+  });
+
+  // Pipe master stdin to child stdin, and child stdout back to master stdout
+  process.stdin.pipe(child.stdin);
+  child.stdout.pipe(process.stdout);
+
+  // Optional: handle errors for visibility
+  child.on('error', (err) => {
+    console.error('Child process error:', err);
+  });
+
+  // Return a promise that resolves on child exit (so caller can await if desired)
+  return new Promise((resolve) => {
+    child.on('exit', (code, signal) => {
+      resolve({ code, signal });
+    });
+  });
 };
 
 // Put your arguments in function call to test this functionality
-spawnChildProcess( /* [someArgument1, someArgument2, ...] */);
+await spawnChildProcess(['value1', '1337', '42']);