Challenge 21 - Create your own sed (#32)

* Completed step 1 with tests for challenge 21 - Write your own sed

* Completed step 2 - support for range of lines using `-n`

* completed step 3 - added support for pattern with `-n` option

* Completed step 4 - added support for `G` option - double spacing a file

* added feature for stripping trailing blank lines

* Updated whole sed. Added functionality for `-i` option

1. Using a custom parser to parse the command line args
2. Added control checks for valid and invalid args
3. Added support for in place option

* Added jsdoc. Updated tests

* Added link to challenge 21 in global README

* Added readme, fixed test

Author: jainmohit2001

README.md

@@ -39,6 +39,7 @@ Checkout my [Notion](https://mohitjain.notion.site/Coding-Challenges-af9b8197a43
 18. [Write Your Own Spotify Client](https://github.com/jainmohit2001/spotify-client)
 19. [Write Your Own Discord Bot](src/19/)
 20. [Write Your Own LinkedIn Carousel Generator](https://github.com/jainmohit2001/carousel-gen)
+21. [Write Your Own Sed](src/21/)
 
 ## Installation
 

jest.config.js

@@ -8,7 +8,7 @@ module.exports = {
     '^.+\\.(ts|tsx)$': 'ts-jest'
   },
   verbose: true,
-  coverageDirectory: './coverage',
+  coverageDirectory: '<rootDir>/coverage',
   collectCoverage: true,
   detectOpenHandles: true,
   silent: false

src/21/README.md

@@ -0,0 +1,51 @@
+# Challenge 1 - Write Your Own Sed
+
+This challenge corresponds to the 21<sup>st</sup> part of the Coding Challenges series by John Crickett https://codingchallenges.fyi/challenges/challenge-sed.
+
+## Description
+
+The Sed tool is written in `sed.ts`. The tool is used to perform basic text transformations on an input stream (a file or input from stdin).
+
+## Usage
+
+You can use `ts-node` to run the tool as follows:
+
+```bash
+# Substitute <this> for <that> everywhere <this> appears in the file <filename>
+npx ts-node sed.ts s/<this>/<that>/g <filename>
+
+# Print lines 2 to 4 from file <filename>
+npx ts-node sed.ts -n "2,4p" <filename>
+
+# Output only lines containing a specific pattern <pattern> from file <filename>
+npx ts-node sed.ts -n /pattern/p <filename>
+
+# Add another line after each line, i.e. double spacing a file.
+npx ts-node sed.ts G <filename>
+
+# Edit in-place: Substitute <this> for <that> everywhere <this> appears in the file <filename>
+npx ts-node sed.ts -i 's/<this>/<that>/g' <filename>
+```
+
+The following options are supported:
+
+- Character replacement
+- Range of lines selection
+- Output only lines containing a specific pattern
+- Double spacing a file using option
+- Strip trailing blank lines from a file
+- Edit in-place
+
+To use the tool in stdin mode, use the following command:
+
+```bash
+cat filename | npx ts-node sed.ts [option]
+```
+
+## Run tests
+
+To run the tests for the Sed tool, go to the root directory of this repository and run the following command:
+
+```bash
+npm test src/21/
+```

src/21/__tests__/sed.test.ts

@@ -0,0 +1,225 @@
+import { spawn } from 'child_process';
+import path from 'path';
+import fs from 'fs';
+import os from 'os';
+import { randomBytes } from 'crypto';
+
+const PATH_TO_SED_JS = './build/21/sed.js';
+const filename = path.join(__dirname, 'test.txt');
+
+describe('Testing invalid args', () => {
+  const args = [
+    [PATH_TO_SED_JS],
+    [PATH_TO_SED_JS, 'invalid-pattern', 'invalid-file.txt']
+  ];
+
+  args.forEach((arg) => {
+    it('should print usage for args: ' + args.toString(), (done) => {
+      const sed = spawn('node', arg);
+      let output = '';
+
+      sed.stdout.on('data', (data) => {
+        output += data.toString();
+      });
+
+      sed.on('close', () => {
+        expect(output).toContain('Usage');
+        done();
+      });
+    });
+  });
+
+  it('should print invalid file with valid pattern', (done) => {
+    const sed = spawn('node', [
+      PATH_TO_SED_JS,
+      's/this/that/',
+      'invalid-file.txt'
+    ]);
+
+    let output = '';
+    sed.stderr.on('data', (data) => {
+      output += data.toString();
+    });
+
+    sed.on('close', () => {
+      expect(output).toContain('Invalid file');
+      done();
+    });
+  });
+
+  it('should print "Invalid pattern or range"', (done) => {
+    const sed = spawn('node', [
+      PATH_TO_SED_JS,
+      '-n',
+      '2,4',
+      'invalid-file.txt'
+    ]);
+    let output = '';
+
+    sed.stderr.on('data', (data) => {
+      output += data.toString();
+    });
+
+    sed.on('close', () => {
+      expect(output).toContain('Invalid pattern or range');
+      done();
+    });
+  });
+
+  it('should print invalid file with valid range', (done) => {
+    const sed = spawn('node', [
+      PATH_TO_SED_JS,
+      '-n',
+      '2,4p',
+      'invalid-file.txt'
+    ]);
+    let output = '';
+
+    sed.stderr.on('data', (data) => {
+      output += data.toString();
+    });
+
+    sed.on('close', () => {
+      expect(output).toContain('Invalid file');
+      done();
+    });
+  });
+});
+
+describe('Testing valid args', () => {
+  it('should replace all occurrences', (done) => {
+    const pattern = 's/a/b/';
+    const content = fs.readFileSync(filename).toString();
+    const expectedOutput = content.replaceAll('a', 'b');
+
+    const sed = spawn('node', [PATH_TO_SED_JS, pattern, filename]);
+    let output = '';
+
+    sed.stdout.on('data', (data) => {
+      output += data.toString();
+    });
+
+    sed.on('close', () => {
+      expect(output).toBe(expectedOutput);
+      done();
+    });
+  });
+
+  it('should print only lines mentioned', (done) => {
+    const [start, end] = [2, 4];
+    const range = `${start},${end}p`;
+    const content = fs.readFileSync(filename).toString();
+    const expectedOutput = content
+      .split(/\r\n|\n/)
+      .slice(start, end + 1)
+      .join('\r\n');
+
+    const sed = spawn('node', [PATH_TO_SED_JS, '-n', range, filename]);
+    let output = '';
+
+    sed.stdout.on('data', (data) => {
+      output += data.toString();
+    });
+
+    sed.on('close', () => {
+      expect(output).toBe(expectedOutput);
+      done();
+    });
+  });
+
+  it('should print line containing the specific pattern only', (done) => {
+    const pattern = 'roads';
+    const content = fs.readFileSync(filename).toString();
+    const expectedOutput: string[] = [];
+    content.split(/\r\n|\n/).forEach((line) => {
+      if (line.indexOf(pattern) >= 0) {
+        expectedOutput.push(line);
+      }
+    });
+    const sed = spawn('node', [
+      PATH_TO_SED_JS,
+      '-n',
+      `/${pattern}/p`,
+      filename
+    ]);
+
+    let output = '';
+
+    sed.stdout.on('data', (data) => {
+      output += data.toString();
+    });
+
+    sed.on('close', () => {
+      expect(output).toBe(expectedOutput.join('\r\n'));
+      done();
+    });
+  });
+
+  it('should double space the file correctly', (done) => {
+    const content = fs.readFileSync(filename).toString();
+    const expectedOutput = content.replaceAll(/\r\n|\n/g, '\r\n\r\n');
+    const sed = spawn('node', [PATH_TO_SED_JS, 'G', filename]);
+
+    let output = '';
+
+    sed.stdout.on('data', (data) => {
+      output += data.toString();
+    });
+
+    sed.on('close', () => {
+      expect(output).toBe(expectedOutput);
+      done();
+    });
+  });
+
+  it('should remove trailing blank lines from a file', (done) => {
+    const content = 'content\r\nsome more content    ';
+    const tmpfile = path.join(os.tmpdir(), 'temp-file.txt');
+    fs.writeFileSync(tmpfile, content + '\r\n\r\n\r\n');
+    const sed = spawn('node', [PATH_TO_SED_JS, '/^$/d', tmpfile]);
+
+    let output = '';
+
+    sed.stdout.on('data', (data) => {
+      output += data.toString();
+    });
+
+    sed.on('close', () => {
+      expect(output).toBe(content.trimEnd());
+      done();
+    });
+  });
+
+  it('should support -i option', (done) => {
+    // First create a random test file from the `test.txt`
+    const tempTextFile = path.join(__dirname, randomBytes(8).toString('hex'));
+    fs.writeFileSync(tempTextFile, fs.readFileSync(filename));
+
+    // Prepare args
+    const stringToReplace = 'Life';
+    const stringToReplaceWith = 'Code';
+    const characterReplacementInput = `s/${stringToReplace}/${stringToReplaceWith}/g`;
+
+    const initialContent = fs.readFileSync(tempTextFile).toString();
+    const expectedContent = initialContent.replaceAll(
+      stringToReplace,
+      stringToReplaceWith
+    );
+
+    const sed = spawn('node', [
+      PATH_TO_SED_JS,
+      '-i',
+      characterReplacementInput,
+      tempTextFile
+    ]);
+
+    sed.on('close', () => {
+      const finalContent = fs.readFileSync(tempTextFile).toString();
+      // Unlink random test file
+      fs.unlinkSync(tempTextFile);
+
+      expect(finalContent).toBe(expectedContent);
+      done();
+    });
+  });
+});

src/21/__tests__/test.txt

@@ -0,0 +1,10 @@
+"Life isn’t about getting and having, it’s about giving and being.",
+"Whatever the mind of man can conceive and believe, it can achieve.",
+"Strive not to be a success, but rather to be of value.",
+"Two roads diverged in a wood, and I—I took the one less traveled by, And that has made all the difference.",
+"I attribute my success to this: I never gave or took any excuse.",
+"You miss 100% of the shots you don’t take.",
+"I’ve missed more than 9000 shots in my career. I’ve lost almost 300 games. 26 times I’ve been trusted to take the game winning shot and missed. I’ve failed over and over and over again in my life. And that is why I succeed.",
+"The most difficult thing is the decision to act, the rest is merely tenacity.",
+"Every strike brings me closer to the next home run.",
+"Definiteness of purpose is the starting point of all achievement."