Add exercise grep

Author: TomPradat

exercises/grep/.eslintrc

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+{
+  "root": true,
+  "parser": "babel-eslint",
+  "parserOptions": {
+    "ecmaVersion": 7,
+    "sourceType": "module"
+  },
+  "env": {
+    "es6": true,
+    "node": true,
+    "jest": true
+  },
+  "extends": [
+    "eslint:recommended",
+    "plugin:import/errors",
+    "plugin:import/warnings"
+  ],
+  "rules": {
+    "linebreak-style": "off",
+
+    "import/extensions": "off",
+    "import/no-default-export": "off",
+    "import/no-unresolved": "off",
+    "import/prefer-default-export": "off"
+  }
+}

exercises/grep/babel.config.js

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+module.exports = {
+  presets: [
+    [
+      '@babel/env',
+      {
+        targets: {
+          node: 'current',
+        },
+        useBuiltIns: false,
+      },
+
+    ],
+  ],
+};

exercises/grep/data/iliad.txt

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+Achilles sing, O Goddess! Peleus' son;
+His wrath pernicious, who ten thousand woes
+Caused to Achaia's host, sent many a soul
+Illustrious into Ades premature,
+And Heroes gave (so stood the will of Jove)
+To dogs and to all ravening fowls a prey,
+When fierce dispute had separated once
+The noble Chief Achilles from the son
+Of Atreus, Agamemnon, King of men.

exercises/grep/data/midsummer-night.txt

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+I do entreat your grace to pardon me.
+I know not by what power I am made bold,
+Nor how it may concern my modesty,
+In such a presence here to plead my thoughts;
+But I beseech your grace that I may know
+The worst that may befall me in this case,
+If I refuse to wed Demetrius.

exercises/grep/data/paradise-lost.txt

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+Of Mans First Disobedience, and the Fruit
+Of that Forbidden Tree, whose mortal tast
+Brought Death into the World, and all our woe,
+With loss of Eden, till one greater Man
+Restore us, and regain the blissful Seat,
+Sing Heav'nly Muse, that on the secret top
+Of Oreb, or of Sinai, didst inspire
+That Shepherd, who first taught the chosen Seed

exercises/grep/example.js

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+#!/usr/bin/env node
+const fs = require('fs')
+
+// Helpers
+const availables_options = [
+  'n', // add line numbers
+  'l', // print file names where pattern is found
+  'i', // ignore case
+  'v', // reverse files results
+  'x'  // match entire line 
+];
+
+const does_line_matche_pattern = (line, pattern) => {
+  let left = line;
+  let right = pattern;
+
+  if (is_option_set('i')) {
+    left = line.toLowerCase()
+    right = pattern.toLowerCase()
+  }
+
+  if (is_option_set('x')) {
+    return left === right;
+  }
+
+  return left.match(right) !== null;
+
+}
+
+const getConfigFromArgs = () => {
+  const config = {
+    'pattern': '',
+    'options': [],
+    'files': []
+  };
+
+  let has_pattern_been_found = false;
+
+  process.argv.slice(2).forEach(val => {
+    if (has_pattern_been_found) {
+      config.files.push(val)
+    } else if (val.indexOf('-') !== -1) {
+      const option = val.replace('-', '')
+
+      if (!availables_options.includes(option)) {
+        throw new Error(`Unknown option ${option}`)
+      }
+
+      config.options.push(option)
+    } else {
+      has_pattern_been_found = true
+      config.pattern = val
+    }
+  })
+
+  return config;
+}
+
+const config = getConfigFromArgs()
+const is_option_set = option => config.options.includes(option);
+
+// Actual script
+config.files.forEach(file => {
+  const data = fs.readFileSync(file, { encoding: 'utf-8' })
+
+  if (is_option_set('l')) {
+    data.split('\n').find(line => {
+      const does_line_match_pattern = does_line_matche_pattern(line, config.pattern)
+      
+      return is_option_set('v') ? !does_line_match_pattern : does_line_match_pattern
+    }) && console.log(file)
+  } else {
+    data.split('\n').forEach((line, index) => {
+      let result = '';
+      let should_output_line = does_line_matche_pattern(line, config.pattern);
+  
+      if (is_option_set('v')) {
+        should_output_line = !should_output_line;
+      }
+     
+      if (should_output_line) {
+        if (config.files.length > 1) {
+          result += `${file}:`
+        }
+
+        if (is_option_set('n')) {
+          result += `${index+1}:`;
+        }
+  
+        result += line;
+  
+        console.log(result)
+      }
+    })
+  }
+});