Refactor cat and wc tools: improve line handling and output formatting

Author: enjoy15

implement-shell-tools/cat/cat.js

@@ -1,7 +1,6 @@
 #!/usr/bin/env node
 
 const fs = require('fs');
-const path = require('path');
 
 function cat(files, options) {
   let lineNumber = 1;
@@ -10,16 +9,23 @@ function cat(files, options) {
     try {
       const data = fs.readFileSync(file, 'utf8');
       const lines = data.split('\n');
+      const hasTrailingNewline = data.endsWith('\n');
+
+      lines.forEach((line, index) => {
+        const isVirtualTrailingLine = hasTrailingNewline && index === lines.length - 1;
+        if (isVirtualTrailingLine) {
+          return;
+        }
 
-      lines.forEach((line) => {
         let prefix = '';
-        if (options.numberNonEmpty && line.trim()) {
-          prefix = `${lineNumber}\t`;
-        } else if (options.numberLines) {
-          prefix = `${lineNumber}\t`;
+        const shouldNumberLine = options.numberLines || (options.numberNonEmpty && line.length > 0);
+        if (shouldNumberLine) {
+          prefix = `${String(lineNumber).padStart(6)}\t`;
+          lineNumber++;
         }
-        console.log(`${prefix}${line}`);
-        if (prefix) lineNumber++;
+
+        const shouldAppendNewline = hasTrailingNewline || index < lines.length - 1;
+        process.stdout.write(`${prefix}${line}${shouldAppendNewline ? '\n' : ''}`);
       });
     } catch (err) {
       if (err.code === 'ENOENT') {

implement-shell-tools/wc/wc.js

@@ -2,28 +2,55 @@
 
 const fs = require('fs');
 
-function countFile(file, options) {
+function countFile(file) {
   try {
     const data = fs.readFileSync(file, 'utf8');
 
-    const lines = data.split('\n').length;
+    const lines = (data.match(/\n/g) || []).length;
     const words = data.split(/\s+/).filter(Boolean).length;
     const bytes = Buffer.byteLength(data, 'utf8');
 
-    const results = [];
-    if (options.lines || (!options.lines && !options.words && !options.bytes)) results.push(lines);
-    if (options.words || (!options.lines && !options.words && !options.bytes)) results.push(words);
-    if (options.bytes || (!options.lines && !options.words && !options.bytes)) results.push(bytes);
-
-    console.log(`${results.join('\t')}\t${file}`);
-
     return { lines, words, bytes };
   } catch (err) {
     console.error(`wc: ${file}: ${err.code === 'ENOENT' ? 'No such file or directory' : 'An error occurred'}`);
     process.exit(1);
   }
 }
 
+function selectedKeys(options) {
+  const keys = [];
+  if (options.lines) keys.push('lines');
+  if (options.words) keys.push('words');
+  if (options.bytes) keys.push('bytes');
+  return keys;
+}
+
+function valuesForKeys(counts, keys) {
+  return keys.map((key) => counts[key]);
+}
+
+function printRows(rows, keys) {
+  const alignColumns = keys.length > 1 || rows.length > 1;
+
+  if (!alignColumns) {
+    const [values, name] = rows[0];
+    console.log(`${values[0]} ${name}`);
+    return;
+  }
+
+  const widths = keys.map((_, index) => {
+    const maxLen = Math.max(...rows.map(([values]) => String(values[index]).length));
+    return Math.max(3, maxLen);
+  });
+
+  rows.forEach(([values, name]) => {
+    const formattedValues = values
+      .map((value, index) => String(value).padStart(widths[index], ' '))
+      .join(' ');
+    console.log(`${formattedValues} ${name}`);
+  });
+}
+
 function main() {
   const args = process.argv.slice(2);
   const options = {
@@ -46,6 +73,12 @@ function main() {
     }
   });
 
+  if (!options.lines && !options.words && !options.bytes) {
+    options.lines = true;
+    options.words = true;
+    options.bytes = true;
+  }
+
   if (files.length === 0) {
     console.error('Usage: wc [-l | -w | -c] <file>...');
     process.exit(1);
@@ -54,22 +87,23 @@ function main() {
   let totalLines = 0;
   let totalWords = 0;
   let totalBytes = 0;
+  const keys = selectedKeys(options);
+  const rows = [];
 
   files.forEach((file) => {
-    const { lines, words, bytes } = countFile(file, options);
+    const counts = countFile(file);
+    const { lines, words, bytes } = counts;
     totalLines += lines;
     totalWords += words;
     totalBytes += bytes;
+    rows.push([valuesForKeys(counts, keys), file]);
   });
 
   if (files.length > 1) {
-    const totalResults = [];
-    if (options.lines || (!options.lines && !options.words && !options.bytes)) totalResults.push(totalLines);
-    if (options.words || (!options.lines && !options.words && !options.bytes)) totalResults.push(totalWords);
-    if (options.bytes || (!options.lines && !options.words && !options.bytes)) totalResults.push(totalBytes);
-
-    console.log(`${totalResults.join('\t')}\ttotal`);
+    rows.push([valuesForKeys({ lines: totalLines, words: totalWords, bytes: totalBytes }, keys), 'total']);
   }
+
+  printRows(rows, keys);
 }
 
 main();