Complete the cat implementation

Author: anosidium

implement-shell-tools/cat/cat.mjs

@@ -10,3 +10,53 @@ program.parse();
 
 const { number, numberNonblank } = program.opts();
 const paths = program.args;
+
+async function processFile(path) {
+  try {
+    const stat = await fs.stat(path);
+
+    if (stat.isDirectory()) {
+      console.error(`${path}: Is a directory`);
+      return;
+    }
+
+    const content = await fs.readFile(path, { encoding: "utf-8" });
+    const lines = content.split("\n");
+    const hasTrailingNewLine = content.endsWith("\n");
+    const effectiveLines = hasTrailingNewLine ? lines.slice(0, -1) : lines;
+    let lineNumber = 1;
+
+    const processed = effectiveLines.map((line) => {
+      if (numberNonblank) {
+        if (line.trim() !== "") {
+          const result = `${lineNumber}\t${line}`;
+          lineNumber += 1;
+          return result;
+        }
+
+        return line;
+      }
+
+      if (number) {
+        const result = `${lineNumber}\t${line}`;
+        lineNumber += 1;
+        return result;
+      }
+
+      return line;
+    });
+
+    const output = processed.join("\n");
+    console.log(output);
+  } catch (error) {
+    console.error(`${path}: ${error.message}`);
+  }
+}
+
+try {
+  for (const path of paths) {
+    await processFile(path);
+  }
+} catch (error) {
+  console.error(error.message);
+}