Refactor web CLI into focused modules (#1837)

packages/web/bin/lib/cli-log-files.js

@@ -0,0 +1,93 @@
+import fs from 'fs';
+
+const DEFAULT_TAIL_LINES = 200;
+const LOG_ROTATE_MAX_BYTES = 10 * 1024 * 1024;
+const LOG_ROTATE_KEEP = 5;
+
+function rotateLogFile(logPath) {
+  try {
+    const stats = fs.statSync(logPath);
+    if (stats.size < LOG_ROTATE_MAX_BYTES) {
+      return;
+    }
+  } catch {
+    return;
+  }
+
+  for (let i = LOG_ROTATE_KEEP - 1; i >= 1; i--) {
+    const src = `${logPath}.${i}`;
+    const dst = `${logPath}.${i + 1}`;
+    if (fs.existsSync(src)) {
+      try {
+        fs.renameSync(src, dst);
+      } catch {
+      }
+    }
+  }
+
+  try {
+    if (fs.existsSync(logPath)) {
+      fs.renameSync(logPath, `${logPath}.1`);
+    }
+  } catch {
+  }
+}
+
+
+function readTailLines(filePath, lineCount = DEFAULT_TAIL_LINES) {
+  if (!fs.existsSync(filePath)) {
+    return [];
+  }
+  const raw = fs.readFileSync(filePath, 'utf8');
+  const lines = raw.split(/\r?\n/);
+  if (lines.length && lines[lines.length - 1] === '') {
+    lines.pop();
+  }
+  return lines.slice(Math.max(0, lines.length - lineCount));
+}
+
+function followFile(filePath, onLine) {
+  let position = 0;
+  try {
+    position = fs.statSync(filePath).size;
+  } catch {
+    position = 0;
+  }
+
+  let remainder = '';
+  const interval = setInterval(() => {
+    try {
+      const stats = fs.statSync(filePath);
+      if (stats.size < position) {
+        position = 0;
+      }
+      if (stats.size === position) {
+        return;
+      }
+
+      const fd = fs.openSync(filePath, 'r');
+      try {
+        const length = stats.size - position;
+        const buffer = Buffer.alloc(length);
+        fs.readSync(fd, buffer, 0, length, position);
+        position = stats.size;
+        const chunk = remainder + buffer.toString('utf8');
+        const parts = chunk.split(/\r?\n/);
+        remainder = parts.pop() || '';
+        for (const line of parts) {
+          onLine(line);
+        }
+      } finally {
+        fs.closeSync(fd);
+      }
+    } catch {
+    }
+  }, 400);
+
+  return () => {
+    clearInterval(interval);
+  };
+}
+
+
+export { rotateLogFile, readTailLines, followFile };