feat: functional download server

using micro

src/logger.js

@@ -0,0 +1,10 @@
+const pino = require('pino');
+
+const LOG_LEVEL = process.env.NODE_ENV === 'production' ? 'info' : 'debug';
+
+const logger = pino({
+  prettyPrint: process.env.NODE_ENV !== 'production',
+  level: LOG_LEVEL,
+});
+
+module.exports = logger;

src/server.js

@@ -1,3 +1,94 @@
-module.exports = function server() {
-  console.log('Server...');
+const path = require('path');
+const fs = require('fs');
+const spawn = require('cross-spawn');
+const logger = require('./logger');
+
+const sendError = (res, code) => {
+  res.writeHeader(code);
+  res.write(code === 400 ? 'Bad Request' : 'Internal Server Error');
+  res.end();
+};
+
+module.exports = async function server(req, res) {
+  let sent = false;
+  let filename;
+  const { url, format } = req.queryParams;
+
+  logger.debug(`Request: ${req.url}`);
+
+  if (!url) {
+    sendError(res, 400);
+    return;
+  }
+
+  const dataPath = path.resolve(__dirname, '../data');
+
+  const params = [url];
+
+  if (format) {
+    params.unshift(format);
+    params.unshift('--format');
+  }
+
+  logger.info(`Downloading ${url}`);
+  const proc = spawn('youtube-dl', params, {
+    stdio: 'pipe',
+    cwd: dataPath,
+  });
+
+  proc.stdout.on('data', data => {
+    const match = data.toString().match(/\[download\] Destination: (.+)/i);
+    const existsMatch = data.toString().match(/\[download\] (.+) has already been downloaded/i);
+
+    if (match !== null) {
+      // eslint-disable-next-line prefer-destructuring
+      filename = match[1];
+    } else if (existsMatch !== null) {
+      // eslint-disable-next-line prefer-destructuring
+      filename = existsMatch[1];
+    }
+  });
+
+  proc.on('error', err => {
+    logger.error(err);
+    logger.info(`child process exited with code ${err.code}`);
+    if (!sent) {
+      sendError(res, 500);
+      sent = true;
+    }
+  });
+
+  proc.on('close', code => {
+    logger.info(`child process exited with code ${code}`);
+
+    if (!filename) {
+      logger.error('Failed to capture download filename');
+      sendError(res, 500);
+      sent = true;
+      return;
+    }
+
+    const dlFilepath = path.join(__dirname, '../data', filename);
+    logger.debug(`Downloaded file is ${dlFilepath}`);
+
+    if (!sent) {
+      fs.readFile(dlFilepath, (err, fileBuffer) => {
+        if (err) {
+          sendError(res, 500);
+          sent = true;
+          return;
+        }
+
+        res.writeHead(200, {
+          'Content-Type': 'application/octet-stream',
+          'Content-Length': fileBuffer.length,
+          'Content-disposition': `attachment; filename=${filename}`,
+        });
+        res.write(fileBuffer);
+        res.end();
+        sent = true;
+      });
+    }
+    sent = true;
+  });
 };