refactor: split downloader into modules

lib/network.js

@@ -0,0 +1,84 @@
+const fs = require('fs');
+const http = require('http');
+const https = require('https');
+
+function getProtocol(url) {
+  return url.startsWith('https') ? https : http;
+}
+
+function fetchJSON(url) {
+  return new Promise((resolve, reject) => {
+    getProtocol(url).get(url, (res) => {
+      let data = '';
+      res.on('data', chunk => data += chunk);
+      res.on('end', () => {
+        try { resolve(JSON.parse(data)); }
+        catch { reject(new Error(`JSON 解析失败: ${data.slice(0, 200)}`)); }
+      });
+    }).on('error', reject);
+  });
+}
+
+function downloadFile(url, dest, showProgress = true) {
+  return new Promise((resolve, reject) => {
+    getProtocol(url).get(url, (res) => {
+      if (res.statusCode >= 300 && res.statusCode < 400 && res.headers.location) {
+        return downloadFile(res.headers.location, dest, showProgress).then(resolve).catch(reject);
+      }
+      if (res.statusCode !== 200) return reject(new Error(`HTTP ${res.statusCode}`));
+
+      const total = parseInt(res.headers['content-length'], 10);
+      let downloaded = 0;
+      let lastTime = Date.now();
+      let lastBytes = 0;
+      const file = fs.createWriteStream(dest);
+
+      res.on('data', (chunk) => {
+        downloaded += chunk.length;
+        if (!showProgress) return;
+        const now = Date.now();
+        const elapsed = (now - lastTime) / 1000;
+        if (elapsed < 0.3) return;
+
+        const speed = (downloaded - lastBytes) / elapsed;
+        lastTime = now;
+        lastBytes = downloaded;
+        const speedStr = speed >= 1048576
+          ? `${(speed / 1048576).toFixed(1)} MB/s`
+          : `${(speed / 1024).toFixed(0)} KB/s`;
+
+        if (total) {
+          const pct = downloaded / total;
+          const barWidth = 30;
+          const filled = Math.round(pct * barWidth);
+          const bar = '█'.repeat(filled) + '░'.repeat(barWidth - filled);
+          const eta = speed > 0 ? Math.ceil((total - downloaded) / speed) : 0;
+          const etaStr = eta > 60 ? `${Math.floor(eta / 60)}m${eta % 60}s` : `${eta}s`;
+          process.stdout.write(`\r  ⬇️  [${bar}] ${(pct * 100).toFixed(1)}%  ${(downloaded / 1048576).toFixed(1)}/${(total / 1048576).toFixed(1)} MB  ${speedStr}  ETA ${etaStr}   `);
+        } else {
+          process.stdout.write(`\r  ⬇️  ${(downloaded / 1048576).toFixed(1)} MB  ${speedStr}   `);
+        }
+      });
+
+      res.pipe(file);
+      file.on('finish', () => { file.close(); if (showProgress) console.log(); resolve(); });
+      file.on('error', (err) => { fs.unlink(dest, () => {}); reject(err); });
+    }).on('error', reject);
+  });
+}
+
+function downloadBuffer(url) {
+  return new Promise((resolve, reject) => {
+    getProtocol(url).get(url, (res) => {
+      if (res.statusCode >= 300 && res.statusCode < 400 && res.headers.location) {
+        return downloadBuffer(res.headers.location).then(resolve).catch(reject);
+      }
+      if (res.statusCode !== 200) return reject(new Error(`HTTP ${res.statusCode}`));
+      const chunks = [];
+      res.on('data', chunk => chunks.push(chunk));
+      res.on('end', () => resolve(Buffer.concat(chunks)));
+    }).on('error', reject);
+  });
+}
+
+module.exports = { fetchJSON, downloadFile, downloadBuffer };