pref(downloadInfo): optimize requests

Author: ido-pluto

README.md

@@ -56,7 +56,11 @@ import {downloadFileBrowser} from "ipull/dist/browser.js";
 
 const downloader = await downloadFileBrowser({
     url: 'https://example.com/file.large',
-    acceptRangeIsKnown: true // cors origin request will not return the range header, but we can force it to be true (multi-connection download)
+    acceptRangeIsKnown: true, // cors origin request will not return the range header, but we can force it to be true (multi-connection download)
+    // defaultFetchDownloadInfo: { // if we know the file size and other info, we can set it manually to overcome CORS issues && prevent multiple requests
+    //     acceptRanges: true,
+    //     length: 40789822,
+    // }
 });
 
 await downloader.download();

src/download/download-engine/streams/download-engine-fetch-stream/download-engine-fetch-stream-fetch.ts

@@ -101,8 +101,14 @@ export default class DownloadEngineFetchStreamFetch extends BaseDownloadEngineFe
         const fileName = parseContentDisposition(response.headers.get("content-disposition"));
 
         let length = parseInt(response.headers.get("content-length")!) || 0;
-        if (response.headers.get("content-encoding") || browserCheck() && MIN_LENGTH_FOR_MORE_INFO_REQUEST < length) {
-            length = acceptRange ? await this.fetchDownloadInfoWithoutRetryContentRange(url, method === "GET" ? response : undefined) : 0;
+        const contentEncoding = response.headers.get("content-encoding");
+
+        if (contentEncoding && contentEncoding !== "identity") {
+            length = 0; // If content is encoded, we cannot determine the length reliably
+        }
+
+        if (acceptRange && length === 0 && browserCheck() && MIN_LENGTH_FOR_MORE_INFO_REQUEST < length) {
+            length = await this.fetchDownloadInfoWithoutRetryContentRange(url, method === "GET" ? response : undefined);
         }
 
         return {

src/download/download-engine/streams/download-engine-fetch-stream/download-engine-fetch-stream-xhr.ts

@@ -204,14 +204,22 @@ export default class DownloadEngineFetchStreamXhr extends BaseDownloadEngineFetc
 
             xhr.onload = async () => {
                 if (xhr.status >= 200 && xhr.status < 300) {
-                    const contentLength = parseInt(xhr.getResponseHeader("content-length")!);
-                    const length = MIN_LENGTH_FOR_MORE_INFO_REQUEST < contentLength ? await this.fetchDownloadInfoWithoutRetryContentRange(url, method === "GET" ? xhr : undefined) : 0;
                     const fileName = parseContentDisposition(xhr.getResponseHeader("content-disposition"));
                     const acceptRange = this.options.acceptRangeIsKnown ?? xhr.getResponseHeader("Accept-Ranges") === "bytes";
+                    const contentEncoding = xhr.getResponseHeader("content-encoding");
+
+                    let length = parseInt(xhr.getResponseHeader("content-length")!) || 0;
+                    if (contentEncoding && contentEncoding !== "identity") {
+                        length = 0; // If content is encoded, we cannot determine the length reliably
+                    }
+
+                    if (acceptRange && length === 0 && MIN_LENGTH_FOR_MORE_INFO_REQUEST < length) {
+                        length = await this.fetchDownloadInfoWithoutRetryContentRange(url, method === "GET" ? xhr : undefined);
+                    }
 
                     resolve({
-                        length,
                         acceptRange,
+                        length,
                         newURL: xhr.responseURL,
                         fileName
                     });