Fix download from URL for Google Drive and Dropbox

For URLs to download books in Google Drive and Dropbox, the URL provided
by the user needs to be fixed up before a download can be attempted.

Tested book download from Google Drive and Dropbox URLs for individual
files and zip files.

Fixes: #1077
Signed-off-by: Nithya Vasudevan <[email protected]>

BookPlayer/Library/ItemList Screen/ItemListViewModel.swift

@@ -925,7 +925,7 @@ class ItemListViewModel: ViewModelProtocol {
           BPActionItem(
             title: "download_title".localized,
             inputHandler: { [weak self] url in
-              if let bookUrl = URL(string: url) {
+              if let bookUrl = self?.getDownloadURL(for: url) {
                 self?.handleDownload(bookUrl)
               } else {
                 self?.sendEvent(.showAlert(
@@ -1311,6 +1311,43 @@ extension ItemListViewModel {
       )
     ))
   }
+
+  func getDownloadURL(for givenString : String) -> URL? {
+    let givenUrl = URL(string: givenString)
+
+    if let givenUrl, let hostname = givenUrl.host {
+      if hostname == "drive.google.com" {
+        return getGoogleDriveURL(for: givenUrl)
+      } else if hostname == "www.dropbox.com" {
+        return getDropboxURL(for: givenUrl)
+      }
+    }
+    return nil
+  }
+
+  func getGoogleDriveURL(for url: URL) -> URL?
+  {
+    let pathComponents = url.pathComponents
+    if let index = pathComponents.firstIndex(of: "d"), index + 1 < pathComponents.count {
+      return URL(string: "https://drive.google.com/uc?export=download&id=" + pathComponents[index + 1])
+    }
+    return nil;
+  }
+
+  func getDropboxURL (for url : URL) -> URL?
+  {
+    guard var urlComponents = URLComponents(url: url, resolvingAgainstBaseURL: false) else {
+        return nil
+    }
+    var queryItems = urlComponents.queryItems ?? []
+    if let index = queryItems.firstIndex(where: {$0.name == "dl"}) {
+      queryItems[index].value = "1"
+    } else {
+      queryItems.append(URLQueryItem(name: "dl", value: "1"))
+    }
+    urlComponents.queryItems = queryItems
+    return urlComponents.url
+  }
 }
 
 extension ItemListViewModel: AlertPresenter {