space-ios/File Provider Extension/FileProviderExtension+Thumbnail.swift

//
//  FileProviderExtension+Thumbnail.swift
//  PickerFileProvider
//
//  Created by Marino Faggiana on 28/05/18.
//  Copyright © 2018 Marino Faggiana. All rights reserved.
//
//  Author Marino Faggiana <marino.faggiana@nextcloud.com>
//
//  This program is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program.  If not, see <http://www.gnu.org/licenses/>.
//

import UIKit
import FileProvider
import NextcloudKit

extension FileProviderExtension {

    override func fetchThumbnails(for itemIdentifiers: [NSFileProviderItemIdentifier], requestedSize size: CGSize, perThumbnailCompletionHandler: @escaping (NSFileProviderItemIdentifier, Data?, Error?) -> Void, completionHandler: @escaping (Error?) -> Void) -> Progress {

        let progress = Progress(totalUnitCount: Int64(itemIdentifiers.count))
        var counterProgress: Int64 = 0

        for itemIdentifier in itemIdentifiers {

            guard let metadata = fileProviderUtility.shared.getTableMetadataFromItemIdentifier(itemIdentifier) else {
                counterProgress += 1
                if counterProgress == progress.totalUnitCount { completionHandler(nil) }
                continue
            }

            if metadata.hasPreview {

                let fileNamePath = CCUtility.returnFileNamePath(fromFileName: metadata.fileName, serverUrl: metadata.serverUrl, urlBase: metadata.urlBase, userId: metadata.userId, account: metadata.account)!
                let fileNameIconLocalPath = CCUtility.getDirectoryProviderStorageIconOcId(metadata.ocId, etag: metadata.etag)!

                if let urlBase = metadata.urlBase.urlEncoded,
                   let fileNamePath = fileNamePath.urlEncoded,
                   let url = URL(string: "\(urlBase)/index.php/core/preview.png?file=\(fileNamePath)&x=\(size.width)&y=\(size.height)&a=1&mode=cover") {

                    NextcloudKit.shared.getPreview(url: url) { _, data, error in
                        if error == .success && data != nil {
                            do {
                                try data!.write(to: URL(fileURLWithPath: fileNameIconLocalPath), options: .atomic)
                            } catch { }
                            perThumbnailCompletionHandler(itemIdentifier, data, nil)
                        } else {
                            perThumbnailCompletionHandler(itemIdentifier, nil, NSFileProviderError(.serverUnreachable))
                        }
                        counterProgress += 1
                        if counterProgress == progress.totalUnitCount {
                            completionHandler(nil)
                        }
                    }
                }

            } else {
                counterProgress += 1
                if counterProgress == progress.totalUnitCount {
                    completionHandler(nil)
                }
            }
        }

        return progress
    }

}