/*
Copyright 2024 New Vector Ltd.
Copyright 2019 The Matrix.org Foundation C.I.C

SPDX-License-Identifier: AGPL-3.0-only
Please see LICENSE in the repository root for full details.
 */

import UIKit
import AVFoundation

/// MXKVideoThumbnailGenerator is a utility class to generate a thumbnail image from a video file.
@objcMembers
public class MXKVideoThumbnailGenerator: NSObject {
    
    public static let shared = MXKVideoThumbnailGenerator()
    
    // MARK - Public
    
    /// Generate thumbnail image from a video URL.
    /// Note: Do not make `maximumSize` optional with default nil value for Objective-C compatibility.
    ///
    /// - Parameters:
    ///   - url: Video URL.
    ///   - maximumSize: Maximum dimension for generated thumbnail image.
    /// - Returns: Thumbnail image or nil.
    public func generateThumbnail(from url: URL, with maximumSize: CGSize) -> UIImage? {
        let finalSize: CGSize? = maximumSize != .zero ? maximumSize : nil
        return self.generateThumbnail(from: url, with: finalSize)
    }    
    
    /// Generate thumbnail image from a video URL.
    ///
    /// - Parameter url: Video URL.
    /// - Returns: Thumbnail image or nil.
    public func generateThumbnail(from url: URL) -> UIImage? {
        return generateThumbnail(from: url, with: nil)
    }
    
    // MARK - Private
    
    /// Generate thumbnail image from a video URL.
    ///
    /// - Parameters:
    ///   - url: Video URL.
    ///   - maximumSize: Maximum dimension for generated thumbnail image or nil to keep video dimension.
    /// - Returns: Thumbnail image or nil.
    private func generateThumbnail(from url: URL, with maximumSize: CGSize?) -> UIImage? {
        let thumbnailImage: UIImage?
        
        let asset = AVAsset(url: url)
        let assetImageGenerator = AVAssetImageGenerator(asset: asset)
        assetImageGenerator.appliesPreferredTrackTransform = true
        if let maximumSize = maximumSize {
            assetImageGenerator.maximumSize = maximumSize
        }
        do {
            // Generate thumbnail from first video image
            let image = try assetImageGenerator.copyCGImage(at: .zero, actualTime: nil)
            thumbnailImage = UIImage(cgImage: image)
        } catch {
            MXLog.error("[MXKVideoThumbnailGenerator] generateThumbnail:", context: error)
            thumbnailImage = nil
        }
        
        return thumbnailImage
    }
}