Sora/Sora/Utils/ContinueWatching/DownloadManager.swift

//
//  DownloadManager.swift
//  Sulfur
//
//  Created by Francesco on 29/04/25.
//

import AVFoundation
import AVKit
import SwiftUI

class DownloadManager: NSObject, ObservableObject {
    @Published var activeDownloads: [(URL, Double)] = []
    @Published var localPlaybackURL: URL?

    private var assetDownloadURLSession: AVAssetDownloadURLSession!
    private var activeDownloadTasks: [URLSessionTask: URL] = [:]

    override init() {
        super.init()
        initializeDownloadSession()
        loadLocalContent()
    }

    private func initializeDownloadSession() {
        let configuration = URLSessionConfiguration.background(withIdentifier: "hls-downloader")
        assetDownloadURLSession = AVAssetDownloadURLSession(
            configuration: configuration,
            assetDownloadDelegate: self,
            delegateQueue: .main
        )
    }

    func downloadAsset(from url: URL) {
        let asset = AVURLAsset(url: url)
        let task = assetDownloadURLSession.makeAssetDownloadTask(
            asset: asset,
            assetTitle: "Offline Video",
            assetArtworkData: nil,
            options: nil
        )

        task?.resume()
        activeDownloadTasks[task!] = url
    }

    private func loadLocalContent() {
        guard let documents = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first else { return }

        do {
            let contents = try FileManager.default.contentsOfDirectory(
                at: documents,
                includingPropertiesForKeys: nil,
                options: .skipsHiddenFiles
            )

            if let localURL = contents.first(where: { $0.pathExtension == "movpkg" }) {
                localPlaybackURL = localURL
            }
        } catch {
            print("Error loading local content: \(error)")
        }
    }
}

extension DownloadManager: AVAssetDownloadDelegate {
    func urlSession(
        _ session: URLSession,
        assetDownloadTask: AVAssetDownloadTask,
        didFinishDownloadingTo location: URL
    ) {
        activeDownloadTasks.removeValue(forKey: assetDownloadTask)
        localPlaybackURL = location
    }

    func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
        guard let error else { return }
        print("Download error: \(error.localizedDescription)")
        activeDownloadTasks.removeValue(forKey: task)
    }

    func urlSession(
        _ session: URLSession,
        assetDownloadTask: AVAssetDownloadTask,
        didLoad timeRange: CMTimeRange,
        totalTimeRangesLoaded loadedTimeRanges: [NSValue],
        timeRangeExpectedToLoad: CMTimeRange
    ) {
        guard let url = activeDownloadTasks[assetDownloadTask] else { return }
        let progress = loadedTimeRanges
            .map { $0.timeRangeValue.duration.seconds / timeRangeExpectedToLoad.duration.seconds }
            .reduce(0, +)

        if let index = activeDownloads.firstIndex(where: { $0.0 == url }) {
            activeDownloads[index].1 = progress
        } else {
            activeDownloads.append((url, progress))
        }
    }
}