import Foundation

struct PlaybackProgress {
    struct RecentMedia: Equatable, Identifiable {
        let url: URL
        let title: String
        var id: URL { url }
    }

    private let defaults: UserDefaults

    init(defaults: UserDefaults = .standard) {
        self.defaults = defaults
        // Migrate the old shared dictionary once; separate keys prevent cross-player lost updates.
        if let positions = defaults.dictionary(forKey: "playbackPositions") as? [String: Double] {
            for (identity, position) in positions where position.isFinite && position > 0 {
                let key = "playbackPosition:" + identity
                if defaults.object(forKey: key) == nil { defaults.set(position, forKey: key) }
            }
            defaults.removeObject(forKey: "playbackPositions")
        }
    }

    func position(for url: URL) -> Double? {
        guard let position = defaults.object(forKey: key(for: url)) as? Double,
              position.isFinite, position > 0 else { return nil }
        return position
    }

    func save(_ position: Double?, for url: URL) {
        let key = key(for: url)
        let position = position.flatMap { $0.isFinite && $0 > 0 ? $0 : nil }
        guard (defaults.object(forKey: key) as? Double) != position else { return }
        defaults.set(position, forKey: key)
    }

    var recentMedia: [RecentMedia] {
        (defaults.array(forKey: "recentMedia") as? [[String: String]] ?? []).compactMap {
            guard let text = $0["url"], let url = URL(string: text), let title = $0["title"] else { return nil }
            return RecentMedia(url: url, title: title)
        }
    }

    func recordRecent(_ url: URL, title: String) {
        let url = url.isFileURL ? url.standardizedFileURL.resolvingSymlinksInPath() : url
        var entries = recentMedia
        entries.removeAll { $0.url == url }
        entries.insert(RecentMedia(url: url, title: title), at: 0)
        defaults.set(entries.prefix(6).map { ["url": $0.url.absoluteString, "title": $0.title] },
                     forKey: "recentMedia")
    }

    private func key(for url: URL) -> String {
        // YouTube callers supply the canonical webpage URL, never an expiring media URL.
        return "playbackPosition:" + (url.isFileURL ? url.standardizedFileURL.resolvingSymlinksInPath().absoluteString : url.absoluteString)
    }
}