import Foundation

// MARK: - ChapterReaderViewModel

@Observable @MainActor
final class ChapterReaderViewModel {
    let slug: String
    private(set) var chapter: Int

    var content: ChapterResponse?
    var isLoading = false
    var error: String?

    init(slug: String, chapter: Int) {
        self.slug = slug
        self.chapter = chapter
    }

    /// Switch to a different chapter in-place; `chapter` change causes `.task(id: chapter)` to re-fire `load()`.
    func switchChapter(to newChapter: Int) {
        guard newChapter != chapter else { return }
        chapter = newChapter
        content = nil
        error = nil
    }

    func load() async {
        isLoading = true
        error = nil
        do {
            content = try await APIClient.shared.chapterContent(slug: slug, chapter: chapter)
            try? await APIClient.shared.setProgress(slug: slug, chapter: chapter)
        } catch {
            if !(error is CancellationError) {
                self.error = error.localizedDescription
            }
        }
        isLoading = false
    }

    func toggleAudio(audioPlayer: AudioPlayerService, settings: UserSettings) {
        guard let content else { return }

        let isCurrent = audioPlayer.isActive
            && audioPlayer.slug == slug
            && audioPlayer.chapter == chapter

        if isCurrent {
            audioPlayer.togglePlayPause()
        } else {
            let voice = BookVoicePreferences.shared.voiceWithFallback(
                for: slug,
                globalVoice: settings.voice
            )
            audioPlayer.load(
                slug: slug,
                chapter: chapter,
                chapterTitle: content.chapter.title,
                bookTitle: content.book.title,
                coverURL: content.book.cover,
                voice: voice,
                speed: settings.speed,
                chapters: content.chapters,
                nextChapter: content.next,
                prevChapter: content.prev
            )
        }
    }
}