import Foundation
import Observation
import VelodyDomain
import VelodyPersistence

@MainActor
@Observable
final class MacLibraryViewModel {
    var tracks: [LibraryTrack] = []
    var selectedFolderPath = "No folder selected"
    var scanStatus = "Choose a folder to begin local discovery."
    var discoveredTrackCount = 0
    var isScanning = false

    private let folderAccessService: any VelodyPersistence.FolderAccessService
    private let localMusicScanner: any LocalMusicScanner
    private let store = InMemoryLocalLibraryStore()
    private var hasLoaded = false

    init() {
        let folderAccessService = FolderAccessService()
        let localMusicScanner = FileSystemLocalMusicScanner(
            metadataReader: AVFoundationMetadataReader()
        )

        self.folderAccessService = folderAccessService
        self.localMusicScanner = localMusicScanner

        if let url = folderAccessService.storedFolderURL() {
            selectedFolderPath = url.path
            scanStatus = "Folder restored. Run a manual scan to discover MP3 files."
        }
    }

    func loadIfNeeded() async {
        guard !hasLoaded else { return }
        hasLoaded = true
        tracks = await store.loadTracks()
        discoveredTrackCount = tracks.count
    }

    func chooseFolder() {
        if let url = folderAccessService.chooseFolder() {
            selectedFolderPath = url.path
            scanStatus = "Folder selected. Run a manual scan to discover MP3 files."
            tracks = []
            discoveredTrackCount = 0
            Task {
                await store.replaceTracks([])
            }
        }
    }

    func scanMP3Files() async {
        guard let folderURL = folderAccessService.storedFolderURL() else {
            scanStatus = "Choose a folder before scanning."
            return
        }

        isScanning = true
        scanStatus = "Scanning MP3 files..."
        defer {
            isScanning = false
        }

        do {
            let discoveredTracks = try await localMusicScanner.scanFolder(at: folderURL)
            await store.replaceTracks(discoveredTracks)
            tracks = await store.loadTracks()
            discoveredTrackCount = tracks.count
            scanStatus = "Scan finished. Found \(discoveredTrackCount) MP3 file(s)."
        } catch {
            scanStatus = "Scan failed: \(error.localizedDescription)"
        }
    }
}