import Foundation
import Combine

final class MainContentAllViewModel: ObservableObject {
    private let repository = MainContentAllRepository()
    private var subscription = Set<AnyCancellable>()
    private let pageSize = 20
    private var latestRequestId = 0

    @Published var selectedType: MainContentAllType = .audio
    @Published var selectedSort: ContentSort = .latest
    @Published var selectedDayOfWeek: SeriesPublishedDaysOfWeek = .currentDeviceDay
    @Published var response: MainContentAllTabResponse?
    @Published var audios = [MainContentAudioResponse]()
    @Published var series = [MainContentSeriesResponse]()
    @Published var page = 0
    @Published var size = 20
    @Published var hasNext = false
    @Published var hasLoaded = false
    @Published var isLoading = false
    @Published var isLoadingNextPage = false
    @Published var errorMessage = ""
    @Published var isShowPopup = false

    var allowedSorts: [ContentSort] {
        selectedType == .free ? [.latest, .popular] : ContentSort.allCases
    }

    var shouldShowEmptyState: Bool {
        guard hasLoaded, isLoading == false else { return false }
        return selectedType.usesAudioItems ? audios.isEmpty : series.isEmpty
    }

    func fetchFirstPageIfNeeded() {
        guard hasLoaded == false else { return }
        fetchFirstPage()
    }

    func fetchFirstPage() {
        fetchContents(page: 0, isNextPage: false)
    }

    func selectType(_ type: MainContentAllType) {
        guard selectedType != type else { return }

        selectedType = type
        if allowedSorts.contains(selectedSort) == false {
            selectedSort = .latest
        }
        clearItems()
        fetchFirstPage()
    }

    func selectSort(_ sort: ContentSort) {
        guard allowedSorts.contains(sort), selectedSort != sort else { return }

        selectedSort = sort
        clearItems()
        fetchFirstPage()
    }

    func selectDayOfWeek(_ dayOfWeek: SeriesPublishedDaysOfWeek) {
        guard selectedType == .series, selectedDayOfWeek != dayOfWeek else { return }

        selectedDayOfWeek = dayOfWeek
        clearItems()
        fetchFirstPage()
    }

    func fetchNextPageIfNeeded(currentAudio: MainContentAudioResponse) {
        guard audios.last?.audioContentId == currentAudio.audioContentId else { return }
        fetchNextPageIfPossible()
    }

    func fetchNextPageIfNeeded(currentSeries: MainContentSeriesResponse) {
        guard series.last?.seriesId == currentSeries.seriesId else { return }
        fetchNextPageIfPossible()
    }

    private func fetchNextPageIfPossible() {
        guard hasNext, isLoading == false, isLoadingNextPage == false else { return }
        fetchContents(page: page + 1, isNextPage: true)
    }

    private func fetchContents(page requestPage: Int, isNextPage: Bool) {
        latestRequestId += 1
        let requestId = latestRequestId

        if isNextPage {
            isLoadingNextPage = true
        } else {
            isLoading = true
        }

        repository.getContents(
            type: selectedType,
            sort: selectedSort,
            page: requestPage,
            size: pageSize,
            dayOfWeek: selectedDayOfWeek
        )
        .sink { [weak self] result in
            guard let self else { return }
            guard requestId == self.latestRequestId else { return }

            switch result {
            case .finished:
                DEBUG_LOG("finish")
            case .failure(let error):
                ERROR_LOG(error.localizedDescription)
                self.applyFailureState()
            }
        } receiveValue: { [weak self] response in
            guard let self else { return }
            guard requestId == self.latestRequestId else { return }

            do {
                let jsonDecoder = JSONDecoder()
                let decoded = try jsonDecoder.decode(ApiResponse<MainContentAllTabResponse>.self, from: response.data)

                if let data = decoded.data, decoded.success {
                    self.applySuccessState(data, isNextPage: isNextPage)
                } else {
                    self.errorMessage = decoded.message ?? I18n.MainContentAll.loadFailedMessage
                    self.isShowPopup = true
                }
            } catch {
                ERROR_LOG(error.localizedDescription)
                self.errorMessage = I18n.MainContentAll.loadFailedMessage
                self.isShowPopup = true
            }

            self.hasLoaded = true
            self.isLoading = false
            self.isLoadingNextPage = false
        }
        .store(in: &subscription)
    }

    private func applySuccessState(_ data: MainContentAllTabResponse, isNextPage: Bool) {
        response = data
        selectedType = data.type
        selectedSort = data.sort
        if let dayOfWeek = data.dayOfWeek {
            selectedDayOfWeek = dayOfWeek
        }
        page = data.page
        size = data.size
        hasNext = data.hasNext

        if data.type.usesAudioItems {
            if isNextPage {
                audios.append(contentsOf: data.audios)
            } else {
                audios = data.audios
                series = []
            }
        } else {
            if isNextPage {
                series.append(contentsOf: data.series)
            } else {
                series = data.series
                audios = []
            }
        }
    }

    private func applyFailureState() {
        errorMessage = I18n.MainContentAll.loadFailedMessage
        isShowPopup = true
        hasLoaded = true
        isLoading = false
        isLoadingNextPage = false
    }

    private func clearItems() {
        audios = []
        series = []
        response = nil
        page = 0
        hasNext = false
    }
}


extension SeriesPublishedDaysOfWeek {
    static var currentDeviceDay: SeriesPublishedDaysOfWeek {
        switch Calendar.current.component(.weekday, from: Date()) {
        case 1:
            return .SUN
        case 2:
            return .MON
        case 3:
            return .TUE
        case 4:
            return .WED
        case 5:
            return .THU
        case 6:
            return .FRI
        case 7:
            return .SAT
        default:
            return .SUN
        }
    }

    static var allFilterCases: [SeriesPublishedDaysOfWeek] {
        [.MON, .TUE, .WED, .THU, .FRI, .SAT, .SUN, .RANDOM]
    }

    var shortTitle: String {
        switch self {
        case .SUN:
            return I18n.MainContentAll.DayOfWeek.sun
        case .MON:
            return I18n.MainContentAll.DayOfWeek.mon
        case .TUE:
            return I18n.MainContentAll.DayOfWeek.tue
        case .WED:
            return I18n.MainContentAll.DayOfWeek.wed
        case .THU:
            return I18n.MainContentAll.DayOfWeek.thu
        case .FRI:
            return I18n.MainContentAll.DayOfWeek.fri
        case .SAT:
            return I18n.MainContentAll.DayOfWeek.sat
        case .RANDOM:
            return I18n.MainContentAll.DayOfWeek.random
        }
    }
}