import Foundation
import Combine

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

    @Published var isLoading = false
    @Published var isLoadingNextPage = false
    @Published var response: CreatorChannelSeriesTabResponse?
    @Published var series = [CreatorChannelSeriesResponse]()
    @Published var selectedSort: ContentSort = .latest
    @Published var page = 0
    @Published var size = 20
    @Published var hasNext = false
    @Published var hasLoaded = false
    @Published var errorMessage = ""
    @Published var isShowPopup = false

    func fetchFirstPage(creatorId: Int) {
        fetchSeries(creatorId: creatorId, page: 0, isNextPage: false)
    }

    func fetchNextPageIfNeeded(creatorId: Int, currentItem: CreatorChannelSeriesResponse) {
        guard series.last?.seriesId == currentItem.seriesId else { return }
        guard hasNext, isLoadingNextPage == false, isLoading == false else { return }

        fetchSeries(creatorId: creatorId, page: page + 1, isNextPage: true)
    }

    func selectSort(_ sort: ContentSort, creatorId: Int) {
        guard selectedSort != sort else { return }

        selectedSort = sort
        fetchFirstPage(creatorId: creatorId)
    }

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

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

        repository.getSeries(creatorId: creatorId, page: requestPage, size: pageSize, sort: selectedSort)
            .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<CreatorChannelSeriesTabResponse>.self, from: response.data)

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

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

    private func applySuccessState(_ data: CreatorChannelSeriesTabResponse, isNextPage: Bool) {
        response = data
        selectedSort = data.sort
        page = data.page
        size = data.size
        hasNext = data.hasNext

        if isNextPage {
            series.append(contentsOf: data.series)
        } else {
            series = data.series
        }
    }

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