//
// Swiftfin is subject to the terms of the Mozilla Public
// License, v2.0. If a copy of the MPL was not distributed with this
// file, you can obtain one at https://mozilla.org/MPL/2.0/.
//
// Copyright (c) 2022 Jellyfin & Jellyfin Contributors
//

import Combine
import Foundation
import JellyfinAPI
import Stinsen

final class SeasonItemViewModel: ItemViewModel, EpisodesRowManager {

    @RouterObject
    var itemRouter: ItemCoordinator.Router?
    @Published
    var episodes: [BaseItemDto] = []
    @Published
    var seriesItem: BaseItemDto?
    @Published
    var seasonsEpisodes: [BaseItemDto: [BaseItemDto]] = [:]
    @Published
    var selectedSeason: BaseItemDto?

    override init(item: BaseItemDto) {
        super.init(item: item)

        getSeriesItem()
        selectedSeason = item
        retrieveSeasons()
        requestEpisodes()
    }

    override func playButtonText() -> String {

        if item.unaired {
            return L10n.unaired
        }

        guard let playButtonItem = playButtonItem, let episodeLocator = playButtonItem.getEpisodeLocator() else { return L10n.play }
        return episodeLocator
    }

    private func requestEpisodes() {
        LogManager.log
            .debug("Getting episodes in season \(item.id!) (\(item.name!)) of show \(item.seriesId!) (\(item.seriesName!))")
        TvShowsAPI.getEpisodes(
            seriesId: item.seriesId ?? "",
            userId: SessionManager.main.currentLogin.user.id,
            fields: [.primaryImageAspectRatio, .seriesPrimaryImage, .seasonUserData, .overview, .genres, .people],
            seasonId: item.id ?? ""
        )
        .trackActivity(loading)
        .sink(receiveCompletion: { [weak self] completion in
            self?.handleAPIRequestError(completion: completion)
        }, receiveValue: { [weak self] response in
            guard let self = self else { return }
            self.episodes = response.items ?? []
            LogManager.log.debug("Retrieved \(String(self.episodes.count)) episodes")

            self.setNextUpInSeason()
        })
        .store(in: &cancellables)
    }

    private func setNextUpInSeason() {

        TvShowsAPI.getNextUp(
            userId: SessionManager.main.currentLogin.user.id,
            fields: [.primaryImageAspectRatio, .seriesPrimaryImage, .seasonUserData, .overview, .genres, .people],
            seriesId: item.seriesId ?? "",
            enableUserData: true
        )
        .trackActivity(loading)
        .sink(receiveCompletion: { [weak self] completion in
            self?.handleAPIRequestError(completion: completion)
        }, receiveValue: { [weak self] response in
            guard let self = self else { return }

            // Find the nextup item that belongs to current season.
            if let nextUpItem = (response.items ?? []).first(where: { episode in
                !episode.unaired && !episode.missing && episode.seasonId ?? "" == self.item.id!
            }) {
                self.playButtonItem = nextUpItem
                LogManager.log.debug("Nextup in season \(self.item.id!) (\(self.item.name!)): \(nextUpItem.id!)")
            }

            if self.playButtonItem == nil && !self.episodes.isEmpty {
                // Fallback to the old mechanism:
                // Sets the play button item to the "Next up" in the season based upon
                // the watched status of episodes in the season.
                // Default to the first episode of the season if all have been watched.
                var firstUnwatchedSearch: BaseItemDto?

                for episode in self.episodes {
                    guard let played = episode.userData?.played else { continue }
                    if !played {
                        firstUnwatchedSearch = episode
                        break
                    }
                }

                if let firstUnwatched = firstUnwatchedSearch {
                    self.playButtonItem = firstUnwatched
                } else {
                    guard let firstEpisode = self.episodes.first else { return }
                    self.playButtonItem = firstEpisode
                }
            }
        })
        .store(in: &cancellables)
    }

    private func getSeriesItem() {
        guard let seriesID = item.seriesId else { return }
        UserLibraryAPI.getItem(
            userId: SessionManager.main.currentLogin.user.id,
            itemId: seriesID
        )
        .trackActivity(loading)
        .sink { [weak self] completion in
            self?.handleAPIRequestError(completion: completion)
        } receiveValue: { [weak self] seriesItem in
            self?.seriesItem = seriesItem
        }
        .store(in: &cancellables)
    }
}