//
// 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
import SwiftUICollection

final class TVLibrariesViewModel: ViewModel {

    @Published
    var rows = [LibraryRow]()
    @Published
    var totalPages = 0
    @Published
    var currentPage = 0
    @Published
    var hasNextPage = false
    @Published
    var hasPreviousPage = false

    private var libraries = [BaseItemDto]()
    private let columns: Int

    @RouterObject
    private var router: TVLibrariesCoordinator.Router?

    init(columns: Int = 7) {
        self.columns = columns
        super.init()

        requestLibraries()
    }

    func requestLibraries() {

        UserViewsAPI.getUserViews(userId: SessionManager.main.currentLogin.user.id)
            .trackActivity(loading)
            .sink(receiveCompletion: { completion in
                self.handleAPIRequestError(completion: completion)
            }, receiveValue: { response in
                if let responseItems = response.items {
                    self.libraries = []
                    for library in responseItems {
                        if library.collectionType == "tvshows" {
                            self.libraries.append(library)
                        }
                    }
                    self.rows = self.calculateRows()
                    if self.libraries.count == 1, let library = self.libraries.first {
                        // make this library the root of this stack
                        self.router?.coordinator.root(\.rootLibrary, library)
                    }
                }
            })
            .store(in: &cancellables)
    }

    private func calculateRows() -> [LibraryRow] {
        guard !libraries.isEmpty else { return [] }
        let rowCount = libraries.count / columns
        var calculatedRows = [LibraryRow]()
        for i in 0 ... rowCount {
            let firstItemIndex = i * columns
            var lastItemIndex = firstItemIndex + columns
            if lastItemIndex > libraries.count {
                lastItemIndex = libraries.count
            }

            var rowCells = [LibraryRowCell]()
            for item in libraries[firstItemIndex ..< lastItemIndex] {
                let newCell = LibraryRowCell(item: item)
                rowCells.append(newCell)
            }
            if i == rowCount && hasNextPage {
                var loadingCell = LibraryRowCell(item: nil)
                loadingCell.loadingCell = true
                rowCells.append(loadingCell)
            }

            calculatedRows.append(LibraryRow(
                section: i,
                items: rowCells
            ))
        }
        return calculatedRows
    }
}