metatext/ServiceLayer/Sources/ServiceLayer/Services/StatusListService.swift

// Copyright © 2020 Metabolist. All rights reserved.

import Combine
import DB
import Foundation
import Mastodon
import MastodonAPI

public struct StatusListService {
    public let sections: AnyPublisher<[[Timeline.Item]], Error>
    public let nextPageMaxIDs: AnyPublisher<String?, Never>
    public let contextParentID: String?
    public let title: String?
    public let navigationService: NavigationService

    private let filterContext: Filter.Context
    private let mastodonAPIClient: MastodonAPIClient
    private let contentDatabase: ContentDatabase
    private let requestClosure: (_ maxID: String?, _ minID: String?) -> AnyPublisher<Never, Error>
}

extension StatusListService {
    init(timeline: Timeline, mastodonAPIClient: MastodonAPIClient, contentDatabase: ContentDatabase) {
        var title: String?

        if case let .tag(tag) = timeline {
            title = "#".appending(tag)
        }

        let nextPageMaxIDsSubject = PassthroughSubject<String?, Never>()

        self.init(sections: contentDatabase.observation(timeline: timeline),
                  nextPageMaxIDs: nextPageMaxIDsSubject.eraseToAnyPublisher(),
                  contextParentID: nil,
                  title: title,
                  navigationService: NavigationService(
                    status: nil,
                    mastodonAPIClient: mastodonAPIClient,
                    contentDatabase: contentDatabase),
                  filterContext: timeline.filterContext,
                  mastodonAPIClient: mastodonAPIClient,
                  contentDatabase: contentDatabase) { maxID, minID in
            mastodonAPIClient.pagedRequest(timeline.endpoint, maxID: maxID, minID: minID)
                .handleEvents(receiveOutput: { nextPageMaxIDsSubject.send($0.info.maxID) })
                .flatMap { contentDatabase.insert(statuses: $0.result, timeline: timeline) }
                .eraseToAnyPublisher()
        }
    }

    init(statusID: String, mastodonAPIClient: MastodonAPIClient, contentDatabase: ContentDatabase) {
        self.init(sections: contentDatabase.contextObservation(parentID: statusID),
                  nextPageMaxIDs: Empty().eraseToAnyPublisher(),
                  contextParentID: statusID,
                  title: nil,
                  navigationService: NavigationService(
                    status: nil,
                    mastodonAPIClient: mastodonAPIClient,
                    contentDatabase: contentDatabase),
                  filterContext: .thread,
                  mastodonAPIClient: mastodonAPIClient,
                  contentDatabase: contentDatabase) { _, _ in
            Publishers.Merge(
                mastodonAPIClient.request(StatusEndpoint.status(id: statusID))
                    .flatMap(contentDatabase.insert(status:))
                    .eraseToAnyPublisher(),
                mastodonAPIClient.request(ContextEndpoint.context(id: statusID))
                    .flatMap { contentDatabase.insert(context: $0, parentID: statusID) }
                    .eraseToAnyPublisher())
                .eraseToAnyPublisher()
        }
    }
}

public extension StatusListService {
    func request(maxID: String?, minID: String?) -> AnyPublisher<Never, Error> {
        requestClosure(maxID, minID)
    }
}