import Foundation
import Models
import Services
import Utils
import Views

final class ExtensionSaveService {
  #if os(macOS)
    let services = Services()
  #endif

  let queue: OperationQueue

  init() {
    self.queue = OperationQueue()
  }

  #if os(iOS)
    private func queueSaveOperation(
      _ pageScrape: PageScrapePayload,
      shareExtensionViewModel: ShareExtensionChildViewModel
    ) {
      ProcessInfo().performExpiringActivity(withReason: "app.omnivore.SaveActivity") { [self] expiring in
        guard !expiring else {
          self.queue.cancelAllOperations()
          self.queue.waitUntilAllOperationsAreFinished()
          return
        }

        let operation = SaveOperation(pageScrapePayload: pageScrape, shareExtensionViewModel: shareExtensionViewModel)

        self.queue.addOperation(operation)
        self.queue.waitUntilAllOperationsAreFinished()
      }
    }
  #endif

  public func save(_ extensionContext: NSExtensionContext, shareExtensionViewModel: ShareExtensionChildViewModel) {
    PageScraper.scrape(extensionContext: extensionContext) { [weak self] result in
      guard let self = self else { return }

      switch result {
      case let .success(payload):
        DispatchQueue.main.async {
          shareExtensionViewModel.status = .saved

          let url = URLComponents(string: payload.url)
          let hostname = URL(string: payload.url)?.host ?? ""

          switch payload.contentType {
          case let .html(html: _, title: title, iconURL: iconURL):
            shareExtensionViewModel.title = title
            shareExtensionViewModel.iconURL = iconURL
            shareExtensionViewModel.url = hostname
          case .none:
            shareExtensionViewModel.url = hostname
            shareExtensionViewModel.title = payload.url
            if var url = url {
              url.path = "/favicon.ico"
              shareExtensionViewModel.iconURL = url.url?.absoluteString
            }
          case let .pdf(localUrl: localUrl):
            shareExtensionViewModel.url = hostname
            shareExtensionViewModel.title = PDFUtils.titleFromPdfFile(localUrl.absoluteString)
            Task {
              let localThumbnail = try await PDFUtils.createThumbnailFor(inputUrl: localUrl)
              DispatchQueue.main.async {
                shareExtensionViewModel.iconURL = localThumbnail?.absoluteString
              }
            }
          }
        }

        #if os(iOS)
          self.queueSaveOperation(payload, shareExtensionViewModel: shareExtensionViewModel)
        #else
          Task {
            await shareExtensionViewModel.createPage(services: self.services, pageScrapePayload: payload)
          }
        #endif
      case .failure:
        DispatchQueue.main.async {
          shareExtensionViewModel.status = .failed(error: .unknown(description: "Could not retrieve content"))
        }
      }
    }
  }

  final class SaveOperation: Operation, URLSessionDelegate {
    let services: Services
    let pageScrapePayload: PageScrapePayload
    let shareExtensionViewModel: ShareExtensionChildViewModel

    var queue: OperationQueue?
    var uploadTask: URLSessionTask?

    // swiftlint:disable:next nesting
    enum State: Int {
      case created
      case started
      case finished
    }

    init(pageScrapePayload: PageScrapePayload, shareExtensionViewModel: ShareExtensionChildViewModel) {
      self.pageScrapePayload = pageScrapePayload
      self.shareExtensionViewModel = shareExtensionViewModel

      self.state = .created
      self.services = Services()
    }

    public var state: State = .created {
      willSet {
        willChangeValue(forKey: "isReady")
        willChangeValue(forKey: "isExecuting")
        willChangeValue(forKey: "isFinished")
        willChangeValue(forKey: "isCancelled")
      }
      didSet {
        didChangeValue(forKey: "isCancelled")
        didChangeValue(forKey: "isFinished")
        didChangeValue(forKey: "isExecuting")
        didChangeValue(forKey: "isReady")
      }
    }

    override var isAsynchronous: Bool {
      true
    }

    override var isReady: Bool {
      true
    }

    override var isExecuting: Bool {
      self.state == .started
    }

    override var isFinished: Bool {
      self.state == .finished
    }

    override func start() {
      guard !isCancelled else { return }
      state = .started
      queue = OperationQueue()

      Task {
        let pageCreated = await shareExtensionViewModel.createPage(
          services: services,
          pageScrapePayload: pageScrapePayload
        )
        if pageCreated {
          state = .finished
        }
      }
    }

    override func cancel() {
      super.cancel()
    }
  }
}

extension ShareExtensionChildViewModel {
  func createPage(services: Services, pageScrapePayload: PageScrapePayload) async -> Bool {
    var newRequestID: String?

    do {
      try await services.dataService.persistPageScrapePayload(pageScrapePayload, requestId: requestId)
    } catch {
      updateStatusOnMain(
        requestId: nil,
        newStatus: .failed(error: SaveArticleError.unknown(description: "Unable to access content"))
      )
      return false
    }

    do {
      updateStatusOnMain(requestId: requestId, newStatus: .saved)

      switch pageScrapePayload.contentType {
      case .none:
        newRequestID = try await services.dataService.createPageFromUrl(id: requestId, url: pageScrapePayload.url)
      case let .pdf(localUrl):
        try await services.dataService.createPageFromPdf(
          id: requestId,
          localPdfURL: localUrl,
          url: pageScrapePayload.url
        )
      case let .html(html, title, _):
        newRequestID = try await services.dataService.createPage(
          id: requestId,
          originalHtml: html,
          title: title,
          url: pageScrapePayload.url
        )
      }
    } catch {
      updateStatusOnMain(
        requestId: nil,
        newStatus: .syncFailed(error: SaveArticleError.unknown(description: "Unknown Error"))
      )
      return false
    }

    updateStatusOnMain(requestId: newRequestID, newStatus: .synced)
    return true
  }

  func updateStatusOnMain(requestId: String?, newStatus: ShareExtensionStatus) {
    DispatchQueue.main.async {
      self.status = newStatus
      if let requestId = requestId {
        self.requestId = requestId
      }
    }
  }
}