import Foundation

final class RDEPUBReaderLocationCoordinator {
    private unowned let context: RDEPUBReaderContext

    init(context: RDEPUBReaderContext) {
        self.context = context
    }

    @discardableResult
    func restoreReadingLocation(_ location: RDEPUBLocation, animated: Bool = false) -> Bool {
        guard let controller = context.controller,
              let readerView = context.readerView else { return false }
        guard let targetPageNumber = controller.pageNumber(for: location) else {
            readerView.transitionToPage(pageNum: 0)
            context.readingSession?.transition(to: .idle)
            return false
        }

        if context.textBook == nil {
            _ = context.readingSession?.queueNavigation(
                to: location,
                relativeToSpineIndex: nil,
                bookIdentifier: context.currentBookIdentifier
            )
        } else {
            context.readingSession?.transition(to: .jumping)
        }
        readerView.transitionToPage(pageNum: max(targetPageNumber - 1, 0), animated: animated)
        return true
    }

    func currentVisibleLocation() -> RDEPUBLocation? {
        guard let controller = context.controller,
              let readerView = context.readerView else {
            return nil
        }
        if context.textBook != nil, readerView.currentPage >= 0 {
            return controller.resolvedTextLocation(forPageNumber: readerView.currentPage + 1)
        }
        return context.readingSession?.currentReadingLocation(bookIdentifier: context.currentBookIdentifier)
    }

    func persistenceLocation() -> RDEPUBLocation? {
        guard let controller = context.controller,
              let currentBookIdentifier = context.currentBookIdentifier else {
            return nil
        }
        return controller.persistence?.loadLocation(for: currentBookIdentifier)
    }

    func persist(location: RDEPUBLocation) {
        guard let controller = context.controller,
              let currentBookIdentifier = context.currentBookIdentifier else { return }
        controller.persistence?.saveLocation(location, for: currentBookIdentifier)
        controller.delegate?.epubReader(controller, didUpdateLocation: location)
        controller.delegate?.epubReader(controller, didUpdateCurrentTableOfContentsItem: controller.currentTableOfContentsItem)
        controller.updateBookmarkChrome()
    }
}