//
//  ThreadViewController+Provider.swift
//  Mastodon
//
//  Created by MainasuK Cirno on 2021-4-12.
//

import UIKit
import Combine
import CoreData
import CoreDataStack

// MARK: - StatusProvider
extension ThreadViewController: StatusProvider {
    
    func status() -> Future<Status?, Never> {
        return Future { promise in promise(.success(nil)) }
    }
    
    func status(for cell: UITableViewCell?, indexPath: IndexPath?) -> Future<Status?, Never> {
        return Future { promise in
            guard let diffableDataSource = self.viewModel.diffableDataSource else {
                assertionFailure()
                promise(.success(nil))
                return
            }
            guard let indexPath = indexPath ?? cell.flatMap({ self.tableView.indexPath(for: $0) }),
                  let item = diffableDataSource.itemIdentifier(for: indexPath) else {
                promise(.success(nil))
                return
            }
            
            switch item {
            case .root(let statusObjectID, _),
                 .reply(let statusObjectID, _),
                 .leaf(let statusObjectID, _):
                let managedObjectContext = self.viewModel.context.managedObjectContext
                managedObjectContext.perform {
                    let status = managedObjectContext.object(with: statusObjectID) as? Status
                    promise(.success(status))
                }
            default:
                promise(.success(nil))
            }
        }
    }
    
    func status(for cell: UICollectionViewCell) -> Future<Status?, Never> {
        return Future { promise in promise(.success(nil)) }
    }
    
    var managedObjectContext: NSManagedObjectContext {
        return viewModel.context.managedObjectContext
    }
    
    var tableViewDiffableDataSource: UITableViewDiffableDataSource<StatusSection, Item>? {
        return viewModel.diffableDataSource
    }
    
    func item(for cell: UITableViewCell?, indexPath: IndexPath?) -> Item? {
        guard let diffableDataSource = self.viewModel.diffableDataSource else {
            assertionFailure()
            return nil
        }
        
        guard let indexPath = indexPath ?? cell.flatMap({ self.tableView.indexPath(for: $0) }),
              let item = diffableDataSource.itemIdentifier(for: indexPath) else {
            return nil
        }
        
        return item
    }
    
    func items(indexPaths: [IndexPath]) -> [Item] {
        guard let diffableDataSource = self.viewModel.diffableDataSource else {
            assertionFailure()
            return []
        }
        
        var items: [Item] = []
        for indexPath in indexPaths {
            guard let item = diffableDataSource.itemIdentifier(for: indexPath) else { continue }
            items.append(item)
        }
        return items
    }

    func statusObjectItems(indexPaths: [IndexPath]) -> [StatusObjectItem] {
        guard let diffableDataSource = self.viewModel.diffableDataSource else { return [] }
        let items = indexPaths.compactMap { diffableDataSource.itemIdentifier(for: $0)?.statusObjectItem }
        return items
    }
    
}

extension ThreadViewController: UserProvider {}