// Copyright SIX DAY LLC. All rights reserved.

import Foundation
import UIKit
import StatefulViewController
import Result

protocol TokensViewControllerDelegate: class {
    func didSelect(token: TokenObject, in viewController: UIViewController)
    func didDelete(token: TokenObject, in viewController: UIViewController)
}

class TokensViewController: UIViewController {

    private let dataStore: TokensDataStore

    var viewModel: TokensViewModel = TokensViewModel(tokens: [], tickers: .none) {
        didSet {
            refreshView(viewModel: viewModel)
        }
    }
    let account: Account
    let tableView: UITableView
    let refreshControl = UIRefreshControl()
    weak var delegate: TokensViewControllerDelegate?

    init(
        account: Account,
        dataStore: TokensDataStore
    ) {
        self.account = account
        self.dataStore = dataStore

        tableView = UITableView(frame: .zero, style: .plain)

        super.init(nibName: nil, bundle: nil)

        dataStore.delegate = self

        tableView.translatesAutoresizingMaskIntoConstraints = false
        tableView.delegate = self
        tableView.dataSource = self
        tableView.separatorStyle = .none
        tableView.backgroundColor = .white
        tableView.rowHeight = 72
        view.addSubview(tableView)

        NSLayoutConstraint.activate([
            tableView.topAnchor.constraint(equalTo: view.topAnchor),
            tableView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            tableView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
            tableView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
        ])

        refreshControl.addTarget(self, action: #selector(pullToRefresh), for: .valueChanged)
        tableView.addSubview(refreshControl)

        errorView = ErrorView(onRetry: fetch)
        loadingView = LoadingView()
        emptyView = EmptyView(
            title: NSLocalizedString("emptyView.noTokens.label.title", value: "You haven't received any tokens yet!", comment: ""),
            onRetry: fetch
        )

        refreshView(viewModel: viewModel)
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        fetch()
    }

    @objc func pullToRefresh() {
        refreshControl.beginRefreshing()
        fetch()
    }

    func fetch() {
        startLoading()
        dataStore.fetch()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func refreshView(viewModel: TokensViewModel) {
        title = viewModel.title
        view.backgroundColor = viewModel.backgroundColor

        let header = TokensHeaderView(frame: .zero)
        header.amountLabel.text = viewModel.headerBalance
        header.amountLabel.textColor = viewModel.headerBalanceTextColor
        header.backgroundColor = viewModel.headerBackgroundColor
        header.amountLabel.font = viewModel.headerBalanceFont
        header.frame.size = header.systemLayoutSizeFitting(UILayoutFittingExpandedSize)
        tableView.tableHeaderView = header

        let footer = TokensFooterView(frame: .zero)
        footer.textLabel.text = viewModel.footerTitle
        footer.textLabel.font = viewModel.footerTextFont
        footer.textLabel.textColor = viewModel.footerTextColor
        footer.frame.size = header.systemLayoutSizeFitting(UILayoutFittingExpandedSize)

        tableView.tableFooterView = footer
    }
}

extension TokensViewController: StatefulViewController {
    func hasContent() -> Bool {
        return viewModel.hasContent
    }
}

extension TokensViewController: UITableViewDelegate {
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        tableView.deselectRow(at: indexPath, animated: true)

        let token = viewModel.item(for: indexPath.row, section: indexPath.section)
        delegate?.didSelect(token: token, in: self)
    }

    func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
        return viewModel.canDelete(for: indexPath.row, section: indexPath.section)
    }

    func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
        if editingStyle == UITableViewCellEditingStyle.delete {
            delegate?.didDelete(token: viewModel.item(for: indexPath.row, section: indexPath.section), in: self)
        }
    }

    func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
        return 80
    }
}

extension TokensViewController: TokensDataStoreDelegate {
    func didUpdate(result: Result<TokensViewModel, TokenError>) {
        switch result {
        case .success(let viewModel):
            self.viewModel = viewModel
            endLoading()
        case .failure(let error):
            endLoading(error: error)
        }
        tableView.reloadData()

        if refreshControl.isRefreshing {
            refreshControl.endRefreshing()
        }
    }
}

extension TokensViewController: UITableViewDataSource {
    func numberOfSections(in tableView: UITableView) -> Int {
        return viewModel.numberOfSections
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let token = viewModel.item(for: indexPath.row, section: indexPath.section)

        let cell = TokenViewCell(style: .default, reuseIdentifier: TokenViewCell.identifier)
        cell.configure(
            viewModel: .init(
                token: token,
                ticker: viewModel.ticker(for: token)
            )
        )
        return cell
    }

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return viewModel.numberOfItems(for: section)
    }
}