import UIKit

@MainActor
final class ServersViewController: UITableViewController {
    private let context: AppContext
    private var servers: [ServerRow] = []

    init(context: AppContext) {
        self.context = context
        super.init(style: .plain)
        title = "Servers"
        tableView.backgroundColor = .systemGroupedBackground
        tableView.separatorInset = .zero
    }

    @available(*, unavailable)
    required init?(coder: NSCoder) { fatalError("init(coder:) is not supported") }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        servers = context.core.servers()
        tableView.reloadData()
        tableView.backgroundView = servers.isEmpty
            ? EmptyBackgroundView(title: "No servers", detail: "Add a code hosting server to get started.")
            : nil
        navigationItem.rightBarButtonItem = UIBarButtonItem(
            systemItem: .add,
            primaryAction: UIAction { [weak self] _ in self?.showAddServer() }
        )
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        servers.count
    }

    override func tableView(
        _ tableView: UITableView,
        cellForRowAt indexPath: IndexPath
    ) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "server")
            ?? UITableViewCell(style: .subtitle, reuseIdentifier: "server")
        let server = servers[indexPath.row]
        configureTextCell(cell, title: server.name, detail: server.url)
        cell.accessoryType = .disclosureIndicator
        return cell
    }

    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        tableView.deselectRow(at: indexPath, animated: true)
        do {
            try context.selectServer(index: UInt32(indexPath.row))
        } catch {
            show(error: error)
        }
    }

    private func showAddServer() {
        let controller = AddServerViewController(context: context) { [weak self] in
            guard let self else { return }
            self.servers = self.context.core.servers()
            self.tableView.reloadData()
        }
        present(UINavigationController(rootViewController: controller), animated: true)
    }
}
@MainActor
final class AddServerViewController: UITableViewController, UITextFieldDelegate {
    private let context: AppContext
    private let completion: () -> Void
    private let nameField = UITextField()
    private let urlField = UITextField()
    private let tokenField = UITextField()
    private let providerButton = UIButton(type: .system)
    private var provider = ServerProvider.gitea
    private var saveButton: UIBarButtonItem!

    init(context: AppContext, completion: @escaping () -> Void) {
        self.context = context
        self.completion = completion
        super.init(style: .insetGrouped)
        title = "Add Server"
    }

    @available(*, unavailable)
    required init?(coder: NSCoder) { fatalError("init(coder:) is not supported") }

    override func viewDidLoad() {
        super.viewDidLoad()
        navigationItem.leftBarButtonItem = UIBarButtonItem(
            systemItem: .cancel,
            primaryAction: UIAction { [weak self] _ in self?.dismiss(animated: true) }
        )
        saveButton = UIBarButtonItem(
            title: "Add",
            style: .done,
            target: self,
            action: #selector(save)
        )
        navigationItem.rightBarButtonItem = saveButton
        configure(nameField, placeholder: "Work", contentType: .name)
        configure(urlField, placeholder: "https://gitea.example.com", contentType: .URL)
        urlField.keyboardType = .URL
        urlField.autocapitalizationType = .none
        configure(tokenField, placeholder: "Access token", contentType: nil)
        tokenField.isSecureTextEntry = true
        tokenField.autocapitalizationType = .none
        tokenField.returnKeyType = .done
        configureProviderButton()
    }

    override func numberOfSections(in tableView: UITableView) -> Int { 4 }
    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int { 1 }

    override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
        ["API provider", "Name", "Server URL", "Access token"][section]
    }

    override func tableView(
        _ tableView: UITableView,
        cellForRowAt indexPath: IndexPath
    ) -> UITableViewCell {
        let cell = UITableViewCell(style: .default, reuseIdentifier: nil)
        let control: UIView = indexPath.section == 0
            ? providerButton
            : [nameField, urlField, tokenField][indexPath.section - 1]
        control.translatesAutoresizingMaskIntoConstraints = false
        cell.contentView.addSubview(control)
        NSLayoutConstraint.activate([
            control.leadingAnchor.constraint(equalTo: cell.contentView.leadingAnchor, constant: 16),
            control.trailingAnchor.constraint(equalTo: cell.contentView.trailingAnchor, constant: -16),
            control.topAnchor.constraint(equalTo: cell.contentView.topAnchor),
            control.bottomAnchor.constraint(equalTo: cell.contentView.bottomAnchor),
            cell.contentView.heightAnchor.constraint(greaterThanOrEqualToConstant: 48),
        ])
        return cell
    }

    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        if textField === nameField { urlField.becomeFirstResponder() }
        else if textField === urlField { tokenField.becomeFirstResponder() }
        else { save() }
        return true
    }

    @objc private func save() {
        view.endEditing(true)
        saveButton.isEnabled = false
        let spinner = UIActivityIndicatorView(style: .medium)
        spinner.startAnimating()
        navigationItem.rightBarButtonItem = UIBarButtonItem(customView: spinner)
        Task {
            do {
                let index = try await context.core.addServer(
                    name: nameField.text ?? "",
                    url: urlField.text ?? "",
                    token: tokenField.text ?? "",
                    provider: provider
                )
                try context.didAddServer(index: index)
                completion()
                dismiss(animated: true)
            } catch {
                navigationItem.rightBarButtonItem = saveButton
                saveButton.isEnabled = true
                show(error: error)
            }
        }
    }

    private func configure(
        _ field: UITextField,
        placeholder: String,
        contentType: UITextContentType?
    ) {
        field.placeholder = placeholder
        field.textContentType = contentType
        field.clearButtonMode = .whileEditing
        field.delegate = self
        field.returnKeyType = .next
        field.adjustsFontForContentSizeCategory = true
        field.font = .preferredFont(forTextStyle: .body)
    }

    private func configureProviderButton() {
        providerButton.contentHorizontalAlignment = .leading
        providerButton.showsMenuAsPrimaryAction = true
        providerButton.changesSelectionAsPrimaryAction = true
        providerButton.accessibilityLabel = "API provider"
        providerButton.accessibilityValue = "Gitea"
        providerButton.menu = UIMenu(options: .singleSelection, children: [
            UIAction(title: "Gitea", state: .on) { [weak self] _ in
                self?.provider = .gitea
                self?.urlField.placeholder = "https://gitea.example.com"
                self?.providerButton.accessibilityValue = "Gitea"
            },
            UIAction(title: "Forgejo") { [weak self] _ in
                self?.provider = .forgejo
                self?.urlField.placeholder = "https://forgejo.example.com"
                self?.providerButton.accessibilityValue = "Forgejo"
            },
        ])
    }
}