/*
Copyright 2019-2024 New Vector Ltd.

SPDX-License-Identifier: AGPL-3.0-only
Please see LICENSE in the repository root for full details.
 */

import Foundation

@objc protocol SettingsDiscoveryTableViewSectionDelegate: AnyObject {
    
    func settingsDiscoveryTableViewSection(_ settingsDiscoveryTableViewSection: SettingsDiscoveryTableViewSection, tableViewCellClass: MXKTableViewCell.Type, forRow: Int) -> MXKTableViewCell
    func settingsDiscoveryTableViewSectionDidUpdate(_ settingsDiscoveryTableViewSection: SettingsDiscoveryTableViewSection)
}

private enum DiscoverySectionRows {
    case button(title: String, action: () -> Void)
    case threePid(threePid: MX3PID)
}

@objc final class SettingsDiscoveryTableViewSection: NSObject, Themable {
    
    // MARK: - Constants
    
    private enum Constants {
        static let defaultFont = UIFont.systemFont(ofSize: 17.0)
    }
    
    // MARK: - Properties
    
    @objc weak var delegate: SettingsDiscoveryTableViewSectionDelegate?
    
    @objc var attributedFooterTitle: NSAttributedString?
    @objc var footerShouldScrollToUserSettings = false
    
    // MARK: Private
    
    private var theme: Theme!
    private var viewModel: SettingsDiscoveryViewModel
    
    // Need to know the state to make `cellForRow` deliver cells accordingly
    private var viewState: SettingsDiscoveryViewState = .loading {
        didSet {
            self.updateRows()
        }
    }
    
    private var discoveryRows: [DiscoverySectionRows] = []
    
    // MARK: - Setup
    
    @objc init(viewModel: SettingsDiscoveryViewModel) {
        self.theme = ThemeService.shared().theme
        self.viewModel = viewModel
        super.init()
        self.viewModel.viewDelegate = self
        
        self.viewModel.process(viewAction: .load)
        
        self.registerThemeServiceDidChangeThemeNotification()
    }
    
    // MARK: - Public
    
    @objc func numberOfRows() -> Int {
        return self.discoveryRows.count
    }
    
    @objc func cellForRow(atRow row: Int) -> UITableViewCell {

        let discoveryRow = self.discoveryRows[row]

        var cell: UITableViewCell?
        
        let enableInteraction: Bool
        
        if case .loading = self.viewState {
            enableInteraction = false
        } else {
            enableInteraction = true
        }
        
        switch discoveryRow {
        case .button(title: let title, action: let action):
            if let buttonCell: MXKTableViewCellWithButton = self.cellType(at: row) {
                buttonCell.mxkButton.setTitle(title, for: .normal)
                buttonCell.mxkButton.setTitle(title, for: .highlighted)
                buttonCell.mxkButton.vc_addAction(action: action)
                buttonCell.mxkButton.isEnabled = enableInteraction
                cell = buttonCell
            }
        case .threePid(let threePid):
            if let detailCell: MXKTableViewCell = self.cellType(at: row) {
                detailCell.vc_setAccessoryDisclosureIndicator(withTheme: self.theme)
                
                let formattedThreePid: String?
                
                switch threePid.medium {
                case .email:
                    formattedThreePid = threePid.address                  
                case .msisdn:
                    formattedThreePid = MXKTools.readableMSISDN(threePid.address)
                default:
                    formattedThreePid = nil
                }
                
                detailCell.textLabel?.text = formattedThreePid
                detailCell.isUserInteractionEnabled = enableInteraction
                cell = detailCell
            }
        }
        
        return cell ?? UITableViewCell()
    }
    
    @objc func reload() {
        self.viewModel.process(viewAction: .load)
    }
    
    @objc func selectRow(_ row: Int) {
        let discoveryRow = self.discoveryRows[row]
        
        switch discoveryRow {
        case .threePid(threePid: let threePid):
            self.viewModel.process(viewAction: .select(threePid: threePid))
        default:
            break
        }
    }
    
    func update(theme: Theme) {
        self.theme = theme
        
        self.updateRows()
    }
    
    // MARK: - Private
    
    private func registerThemeServiceDidChangeThemeNotification() {
        NotificationCenter.default.addObserver(self, selector: #selector(themeDidChange), name: .themeServiceDidChangeTheme, object: nil)
    }
    
    @objc private func themeDidChange() {
        self.update(theme: ThemeService.shared().theme)
    }
    
    private func cellType<T: MXKTableViewCell>(at row: Int) -> T? {
        let klass: T.Type = T.self
        let tableViewCell = delegate?.settingsDiscoveryTableViewSection(self, tableViewCellClass: klass, forRow: row)
        return tableViewCell as? T
    }
    
    private func updateRows() {
        
        // reset the footer
        attributedFooterTitle = nil
        footerShouldScrollToUserSettings = false
        
        let discoveryRows: [DiscoverySectionRows]
        
        switch self.viewState {
        case .loading:
            discoveryRows = self.discoveryRows
        case .loaded(let displayMode):
            switch displayMode {
            case .noIdentityServer:
                discoveryRows = []
                attributedFooterTitle = NSAttributedString(string: VectorL10n.settingsDiscoveryNoIdentityServer)
            case .termsNotSigned(let host):
                discoveryRows = [
                    .button(title: VectorL10n.settingsDiscoveryAcceptTerms, action: { [weak self] in
                        self?.viewModel.process(viewAction: .acceptTerms)
                    })
                ]
                
                attributedFooterTitle = NSAttributedString(string: VectorL10n.settingsDiscoveryTermsNotSigned(host))
            case .noThreePidsAdded:
                discoveryRows = []
                
                attributedFooterTitle = threePidsManagementInfoAttributedString()
                footerShouldScrollToUserSettings = true
            case .threePidsAdded(let emails, let phoneNumbers):
                
                let emailThreePids = emails.map { (email) -> DiscoverySectionRows in
                    return .threePid(threePid: email)
                }
                
                let phoneNumbersThreePids = phoneNumbers.map { (phoneNumber) -> DiscoverySectionRows in
                    return .threePid(threePid: phoneNumber)
                }
                
                discoveryRows = emailThreePids + phoneNumbersThreePids
                
                attributedFooterTitle = threePidsManagementInfoAttributedString()
                footerShouldScrollToUserSettings = true
            }
        case .error:
            discoveryRows = [
                .button(title: VectorL10n.retry, action: { [weak self] in
                    self?.viewModel.process(viewAction: .load)
                })
            ]
            attributedFooterTitle = NSAttributedString(string: VectorL10n.settingsDiscoveryErrorMessage)
        }
        
        self.discoveryRows = discoveryRows
    }
    
    private func threePidsManagementInfoAttributedString() -> NSAttributedString {
        let attributedInfoString = NSMutableAttributedString(string: VectorL10n.settingsDiscoveryThreePidsManagementInformationPart1)
        attributedInfoString.append(NSAttributedString(string: VectorL10n.settingsDiscoveryThreePidsManagementInformationPart2,
                                                       attributes: [.foregroundColor: self.theme.tintColor]))
        attributedInfoString.append(NSAttributedString(string: VectorL10n.settingsDiscoveryThreePidsManagementInformationPart3))
        return attributedInfoString
    }
}

// MARK: - SettingsDiscoveryViewModelViewDelegate
extension SettingsDiscoveryTableViewSection: SettingsDiscoveryViewModelViewDelegate {
    
    func settingsDiscoveryViewModel(_ viewModel: SettingsDiscoveryViewModelType, didUpdateViewState viewState: SettingsDiscoveryViewState) {
        self.viewState = viewState
        
        // The tableview datasource will call `self.cellForRow()`
        self.delegate?.settingsDiscoveryTableViewSectionDidUpdate(self)
    }
}