//
//  ToolbarView.swift
//  Gemini-iOS
//
//  Created by Shadowfacts on 12/19/20.
//

import UIKit
import BrowserCore
import Combine

class ToolbarView: UIView {

    let navigator: NavigationManager
    
    var showTableOfContents: (() -> Void)?
    var showShareSheet: ((UIView) -> Void)?
    var showPreferences: (() -> Void)?
    
    private var border: UIView!
    private var buttonsStack: UIStackView!
    private var toolbarButtons: [ToolbarItem: UIButton] = [:]
    
    private var cancellables = [AnyCancellable]()
    
    init(navigator: NavigationManager) {
        self.navigator = navigator
        
        super.init(frame: .zero)
        
        backgroundColor = .systemBackground
        
        border = UIView()
        border.translatesAutoresizingMaskIntoConstraints = false
        border.backgroundColor = UIColor(white: traitCollection.userInterfaceStyle == .dark ? 0.25 : 0.75, alpha: 1)
        addSubview(border)
        NSLayoutConstraint.activate([
            border.leadingAnchor.constraint(equalTo: leadingAnchor),
            border.trailingAnchor.constraint(equalTo: trailingAnchor),
            border.topAnchor.constraint(equalTo: topAnchor),
            border.heightAnchor.constraint(equalToConstant: 1),
        ])
        
        buttonsStack = UIStackView()
        buttonsStack.axis = .horizontal
        buttonsStack.distribution = .fillEqually
        buttonsStack.alignment = .fill
        buttonsStack.translatesAutoresizingMaskIntoConstraints = false
        addSubview(buttonsStack)
        let safeAreaConstraint = buttonsStack.bottomAnchor.constraint(equalTo: safeAreaLayoutGuide.bottomAnchor)
        safeAreaConstraint.priority = .defaultHigh
        NSLayoutConstraint.activate([
            buttonsStack.leadingAnchor.constraint(equalTo: leadingAnchor),
            buttonsStack.trailingAnchor.constraint(equalTo: trailingAnchor),
            buttonsStack.topAnchor.constraint(equalTo: topAnchor, constant: 5),
            safeAreaConstraint,
            buttonsStack.bottomAnchor.constraint(lessThanOrEqualTo: bottomAnchor, constant: -8)
        ])
        
        updateNavigationButtons()
        
        navigator.navigationOperation
            .sink { [unowned self] (_) in
                self.updateNavigationButtons()
            }
            .store(in: &cancellables)
        
        Preferences.shared.$toolbar
            .sink { [unowned self] (newValue) in
                self.createToolbarButtons(newValue)
            }
            .store(in: &cancellables)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
        super.traitCollectionDidChange(previousTraitCollection)
        
        border.backgroundColor = UIColor(white: traitCollection.userInterfaceStyle == .dark ? 0.25 : 0.75, alpha: 1)
    }
    
    private func createToolbarButtons(_ items: [ToolbarItem] = Preferences.shared.toolbar) {
        toolbarButtons = [:]
        buttonsStack.arrangedSubviews.forEach { $0.removeFromSuperview() }
        
        for item in items {
            let button = createButton(item)
            toolbarButtons[item] = button
            buttonsStack.addArrangedSubview(button)
        }
        
        updateNavigationButtons()
    }
    
    private func createButton(_ item: ToolbarItem) -> UIButton {
        let button = UIButton()
        let symbolConfig = UIImage.SymbolConfiguration(pointSize: 24)
        button.setImage(UIImage(systemName: item.imageName, withConfiguration: symbolConfig)!, for: .normal)
        button.accessibilityLabel = item.displayName
        button.isPointerInteractionEnabled = true
        
        switch item {
        case .back:
            button.addTarget(navigator, action: #selector(NavigationManager.goBack), for: .touchUpInside)
            // fallback for when UIButton.menu isn't available
            if #available(iOS 14.0, *) {
            } else {
                button.addInteraction(UIContextMenuInteraction(delegate: self))
            }
            
        case .forward:
            button.addTarget(navigator, action: #selector(NavigationManager.goForward), for: .touchUpInside)
            if #available(iOS 14.0, *) {
            } else {
                button.addInteraction(UIContextMenuInteraction(delegate: self))
            }
            
        case .reload:
            button.addTarget(navigator, action: #selector(NavigationManager.reload), for: .touchUpInside)
            
        case .share:
            button.addTarget(self, action: #selector(sharePressed), for: .touchUpInside)
            
        case .home:
            button.addTarget(self, action: #selector(homePressed), for: .touchUpInside)
            
        case .tableOfContents:
            button.addTarget(self, action: #selector(tableOfContentsPressed), for: .touchUpInside)
            
        case .preferences:
            button.addTarget(self, action: #selector(prefsPressed), for: .touchUpInside)
        }
        
        return button
    }
    
    private func updateNavigationButtons() {
        if let backButton = toolbarButtons[.back] {
            backButton.isEnabled = navigator.backStack.count > 0
            if #available(iOS 14.0, *) {
                let back = navigator.backStack.suffix(5).enumerated().reversed().map { (index, entry) -> UIAction in
                    let backCount = min(5, navigator.backStack.count) - index
                    if #available(iOS 15.0, *),
                       let title = entry.title {
                        return UIAction(title: title, subtitle: BrowserHelper.urlForDisplay(entry.url)) { [unowned self] (_) in
                            self.navigator.back(count: backCount)
                        }
                    } else {
                        return UIAction(title: BrowserHelper.urlForDisplay(entry.url)) { [unowned self] (_) in
                            self.navigator.back(count: backCount)
                        }
                    }
                }
                backButton.menu = UIMenu(children: back)
            }
        }
        
        if let forwardsButton = toolbarButtons[.forward] {
            forwardsButton.isEnabled = navigator.forwardStack.count > 0
            if #available(iOS 14.0, *) {
                let forward = navigator.forwardStack.prefix(5).enumerated().map { (index, entry) -> UIAction in
                    let forwardCount = index + 1
                    if #available(iOS 15.0, *),
                       let title = entry.title {
                        return UIAction(title: title, subtitle: BrowserHelper.urlForDisplay(entry.url)) { [unowned self] (_) in
                            self.navigator.forward(count: forwardCount)
                        }
                    } else {
                        return UIAction(title: BrowserHelper.urlForDisplay(entry.url)) { [unowned self] (_) in
                            self.navigator.forward(count: forwardCount)
                        }
                    }
                }
                forwardsButton.menu = UIMenu(children: forward)
            }
        }
    }
    
    @objc private func tableOfContentsPressed() {
        showTableOfContents?()
    }
    
    @objc private func sharePressed() {
        showShareSheet?(toolbarButtons[.share]!)
    }
    
    @objc private func prefsPressed() {
        showPreferences?()
    }
    
    @objc private func homePressed() {
        navigator.changeURL(Preferences.shared.homepage)
    }

}

extension ToolbarView: UIContextMenuInteractionDelegate {
    func contextMenuInteraction(_ interaction: UIContextMenuInteraction, configurationForMenuAtLocation location: CGPoint) -> UIContextMenuConfiguration? {
        // this path is only used on <iOS 14, on >=iOS 14, we don't create a UIContextMenuInteraction
        if let backButton = toolbarButtons[.back],
           interaction.view == backButton {
            return UIContextMenuConfiguration(identifier: nil, previewProvider: { nil }) { (_) -> UIMenu? in
                let children = self.navigator.backStack.suffix(5).enumerated().map { (index, entry) in
                    UIAction(title: BrowserHelper.urlForDisplay(entry.url)) { (_) in
                        self.navigator.back(count: min(5, self.navigator.backStack.count) - index)
                    }
                }
                return UIMenu(title: "", image: nil, identifier: nil, options: [], children: children)
            }
        } else if let forwardsButton = toolbarButtons[.forward],
                  interaction.view == forwardsButton {
            return UIContextMenuConfiguration(identifier: nil, previewProvider: { nil }) { (_) -> UIMenu? in
                let children = self.navigator.forwardStack.prefix(5).enumerated().map { (index, entry) -> UIAction in
                    let forwardCount = index + 1
                    return UIAction(title: BrowserHelper.urlForDisplay(entry.url)) { (_) in
                        self.navigator.forward(count: forwardCount)
                    }
                }
                return UIMenu(title: "", image: nil, identifier: nil, options: [], children: children)
            }
        } else {
            return nil
        }
    }
}