//
//  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 backButton: UIButton!
    private var forwardsButton: UIButton!
    private var reloadButton: UIButton!
    private var tableOfContentsButton: UIButton!
    private var shareButton: UIButton!
    private var prefsButton: 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),
        ])
        
        let symbolConfig = UIImage.SymbolConfiguration(pointSize: 24)
        
        backButton = UIButton()
        backButton.addTarget(navigator, action: #selector(NavigationManager.goBack), for: .touchUpInside)
        backButton.isEnabled = navigator.backStack.count > 0
        backButton.setImage(UIImage(systemName: "arrow.left", withConfiguration: symbolConfig), for: .normal)
        backButton.accessibilityLabel = "Back"
        backButton.isPointerInteractionEnabled = true
        // fallback for when UIButton.menu isn't available
        if #available(iOS 14.0, *) {
        } else {
            backButton.addInteraction(UIContextMenuInteraction(delegate: self))
        }
        
        forwardsButton = UIButton()
        forwardsButton.addTarget(navigator, action: #selector(NavigationManager.goForward), for: .touchUpInside)
        forwardsButton.isEnabled = navigator.forwardStack.count > 0
        forwardsButton.setImage(UIImage(systemName: "arrow.right", withConfiguration: symbolConfig), for: .normal)
        forwardsButton.accessibilityLabel = "Forward"
        forwardsButton.isPointerInteractionEnabled = true
        if #available(iOS 14.0, *) {
        } else {
            forwardsButton.addInteraction(UIContextMenuInteraction(delegate: self))
        }
        
        reloadButton = UIButton()
        reloadButton.addTarget(navigator, action: #selector(NavigationManager.reload), for: .touchUpInside)
        reloadButton.setImage(UIImage(systemName: "arrow.clockwise", withConfiguration: symbolConfig), for: .normal)
        reloadButton.accessibilityLabel = "Reload"
        reloadButton.isPointerInteractionEnabled = true
        
        tableOfContentsButton = UIButton()
        tableOfContentsButton.addTarget(self, action: #selector(tableOfContentsPressed), for: .touchUpInside)
        tableOfContentsButton.setImage(UIImage(systemName: "list.bullet.indent", withConfiguration: symbolConfig), for: .normal)
        tableOfContentsButton.accessibilityLabel = "Table of Contents"
        tableOfContentsButton.isPointerInteractionEnabled = true
        
        shareButton = UIButton()
        shareButton.addTarget(self, action: #selector(sharePressed), for: .touchUpInside)
        shareButton.setImage(UIImage(systemName: "square.and.arrow.up", withConfiguration: symbolConfig), for: .normal)
        shareButton.accessibilityLabel = "Share"
        shareButton.isPointerInteractionEnabled = true
        
        prefsButton = UIButton()
        prefsButton.addTarget(self, action: #selector(prefsPressed), for: .touchUpInside)
        prefsButton.setImage(UIImage(systemName: "gear", withConfiguration: symbolConfig), for: .normal)
        prefsButton.accessibilityLabel = "Preferences"
        prefsButton.isPointerInteractionEnabled = true
        
        let stack = UIStackView(arrangedSubviews: [
            backButton,
            forwardsButton,
            reloadButton,
            tableOfContentsButton,
            shareButton,
            prefsButton,
        ])
        stack.axis = .horizontal
        stack.distribution = .fillEqually
        stack.alignment = .fill
        stack.translatesAutoresizingMaskIntoConstraints = false
        addSubview(stack)
        let safeAreaConstraint = stack.bottomAnchor.constraint(equalTo: safeAreaLayoutGuide.bottomAnchor)
        safeAreaConstraint.priority = .defaultHigh
        NSLayoutConstraint.activate([
            stack.leadingAnchor.constraint(equalTo: leadingAnchor),
            stack.trailingAnchor.constraint(equalTo: trailingAnchor),
            stack.topAnchor.constraint(equalTo: topAnchor, constant: 5),
            safeAreaConstraint,
            stack.bottomAnchor.constraint(lessThanOrEqualTo: bottomAnchor, constant: -8)
        ])
        
        updateNavigationButtons()
        
        navigator.navigationOperation
            .sink { (_) in
                self.updateNavigationButtons()
            }
            .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 updateNavigationButtons() {
        backButton.isEnabled = navigator.backStack.count > 0
        forwardsButton.isEnabled = navigator.forwardStack.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)

            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?(shareButton)
    }
    
    @objc private func prefsPressed() {
        showPreferences?()
    }

}

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 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 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
        }
    }
}