//
//  URLBar.swift
//  SBrowser
//
//  Created by James Magahern on 7/23/20.
//

import UIKit

class URLBar: UIView
{
    let textField = UITextField(frame: .zero)
    let refreshButton = UIButton(frame: .zero)
    let errorButton = UIButton(frame: .zero)
    
    public enum LoadProgress {
        case complete
        case loading(progress: Double)
        case error(error: Error)
    }
    
    public var loadProgress: LoadProgress = .complete {
        didSet { updateProgressIndicator() }
    }
    
    private let backgroundView = UIVisualEffectView(effect: UIBlurEffect(style: .systemThickMaterial))
    private let shadowView = UIView(frame: .zero)
    private let progressIndicatorView = ProgressIndicatorView()
    private let fadeMaskView = UIImageView(frame: .zero)
    
    private let refreshImage = UIImage(systemName: "arrow.clockwise")
    private let stopImage = UIImage(systemName: "xmark")
    
    private let backgroundCornerRadius: CGFloat = 8
    
    convenience init() {
        self.init(frame: .zero)
        
        backgroundColor = .clear
        
        backgroundView.layer.masksToBounds = true
        backgroundView.layer.cornerRadius = backgroundCornerRadius
        backgroundView.layer.borderWidth = 1
        backgroundView.layer.borderColor = UIColor.secondarySystemFill.cgColor
        backgroundView.isUserInteractionEnabled = false
        addSubview(backgroundView)
        
        backgroundView.contentView.addSubview(progressIndicatorView)
        
        textField.backgroundColor = .clear
        textField.textContentType = .URL
        textField.keyboardType = .webSearch
        textField.autocorrectionType = .no
        textField.autocapitalizationType = .none
        textField.font = .systemFont(ofSize: 14.0)
        textField.clearingBehavior = .clearOnInsertionAndShowSelectionTint
        textField.clearButtonMode = .whileEditing
        textField.addAction(UIAction(handler: { [unowned self] _ in
            // Mask view visibility is affected by editing state.
            self.layoutSubviews()
        }), for: [ .editingDidBegin, .editingDidEnd ])
        addSubview(textField)
        
        textField.addAction(.init(handler: { [textField, refreshButton] _ in
            refreshButton.isHidden = textField.isFirstResponder
        }), for: [ .editingDidBegin, .editingDidEnd ])
        
        refreshButton.tintColor = .secondaryLabel
        refreshButton.setImage(refreshImage, for: .normal)
        addSubview(refreshButton)
        
        errorButton.backgroundColor = .systemRed
        errorButton.layer.cornerRadius = 3.0
        errorButton.layer.masksToBounds = true
        errorButton.titleLabel?.font = UIFont.boldSystemFont(ofSize: 11.0)
        errorButton.setTitleColor(.white, for: .normal)
        errorButton.setTitle("ERR", for: .normal)
        addSubview(errorButton)
        
        setErrorButtonAnimating(false)
    }
    
    private func updateProgressIndicator() {
        setErrorButtonAnimating(false)
        
        UIView.animate(withDuration: 0.4) {
            switch self.loadProgress {
            case .complete:
                self.refreshButton.setImage(self.refreshImage, for: .normal)
                self.progressIndicatorView.progress = 1.0
                UIView.animate(withDuration: 0.5, delay: 0.5, options: AnimationOptions()) {
                    self.progressIndicatorView.alpha = 0.0
                } completion: { _ in
                    // Reset back to zero
                    self.progressIndicatorView.progress = 0.0
                }
                
            case .loading(let progress):
                self.refreshButton.setImage(self.stopImage, for: .normal)
                self.progressIndicatorView.progress = progress
                self.progressIndicatorView.alpha = 1.0
                
            case .error(let error):
                self.setErrorButtonAnimating(true)
                self.progressIndicatorView.alpha = 0.0
                self.progressIndicatorView.progress = 0.0
                
                if let nserror = error as NSError? {
                    self.errorButton.setTitle("\(nserror.code)", for: .normal)
                } else {
                    self.errorButton.setTitle("ERR", for: .normal)
                }
            }
        }
        
        self.setNeedsLayout()
    }
    
    override var intrinsicContentSize: CGSize {
        let preferredHeight = CGFloat(34)
        return CGSize(width: 1000.0, height: preferredHeight)
    }
    
    private func fadeBackgroundImageForSize(_ size: CGSize, cutoffLocation: CGFloat) -> UIImage? {
        var image: UIImage? = nil
        
        UIGraphicsBeginImageContext(CGSize(width: size.width, height: 1.0))
        if let context = UIGraphicsGetCurrentContext() {
            let gradientColorsArray = [
                UIColor(white: 1.0, alpha: 1.0).cgColor,
                UIColor(white: 1.0, alpha: 1.0).cgColor,
                UIColor(white: 1.0, alpha: 0.08).cgColor,
                UIColor(white: 1.0, alpha: 0.08).cgColor
            ]
            
            let locations: [CGFloat] = [
                0.0, cutoffLocation, cutoffLocation + 0.10, 1.0
            ]
            
            if let gradient = CGGradient(colorsSpace: nil, colors: gradientColorsArray as CFArray, locations: locations) {
                context.drawLinearGradient(gradient, start: .zero, end: CGPoint(x: size.width, y: 0.0), options: CGGradientDrawingOptions())
            }
            
            image = UIGraphicsGetImageFromCurrentImageContext()
            UIGraphicsEndImageContext();
        }
        
        return image
    }
    
    private func setErrorButtonAnimating(_ animating: Bool) {
        let animationKey = "blinkAnimation"
        if animating {
            let blinkAnimation = CAKeyframeAnimation(keyPath: "opacity")
            blinkAnimation.calculationMode = .discrete
            blinkAnimation.values = [ 1.0, 0.1, 1.0 ]
            blinkAnimation.keyTimes = [ 0.0, 0.5, 1.0 ]
            blinkAnimation.duration = 1.0
            blinkAnimation.repeatCount = .infinity
            
            self.errorButton.layer.add(blinkAnimation, forKey: animationKey)
        } else {
            self.errorButton.layer.removeAnimation(forKey: animationKey)
        }
    }
    
    override func layoutSubviews() {
        super.layoutSubviews()
        backgroundView.frame = bounds
        shadowView.frame = bounds
        progressIndicatorView.frame = backgroundView.contentView.bounds
        textField.frame = bounds.insetBy(dx: 6.0, dy: 0)
        
        var fadeCutoffLocation: CGFloat = 0.8
        
        // Refresh button
        let refreshButtonSize = CGSize(width: textField.frame.height, height: textField.frame.height)
        refreshButton.frame = CGRect(origin: CGPoint(x: bounds.width - refreshButtonSize.width, y: 0), size: refreshButtonSize)
        
        // Error button
        if case .error(error: _) = loadProgress, !textField.isFirstResponder {
            errorButton.isHidden = false
            errorButton.sizeToFit()
            errorButton.frame = CGRect(
                x: refreshButton.frame.minX - errorButton.frame.width - 8.0,
                y: 0.0,
                width: errorButton.frame.width + 8.0,
                height: 22.0
            )
            errorButton.frame = errorButton.frame.centeredY(inRect: bounds)
            fadeCutoffLocation = (errorButton.frame.minX / bounds.width) - 0.1
        } else {
            errorButton.isHidden = true
        }
        
        // Fade mask
        fadeMaskView.frame = textField.bounds
        fadeMaskView.image = fadeBackgroundImageForSize(fadeMaskView.frame.size, cutoffLocation: fadeCutoffLocation)
        if !textField.isFirstResponder {
            textField.mask = fadeMaskView
        } else {
            textField.mask = nil
        }
    }
}

class ProgressIndicatorView: UIView
{
    public var progress: Double = 0.0 {
        didSet { layoutSubviews() }
    }
    
    private let progressFillView = UIView(frame: .zero)
    
    convenience init() {
        self.init(frame: .zero)
        
        progressFillView.backgroundColor = .systemBlue
        progressFillView.alpha = 0.3
        addSubview(progressFillView)
    }
    
    override func layoutSubviews() {
        super.layoutSubviews()
        
        let width = CGFloat(progress) * bounds.width
        progressFillView.frame = CGRect(origin: .zero, size: CGSize(width: width, height: bounds.height))
    }
}