Signal-iOS/SignalUI/Appearance/ColorOrGradient+SignalUI.swift

//
// Copyright 2021 Signal Messenger, LLC
// SPDX-License-Identifier: AGPL-3.0-only
//

import Foundation
public import SignalServiceKit
import UIKit

// MARK: -

/// ColorOrGradientSetting is used for persistence and comparison.
/// ColorOrGradientValue is used for rendering.
public enum ColorOrGradientValue: CustomStringConvertible {
    case transparent
    case blur(blurEffect: UIVisualEffect)
    case solidColor(color: UIColor)
    /// If angleRadians = 0, gradientColor1 is N.
    /// If angleRadians = PI / 2, gradientColor1 is E.
    /// etc.
    case gradient(
        gradientColor1: UIColor,
        gradientColor2: UIColor,
        angleRadians: CGFloat,
    )

    public var description: String {
        switch self {
        case .transparent:
            return "[transparent]"
        case .blur:
            return "[blur]"
        case .solidColor(let color):
            return "[solidColor: \(color.asOWSColor)]"
        case .gradient(let gradientColor1, let gradientColor2, let angleRadians):
            return "[gradient gradientColor1: \(gradientColor1.asOWSColor), gradientColor2: \(gradientColor2.asOWSColor), angleRadians: \(angleRadians)]"
        }
    }
}

// MARK: -

public enum ColorOrGradientThemeMode: Int {
    case auto
    case alwaysLight
    case alwaysDark
}

// MARK: -

public extension ColorOrGradientSetting {
    var asValue: ColorOrGradientValue {
        asValue(themeMode: .auto)
    }

    func asValue(themeMode: ColorOrGradientThemeMode) -> ColorOrGradientValue {
        let shouldUseDarkColors: Bool = {
            switch themeMode {
            case .auto:
                return Theme.isDarkThemeEnabled
            case .alwaysDark:
                return true
            case .alwaysLight:
                return false
            }
        }()

        switch self {
        case .solidColor(let solidColor):
            return .solidColor(color: solidColor.asUIColor)
        case .themedColor(let lightThemeColor, let darkThemeColor):
            let color = shouldUseDarkColors ? darkThemeColor : lightThemeColor
            return .solidColor(color: color.asUIColor)
        case .gradient(let gradientColor1, let gradientColor2, let angleRadians):
            return .gradient(
                gradientColor1: gradientColor1.asUIColor,
                gradientColor2: gradientColor2.asUIColor,
                angleRadians: angleRadians,
            )
        case .themedGradient(
            let lightGradientColor1,
            let lightGradientColor2,
            let darkGradientColor1,
            let darkGradientColor2,
            let angleRadians,
        ):
            let gradientColor1 = shouldUseDarkColors ? darkGradientColor1 : lightGradientColor1
            let gradientColor2 = shouldUseDarkColors ? darkGradientColor2 : lightGradientColor2
            return .gradient(
                gradientColor1: gradientColor1.asUIColor,
                gradientColor2: gradientColor2.asUIColor,
                angleRadians: angleRadians,
            )
        }
    }
}

// MARK: -

public extension UIColor {
    var asOWSColor: OWSColor {
        let (red, green, blue, _) = self.components() ?? (0, 0, 0, 0)
        return OWSColor(red: red.clamp01(), green: green.clamp01(), blue: blue.clamp01())
    }
}

// MARK: -

public extension ColorOrGradientValue {

    func asChatUIElementTintColor() -> UIColor {
        let bubbleColor: UIColor = {
            switch self {
            case .transparent, .blur:
                return .Signal.accent

            case .solidColor(let color):
                return color

            case .gradient(let gradientColor1, let gradientColor2, _):
                return gradientColor1.midPoint(with: gradientColor2)
            }
        }()
        let lightThemeFinalColor = bubbleColor.blendedWithOverlay(.white, opacity: 0.16)
        let darkThemeFinalColor = bubbleColor.blendedWithOverlay(.black, opacity: 0.1)
        return UIColor(
            light: lightThemeFinalColor,
            dark: darkThemeFinalColor,
        )
    }
}