import UIKit

enum RDEPUBTextPageLayoutMetrics {

    static let pageNumberTrailingPadding: CGFloat = 4

    static let pageNumberFooterPadding: CGFloat = 8

    static let pageNumberReservedHeight: CGFloat = ceil(UIFont.systemFont(ofSize: 13).lineHeight) + pageNumberFooterPadding

    static func contentInsets(
        configuration: RDEPUBReaderConfiguration,
        safeAreaInsets: UIEdgeInsets
    ) -> UIEdgeInsets {
        let configInsets = configuration.reflowableContentInsets
        return UIEdgeInsets(
            top: max(configInsets.top, safeAreaInsets.top),
            left: max(configInsets.left, safeAreaInsets.left),
            bottom: max(configInsets.bottom, safeAreaInsets.bottom) + pageNumberReservedHeight,
            right: max(configInsets.right, safeAreaInsets.right)
        )
    }
}

final class RDEPUBReaderEnvironment {

    weak var controller: RDEPUBReaderController?

    weak var readerView: RDReaderView?

    var displayEnvironment: any RDEPUBReaderDisplayEnvironment

    init(
        controller: RDEPUBReaderController,
        readerView: RDReaderView,
        displayEnvironment: any RDEPUBReaderDisplayEnvironment
    ) {
        self.controller = controller
        self.readerView = readerView
        self.displayEnvironment = displayEnvironment
    }

    func currentLayoutContext(configuration: RDEPUBReaderConfiguration) -> RDEPUBNavigatorLayoutContext {
        let containerSize = readerView?.bounds.size ?? .zero
        let viewSize = controller?.view.bounds.size ?? containerSize
        let resolvedSize = containerSize == .zero ? viewSize : containerSize
        return RDEPUBNavigatorLayoutContext(
            containerSize: resolvedSize,
            pagesPerScreen: readerView?.pagesPerScreen ?? 1,
            safeAreaInsets: RDEPUBSafeArea.resolve(controller?.view.safeAreaInsets),
            userInterfaceIdiom: controller?.traitCollection.userInterfaceIdiom ?? .phone,
            reflowableContentInsets: configuration.reflowableContentInsets
        )
    }

    func currentTextRenderStyle(configuration: RDEPUBReaderConfiguration) -> RDEPUBTextRenderStyle {
        let font = configuration.fontChoice.font(ofSize: configuration.fontSize)
        let lineSpacing = max(font.lineHeight * (configuration.lineHeightMultiple - 1), 4)
        return RDEPUBTextRenderStyle(
            font: font,
            lineSpacing: lineSpacing,
            textColor: configuration.theme.contentTextColor,
            backgroundColor: configuration.theme.contentBackgroundColor
        )
    }

    func currentTextLayoutConfig(
        configuration: RDEPUBReaderConfiguration,
        pageSize: CGSize
    ) -> RDEPUBTextLayoutConfig {
        let safeAreaInsets = RDEPUBSafeArea.resolve(controller?.view.safeAreaInsets)
        return RDEPUBTextLayoutConfig(
            frameWidth: max(pageSize.width, 1),
            frameHeight: max(pageSize.height, 1),
            edgeInsets: RDEPUBTextPageLayoutMetrics.contentInsets(
                configuration: configuration,
                safeAreaInsets: safeAreaInsets
            ),
            numberOfColumns: configuration.numberOfColumns,
            columnGap: configuration.columnGap,
            avoidOrphans: false,
            avoidWidows: false,
            avoidPageBreakInsideEnabled: true,
            hyphenation: true,
            imageMaxHeightRatio: 0.85,
            fallbackViewportSize: displayEnvironment.fallbackViewportSize
        )
    }

    var currentBrightness: CGFloat {
        get { displayEnvironment.currentBrightness }
        set { displayEnvironment.currentBrightness = newValue }
    }

    var fallbackViewportSize: CGSize {
        displayEnvironment.fallbackViewportSize
    }
}