import Foundation

public struct RDEPUBLocation: Codable, Equatable {

    public var bookIdentifier: String?

    public var href: String

    public var progression: Double

    public var lastProgression: Double?

    public var fragment: String?

    public var rangeAnchor: RDEPUBTextRangeAnchor?

    public var cfi: String?

    public var lastCFI: String?

    public var rangeCFI: String?

    public init(
        bookIdentifier: String? = nil,
        href: String,
        progression: Double,
        lastProgression: Double? = nil,
        fragment: String? = nil,
        rangeAnchor: RDEPUBTextRangeAnchor? = nil,
        cfi: String? = nil,
        lastCFI: String? = nil,
        rangeCFI: String? = nil
    ) {
        self.bookIdentifier = bookIdentifier
        self.href = href
        self.progression = Self.clamp(progression)
        self.lastProgression = lastProgression.map(Self.clamp)
        self.fragment = fragment?.nilIfEmpty
        self.rangeAnchor = rangeAnchor
        self.cfi = cfi?.nilIfEmpty
        self.lastCFI = lastCFI?.nilIfEmpty
        self.rangeCFI = rangeCFI?.nilIfEmpty
    }

    public var navigationProgression: Double {
        let end = lastProgression ?? progression
        if end.isNaN || end.isInfinite {
            return progression
        }
        return Self.clamp((progression + end) / 2.0)
    }

    private static func clamp(_ value: Double) -> Double {
        guard value.isFinite else { return 0 }
        return min(1, max(0, value))
    }
}

public struct RDEPUBViewportResource: Codable, Equatable {

    public var href: String

    public var spineIndex: Int

    public var progression: Double

    public var lastProgression: Double?

    public var fragment: String?

    public init(
        href: String,
        spineIndex: Int,
        progression: Double,
        lastProgression: Double? = nil,
        fragment: String? = nil
    ) {
        self.href = href
        self.spineIndex = spineIndex
        self.progression = progression
        self.lastProgression = lastProgression
        self.fragment = fragment
    }
}

public struct RDEPUBViewport: Codable, Equatable {

    public var resources: [RDEPUBViewportResource]

    public var visiblePageNumber: Int

    public var chapterIndex: Int?

    public var isFixedLayout: Bool

    public init(
        resources: [RDEPUBViewportResource],
        visiblePageNumber: Int,
        chapterIndex: Int? = nil,
        isFixedLayout: Bool
    ) {
        self.resources = resources
        self.visiblePageNumber = visiblePageNumber
        self.chapterIndex = chapterIndex
        self.isFixedLayout = isFixedLayout
    }
}

public struct RDEPUBReadingContext: Codable, Equatable {

    public var location: RDEPUBLocation

    public var viewport: RDEPUBViewport

    public var pageNumber: Int

    public var chapterIndex: Int?

    public init(
        location: RDEPUBLocation,
        viewport: RDEPUBViewport,
        pageNumber: Int,
        chapterIndex: Int? = nil
    ) {
        self.location = location
        self.viewport = viewport
        self.pageNumber = pageNumber
        self.chapterIndex = chapterIndex
    }
}