import SwiftUI

final class ImageResource: ObservableObject {

    /// Globally unique id
    @Published
    var id: String

    @Published
    var altText: LocalizedText

    @Published
    var size: CGSize = .zero

    var aspectRatio: CGFloat {
        guard size.height > 0 else {
            return 0
        }
        return size.width / size.height
    }

    private let source: ImageSource

    init(uniqueId: String, altText: LocalizedText, fileUrl: URL) {
        self.id = uniqueId
        self.source = .file(fileUrl)
        self.altText = altText
    }

    init(resourceName: String) {
        self.id = resourceName
        self.source = .resource(resourceName)
        self.altText = .init(en: "A test image included in the bundle", de: "Ein Test-Image aus dem Bundle")
    }

    private enum ImageSource {
        case file(URL)
        case resource(String)
    }
}

extension ImageResource: Identifiable {

}

extension ImageResource: Equatable {

    static func == (lhs: ImageResource, rhs: ImageResource) -> Bool {
        lhs.id == rhs.id
    }
}

extension ImageResource: Hashable {

    func hash(into hasher: inout Hasher) {
        hasher.combine(id)
    }
}

extension ImageResource {

    var imageToDisplay: Image {
        switch source {
        case .file(let url):
            return image(at: url)
        case .resource(let name):
            return .init(name)
        }
    }

    private func image(at url: URL) -> Image {
        let imageData: Data
        do {
            imageData = try Data(contentsOf: url)
        } catch {
            print("Failed to load image data from \(url.path): \(error)")
            return failureImage
        }
        guard let loadedImage = NSImage(data: imageData) else {
            print("Failed to create image from \(url.path)")
            return failureImage
        }
        if self.size == .zero && loadedImage.size != .zero {
            DispatchQueue.main.async {
                self.size = loadedImage.size
            }
        }
        return .init(nsImage: loadedImage)
    }

    private var failureImage: SwiftUI.Image {
        Image(systemSymbol: .exclamationmarkTriangle)
    }

}