//
//  ReferenceImageProvider.swift
//  GasTankAR
//
//  Created by Dennis Nemec on 26.08.26.
//

import ARKit
import UIKit

/// Liefert die Referenzbilder für die Anker-Erkennung. Bevorzugt die AR-Ressourcengruppe
/// „ARMarkers"; fällt sonst auf einen programmatisch erzeugten Platzhalter-Marker zurück.
enum ReferenceImageProvider {
    static func load() -> Set<ARReferenceImage> {
        if let group = ARReferenceImage.referenceImages(inGroupNamed: "ARMarkers", bundle: .main) {
            return group
        }
        if let placeholder = makePlaceholder() {
            return [placeholder]
        }
        return []
    }

    private static func makePlaceholder() -> ARReferenceImage? {
        let size = CGSize(width: 512, height: 512)
        let renderer = UIGraphicsImageRenderer(size: size)
        let image = renderer.image { context in
            let cg = context.cgContext
            UIColor.white.setFill()
            cg.fill(CGRect(origin: .zero, size: size))

            let palette: [UIColor] = [.black, .systemBlue, .systemRed, .systemGreen, .systemOrange, .systemPurple]
            let cells = 8
            let cellSize = size.width / CGFloat(cells)
            for row in 0..<cells {
                for column in 0..<cells {
                    let index = (row * cells + column) % palette.count
                    palette[index].setFill()
                    let rect = CGRect(
                        x: CGFloat(column) * cellSize,
                        y: CGFloat(row) * cellSize,
                        width: cellSize,
                        height: cellSize
                    )
                    if (row + column).isMultiple(of: 2) {
                        cg.fillEllipse(in: rect.insetBy(dx: 4, dy: 4))
                    } else {
                        cg.fill(rect.insetBy(dx: 6, dy: 6))
                    }
                }
            }
        }
        guard let cgImage = image.cgImage else { return nil }
        return ARReferenceImage(cgImage, orientation: .up, physicalWidth: 0.15)
    }
}