import Vision
import CoreGraphics
import ImageIO

class FeatureMatcher {
    static let revision = VNGenerateImageFeaturePrintRequest.Revision.revision1

    static func generateFingerprint(from image: CGImage, orientation: CGImagePropertyOrientation = .up) async throws -> VNFeaturePrintObservation {
        let req = VNGenerateImageFeaturePrintRequest()
        req.revision = revision
        req.imageCropAndScaleOption = .scaleFill
        let handler = VNImageRequestHandler(cgImage: image, orientation: orientation, options: [:])
        try handler.perform([req])

        guard let result = req.results?.first as? VNFeaturePrintObservation else {
            throw NSError(domain: "FeatureMatcher", code: -1, userInfo: [NSLocalizedDescriptionKey: "No features detected"])
        }
        return result
    }

    static func identify(scan: VNFeaturePrintObservation, database: [CardMetadata], cache: [UUID: VNFeaturePrintObservation]) -> MatchResult {
        var candidates: [(CardMetadata, Float)] = []
        for card in database {
            guard let obs = cache[card.id] else { continue }
            var dist: Float = 0
            if (try? scan.computeDistance(&dist, to: obs)) != nil && dist < 18.0 {
                candidates.append((card, dist))
            }
        }
        let sorted = candidates.sorted { $0.1 < $1.1 }
        guard let best = sorted.first else { return .unknown }

        if best.1 < 6.0 { return .exact(best.0) }
        let close = sorted.filter { $0.1 < (best.1 + 3.0) }
        if close.count > 1 { return .ambiguous(name: best.0.name, candidates: close.map { $0.0 }) }
        return .exact(best.0)
    }
}