import UIKit

enum CardRecognitionPipelineError: LocalizedError {
    case ocrUnavailable(String)

    var errorDescription: String? {
        switch self {
        case .ocrUnavailable(let message):
            return message
        }
    }
}

struct CardRecognitionPipeline {
    let preprocessor: ImagePreprocessor
    let networkStatusProvider: any NetworkStatusProviding
    let cloudOCRClient: any CloudOCRClient
    let fallbackOCR: any CardTextRecognizing
    let extractor: CardTextHeuristicExtractor
    let enhancer: any CardFieldEnhancing

    init(
        preprocessor: ImagePreprocessor = ImagePreprocessor(),
        networkStatusProvider: any NetworkStatusProviding,
        cloudOCRClient: any CloudOCRClient = StubCloudOCRClient(),
        fallbackOCR: any CardTextRecognizing = VisionCardOCRService(),
        extractor: CardTextHeuristicExtractor = CardTextHeuristicExtractor(),
        enhancer: any CardFieldEnhancing = NoOpCardFieldEnhancer()
    ) {
        self.preprocessor = preprocessor
        self.networkStatusProvider = networkStatusProvider
        self.cloudOCRClient = cloudOCRClient
        self.fallbackOCR = fallbackOCR
        self.extractor = extractor
        self.enhancer = enhancer
    }

    func recognizeCard(in image: UIImage) async throws -> RecognitionSession {
        let preparedImage = try preprocessor.prepare(image)

        if networkStatusProvider.isOnline,
           let cloudResponse = try? await cloudOCRClient.recognizeText(from: CloudOCRRequest(jpegData: preparedImage.uploadJPEGData)),
           !cloudResponse.markdown.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty {
            let cloudLines = cloudResponse.markdown
                .split(whereSeparator: \.isNewline)
                .map { RecognizedTextLine(text: String($0), confidence: 0.95, normalizedBounds: .zero) }
            let payload = OCRTextPayload(rawText: cloudResponse.markdown, lines: cloudLines, averageConfidence: 0.95)
            var draft = extractor.extract(payload: payload, source: .cloud)
            draft = await enhancer.enhance(draft: draft, rawText: payload.rawText)
            return RecognitionSession(draft: draft, thumbnailJPEGData: preparedImage.thumbnailJPEGData)
        }

        let note = networkStatusProvider.isOnline
            ? "Cloud OCR is stubbed in this MVP, so StackDex used the local Vision pipeline."
            : "Offline erkannt — Ergebnis kann weniger genau sein."
        let source: RecognitionSource = networkStatusProvider.isOnline ? .onDeviceFallback : .onDeviceOffline

        let payload = try await fallbackOCR.recognizeText(in: preparedImage)
        var draft = extractor.extract(payload: payload, source: source, notes: [note])
        draft = await enhancer.enhance(draft: draft, rawText: payload.rawText)

        return RecognitionSession(draft: draft, thumbnailJPEGData: preparedImage.thumbnailJPEGData)
    }
}