import Foundation
import UIKit

/// Drives the "Beleg scannen" flow: takes a captured/picked `UIImage`,
/// uploads it to `POST /api/scan` for AI extraction, and hands the resulting
/// `Receipt` back to the view. Does NOT persist anything itself — saving
/// happens later in `ReceiptReviewView` via `ReceiptsAPI.sync(...)`.
@MainActor
final class ScanViewModel: ObservableObject {
    @Published var isUploading = false
    @Published var errorMessage: String?

    /// Converts the image to JPEG and uploads it for extraction.
    /// Returns the extracted `Receipt` on success, or `nil` on failure
    /// (in which case `errorMessage` is set to German user-facing text).
    func uploadAndExtract(image: UIImage) async -> Receipt? {
        guard let data = image.jpegData(compressionQuality: 0.85) else {
            errorMessage = "Bild konnte nicht verarbeitet werden."
            return nil
        }
        return await uploadAndExtract(imageData: data)
    }

    /// Same as above, but takes already-encoded JPEG data directly.
    func uploadAndExtract(imageData: Data) async -> Receipt? {
        isUploading = true
        errorMessage = nil
        defer { isUploading = false }

        do {
            let response = try await ReceiptsAPI.scan(
                fileData: imageData,
                fileName: "receipt.jpg",
                mimeType: "image/jpeg"
            )
            guard let receipt = response.receipt else {
                errorMessage = "Es konnten keine Belegdaten erkannt werden."
                return nil
            }
            return receipt
        } catch let error as APIError {
            errorMessage = error.localizedDescription
            return nil
        } catch {
            errorMessage = error.localizedDescription
            return nil
        }
    }
}