PlantGuide/PlantGuide/Domain/UseCases/Identification/IdentifyPlantOnDeviceUseCase.swift

//
//  IdentifyPlantOnDeviceUseCase.swift
//  PlantGuide
//
//  Created on 1/21/26.
//

import Foundation
import UIKit

// MARK: - IdentifyPlantUseCaseProtocol

/// Protocol for plant identification use cases (both on-device and remote)
protocol IdentifyPlantUseCaseProtocol: Sendable {
    /// Identifies a plant from an image
    /// - Parameter image: The UIImage containing the plant to identify
    /// - Returns: An array of view-layer predictions
    /// - Throws: If identification fails
    func execute(image: UIImage) async throws -> [ViewPlantPrediction]
}

// MARK: - IdentifyPlantOnDeviceUseCase

/// Use case for identifying plants using on-device machine learning
struct IdentifyPlantOnDeviceUseCase: IdentifyPlantUseCaseProtocol {

    // MARK: - Dependencies

    private let imagePreprocessor: any ImagePreprocessorProtocol
    private let classificationService: any PlantClassificationServiceProtocol

    // MARK: - Initialization

    init(
        imagePreprocessor: any ImagePreprocessorProtocol,
        classificationService: any PlantClassificationServiceProtocol
    ) {
        self.imagePreprocessor = imagePreprocessor
        self.classificationService = classificationService
    }

    // MARK: - IdentifyPlantUseCaseProtocol

    /// Identifies a plant and returns view-layer predictions
    func execute(image: UIImage) async throws -> [ViewPlantPrediction] {
        // Preprocess the image for classification
        let preprocessedImage = try await imagePreprocessor.preprocess(image)

        // Run classification on the preprocessed image
        let predictions = try await classificationService.classify(image: preprocessedImage)

        guard !predictions.isEmpty else {
            throw IdentifyPlantOnDeviceUseCaseError.noMatchesFound
        }

        // Map ML predictions to view-layer predictions
        return predictions.map { prediction in
            ViewPlantPrediction(
                id: prediction.id,
                speciesName: prediction.scientificName,
                commonName: prediction.commonNames.first,
                confidence: Double(prediction.confidence)
            )
        }
    }
}

// MARK: - IdentifyPlantOnDeviceUseCaseError

/// Errors that can occur during on-device plant identification
enum IdentifyPlantOnDeviceUseCaseError: Error, LocalizedError {
    /// No matches were found for the provided image
    case noMatchesFound

    var errorDescription: String? {
        switch self {
        case .noMatchesFound:
            return "No plant matches were found in the image"
        }
    }
}