//
//  TravelAlbumAutoRetouchProcessor.swift
//  suixinkan
//

import Foundation
import UIKit

/// 自动 AI 修图处理接口，把本地原图与已选模板转换为可持久化的结果数据。
@MainActor
protocol TravelAlbumAutoRetouchProcessing {
    /// 按指定模板处理一张本地照片。
    func process(sourceURL: URL, preset: TravelAlbumEditPreset) async throws -> Data
}

/// 使用项目现有 Core Image 效果生成自动修图演示结果。
@MainActor
final class TravelAlbumAutoRetouchProcessor: TravelAlbumAutoRetouchProcessing {
    private let processingDelayNanoseconds: UInt64

    /// 创建本地修图处理器，默认保留短暂处理时间用于展示“修图中”状态。
    init(processingDelayNanoseconds: UInt64 = 900_000_000) {
        self.processingDelayNanoseconds = processingDelayNanoseconds
    }

    func process(sourceURL: URL, preset: TravelAlbumEditPreset) async throws -> Data {
        let sourceData = try Data(contentsOf: sourceURL)
        guard let sourceImage = UIImage(data: sourceData) else {
            throw TravelAlbumAutoRetouchError.invalidSourceImage
        }
        if processingDelayNanoseconds > 0 {
            try await Task.sleep(nanoseconds: processingDelayNanoseconds)
        }
        try Task.checkCancellation()
        let editedImage = TravelAlbumAIEditImageProcessor.render(effect: preset.effect, source: sourceImage)
        guard let resultData = editedImage.jpegData(compressionQuality: 0.92) else {
            throw TravelAlbumAutoRetouchError.resultEncodingFailed
        }
        return resultData
    }
}

/// 本地自动 AI 修图过程的可展示错误。
enum TravelAlbumAutoRetouchError: LocalizedError, Equatable {
    case invalidSourceImage
    case resultEncodingFailed
    case invalidImageData

    var errorDescription: String? {
        switch self {
        case .invalidSourceImage:
            return "原图无法读取，修图失败"
        case .resultEncodingFailed:
            return "修图结果生成失败"
        case .invalidImageData:
            return "修图结果无法读取"
        }
    }
}