//
//  UIImage+Extension.swift
//  Lanu
//
//  Created by OneeChan on 2025/11/16.
//

import Foundation
import Photos


extension UIImage {
    /// 生成线性渐变图片
    /// - Parameters:
    ///   - colors: 渐变颜色数组（至少两种）
    ///   - size: 图片尺寸
    ///   - startPoint: 渐变起点（坐标系：左上角(0,0)，右下角(1,1)）
    ///   - endPoint: 渐变终点
    /// - Returns: 生成的渐变图片（nil 表示参数无效）
    static func generateLinearGradientImage(
        colors: [UIColor],
        size: CGSize,
        location: [NSNumber],
        startPoint: CGPoint = CGPoint(x: 0, y: 0),
        endPoint: CGPoint = CGPoint(x: 1, y: 0)
    ) -> UIImage? {
        // 校验参数有效性
        guard colors.count >= 2, size.width > 0, size.height > 0 else {
            return nil
        }
        
        // 创建渐变图层
        let gradientLayer = CAGradientLayer()
        gradientLayer.frame = CGRect(origin: .zero, size: size)
        gradientLayer.colors = colors.map { $0.cgColor } // 转换为 CGColor
        gradientLayer.locations = location
        gradientLayer.startPoint = startPoint
        gradientLayer.endPoint = endPoint
        
        // 渲染图层为图片
        let renderer = UIGraphicsImageRenderer(size: size)
        return renderer.image { _ in
            gradientLayer.render(in: UIGraphicsGetCurrentContext()!)
        }
    }
}

enum LNImageCompressType {
    case none
    case avatar
    case photoWall
    
    var maxSize: CGSize {
        switch self {
        case .none: .zero
        case .avatar: .init(width: 600, height: 600)
        case .photoWall: .init(width: 750, height: 1334)
        }
    }
}

extension UIImage {
    func saveToLibrary(completion: ((Bool, Error?) -> Void)?) {
        // 步骤1：检查并请求相册权限
        PHPhotoLibrary.requestAuthorization { status in
            DispatchQueue.main.async { // 回调默认在子线程，切回主线程处理UI
                switch status {
                case .authorized, .limited: // 授权（含iOS 14+有限授权）
                    // 步骤2：异步保存图片到相册
                    PHPhotoLibrary.shared().performChanges({
                        // 创建保存请求
                        PHAssetChangeRequest.creationRequestForAsset(from: self)
                    }) { success, error in
                        DispatchQueue.main.async {
                            completion?(success, error)
                        }
                    }
                    
                case .denied, .restricted: // 权限拒绝/受限
                    let error = NSError(domain: "AlbumError", code: -1, userInfo: [
                        NSLocalizedDescriptionKey: "相册权限已拒绝，请前往设置开启"
                    ])
                    completion?(false, error)
                    
                case .notDetermined: // 理论上不会走到这里（requestAuthorization已触发授权）
                    completion?(false, NSError(domain: "AlbumError", code: -2, userInfo: [
                        NSLocalizedDescriptionKey: "权限请求未完成"
                    ]))
                    
                @unknown default:
                    completion?(false, NSError(domain: "AlbumError", code: -3, userInfo: [
                        NSLocalizedDescriptionKey: "未知权限状态"
                    ]))
                }
            }
        }
    }
    
    func compress(type: LNImageCompressType) -> UIImage? {
        let maxSize: CGSize = type.maxSize
        if maxSize == .zero {
            UIGraphicsBeginImageContext(CGSizeMake(size.width, size.height));
            draw(in: .init(origin: .zero, size: size))
            let convertToUpImage = UIGraphicsGetImageFromCurrentImageContext();
            UIGraphicsEndImageContext();
            return convertToUpImage
        }
        
        if size.width <= maxSize.width
            && size.height <= maxSize.height {
            return self
        }
        
        let widthRatio = maxSize.width / size.width
        let heightRatio = maxSize.height / size.height
        let scaleRatio = min(widthRatio, heightRatio)
        
        let newSize = CGSize(width: size.width * scaleRatio,
                             height: size.height * scaleRatio)
        
        let renderer = UIGraphicsImageRenderer(size: newSize)
        let resizedImage = renderer.image { _ in
            draw(in: CGRect(origin: .zero, size: newSize))
        }
        return resizedImage
    }
}