//
//  KMThumbnailCache.swift
//  PDF Reader Pro
//
//  Created by lizhe on 2024/8/9.
//

class KMThumbnailCache: NSObject {
    static let shared = KMThumbnailCache()
    
    private let maxCacheSize = 50
    // 外层字典以文档路径为键，内层字典以缩略图 ID 为键
    private var thumbnails: [String: [String: NSImage]] = [:]
    private var order: [String: [String]] = [:] // 记录每个文档路径的插入顺序

    // 添加缩略图及其文档路径
    func addThumbnail(for path: String, id: String, image: NSImage) {
        // 确保每个路径都有自己的字典和顺序数组
        if thumbnails[path] == nil {
            thumbnails[path] = [:]
            order[path] = []
        }
        
        // 获取当前路径的字典和顺序数组
        var currentThumbnails = thumbnails[path]!
        var currentOrder = order[path]!
        
        // 检查并维持每个路径的最大缓存大小
        if currentThumbnails.count >= maxCacheSize {
            if let oldestID = currentOrder.first {
                currentThumbnails.removeValue(forKey: oldestID)
                currentOrder.removeFirst()
            }
        }
        
        // 添加新缩略图
        currentThumbnails[id] = image
        currentOrder.append(id)
        
        // 更新字典和顺序数组
        thumbnails[path] = currentThumbnails
        order[path] = currentOrder
    }

    // 根据路径和 ID 获取缩略图
    func thumbnail(for path: String, id: String) -> NSImage? {
        return thumbnails[path]?[id]
    }

    // 根据路径和 ID 移除缩略图
    func removeThumbnail(for path: String, id: String) {
        guard var currentThumbnails = thumbnails[path],
              var currentOrder = order[path] else {
            print("Path or ID not found")
            return
        }
        
        if let index = currentOrder.firstIndex(of: id) {
            currentThumbnails.removeValue(forKey: id)
            currentOrder.remove(at: index)
        } else {
            print("ID not found in the given path")
        }
        
        // 更新字典和顺序数组
        thumbnails[path] = currentThumbnails
        order[path] = currentOrder
    }

    // 清空缓存
    func clearCache(for path: String? = nil) {
        if let path = path {
            thumbnails[path]?.removeAll()
            order[path]?.removeAll()
        } else {
            thumbnails.removeAll()
            order.removeAll()
        }
    }
}