//
//  FileLogHandler.swift
//  Pods
//
//  Created by 250102 on 2025/5/21.
//


import Foundation
import os.log

/// 一个rotatable、robust且efficient的文件日志处理器
public class FileLogHandler {
    // MARK: - 日志级别枚举
    
    public enum LogLevel: Int, Comparable {
        case verbose = 0
        case debug = 1
        case info = 2
        case warning = 3
        case error = 4
        case fatal = 5
        
        public static func < (lhs: LogLevel, rhs: LogLevel) -> Bool {
            return lhs.rawValue < rhs.rawValue
        }
        
        public var prefix: String {
            switch self {
            case .verbose: return "V"
            case .debug: return "D"
            case .info: return "I"
            case .warning: return "W"
            case .error: return "E"
            case .fatal: return "WTF"
            }
        }
    }
    
    // MARK: - 旋转配置结构
    
    public struct RotationConfig {
        /// 日志文件旋转前的最大大小（字节）（默认：10MB）
        public var maxFileSize: UInt64
        
        /// 要保留的归档日志文件的最大数量（默认：5）
        public var maxBackupCount: Int
        
        public init(maxFileSize: UInt64 = 10_485_760, // 10MB
                    maxBackupCount: Int = 5) {
            self.maxFileSize = maxFileSize
            self.maxBackupCount = maxBackupCount
        }
    }
    
    // MARK: - 属性
    
    private let fileURL: URL
    private let rotationConfig: RotationConfig
    private let dateFormatter: DateFormatter
    private let minimumLogLevel: LogLevel
    private let queue: DispatchQueue
    private let fileManager: FileManager
    private var fileHandle: FileHandle?
    
    // MARK: - 初始化
    
    /// 初始化一个新的FileLogHandler
    /// - 参数:
    ///   - directory: 日志文件的目录路径
    ///   - filename: 日志文件的基本名称（不带扩展名）
    ///   - rotationConfig: 日志rotation配置
    ///   - minimumLogLevel: 要记录的最小日志级别
    public init(directory: String? = nil, 
                filename: String = "app.log",
                rotationConfig: RotationConfig = RotationConfig(),
                minimumLogLevel: LogLevel = .debug) {
        self.rotationConfig = rotationConfig
        self.minimumLogLevel = minimumLogLevel
        
        // 创建时间戳的日期格式化器
        self.dateFormatter = DateFormatter()
        self.dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss.SSS"
        
        // 创建调度队列以确保线程安全
        self.queue = DispatchQueue(label: "com.fileloghandler.queue", qos: .utility)
        
        // 使用文件管理器
        self.fileManager = FileManager.default
        
        // 确定日志目录
        let baseDirectory: URL
        if let directory = directory {
            baseDirectory = fileManager.urls(for: .cachesDirectory, in: .userDomainMask).first!.appendingPathComponent("Logs", isDirectory: true).appendingPathComponent(directory, isDirectory: true)
        } else {
            // 如果未指定目录，默认为缓存目录
            #if os(macOS)
            let cacheDir = fileManager.urls(for: .cachesDirectory, in: .userDomainMask).first!
            #else
            let cacheDir = fileManager.urls(for: .cachesDirectory, in: .userDomainMask).first!
            #endif
            baseDirectory = cacheDir.appendingPathComponent("Logs", isDirectory: true)
        }
        
        // 如果日志目录不存在，则创建它
        let logsDirectory = baseDirectory
        try? fileManager.createDirectory(at: logsDirectory, withIntermediateDirectories: true, attributes: nil)
        
        // 设置文件URL
        self.fileURL = logsDirectory.appendingPathComponent(filename)
        
        // 打开或创建日志文件
        self.openLogFile()
    }
    
    deinit {
        try? fileHandle?.close()
    }
    
    // MARK: - 公共方法
    
    /// 使用指定级别记录消息
    /// - 参数:
    ///   - message: 要记录的消息
    ///   - level: 日志的严重级别
    ///   - file: 调用日志的文件
    ///   - function: 调用日志的函数
    ///   - line: 调用日志的行
    public func log(_ tag: String, _ message: String,
                    level: LogLevel = .info) {
        guard level >= minimumLogLevel else { return }
        
        queue.async { [weak self] in
            guard let self = self else { return }
            
            // 格式化日志条目
            let timestamp = self.dateFormatter.string(from: Date())
            let pid = ProcessInfo.processInfo.processIdentifier
            let logMessage = "\(timestamp) \(pid) \(level.prefix)/\(tag): \(message)\n"
            
            // 写入日志文件
            self.writeToFile(logMessage)
            
            // 检查是否需要基于文件大小进行rotate
            self.checkSizeRotation()
        }
    }
    
    /// 手动触发日志rotate
    public func rotateLogFile() {
        queue.async { [weak self] in
            self?.performRotation()
        }
    }
    
    // MARK: - 私有方法
    
    private func openLogFile() {
        do {
            // 如果文件不存在，则创建它
            if !fileManager.fileExists(atPath: fileURL.path) {
                try "".write(to: fileURL, atomically: true, encoding: .utf8)
            }
            
            // 打开文件以进行写入
            fileHandle = try FileHandle(forWritingTo: fileURL)
            
            // 移动到文件末尾
            fileHandle?.seekToEndOfFile()
        } catch {
            print("打开日志文件时出错: \(error)")
        }
    }
    
    private func writeToFile(_ message: String) {
        guard let data = message.data(using: .utf8) else { return }
        
        do {
            if fileHandle == nil {
                // 如果fileHandle为nil，尝试重新打开文件
                openLogFile()
            }
            
            if #available(iOS 13.4, macOS 10.15.4, watchOS 6.4, tvOS 13.4, *) {
                try fileHandle?.write(contentsOf: data)
            } else {
                fileHandle?.write(data)
            }
        } catch {
            print("写入日志文件时出错: \(error)")
            
            // 如果无法写入，关闭并尝试重新打开
            try? fileHandle?.close()
            fileHandle = nil
        }
    }
    
    private func checkSizeRotation() {
        do {
            let attributes = try fileManager.attributesOfItem(atPath: fileURL.path)
            let fileSize = attributes[.size] as? UInt64 ?? 0
            
            if fileSize >= rotationConfig.maxFileSize {
                performRotation()
            }
        } catch {
            print("检查文件大小时出错: \(error)")
        }
    }
    
    private func performRotation() {
        do {
            // 关闭当前文件句柄
            try fileHandle?.close()
            fileHandle = nil
            
            // 获取日志目录
            let directory = fileURL.deletingLastPathComponent()
            let filename = fileURL.lastPathComponent
            
            // 获取当前备份日志列表
            let baseFilename = filename
            let pattern = "^\(baseFilename)\\.(\\d+)$"
            let regex = try NSRegularExpression(pattern: pattern, options: [])
            
            let logFiles = try fileManager.contentsOfDirectory(atPath: directory.path)
                .filter { filename in
                    let range = NSRange(location: 0, length: filename.utf16.count)
                    return regex.firstMatch(in: filename, options: [], range: range) != nil
                }
                .sorted { file1, file2 in
                    // 提取备份号并比较
                    let range1 = NSRange(location: 0, length: file1.utf16.count)
                    let range2 = NSRange(location: 0, length: file2.utf16.count)
                    
                    guard let match1 = regex.firstMatch(in: file1, options: [], range: range1),
                          let match2 = regex.firstMatch(in: file2, options: [], range: range2) else {
                        return false
                    }
                    
                    let numberRange1 = match1.range(at: 1)
                    let numberRange2 = match2.range(at: 1)
                    
                    let number1 = strToInt(file1.utf16.dropFirst(baseFilename.utf16.count + 1).prefix(numberRange1.length)) ?? 0
                    let number2 = strToInt(file2.utf16.dropFirst(baseFilename.utf16.count + 1).prefix(numberRange2.length)) ?? 0
                    
                    return number1 < number2
                }
            
            // 如果我们有太多备份日志，则删除旧的备份日志
            if logFiles.count >= rotationConfig.maxBackupCount {
                for i in (rotationConfig.maxBackupCount - 1)..<logFiles.count {
                    try fileManager.removeItem(at: directory.appendingPathComponent(logFiles[i]))
                }
            }
            
            // 移动现有的备份日志
            for i in (0..<logFiles.count).reversed() {
                let file = logFiles[i]
                let range = NSRange(location: 0, length: file.utf16.count)
                guard let match = regex.firstMatch(in: file, options: [], range: range) else {
                    continue
                }
                
                let numberRange = match.range(at: 1)
                guard let number = strToInt(file.utf16.dropFirst(baseFilename.utf16.count + 1).prefix(numberRange.length)) else {
                    continue
                }
                
                if number < rotationConfig.maxBackupCount - 1 {
                    let oldPath = directory.appendingPathComponent(file)
                    let newPath = directory.appendingPathComponent("\(baseFilename).\(number + 1)")
                    try fileManager.moveItem(at: oldPath, to: newPath)
                } else {
                    try fileManager.removeItem(at: directory.appendingPathComponent(file))
                }
            }
            
            // 重命名当前日志文件
            let newBackupPath = directory.appendingPathComponent("\(baseFilename).1")
            try fileManager.moveItem(at: fileURL, to: newBackupPath)
            
            // 创建新的日志文件
            openLogFile()
            
            // 写入rotation消息
            let timestamp = dateFormatter.string(from: Date())
            let rotationMessage = "[\(timestamp)] [I] [FileLogHandler] Rotated\n"
            writeToFile(rotationMessage)
            
        } catch {
            print("rotate日志文件时出错: \(error)")
            
            // 即使rotate失败，也尝试重新打开文件
            openLogFile()
        }
    }
    private func strToInt(_ number: Substring.UTF16View) -> Int? {
        guard let numStr = String(number) else {
            return nil
        }
        return Int(numStr)
    }
}