Imports System.IO
Imports System.Text
Imports System.Collections.Concurrent

Public Module Logger
    Private ReadOnly logDirectory As String = "c:\\logs"
    Private ReadOnly maxLogSizeBytes As Long = 10 * 1024 * 1024 ' 每个文件最大10MB
    Private ReadOnly logRetentionDays As Integer = 1
    Private ReadOnly logLock As New Object()
    Private ReadOnly logQueue As New ConcurrentQueue(Of String)()
    Private ReadOnly logWritingTask As Task

    Public Enum LogLevel
        Info
        Warn
        [Error]
        Debug
    End Enum

    ''' <summary>
    ''' 初始化日志写入任务
    ''' </summary>
    Sub New()
        logWritingTask = Task.Run(AddressOf ProcessLogQueue)
    End Sub

    ''' <summary>
    ''' 异步写入带等级的日志
    ''' </summary>
    Public Sub WriteLog(level As LogLevel, message As String)
        Dim logEntry As String = $"{DateTime.Now:yyyy-MM-dd HH:mm:ss.fff} [{level.ToString().ToUpper()}] {message}"
        logQueue.Enqueue(logEntry)
    End Sub

    ''' <summary>
    ''' 定期从队列中取出日志并写入文件
    ''' </summary>
    Private Async Sub ProcessLogQueue()
        While True
            ' 确保日志写入任务不会频繁创建线程
            If logQueue.IsEmpty Then
                Await Task.Delay(500) ' 等待一段时间再检查队列
            End If
            ' 使用 TryDequeue 从队列中获取 logEntry
            Dim logEntry As String = Nothing
            If logQueue.TryDequeue(logEntry) Then
                WriteLogToFile(logEntry)
            End If
        End While
    End Sub

    ''' <summary>
    ''' 写入日志到文件
    ''' </summary>
    Private Sub WriteLogToFile(logEntry As String)
        Try
            SyncLock logLock
                If Not Directory.Exists(logDirectory) Then
                    Directory.CreateDirectory(logDirectory)
                End If

                CleanupOldLogs()

                Dim todayFile As String = Path.Combine(logDirectory, $"{Date.Today:yyyy-MM-dd}.log")

                If File.Exists(todayFile) Then
                    Dim fileInfo As New FileInfo(todayFile)
                    If fileInfo.Length > maxLogSizeBytes Then
                        BackupAndClear(todayFile)
                    End If
                End If

                Using sw As New StreamWriter(todayFile, append:=True, encoding:=Encoding.UTF8)
                    sw.WriteLine(logEntry)
                End Using
            End SyncLock
        Catch
            ' 忽略日志写入错误
        End Try
    End Sub

    ''' <summary>
    ''' 清理过期的日志文件
    ''' </summary>
    Private Sub CleanupOldLogs()
        Try
            Dim files = Directory.GetFiles(logDirectory)
            For Each file In files
                Dim fileName = Path.GetFileNameWithoutExtension(file)
                Dim dateStr = fileName.Split("_"c).FirstOrDefault()
                If Date.TryParse(dateStr, Nothing) Then
                    Dim fileDate = Date.Parse(dateStr)
                    If (Date.Today - fileDate).Days >= logRetentionDays Then
                        file.Remove(file)
                    End If
                End If
            Next
        Catch
            ' 忽略清理错误
        End Try
    End Sub

    ''' <summary>
    ''' 备份并清空日志文件
    ''' </summary>
    Private Sub BackupAndClear(filePath As String)
        Try
            Dim bakFile As String = filePath.Replace(".log", $"_{DateTime.Now:HHmmss}.bak")
            File.Copy(filePath, bakFile, overwrite:=True)
            File.WriteAllText(filePath, "") ' 清空日志内容
        Catch
            ' 忽略备份错误
        End Try
    End Sub

    ''' <summary>
    ''' 快捷方法：写 Info 日志
    ''' </summary>
    Public Sub Info(message As String)
        'WriteLog(LogLevel.Info, message)
    End Sub

    ''' <summary>
    ''' 快捷方法：写 Warning 日志
    ''' </summary>
    Public Sub Warn(message As String)
        'WriteLog(LogLevel.Warn, message)
    End Sub

    ''' <summary>
    ''' 快捷方法：写 Error 日志
    ''' </summary>
    Public Sub [Error](message As String)
        'WriteLog(LogLevel.Error, message)
    End Sub

    ''' <summary>
    ''' 快捷方法：写 Debug 日志
    ''' </summary>
    Public Sub Debug(message As String)
        'WriteLog(LogLevel.Debug, message)
    End Sub
End Module