B4J=true
Group=Filters
ModulesStructureVersion=1
Type=Class
Version=10.5
@EndOfDesignText@
'Filter class
Sub Class_Globals
    Private RequestCounts As Map
    Private const MAX_REQUESTS_PER_WINDOW As Int = 10 
    Private const WINDOW_MS As Long = 10000            
    
    ' Whitelist Settings
    Private Whitelist As B4XSet
    Private const WHITELIST_FILE As String = "whitelist.txt"
    
    ' Logging Settings
    Private const SECURITY_LOG_FILE As String = "security_violations.log"
    
    ' --- Daily Summary Settings ---
    Private TotalBlocksToday As Int = 0
    Private CurrentDateString As String
    ' ------------------------------
    
    ' Background Worker Settings
    Private CleanupTimer As Timer
    Private const CLEANUP_INTERVAL_MS As Long = 300000 ' Runs every 5 minutes
End Sub

Public Sub Initialize
    RequestCounts.Initialize
    Whitelist.Initialize
    LoadWhitelistFromFile
    
    ' Set the initial date tracking string (format: YYYY-MM-DD)
    DateTime.DateFormat = "yyyy-MM-dd"
    CurrentDateString = DateTime.Date(DateTime.Now)
    
    ' Start background worker
    CleanupTimer.Initialize("CleanupTimer", CLEANUP_INTERVAL_MS)
    CleanupTimer.Enabled = True
End Sub

Private Sub LoadWhitelistFromFile
    Try
        If File.Exists(File.DirApp, WHITELIST_FILE) = False Then
            File.WriteList(File.DirApp, WHITELIST_FILE, Array As String("127.0.0.1"))
        End If
        
        Dim Lines As List = File.ReadList(File.DirApp, WHITELIST_FILE)
        
        Whitelist.Clear
        For Each Entry As String In Lines
            Dim CleanEntry As String = Entry.Trim
            If CleanEntry <> "" And CleanEntry.StartsWith("#") = False Then
                Whitelist.Add(CleanEntry)
            End If
        Next
    Catch
        Log("RateLimiter Error: Whitelist load failed: " & LastException.Message)
    End Try
End Sub

Private Sub LogViolation(Identifier As String, RequestPath As String)
    Dim LogLine As String = $"[${DateTime.Date(DateTime.Now)} ${DateTime.Time(DateTime.Now)}] BLOCKED: ID/IP [${Identifier}] spamming ${RequestPath}${CRLF}"$
    Try
        Dim Out As OutputStream = File.OpenOutput(File.DirApp, SECURITY_LOG_FILE, True)
        Dim tw As TextWriter
        tw.Initialize(Out)
        tw.Write(LogLine)
        tw.Close
        
        ' Increment the daily summary block counter
        TotalBlocksToday = TotalBlocksToday + 1
        
    Catch
        Log("RateLimiter Error: Failed to write to security log: " & LastException.Message)
    End Try
End Sub

' Helper method called by the background worker at midnight
Private Sub GenerateDailySummaryReport(ReportDate As String, BlocksCount As Int)
    Dim ReportFile As String = $"daily_report_${ReportDate}.txt"$
    Dim ReportContent As String = _
        $"=========================================${CRLF}"$ & _
        $"RATE LIMITER DAILY SUMMARY REPORT        ${CRLF}"$ & _
        $"Date: ${ReportDate}                     ${CRLF}"$ & _
        $"=========================================${CRLF}"$ & _
        $"Total Security Interceptions: ${BlocksCount}${CRLF}"$ & _
        $"Status: Completed                         ${CRLF}"$
        
    Try
        File.WriteString(File.DirApp, ReportFile, ReportContent)
        Log("RateLimiter Background Worker: Generated daily summary report file " & ReportFile)
    Catch
        Log("RateLimiter Error: Failed to generate summary report: " & LastException.Message)
    End Try
End Sub

Private Sub IsWhitelisted(Identifier As String, UserIP As String) As Boolean
    If Whitelist.Contains(Identifier) Or Whitelist.Contains(UserIP) Then Return True
    
    ' B4XSet doesn't have Keys property - iterate through all items
    For Each Rule As String In Whitelist.AsList
        If Rule.Contains("*") Then
            Dim Prefix As String = Rule.Replace("*", "")
            If UserIP.StartsWith(Prefix) Then Return True
        End If
    Next
    Return False
End Sub

' Filter event runs on incoming HTTP requests
Public Sub Filter(Req As ServletRequest, Resp As ServletResponse) As Boolean
    Dim ClientIdentifier As String = ""
    Dim AuthHeader As String = Req.GetHeader("Authorization")
    
    If AuthHeader <> "" And AuthHeader <> Null Then
        If AuthHeader.StartsWith("Bearer ") Then
            ClientIdentifier = AuthHeader.SubString(7).Trim
        Else
            ClientIdentifier = AuthHeader.Trim
        End If
    End If
    
    Dim UserIP As String = Req.GetHeader("CF-Connecting-IP")
    If UserIP = "" Or UserIP = Null Then UserIP = Req.RemoteAddress
    
    If ClientIdentifier = "" Then ClientIdentifier = "GUEST-" & UserIP
    
    If IsWhitelisted(ClientIdentifier, UserIP) Then Return True
    
    Dim Now As Long = DateTime.Now
    
    Dim RequestHistory As List
    
    If RequestCounts.ContainsKey(ClientIdentifier) Then
        RequestHistory = RequestCounts.Get(ClientIdentifier)
    Else
        RequestHistory.Initialize
        RequestCounts.Put(ClientIdentifier, RequestHistory)
    End If
    
    Dim CutoffTime As Long = Now - WINDOW_MS
    Do While RequestHistory.Size > 0 And RequestHistory.Get(0) < CutoffTime
        RequestHistory.RemoveAt(0)
    Loop
    
    If RequestHistory.Size >= MAX_REQUESTS_PER_WINDOW Then
        LogViolation(ClientIdentifier, Req.RequestURI)
        
        Resp.Status = 429 
        Resp.SetHeader("Retry-After", Bit.ParseInt(WINDOW_MS / 1000, 10))
        Resp.ContentType = "text/plain"
        Resp.Write("Too Many Requests. Please wait.")
        Return False 
    End If
    
    RequestHistory.Add(Now)
    
    Return True 
End Sub

' Background Worker Event: Cleans memory, reloads files, AND checks for daily reset
Private Sub CleanupTimer_Tick
    LoadWhitelistFromFile
    
    ' 1. Check if the calendar day has rolled over
    DateTime.DateFormat = "yyyy-MM-dd"
    Dim CheckTodayString As String = DateTime.Date(DateTime.Now)
    
    If CheckTodayString <> CurrentDateString Then
        ' It is a new day! Save yesterday's summary metrics to a file
        GenerateDailySummaryReport(CurrentDateString, TotalBlocksToday)
        
        ' Reset counters for the brand new day
        TotalBlocksToday = 0
        CurrentDateString = CheckTodayString
    End If
    
    ' 2. Clean up stale IP histories from the Map to free RAM
    Dim Now As Long = DateTime.Now
    Dim CutoffTime As Long = Now - WINDOW_MS
    Dim IDsToRemove As List
    IDsToRemove.Initialize
    
    For Each Identifier As String In RequestCounts.Keys
        Dim RequestHistory As List = RequestCounts.Get(Identifier)
        
        Do While RequestHistory.Size > 0 And RequestHistory.Get(0) < CutoffTime
            RequestHistory.RemoveAt(0)
        Loop
        
        If RequestHistory.Size = 0 Then
            IDsToRemove.Add(Identifier)
        End If
    Next
    
    For Each InactiveID As String In IDsToRemove
        RequestCounts.Remove(InactiveID)
    Next
End Sub