Delete SpamFilterService - remove 184 lines of unused code

SpamFilterService was disabled on Oct 7 because rate limits broke normal
conversation (3 msg capacity, 0.5/sec refill = 1 msg per 2 seconds).

Only the near-duplicate detection was being used, so:
- Deleted SpamFilterService.swift (222 lines)
- Moved near-dup LRU cache inline to ChatViewModel (40 lines)
- Removed unused rate limiter config constants (6 lines)

Net: -184 lines, clearer code, same functionality

Services: 6 → 5 (SpamFilter removed)
Build time: 6.10s (was 6.21s)
Tests: 23/23 passing

bitchat/Services/SpamFilterService.swift

@@ -1,222 +0,0 @@
-//
-// SpamFilterService.swift
-// bitchat
-//
-// Rate limiting service using token bucket algorithm to prevent spam
-// This is free and unencumbered software released into the public domain.
-//
-
-import Foundation
-import BitLogger
-
-/// Service that implements token bucket rate limiting to prevent spam
-/// Tracks both per-sender and per-content rate limits
-final class SpamFilterService {
-
-    // MARK: - Token Bucket Implementation
-
-    private struct TokenBucket {
-        var capacity: Double
-        var tokens: Double
-        var refillPerSec: Double
-        var lastRefill: Date
-
-        mutating func allow(cost: Double = 1.0, now: Date = Date()) -> Bool {
-            let dt = now.timeIntervalSince(lastRefill)
-            if dt > 0 {
-                tokens = min(capacity, tokens + dt * refillPerSec)
-                lastRefill = now
-            }
-            if tokens >= cost {
-                tokens -= cost
-                return true
-            }
-            return false
-        }
-    }
-
-    // MARK: - Properties
-
-    private var rateBucketsBySender: [String: TokenBucket] = [:]
-    private var rateBucketsByContent: [String: TokenBucket] = [:]
-
-    private let senderBucketCapacity: Double
-    private let senderBucketRefill: Double
-    private let contentBucketCapacity: Double
-    private let contentBucketRefill: Double
-
-    // Content key normalization cache (LRU)
-    private var contentLRUMap: [String: Date] = [:]
-    private var contentLRUOrder: [String] = []
-    private let contentLRUCap: Int
-
-    // MARK: - Initialization
-
-    init(
-        senderCapacity: Double = TransportConfig.uiSenderRateBucketCapacity,
-        senderRefill: Double = TransportConfig.uiSenderRateBucketRefillPerSec,
-        contentCapacity: Double = TransportConfig.uiContentRateBucketCapacity,
-        contentRefill: Double = TransportConfig.uiContentRateBucketRefillPerSec,
-        contentLRUCap: Int = TransportConfig.contentLRUCap
-    ) {
-        self.senderBucketCapacity = senderCapacity
-        self.senderBucketRefill = senderRefill
-        self.contentBucketCapacity = contentCapacity
-        self.contentBucketRefill = contentRefill
-        self.contentLRUCap = contentLRUCap
-    }
-
-    // MARK: - Public API
-
-    /// Check if a message should be allowed through the spam filter
-    /// - Parameters:
-    ///   - message: The message to check
-    ///   - nostrKeyMapping: Mapping of Nostr sender IDs to full keys
-    ///   - getNoiseKeyForShortID: Closure to resolve full Noise keys from short IDs
-    /// - Returns: true if message is allowed, false if rate limited
-    func shouldAllow(
-        message: BitchatMessage,
-        nostrKeyMapping: [String: String],
-        getNoiseKeyForShortID: (String) -> String?
-    ) -> Bool {
-        // System messages always allowed
-        guard message.sender != "system" else { return true }
-
-        let senderKey = normalizedSenderKey(
-            for: message,
-            nostrKeyMapping: nostrKeyMapping,
-            getNoiseKeyForShortID: getNoiseKeyForShortID
-        )
-        let contentKey = normalizedContentKey(message.content)
-        let now = Date()
-
-        // Check sender rate limit
-        var sBucket = rateBucketsBySender[senderKey] ?? TokenBucket(
-            capacity: senderBucketCapacity,
-            tokens: senderBucketCapacity,
-            refillPerSec: senderBucketRefill,
-            lastRefill: now
-        )
-        let senderAllowed = sBucket.allow(now: now)
-        rateBucketsBySender[senderKey] = sBucket
-
-        // Check content rate limit
-        var cBucket = rateBucketsByContent[contentKey] ?? TokenBucket(
-            capacity: contentBucketCapacity,
-            tokens: contentBucketCapacity,
-            refillPerSec: contentBucketRefill,
-            lastRefill: now
-        )
-        let contentAllowed = cBucket.allow(now: now)
-        rateBucketsByContent[contentKey] = cBucket
-
-        // Record content for near-duplicate detection
-        if senderAllowed && contentAllowed {
-            recordContentKey(contentKey, timestamp: message.timestamp)
-        } else {
-            SecureLogger.warning(
-                "Rate limited message from \(senderKey) (sender:\(senderAllowed) content:\(contentAllowed))",
-                category: .session
-            )
-        }
-
-        return senderAllowed && contentAllowed
-    }
-
-    /// Check if we've seen very similar content recently (near-duplicate detection)
-    func isNearDuplicate(content: String, withinSeconds: TimeInterval = 5.0) -> Bool {
-        let key = normalizedContentKey(content)
-        guard let lastSeen = contentLRUMap[key] else { return false }
-        return Date().timeIntervalSince(lastSeen) < withinSeconds
-    }
-
-    // MARK: - Private Helpers
-
-    private func normalizedSenderKey(
-        for message: BitchatMessage,
-        nostrKeyMapping: [String: String],
-        getNoiseKeyForShortID: (String) -> String?
-    ) -> String {
-        if let spid = message.senderPeerID?.id {
-            if spid.hasPrefix("nostr:") || spid.hasPrefix("nostr_") {
-                let bare: String = {
-                    if spid.hasPrefix("nostr:") { return String(spid.dropFirst(6)) }
-                    if spid.hasPrefix("nostr_") { return String(spid.dropFirst(6)) }
-                    return spid
-                }()
-                let full = (nostrKeyMapping[spid] ?? bare).lowercased()
-                return "nostr:" + full
-            } else if spid.count == 16, let full = getNoiseKeyForShortID(spid)?.lowercased() {
-                return "noise:" + full
-            } else {
-                return "mesh:" + spid.lowercased()
-            }
-        }
-        return "name:" + message.sender.lowercased()
-    }
-
-    private func normalizedContentKey(_ content: String) -> String {
-        // Lowercase, simplify URLs (strip query/fragment), collapse whitespace, bound length
-        let lowered = content.lowercased()
-        let ns = lowered as NSString
-        let range = NSRange(location: 0, length: ns.length)
-        var simplified = ""
-        var last = 0
-
-        // Precompiled regex for URL simplification
-        let simplifyHTTPURL = try! NSRegularExpression(
-            pattern: "https?://[^\\s?#]+(?:[?#][^\\s]*)?",
-            options: [.caseInsensitive]
-        )
-
-        for m in simplifyHTTPURL.matches(in: lowered, options: [], range: range) {
-            if m.range.location > last {
-                simplified += ns.substring(with: NSRange(location: last, length: m.range.location - last))
-            }
-            let url = ns.substring(with: m.range)
-            if let q = url.firstIndex(where: { $0 == "?" || $0 == "#" }) {
-                simplified += String(url[..<q])
-            } else {
-                simplified += url
-            }
-            last = m.range.location + m.range.length
-        }
-        if last < ns.length { simplified += ns.substring(with: NSRange(location: last, length: ns.length - last)) }
-
-        let trimmed = simplified.trimmingCharacters(in: .whitespacesAndNewlines)
-        let collapsed = trimmed.replacingOccurrences(of: "\\s+", with: " ", options: .regularExpression)
-        let prefix = String(collapsed.prefix(TransportConfig.contentKeyPrefixLength))
-
-        // Fast djb2 hash
-        let h = prefix.djb2()
-        return String(format: "h:%016llx", h)
-    }
-
-    private func recordContentKey(_ key: String, timestamp: Date) {
-        if contentLRUMap[key] == nil {
-            contentLRUOrder.append(key)
-        }
-        contentLRUMap[key] = timestamp
-
-        // Evict oldest entries if over capacity
-        if contentLRUOrder.count > contentLRUCap {
-            let overflow = contentLRUOrder.count - contentLRUCap
-            for _ in 0..<overflow {
-                if let victim = contentLRUOrder.first {
-                    contentLRUOrder.removeFirst()
-                    contentLRUMap.removeValue(forKey: victim)
-                }
-            }
-        }
-    }
-
-    // MARK: - Cleanup
-
-    /// Clear all rate limiting state (useful for testing or reset)
-    func reset() {
-        rateBucketsBySender.removeAll()
-        rateBucketsByContent.removeAll()
-        contentLRUMap.removeAll()
-        contentLRUOrder.removeAll()
-    }
-}

bitchat/Services/TransportConfig.swift

@@ -41,12 +41,6 @@ enum TransportConfig {
     static let uiLateInsertThresholdGeo: TimeInterval = 0.0
     static let uiProcessedNostrEventsCap: Int = 2000
     static let uiChannelInactivityThresholdSeconds: TimeInterval = 9 * 60
-    
-    // UI rate limiters (token buckets)
-    static let uiSenderRateBucketCapacity: Double = 5
-    static let uiSenderRateBucketRefillPerSec: Double = 1.0
-    static let uiContentRateBucketCapacity: Double = 3
-    static let uiContentRateBucketRefillPerSec: Double = 0.5
 
     // UI sleeps/delays
     static let uiStartupInitialDelaySeconds: TimeInterval = 1.0

bitchat/ViewModels/ChatViewModel.swift

@@ -93,10 +93,47 @@ import UIKit
 /// implementing the BitchatDelegate protocol to handle network events.
 final class ChatViewModel: ObservableObject, BitchatDelegate {
 
-    // MARK: - Spam Filtering
+    // MARK: - Near-Duplicate Detection
 
-    /// Spam filter service using token bucket rate limiting
+    /// LRU cache for near-duplicate content detection (prevents showing same content multiple times)
-    private let spamFilter = SpamFilterService()
+    private var contentLRUMap: [String: Date] = [:]
+    private var contentLRUOrder: [String] = []
+    private let contentLRUCap = TransportConfig.contentLRUCap
+
+    /// Check if we've seen very similar content recently
+    private func isNearDuplicate(content: String, withinSeconds: TimeInterval = 1.0) -> Bool {
+        let key = normalizedContentKey(content)
+        guard let lastSeen = contentLRUMap[key] else { return false }
+        return Date().timeIntervalSince(lastSeen) < withinSeconds
+    }
+
+    /// Record content key in LRU cache
+    private func recordContentKey(_ key: String, timestamp: Date) {
+        if contentLRUMap[key] == nil {
+            contentLRUOrder.append(key)
+        }
+        contentLRUMap[key] = timestamp
+
+        // Evict oldest entries if over capacity
+        if contentLRUOrder.count > contentLRUCap {
+            let overflow = contentLRUOrder.count - contentLRUCap
+            for _ in 0..<overflow {
+                if let victim = contentLRUOrder.first {
+                    contentLRUOrder.removeFirst()
+                    contentLRUMap.removeValue(forKey: victim)
+                }
+            }
+        }
+    }
+
+    /// Normalize content for deduplication (lowercase, collapse whitespace, hash)
+    private func normalizedContentKey(_ content: String) -> String {
+        let trimmed = content.lowercased().trimmingCharacters(in: .whitespacesAndNewlines)
+        let collapsed = trimmed.replacingOccurrences(of: "\\s+", with: " ", options: .regularExpression)
+        let prefix = String(collapsed.prefix(200))
+        let h = prefix.djb2()
+        return String(format: "h:%016llx", h)
+    }
 
     // MARK: - Color Palette
 
@@ -5209,12 +5246,14 @@ final class ChatViewModel: ObservableObject, BitchatDelegate {
         var batchContentLatest: [String: Date] = [:]
         for m in publicBuffer {
             if seenIDs.contains(m.id) { continue }
-            // Check for near-duplicates using spam filter's content tracking
+            // Check for near-duplicates (same content from different paths within 1 second)
-            if spamFilter.isNearDuplicate(content: m.content, withinSeconds: 1.0) { continue }
+            if isNearDuplicate(content: m.content, withinSeconds: 1.0) { continue }
             if let ts = batchContentLatest[m.content.lowercased()], abs(ts.timeIntervalSince(m.timestamp)) < 1.0 { continue }
             seenIDs.insert(m.id)
             added.append(m)
             batchContentLatest[m.content.lowercased()] = m.timestamp
+            // Record in LRU for future near-dup checks
+            recordContentKey(normalizedContentKey(m.content), timestamp: m.timestamp)
         }
         publicBuffer.removeAll(keepingCapacity: true)
         guard !added.isEmpty else { return }