From 67c102385e5a4e3b29c29bbe95071eabd45b4fb9 Mon Sep 17 00:00:00 2001
From: Smoke <86024507+crypto-smoke@users.noreply.github.com>
Date: Wed, 31 Jan 2024 10:18:12 -1000
Subject: add packet deduplicator

---
 dedupe.go | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 dedupe.go

diff --git a/dedupe.go b/dedupe.go
new file mode 100644
index 0000000..2b103b8
--- /dev/null
+++ b/dedupe.go
@@ -0,0 +1,66 @@
+package meshtastic
+
+import (
+	"encoding/hex"
+	"fmt"
+	"hash"
+	"sync"
+	"time"
+)
+
+type PacketDeduplicator struct {
+	hasher       hash.Hash
+	expiresAfter time.Duration
+	sync.RWMutex
+	seen map[string]time.Time
+}
+
+func NewDeduplicator(hasher hash.Hash, expiresAfter time.Duration) *PacketDeduplicator {
+	pd := PacketDeduplicator{
+		seen:         make(map[string]time.Time),
+		hasher:       hasher,
+		expiresAfter: expiresAfter,
+	}
+	go func() {
+		for {
+			time.Sleep(expiresAfter)
+			pd.Lock()
+			for packet, timestamp := range pd.seen {
+				if time.Since(timestamp) > pd.expiresAfter {
+					delete(pd.seen, packet)
+				}
+			}
+			pd.Unlock()
+		}
+	}()
+
+	return &pd
+}
+func (p *PacketDeduplicator) Seen(sender, packetID uint32) bool {
+	asString := fmt.Sprintf("%d-%d", sender, packetID)
+	p.RLock()
+	if _, exists := p.seen[asString]; !exists {
+		p.RUnlock()
+		p.Lock()
+		defer p.Unlock()
+		p.seen[asString] = time.Now()
+		return false
+	}
+	p.RUnlock()
+	return true
+}
+func (p *PacketDeduplicator) SeenData(data []byte) bool {
+	hashed := p.hasher.Sum(data)
+	asHex := hex.EncodeToString(hashed)
+	p.RLock()
+	if _, exists := p.seen[asHex]; !exists {
+		p.RUnlock()
+		p.Lock()
+		defer p.Unlock()
+		p.seen[asHex] = time.Now()
+		return false
+	}
+	p.RUnlock()
+
+	return true
+}
-- 
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