Add dedupe and tests (#4)

* document dedupe.go

* add dedupe test

2 files changed, 75 insertions, 4 deletions

diff --git a/dedupe.go b/dedupe.go
index 2b103b8..97934e0 100644
--- a/dedupe.go
+++ b/dedupe.go
@@ -8,13 +8,17 @@ import (
 	"time"
 )
 
+// PacketDeduplicator is a structure that prevents processing of duplicate packets.
+// It keeps a record of seen packets and the time they were last seen.
 type PacketDeduplicator struct {
-	hasher       hash.Hash
-	expiresAfter time.Duration
-	sync.RWMutex
-	seen map[string]time.Time
+	hasher       hash.Hash            // hasher is used for generating packet identifiers.
+	expiresAfter time.Duration        // expiresAfter defines the duration after which a seen packet record expires.
+	sync.RWMutex                      // RWMutex is used to protect the seen map from concurrent access.
+	seen         map[string]time.Time // seen maps a packet identifier to the last time it was seen.
 }
 
+// NewDeduplicator creates a new PacketDeduplicator with a given hasher and expiration duration for packet records.
+// It starts a background goroutine to periodically clean up expired packet records.
 func NewDeduplicator(hasher hash.Hash, expiresAfter time.Duration) *PacketDeduplicator {
 	pd := PacketDeduplicator{
 		seen:         make(map[string]time.Time),
@@ -36,6 +40,9 @@ func NewDeduplicator(hasher hash.Hash, expiresAfter time.Duration) *PacketDedupl
 
 	return &pd
 }
+
+// Seen checks whether a packet with the given sender and packetID has been seen before.
+// If not, it records the packet as seen and returns false. Otherwise, it returns true.
 func (p *PacketDeduplicator) Seen(sender, packetID uint32) bool {
 	asString := fmt.Sprintf("%d-%d", sender, packetID)
 	p.RLock()
@@ -49,6 +56,9 @@ func (p *PacketDeduplicator) Seen(sender, packetID uint32) bool {
 	p.RUnlock()
 	return true
 }
+
+// SeenData checks whether the data has been seen before based on its hashed value.
+// If not, it records the data as seen and returns false. Otherwise, it returns true.
 func (p *PacketDeduplicator) SeenData(data []byte) bool {
 	hashed := p.hasher.Sum(data)
 	asHex := hex.EncodeToString(hashed)
diff --git a/dedupe_test.go b/dedupe_test.go
new file mode 100644
index 0000000..6388360
--- /dev/null
+++ b/dedupe_test.go
@@ -0,0 +1,61 @@
+package meshtastic_test
+
+import (
+	"crypto/md5"
+	"github.com/crypto-smoke/meshtastic-go"
+	"testing"
+	"time"
+)
+
+func TestPacketDeduplicatorSeen(t *testing.T) {
+	hasher := md5.New()
+	expiresAfter := 100 * time.Millisecond
+	dedup := meshtastic.NewDeduplicator(hasher, expiresAfter)
+
+	sender := uint32(1)
+	packetID := uint32(1)
+
+	// Test Seen with new packetID
+	if dedup.Seen(sender, packetID) {
+		t.Error("Expected the packet to not have been seen")
+	}
+
+	// Test Seen with same packetID again
+	if !dedup.Seen(sender, packetID) {
+		t.Error("Expected the packet to have been seen")
+	}
+
+	// Wait for expiration
+	time.Sleep(expiresAfter + 100*time.Millisecond)
+
+	// Test Seen with same packetID after expiration
+	if dedup.Seen(sender, packetID) {
+		t.Error("Expected the packet to not have been seen after expiration")
+	}
+}
+
+func TestPacketDeduplicatorSeenData(t *testing.T) {
+	hasher := md5.New()
+	expiresAfter := 100 * time.Millisecond
+	dedup := meshtastic.NewDeduplicator(hasher, expiresAfter)
+
+	data := []byte("test data")
+
+	// Test SeenData with new data
+	if dedup.SeenData(data) {
+		t.Error("Expected the data to not have been seen")
+	}
+
+	// Test SeenData with same data again
+	if !dedup.SeenData(data) {
+		t.Error("Expected the data to have been seen")
+	}
+
+	// Wait for expiration
+	time.Sleep(expiresAfter + 100*time.Millisecond)
+
+	// Test SeenData with same data after expiration
+	if dedup.SeenData(data) {
+		t.Error("Expected the data to not have been seen after expiration")
+	}
+}