From f60495ab40248aa441ef19c4025dba2726fcfee1 Mon Sep 17 00:00:00 2001
From: Stephanie Gredell <s.raide@gmail.com>
Date: Wed, 18 Jun 2025 11:02:50 -0700
Subject: [PATCH] Fix up cachenode

---
 internal/simulation/cachenode.go | 93 +++++++++++++++++++++++---------
 1 file changed, 69 insertions(+), 24 deletions(-)

diff --git a/internal/simulation/cachenode.go b/internal/simulation/cachenode.go
index 7668a9c..2f9d6c1 100644
--- a/internal/simulation/cachenode.go
+++ b/internal/simulation/cachenode.go
@@ -1,5 +1,17 @@
 package simulation
 
+import (
+	"math/rand"
+	"sort"
+)
+
+type CacheEntry struct {
+	Value       interface{}
+	Timestamp   int
+	ExpireAt    int
+	AccessCount int
+}
+
 type CacheNode struct {
 	ID             string
 	Label          string
@@ -7,10 +19,11 @@ type CacheNode struct {
 	MaxEntries     int
 	EvictionPolicy string
 	CurrentLoad    int
-	Queue          []Request
-	Cache          map[string]interface{}
+	Queue          []*Request
+	Cache          map[string]CacheEntry
 	Alive          bool
 	Targets        []string
+	Output         []*Request
 }
 
 func (c *CacheNode) GetID() string {
@@ -21,42 +34,74 @@ func (c *CacheNode) Type() string {
 	return "cache"
 }
 
-func (c *CacheNode) GetQueue() []Request {
-	return c.Queue
+func (c *CacheNode) IsAlive() bool {
+	return c.Alive
 }
-func (c *CacheNode) Tick(tick int) {
+
+func (c *CacheNode) Tick(tick int, currentTimeMs int) {
+	for key, entry := range c.Cache {
+		if currentTimeMs > entry.ExpireAt {
+			delete(c.Cache, key)
+		}
+	}
+
 	if len(c.Cache) > c.MaxEntries {
 		evictCount := len(c.Cache) - c.MaxEntries
+		keys := make([]string, 0, len(c.Cache))
+		for k := range c.Cache {
+			keys = append(keys, k)
+		}
 
-		i := 0
+		switch c.EvictionPolicy {
+		case "Random":
+			rand.Shuffle(len(keys), func(i, j int) { keys[i], keys[j] = keys[j], keys[i] })
+		case "LRU":
+			sort.Slice(keys, func(i, j int) bool {
+				return c.Cache[keys[i]].Timestamp < c.Cache[keys[j]].Timestamp
+			})
+		case "LFU":
+			sort.Slice(keys, func(i, j int) bool {
+				return c.Cache[keys[i]].AccessCount < c.Cache[keys[j]].AccessCount
+			})
+		}
 
-		for k := range c.Cache {
-			delete(c.Cache, k)
-			i++
-			if i >= evictCount {
-				break
+		for i := 0; i < evictCount && i < len(keys); i++ {
+			delete(c.Cache, keys[i])
+		}
+	}
+
+	toProcess := min(len(c.Queue), 10)
+	for i := 0; i < toProcess; i++ {
+		req := c.Queue[i]
+		if entry, found := c.Cache[req.ID]; found && currentTimeMs <= entry.ExpireAt {
+			// Cache hit
+			req.LatencyMS += 2
+			req.Path = append(req.Path, c.ID+"(hit)")
+		} else {
+			// Cache miss
+			req.LatencyMS += 5
+			req.Path = append(req.Path, c.ID+"(miss)")
+			c.Cache[req.ID] = CacheEntry{
+				Value:     req,
+				Timestamp: currentTimeMs,
+				ExpireAt:  currentTimeMs + c.CacheTTL*1000,
 			}
+			c.Output = append(c.Output, req)
 		}
 	}
+	c.Queue = c.Queue[toProcess:]
 }
 
 func (c *CacheNode) Receive(req *Request) {
-	c.Queue = append(c.Queue, *req)
+	c.Queue = append(c.Queue, req)
 }
 
 func (c *CacheNode) Emit() []*Request {
-	var out []*Request
-
-	// emit everything in a single tick.
-	for _, req := range c.Queue {
-		// check cache
-		if _, ok := c.Cache[req.ID]; !ok {
-			c.Cache[req.ID] = struct{}{}
-			out = append(out, &req)
-		}
-	}
-	c.Queue = nil
+	out := append([]*Request(nil), c.Output...)
+	c.Output = c.Output[:0]
 	return out
 }
 
-func (c *CacheNode) IsAlive() bool { return c.Alive }
+func (c *CacheNode) AddTarget(targetID string) {
+	c.Targets = append(c.Targets, targetID)
+}