From 5fac4b02e3160469632f9def2d3ac249a39df1cc Mon Sep 17 00:00:00 2001
From: Marco Peereboom <marco@peereboom.us>
Date: Thu, 9 Jan 2025 12:38:58 +0000
Subject: [PATCH] Add tests

---
 database/tbcd/level/blockcache.go | 46 ++++++++++++++++------
 database/tbcd/level/cache_test.go | 65 +++++++++++++++++++++++++++++++
 2 files changed, 99 insertions(+), 12 deletions(-)
 create mode 100644 database/tbcd/level/cache_test.go

diff --git a/database/tbcd/level/blockcache.go b/database/tbcd/level/blockcache.go
index b59dabab3..9b858c97c 100644
--- a/database/tbcd/level/blockcache.go
+++ b/database/tbcd/level/blockcache.go
@@ -13,23 +13,32 @@ import (
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 )
 
-const blockSize = 1677721 // ~1.6MB rough size of a mainnet block as of Jan 2025
+var blockSize = 1677721 // ~1.6MB rough size of a mainnet block as of Jan 2025
 
-type timeBlock struct {
+type blockElement struct {
 	element *list.Element
 	block   []byte
 }
 
+type CacheStats struct {
+	Hits   int
+	Misses int
+	Purges int
+}
+
 type lowIQLRU struct {
 	mtx sync.RWMutex
 
 	size int // this is the approximate max size
 
-	m         map[chainhash.Hash]timeBlock
+	m         map[chainhash.Hash]blockElement
 	totalSize int
 
-	// lru list
+	// lru list, when used move to back of the list
 	l *list.List
+
+	// stats
+	c CacheStats
 }
 
 func (l *lowIQLRU) Put(v *btcutil.Block) {
@@ -43,18 +52,21 @@ func (l *lowIQLRU) Put(v *btcutil.Block) {
 
 	block, err := v.Bytes()
 	if err != nil {
+		// data corruption, panic
 		panic(err)
-		// XXX don't cache but panic for now for diagnostic
 	}
 
 	// evict first element in list
-	if l.totalSize+len(block) >= l.size {
+	if l.totalSize+len(block) > l.size {
 		// LET THEM EAT PANIC
 		re := l.l.Front()
 		rha := l.l.Remove(re)
-		rh := rha.(chainhash.Hash)
-		l.totalSize -= len(l.m[rh].block)
-		delete(l.m, rh)
+		// fmt.Printf("rha %v\n", spew.Sdump(rha))
+		// fmt.Printf("==== re %T rha %T\n", re, rha)
+		rh := rha.(*list.Element).Value.(*chainhash.Hash)
+		l.totalSize -= len(l.m[*rh].block)
+		delete(l.m, *rh)
+		l.c.Purges++
 	}
 
 	// lru list
@@ -62,7 +74,7 @@ func (l *lowIQLRU) Put(v *btcutil.Block) {
 	l.l.PushBack(element)
 
 	// block lookup
-	l.m[*hash] = timeBlock{element: element, block: block}
+	l.m[*hash] = blockElement{element: element, block: block}
 	l.totalSize += len(block)
 }
 
@@ -72,19 +84,29 @@ func (l *lowIQLRU) Get(k *chainhash.Hash) (*btcutil.Block, bool) {
 
 	be, ok := l.m[*k]
 	if !ok {
+		l.c.Misses++
 		return nil, false
 	}
 	b, err := btcutil.NewBlockFromBytes(be.block)
 	if err != nil {
-		panic(err) // XXX delete from cache and return nil, false but panic for diagnostics at this time
+		// panic for diagnostics at this time
+		panic(err)
 	}
 
 	// update access
 	l.l.MoveToBack(be.element)
 
+	l.c.Hits++
+
 	return b, true
 }
 
+func (l *lowIQLRU) Stats() CacheStats {
+	l.mtx.RLock()
+	defer l.mtx.RUnlock()
+	return l.c
+}
+
 func lowIQLRUNewSize(size int) (*lowIQLRU, error) {
 	if size <= 0 {
 		return nil, fmt.Errorf("invalid size: %v", size)
@@ -96,7 +118,7 @@ func lowIQLRUNewSize(size int) (*lowIQLRU, error) {
 	}
 	return &lowIQLRU{
 		size: size,
-		m:    make(map[chainhash.Hash]timeBlock, count),
+		m:    make(map[chainhash.Hash]blockElement, count),
 		l:    list.New(),
 	}, nil
 }
diff --git a/database/tbcd/level/cache_test.go b/database/tbcd/level/cache_test.go
new file mode 100644
index 000000000..b625d015b
--- /dev/null
+++ b/database/tbcd/level/cache_test.go
@@ -0,0 +1,65 @@
+package level
+
+import (
+	"testing"
+
+	"github.com/btcsuite/btcd/btcutil"
+	"github.com/btcsuite/btcd/chaincfg/chainhash"
+	"github.com/btcsuite/btcd/wire"
+	"github.com/davecgh/go-spew/spew"
+)
+
+func newBlock(prevHash *chainhash.Hash, nonce uint32) (chainhash.Hash, *btcutil.Block) {
+	bh := wire.NewBlockHeader(0, prevHash, &chainhash.Hash{}, 0, uint32(nonce))
+	b := wire.NewMsgBlock(bh)
+	return bh.BlockHash(), btcutil.NewBlock(b)
+}
+
+func TestLRUCache(t *testing.T) {
+	maxCache := 10
+	blockSize = 81 // we'll use empty blocks
+	l, err := lowIQLRUNewSize(blockSize * maxCache)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	prevHash := chainhash.Hash{} // genesis
+	blocks := make([]chainhash.Hash, 0, maxCache*2)
+	for i := 0; i < maxCache; i++ {
+		h, b := newBlock(&prevHash, uint32(i))
+		t.Logf("%v: %v", i, h)
+		blocks = append(blocks, h)
+		l.Put(b)
+		prevHash = h
+	}
+
+	// verify stats are 0
+	s := l.Stats()
+	if s.Hits != 0 && s.Misses != 0 && s.Purges != 0 {
+		t.Fatal(spew.Sdump(s))
+	}
+
+	// retrieve all blocks
+	for k := range blocks {
+		if _, ok := l.Get(&blocks[k]); !ok {
+			t.Fatalf("block not found: %v", blocks[k])
+		}
+	}
+
+	// verify hits are maxBlocks
+	s = l.Stats()
+	if s.Hits != 10 && s.Misses != 0 && s.Purges != 0 {
+		t.Fatal(spew.Sdump(s))
+	}
+
+	// purge oldest cache entries
+	for i := maxCache; i < maxCache*2; i++ {
+		h, b := newBlock(&prevHash, uint32(i))
+		t.Logf("%v: %v", i, h)
+		blocks = append(blocks, h)
+		l.Put(b)
+		prevHash = h
+	}
+
+	t.Logf("%v", spew.Sdump(l.Stats()))
+}