negentropy: refactor for allowing different types of storage.

nip77/negentropy/storage/vector/vector.go

@@ -0,0 +1,77 @@
+package vector
+
+import (
+	"encoding/hex"
+	"fmt"
+	"iter"
+	"slices"
+
+	"github.com/nbd-wtf/go-nostr"
+	"github.com/nbd-wtf/go-nostr/nip77/negentropy"
+)
+
+type Vector struct {
+	items  []negentropy.Item
+	sealed bool
+}
+
+func New() *Vector {
+	return &Vector{
+		items: make([]negentropy.Item, 0, 30),
+	}
+}
+
+func (v *Vector) Insert(createdAt nostr.Timestamp, id string) error {
+	if len(id)/2 != 32 {
+		return fmt.Errorf("bad id size for added item: expected %d, got %d", 32, len(id)/2)
+	}
+
+	item := negentropy.Item{Timestamp: createdAt, ID: id}
+	v.items = append(v.items, item)
+	return nil
+}
+
+func (v *Vector) Size() int { return len(v.items) }
+
+func (v *Vector) Seal() {
+	if v.sealed {
+		panic("trying to seal an already sealed vector")
+	}
+	v.sealed = true
+	slices.SortFunc(v.items, negentropy.ItemCompare)
+}
+
+func (v *Vector) GetBound(idx int) negentropy.Bound {
+	if idx < len(v.items) {
+		return negentropy.Bound{Item: v.items[idx]}
+	}
+	return negentropy.InfiniteBound
+}
+
+func (v *Vector) Range(begin, end int) iter.Seq2[int, negentropy.Item] {
+	return func(yield func(int, negentropy.Item) bool) {
+		for i := begin; i < end; i++ {
+			if !yield(i, v.items[i]) {
+				break
+			}
+		}
+	}
+}
+
+func (v *Vector) FindLowerBound(begin, end int, bound negentropy.Bound) int {
+	idx, _ := slices.BinarySearchFunc(v.items[begin:end], bound.Item, negentropy.ItemCompare)
+	return begin + idx
+}
+
+func (v *Vector) Fingerprint(begin, end int) [negentropy.FingerprintSize]byte {
+	var out negentropy.Accumulator
+	out.SetToZero()
+
+	tmp := make([]byte, 32)
+	for _, item := range v.Range(begin, end) {
+		hex.Decode(tmp, []byte(item.ID))
+		out.AddBytes(tmp)
+	}
+
+	return out.GetFingerprint(end - begin)
+}