feat: delete

del.go

@@ -2,7 +2,6 @@ package pail
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"slices"
 
@@ -40,10 +39,73 @@ func Del(ctx context.Context, blocks block.Fetcher, root ipld.Link, key string)
 		return nil, ShardDiff{}, ErrNotFound
 	}
 
-	// var additions []shard.BlockView
-	// removals := path[:]
+	var additions []shard.BlockView
+	removals := path[:]
 
-	// nshard := shard.New(target.Value().Prefix(), target.Value().Entries()[:])
-	// TODO TODO
-	return nil, ShardDiff{}, errors.New("not implemented")
+	var nshard shard.Shard
+	if entry.Value().Shard() != nil {
+		// remove the value from this link+value
+		ents := target.Value().Entries()[:]
+		ents[entryidx] = shard.NewEntry(entry.Key(), shard.NewValue(nil, entry.Value().Shard()))
+		nshard = shard.New(target.Value().Prefix(), ents)
+	} else {
+		ents := slices.Delete(target.Value().Entries()[:], entryidx, entryidx+1)
+		nshard = shard.New(target.Value().Prefix(), ents)
+
+		for i := len(path) - 1; i > 0; i-- {
+			if len(nshard.Entries()) > 0 {
+				break
+			}
+
+			child := path[i]
+			parent := path[i-1]
+
+			ents := parent.Value().Entries()[:]
+			nshard = shard.New(parent.Value().Prefix(), slices.DeleteFunc(ents, func(e shard.Entry) bool {
+				if e.Value().Shard() == nil {
+					return false
+				}
+				// FIXME: what if there is a value in this entry?
+				return e.Value().Shard().String() == child.Link().String()
+			}))
+		}
+	}
+
+	child, err := shard.EncodeBlock(nshard)
+	if err != nil {
+		return nil, ShardDiff{}, err
+	}
+	additions = append(additions, child)
+
+	// path is root -> target, so work backwards, propagating the new shard CID
+	for i := len(path) - 2; i >= 0; i-- {
+		parent := path[i]
+		key := child.Value().Prefix()[len(parent.Value().Prefix()):]
+
+		entries := parent.Value().Entries()[:]
+		for i, e := range entries {
+			if e.Key() == key {
+				if e.Value().Shard() == nil {
+					return nil, ShardDiff{}, fmt.Errorf("\"%s\" is not a shard link in: %s", key, parent.Link().String())
+				}
+				entries[i] = shard.NewEntry(key, shard.NewValue(e.Value().Value(), child.Link()))
+				break
+			}
+		}
+
+		var cshard shard.Shard
+		if parent.Value().Prefix() == "" {
+			cshard = shard.NewRoot(entries)
+		} else {
+			cshard = shard.New(parent.Value().Prefix(), entries)
+		}
+
+		child, err = shard.EncodeBlock(cshard)
+		if err != nil {
+			return nil, ShardDiff{}, err
+		}
+		additions = append(additions, child)
+	}
+
+	return additions[len(additions)-1].Link(), ShardDiff{additions, removals}, nil
 }