[feature] Read + Write tombstones for deleted Actors (#1005)

* [feature] Read + Write tombstones for deleted Actors

* copyTombstone

* update to use resultcache instead of old ttl cache

Signed-off-by: kim <grufwub@gmail.com>

* update go-cache library to fix result cache capacity / ordering bugs

Signed-off-by: kim <grufwub@gmail.com>

* bump go-cache/v3 to v3.1.6 to fix bugs

Signed-off-by: kim <grufwub@gmail.com>

* switch on status code

* better explain ErrGone reasoning

Signed-off-by: kim <grufwub@gmail.com>
Co-authored-by: kim <grufwub@gmail.com>

vendor/codeberg.org/gruf/go-cache/v3/result/key.go

@@ -0,0 +1,184 @@
+package result
+
+import (
+	"reflect"
+	"strings"
+	"sync"
+	"unicode"
+	"unicode/utf8"
+
+	"codeberg.org/gruf/go-byteutil"
+	"codeberg.org/gruf/go-mangler"
+)
+
+// structKeys provides convience methods for a list
+// of struct field combinations used for cache keys.
+type structKeys []keyFields
+
+// get fetches the key-fields for given lookup (else, panics).
+func (sk structKeys) get(lookup string) *keyFields {
+	for i := range sk {
+		if sk[i].lookup == lookup {
+			return &sk[i]
+		}
+	}
+	panic("unknown lookup: \"" + lookup + "\"")
+}
+
+// generate will calculate the value string for each required
+// cache key as laid-out by the receiving structKeys{}.
+func (sk structKeys) generate(a any) []cacheKey {
+	// Get reflected value in order
+	// to access the struct fields
+	v := reflect.ValueOf(a)
+
+	// Iteratively deref pointer value
+	for v.Kind() == reflect.Pointer {
+		if v.IsNil() {
+			panic("nil ptr")
+		}
+		v = v.Elem()
+	}
+
+	// Preallocate expected slice of keys
+	keys := make([]cacheKey, len(sk))
+
+	// Acquire byte buffer
+	buf := bufpool.Get().(*byteutil.Buffer)
+	defer bufpool.Put(buf)
+
+	for i := range sk {
+		// Reset buffer
+		buf.B = buf.B[:0]
+
+		// Set the key-fields reference
+		keys[i].fields = &sk[i]
+
+		// Calculate cache-key value
+		keys[i].populate(buf, v)
+	}
+
+	return keys
+}
+
+// cacheKey represents an actual cache key.
+type cacheKey struct {
+	// value is the actual string representing
+	// this cache key for hashmap lookups.
+	value string
+
+	// fieldsRO is a read-only slice (i.e. we should
+	// NOT be modifying them, only using for reference)
+	// of struct fields encapsulated by this cache key.
+	fields *keyFields
+}
+
+// populate will calculate the cache key's value string for given
+// value's reflected information. Passed encoder is for string building.
+func (k *cacheKey) populate(buf *byteutil.Buffer, v reflect.Value) {
+	// Append each field value to buffer.
+	for _, idx := range k.fields.fields {
+		fv := v.Field(idx)
+		fi := fv.Interface()
+		buf.B = mangler.Append(buf.B, fi)
+		buf.B = append(buf.B, '.')
+	}
+
+	// Drop last '.'
+	buf.Truncate(1)
+
+	// Create string copy from buf
+	k.value = string(buf.B)
+}
+
+// keyFields represents a list of struct fields
+// encompassed in a single cache key, the string name
+// of the lookup, and the lookup map to primary keys.
+type keyFields struct {
+	// lookup is the calculated (well, provided)
+	// cache key lookup, consisting of dot sep'd
+	// struct field names.
+	lookup string
+
+	// fields is a slice of runtime struct field
+	// indices, of the fields encompassed by this key.
+	fields []int
+
+	// pkeys is a lookup of stored struct key values
+	// to the primary cache lookup key (int64).
+	pkeys map[string]int64
+}
+
+// populate will populate this keyFields{} object's .fields member by determining
+// the field names from the given lookup, and querying given reflected type to get
+// the runtime field indices for each of the fields. this speeds-up future value lookups.
+func (kf *keyFields) populate(t reflect.Type) {
+	// Split dot-separated lookup to get
+	// the individual struct field names
+	names := strings.Split(kf.lookup, ".")
+	if len(names) == 0 {
+		panic("no key fields specified")
+	}
+
+	// Pre-allocate slice of expected length
+	kf.fields = make([]int, len(names))
+
+	for i, name := range names {
+		// Get field info for given name
+		ft, ok := t.FieldByName(name)
+		if !ok {
+			panic("no field found for name: \"" + name + "\"")
+		}
+
+		// Check field is usable
+		if !isExported(name) {
+			panic("field must be exported")
+		}
+
+		// Set the runtime field index
+		kf.fields[i] = ft.Index[0]
+	}
+}
+
+// genkey generates a cache key for given key values.
+func genkey(parts ...any) string {
+	if len(parts) < 1 {
+		// Panic to prevent annoying usecase
+		// where user forgets to pass lookup
+		// and instead only passes a key part,
+		// e.g. cache.Get("key")
+		// which then always returns false.
+		panic("no key parts provided")
+	}
+
+	// Acquire buffer and reset
+	buf := bufpool.Get().(*byteutil.Buffer)
+	defer bufpool.Put(buf)
+	buf.Reset()
+
+	// Encode each key part
+	for _, part := range parts {
+		buf.B = mangler.Append(buf.B, part)
+		buf.B = append(buf.B, '.')
+	}
+
+	// Drop last '.'
+	buf.Truncate(1)
+
+	// Return string copy
+	return string(buf.B)
+}
+
+// isExported checks whether function name is exported.
+func isExported(fnName string) bool {
+	r, _ := utf8.DecodeRuneInString(fnName)
+	return unicode.IsUpper(r)
+}
+
+// bufpool provides a memory pool of byte
+// buffers use when encoding key types.
+var bufpool = sync.Pool{
+	New: func() any {
+		return &byteutil.Buffer{B: make([]byte, 0, 512)}
+	},
+}