tag helpers in a separate file and nip10 helpers.

tags.go

@@ -0,0 +1,143 @@
+package nostr
+
+import (
+	"encoding/json"
+	"errors"
+	"strings"
+
+	"golang.org/x/exp/slices"
+)
+
+type Tag []string
+
+// StartsWith checks if a tag contains a prefix.
+// for example,
+//     ["p", "abcdef...", "wss://relay.com"]
+// would match against
+//     ["p", "abcdef..."]
+// or even
+//     ["p", "abcdef...", "wss://"]
+func (tag Tag) StartsWith(prefix []string) bool {
+	prefixLen := len(prefix)
+
+	if prefixLen > len(tag) {
+		return false
+	}
+	// check initial elements for equality
+	for i := 0; i < prefixLen-1; i++ {
+		if prefix[i] != tag[i] {
+			return false
+		}
+	}
+	// check last element just for a prefix
+	return strings.HasPrefix(tag[prefixLen-1], prefix[prefixLen-1])
+}
+
+func (tag Tag) Key() string {
+	if len(tag) > 0 {
+		return tag[0]
+	}
+	return ""
+}
+
+func (tag Tag) Value() string {
+	if len(tag) > 1 {
+		return tag[1]
+	}
+	return ""
+}
+
+func (tag Tag) Relay() string {
+	if tag[0] == "e" || tag[0] == "p" && len(tag) > 2 {
+		return tag[2]
+	}
+	return ""
+}
+
+type Tags []Tag
+
+// GetFirst gets the first tag in tags that matches the prefix, see [Tag.StartsWith]
+func (tags Tags) GetFirst(tagPrefix []string) *Tag {
+	for _, v := range tags {
+		if v.StartsWith(tagPrefix) {
+			return &v
+		}
+	}
+	return nil
+}
+
+// GetLast gets the last tag in tags that matches the prefix, see [Tag.StartsWith]
+func (tags Tags) GetLast(tagPrefix []string) *Tag {
+	for i := len(tags) - 1; i >= 0; i-- {
+		v := tags[i]
+		if v.StartsWith(tagPrefix) {
+			return &v
+		}
+	}
+	return nil
+}
+
+// GetLast gets all the tags that match the prefix, see [Tag.StartsWith]
+func (tags Tags) GetAll(tagPrefix []string) Tags {
+	result := make(Tags, 0, len(tags))
+	for _, v := range tags {
+		if v.StartsWith(tagPrefix) {
+			result = append(result, v)
+		}
+	}
+	return result
+}
+
+// FilterOut removes all tags that match the prefix, see [Tag.StartsWith]
+func (tags Tags) FilterOut(tagPrefix []string) Tags {
+	filtered := make(Tags, 0, len(tags))
+	for _, v := range tags {
+		if !v.StartsWith(tagPrefix) {
+			filtered = append(filtered, v)
+		}
+	}
+	return filtered
+}
+
+// AppendUnique appends a tag if it doesn't exist yet, otherwise does nothing
+func (tags Tags) AppendUnique(tag Tag) Tags {
+	if tags.GetFirst(tag) == nil {
+		return append(tags, tag)
+	} else {
+		return tags
+	}
+}
+
+func (t *Tags) Scan(src interface{}) error {
+	var jtags []byte = make([]byte, 0)
+
+	switch v := src.(type) {
+	case []byte:
+		jtags = v
+	case string:
+		jtags = []byte(v)
+	default:
+		return errors.New("couldn't scan tags, it's not a json string")
+	}
+
+	json.Unmarshal(jtags, &t)
+	return nil
+}
+
+func (tags Tags) ContainsAny(tagName string, values []string) bool {
+	for _, tag := range tags {
+		if len(tag) < 2 {
+			continue
+		}
+
+		if tag[0] != tagName {
+			continue
+		}
+
+		if slices.Contains(values, tag[1]) {
+			return true
+		}
+	}
+
+	return false
+}