add nip92 imeta parsing helper.

nip92/imeta.go

@@ -0,0 +1,73 @@
+package nip92
+
+import (
+	"strconv"
+	"strings"
+
+	"github.com/nbd-wtf/go-nostr"
+)
+
+type IMeta []IMetaEntry
+
+func (imeta IMeta) Get(url string) (IMetaEntry, bool) {
+	for _, entry := range imeta {
+		if entry.URL == url {
+			return entry, true
+		}
+	}
+	return IMetaEntry{}, false
+}
+
+type IMetaEntry struct {
+	URL      string
+	Blurhash string
+	Width    int
+	Height   int
+	Alt      string
+}
+
+func ParseTags(tags nostr.Tags) IMeta {
+	var imeta IMeta
+	for i, tag := range tags {
+		if len(tag) > 2 && tag[0] == "imeta" {
+			entry := IMetaEntry{}
+			for _, item := range tag[1:] {
+				div := strings.Index(item, " ")
+				switch item[0:div] {
+				case "url":
+					entry.URL = item[div+1:]
+				case "alt":
+					entry.Alt = item[div+1:]
+				case "blurhash":
+					entry.Blurhash = item[div+1:]
+				case "dim":
+					xySplit := strings.Index(item[div+1:], "x")
+					if xySplit == -1 {
+						// if any tag is wrong them we don't trust this guy anyway
+						return nil
+					}
+
+					x, err := strconv.Atoi(item[div+1 : div+1+xySplit])
+					if err != nil {
+						return nil
+					}
+					entry.Width = x
+
+					y, err := strconv.Atoi(item[div+1+xySplit+1:])
+					if err != nil {
+						return nil
+					}
+					entry.Height = y
+				}
+			}
+
+			if imeta == nil {
+				imeta = make(IMeta, 1, len(tags)-i)
+				imeta[0] = entry
+			} else {
+				imeta = append(imeta, entry)
+			}
+		}
+	}
+	return imeta
+}