From a4bae38f68f9441c42bedf4ee58ca23d8273f3f7 Mon Sep 17 00:00:00 2001
From: fiatjaf <fiatjaf@gmail.com>
Date: Sun, 29 Dec 2024 14:07:19 -0300
Subject: [PATCH] add nip92 imeta parsing helper.

---
 nip92/imeta.go      |  73 ++++++++++++++++++++++++++++++++
 nip92/imeta_test.go | 100 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 173 insertions(+)
 create mode 100644 nip92/imeta.go
 create mode 100644 nip92/imeta_test.go

diff --git a/nip92/imeta.go b/nip92/imeta.go
new file mode 100644
index 0000000..af2471e
--- /dev/null
+++ b/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
+}
diff --git a/nip92/imeta_test.go b/nip92/imeta_test.go
new file mode 100644
index 0000000..e400748
--- /dev/null
+++ b/nip92/imeta_test.go
@@ -0,0 +1,100 @@
+package nip92
+
+import (
+	"testing"
+
+	"github.com/nbd-wtf/go-nostr"
+	"github.com/stretchr/testify/require"
+)
+
+func TestIMetaParsing(t *testing.T) {
+	for i, tcase := range []struct {
+		expected IMeta
+		tags     nostr.Tags
+	}{
+		{
+			expected: nil,
+			tags:     nostr.Tags{},
+		},
+		{
+			expected: nil,
+			tags:     nostr.Tags{{"t", "nothing"}},
+		},
+		{
+			expected: nil,
+			tags:     nostr.Tags{{"imeta", "nothing"}},
+		},
+		{
+			expected: nil,
+			tags: nostr.Tags{
+				{
+					"imeta",
+					"url https://i.nostr.build/yhsyFkwxWlw7odSB.gif",
+					"blurhash eDG*7p~AE34;E29x^ij?EMWBEMIWI;IpbI0g0gn+%1oyNGEMM|%1n%",
+					"dim 225x191",
+				},
+				{
+					"imeta",
+					"blurhash qwkueh",
+					"dim oxo",
+				},
+			},
+		},
+		{
+			expected: IMeta{
+				{
+					URL:      "https://i.nostr.build/yhsyFkwxWlw7odSB.gif",
+					Blurhash: "eDG*7p~AE34;E29x^ij?EMWBEMIWI;IpbI0g0gn+%1oyNGEMM|%1n%",
+					Width:    225,
+					Height:   191,
+				},
+			},
+			tags: nostr.Tags{
+				{
+					"imeta",
+					"url https://i.nostr.build/yhsyFkwxWlw7odSB.gif",
+					"blurhash eDG*7p~AE34;E29x^ij?EMWBEMIWI;IpbI0g0gn+%1oyNGEMM|%1n%",
+					"dim 225x191",
+				},
+			},
+		},
+		{
+			expected: IMeta{
+				{
+					URL:      "https://image.nostr.build/94060676611fe7fca86588068d3f140607eda443f6d66d6b9754e93b0b8439ac.jpg",
+					Blurhash: "eQF?RxZ}nNo~fk*0s6Z~kYem0iacsRkEsl9eW;oHkDoIxbtSobRkRi",
+					Width:    3024,
+					Height:   3024,
+				},
+				{
+					URL:      "https://image.nostr.build/9bc3998f79c401bc9d3b3b74c1cbff0a3225f754194b94a6f5750ca6ea492846.jpg",
+					Blurhash: "#2Ss1[RO%MIUx]R*-;WUtR0Kt6njof-;xu-pofxt4-M{yExt%2s.xaV[jF4TM|?bt6tmt6tRaybI0KtS=wRkWYWAtRjYt7tR%M?vNerWRjIBV@RjIAxYIpRP_3NGaKWXRj",
+					Width:    1920,
+					Height:   1494,
+					Alt:      "Verifiable file url",
+				},
+			},
+			tags: nostr.Tags{
+				{
+					"imeta",
+					"url https://image.nostr.build/94060676611fe7fca86588068d3f140607eda443f6d66d6b9754e93b0b8439ac.jpg",
+					"blurhash eQF?RxZ}nNo~fk*0s6Z~kYem0iacsRkEsl9eW;oHkDoIxbtSobRkRi",
+					"dim 3024x3024",
+				},
+				{
+					"imeta",
+					"url https://image.nostr.build/9bc3998f79c401bc9d3b3b74c1cbff0a3225f754194b94a6f5750ca6ea492846.jpg",
+					"m image/jpeg",
+					"alt Verifiable file url",
+					"x 80a8f087f6c45ec7fb9e8839e5af095df9b439a0836cdf70a244086b6b2c1a88",
+					"size 121397",
+					"dim 1920x1494",
+					"blurhash #2Ss1[RO%MIUx]R*-;WUtR0Kt6njof-;xu-pofxt4-M{yExt%2s.xaV[jF4TM|?bt6tmt6tRaybI0KtS=wRkWYWAtRjYt7tR%M?vNerWRjIBV@RjIAxYIpRP_3NGaKWXRj",
+					"ox 9bc3998f79c401bc9d3b3b74c1cbff0a3225f754194b94a6f5750ca6ea492846",
+				},
+			},
+		},
+	} {
+		require.Equal(t, tcase.expected, ParseTags(tcase.tags), "case %d", i)
+	}
+}