refactor: consolidate JSON parsing into cached getAppMetadata helper

Performance optimization:
- Create getAppMetadata() helper that parses content JSON once and caches
  the result using Symbol.for('nip89-metadata') as cache key
- All metadata helpers (getAppName, getAppDescription, getAppWebsite) now
  use the cached metadata instead of parsing JSON multiple times
- Prevents redundant JSON.parse() calls when multiple helpers are used

Code cleanup - removed unused functions:
- getAppImage() - no longer used after removing image display
- getHandlersByPlatform() - filtering done in component state
- substituteTemplate() - not needed in current implementation
- hasPlaceholder() - utility never used
- formatAddressPointer() - not needed anymore

Updated tests:
- Replace getAppImage tests with getAppWebsite tests
- Remove tests for deleted utility functions
- All remaining tests pass

This consolidation improves performance by ensuring JSON.parse() is called
at most once per event, regardless of how many metadata fields are accessed.

src/lib/nip89-helpers.test.ts

@@ -2,7 +2,7 @@ import { describe, it, expect } from "vitest";
 import {
   getAppName,
   getAppDescription,
-  getAppImage,
+  getAppWebsite,
   getSupportedKinds,
   getPlatformUrls,
   getAvailablePlatforms,
@@ -10,11 +10,7 @@ import {
   getRecommendedKind,
   parseAddressPointer,
   getHandlerReferences,
-  getHandlersByPlatform,
   getRecommendedPlatforms,
-  substituteTemplate,
-  hasPlaceholder,
-  formatAddressPointer,
 } from "./nip89-helpers";
 import { NostrEvent } from "@/types/nostr";
 
@@ -119,29 +115,24 @@ describe("Kind 31990 (Application Handler) Helpers", () => {
     });
   });
 
-  describe("getAppImage", () => {
-    it("should extract image from content JSON", () => {
+  describe("getAppWebsite", () => {
+    it("should extract website from content JSON", () => {
       const event = createHandlerEvent({
-        content: JSON.stringify({ image: "https://example.com/logo.png" }),
+        content: JSON.stringify({ website: "https://example.com" }),
       });
-      expect(getAppImage(event)).toBe("https://example.com/logo.png");
+      expect(getAppWebsite(event)).toBe("https://example.com");
     });
 
-    it("should extract picture field as fallback", () => {
+    it("should return undefined if no website field", () => {
       const event = createHandlerEvent({
-        content: JSON.stringify({ picture: "https://example.com/pic.png" }),
+        content: JSON.stringify({ name: "App" }),
       });
-      expect(getAppImage(event)).toBe("https://example.com/pic.png");
+      expect(getAppWebsite(event)).toBeUndefined();
     });
 
-    it("should prefer image over picture", () => {
-      const event = createHandlerEvent({
-        content: JSON.stringify({
-          image: "https://example.com/logo.png",
-          picture: "https://example.com/pic.png",
-        }),
-      });
-      expect(getAppImage(event)).toBe("https://example.com/logo.png");
+    it("should return undefined if content is empty", () => {
+      const event = createHandlerEvent({ content: "" });
+      expect(getAppWebsite(event)).toBeUndefined();
     });
   });
 
@@ -351,39 +342,6 @@ describe("Kind 31989 (Handler Recommendation) Helpers", () => {
     });
   });
 
-  describe("getHandlersByPlatform", () => {
-    it("should filter handlers by platform", () => {
-      const event = createRecommendationEvent({
-        tags: [
-          ["d", "9802"],
-          ["a", "31990:pubkey1:handler1", "", "web"],
-          ["a", "31990:pubkey2:handler2", "", "ios"],
-          ["a", "31990:pubkey3:handler3", "", "web"],
-        ],
-      });
-      const webHandlers = getHandlersByPlatform(event, "web");
-      expect(webHandlers).toHaveLength(2);
-      expect(webHandlers[0].platform).toBe("web");
-      expect(webHandlers[1].platform).toBe("web");
-
-      const iosHandlers = getHandlersByPlatform(event, "ios");
-      expect(iosHandlers).toHaveLength(1);
-      expect(iosHandlers[0].platform).toBe("ios");
-    });
-
-    it("should return all handlers if no platform specified", () => {
-      const event = createRecommendationEvent({
-        tags: [
-          ["d", "9802"],
-          ["a", "31990:pubkey1:handler1", "", "web"],
-          ["a", "31990:pubkey2:handler2", "", "ios"],
-        ],
-      });
-      const allHandlers = getHandlersByPlatform(event);
-      expect(allHandlers).toHaveLength(2);
-    });
-  });
-
   describe("getRecommendedPlatforms", () => {
     it("should return unique platforms from handler references", () => {
       const event = createRecommendationEvent({
@@ -410,46 +368,3 @@ describe("Kind 31989 (Handler Recommendation) Helpers", () => {
     });
   });
 });
-
-describe("URL Template Utilities", () => {
-  describe("substituteTemplate", () => {
-    it("should replace <bech32> placeholder with entity", () => {
-      const template = "https://app.com/view/<bech32>";
-      const result = substituteTemplate(template, "nevent1abc123");
-      expect(result).toBe("https://app.com/view/nevent1abc123");
-    });
-
-    it("should replace multiple occurrences", () => {
-      const template = "https://app.com/<bech32>/view/<bech32>";
-      const result = substituteTemplate(template, "note1xyz");
-      expect(result).toBe("https://app.com/note1xyz/view/note1xyz");
-    });
-
-    it("should return unchanged if no placeholder", () => {
-      const template = "https://app.com/view";
-      const result = substituteTemplate(template, "nevent1abc");
-      expect(result).toBe("https://app.com/view");
-    });
-  });
-
-  describe("hasPlaceholder", () => {
-    it("should return true if template contains <bech32>", () => {
-      expect(hasPlaceholder("https://app.com/<bech32>")).toBe(true);
-    });
-
-    it("should return false if template does not contain <bech32>", () => {
-      expect(hasPlaceholder("https://app.com/view")).toBe(false);
-    });
-  });
-
-  describe("formatAddressPointer", () => {
-    it("should format address pointer as string", () => {
-      const pointer = {
-        kind: 31990,
-        pubkey: "abcd1234",
-        identifier: "my-handler",
-      };
-      expect(formatAddressPointer(pointer)).toBe("31990:abcd1234:my-handler");
-    });
-  });
-});

src/lib/nip89-helpers.ts

@@ -22,27 +22,41 @@ function getTagValues(event: NostrEvent, tagName: string): string[] {
 // Kind 31990 (Application Handler) Helpers
 // ============================================================================
 
+/**
+ * Get parsed metadata from kind 31990 event content JSON
+ * Caches the parsed result to avoid redundant JSON.parse calls
+ */
+function getAppMetadata(event: NostrEvent): Record<string, any> | null {
+  if (event.kind !== 31990 || !event.content) return null;
+
+  // Use a symbol as cache key to avoid property name conflicts
+  const cacheKey = Symbol.for("nip89-metadata");
+  const cached = (event as any)[cacheKey];
+  if (cached !== undefined) return cached;
+
+  try {
+    const metadata = JSON.parse(event.content);
+    if (metadata && typeof metadata === "object") {
+      (event as any)[cacheKey] = metadata;
+      return metadata;
+    }
+  } catch {
+    // Invalid JSON
+  }
+
+  (event as any)[cacheKey] = null;
+  return null;
+}
+
 /**
  * Extract app name from kind 31990 event content JSON or fallback to d tag
  */
 export function getAppName(event: NostrEvent): string {
   if (event.kind !== 31990) return "";
 
-  // Try to parse content as JSON
-  if (event.content) {
-    try {
-      const metadata = JSON.parse(event.content);
-      if (
-        metadata &&
-        typeof metadata === "object" &&
-        metadata.name &&
-        typeof metadata.name === "string"
-      ) {
-        return metadata.name;
-      }
-    } catch {
-      // Not valid JSON, continue to fallback
-    }
+  const metadata = getAppMetadata(event);
+  if (metadata?.name && typeof metadata.name === "string") {
+    return metadata.name;
   }
 
   // Fallback to d tag identifier
@@ -55,40 +69,31 @@ export function getAppName(event: NostrEvent): string {
  * Checks both 'description' and 'about' fields
  */
 export function getAppDescription(event: NostrEvent): string | undefined {
-  if (event.kind !== 31990 || !event.content) return undefined;
+  if (event.kind !== 31990) return undefined;
 
-  try {
-    const metadata = JSON.parse(event.content);
-    if (metadata && typeof metadata === "object") {
-      // Check description first, then about (common in kind 0 profile format)
-      const desc = metadata.description || metadata.about;
-      if (desc && typeof desc === "string") {
-        return desc;
-      }
+  const metadata = getAppMetadata(event);
+  if (metadata) {
+    // Check description first, then about (common in kind 0 profile format)
+    const desc = metadata.description || metadata.about;
+    if (desc && typeof desc === "string") {
+      return desc;
     }
-  } catch {
-    // Invalid JSON
   }
+
   return undefined;
 }
 
 /**
- * Extract app image URL from kind 31990 event content JSON
+ * Extract website URL from kind 31990 event content JSON
  */
-export function getAppImage(event: NostrEvent): string | undefined {
-  if (event.kind !== 31990 || !event.content) return undefined;
+export function getAppWebsite(event: NostrEvent): string | undefined {
+  if (event.kind !== 31990) return undefined;
 
-  try {
-    const metadata = JSON.parse(event.content);
-    if (metadata && typeof metadata === "object") {
-      const image = metadata.image || metadata.picture;
-      if (image && typeof image === "string") {
-        return image;
-      }
-    }
-  } catch {
-    // Invalid JSON
+  const metadata = getAppMetadata(event);
+  if (metadata?.website && typeof metadata.website === "string") {
+    return metadata.website;
   }
+
   return undefined;
 }
 
@@ -150,26 +155,6 @@ export function getAvailablePlatforms(event: NostrEvent): string[] {
   return Object.keys(getPlatformUrls(event));
 }
 
-/**
- * Extract website URL from kind 31990 event content JSON
- */
-export function getAppWebsite(event: NostrEvent): string | undefined {
-  if (event.kind !== 31990 || !event.content) return undefined;
-
-  try {
-    const metadata = JSON.parse(event.content);
-    if (metadata && typeof metadata === "object") {
-      const website = metadata.website;
-      if (website && typeof website === "string") {
-        return website;
-      }
-    }
-  } catch {
-    // Invalid JSON
-  }
-  return undefined;
-}
-
 /**
  * Get the d tag identifier from kind 31990 event
  */
@@ -255,20 +240,6 @@ export function getHandlerReferences(event: NostrEvent): HandlerReference[] {
   return references;
 }
 
-/**
- * Get handler references filtered by platform
- */
-export function getHandlersByPlatform(
-  event: NostrEvent,
-  platform?: string,
-): HandlerReference[] {
-  const allRefs = getHandlerReferences(event);
-
-  if (!platform) return allRefs;
-
-  return allRefs.filter((ref) => ref.platform === platform);
-}
-
 /**
  * Get unique platforms from handler references in kind 31989
  */
@@ -284,32 +255,3 @@ export function getRecommendedPlatforms(event: NostrEvent): string[] {
 
   return Array.from(platforms).sort();
 }
-
-// ============================================================================
-// URL Template Utilities
-// ============================================================================
-
-/**
- * Substitute <bech32> placeholder in URL template with actual bech32 entity
- */
-export function substituteTemplate(
-  template: string,
-  bech32Entity: string,
-): string {
-  return template.replace(/<bech32>/g, bech32Entity);
-}
-
-/**
- * Check if a string contains the <bech32> placeholder
- */
-export function hasPlaceholder(template: string): boolean {
-  return template.includes("<bech32>");
-}
-
-/**
- * Format an address pointer as a string for display
- * Format: "kind:pubkey:identifier"
- */
-export function formatAddressPointer(pointer: AddressPointer): string {
-  return `${pointer.kind}:${pointer.pubkey}:${pointer.identifier}`;
-}