feat(nip-transformer): add support for hex NIPs like NIP-C7

- Extend pattern to match hex NIP identifiers (NIP-C7, NIP-C0, NIP-A0)
- Normalize hex NIPs to uppercase (nip-c7 -> C7)
- Add tests for hex NIP parsing and normalization

src/lib/nip-transformer.test.ts

@@ -174,4 +174,70 @@ describe("nipReferences transformer", () => {
       expect(nips[1].number).toBe("999");
     });
   });
+
+  describe("hex NIP support", () => {
+    it("should parse hex NIP-C7", () => {
+      const tree = createTree("Code snippets are defined in NIP-C7");
+      const transformer = nipReferences();
+      transformer(tree);
+
+      const nips = getNodesOfType<NipNode>(tree, "nip");
+      expect(nips).toHaveLength(1);
+      expect(nips[0].number).toBe("C7");
+      expect(nips[0].raw).toBe("NIP-C7");
+    });
+
+    it("should parse lowercase hex nip-c7", () => {
+      const tree = createTree("See nip-c7 for code snippets");
+      const transformer = nipReferences();
+      transformer(tree);
+
+      const nips = getNodesOfType<NipNode>(tree, "nip");
+      expect(nips).toHaveLength(1);
+      expect(nips[0].number).toBe("C7"); // Normalized to uppercase
+      expect(nips[0].raw).toBe("nip-c7");
+    });
+
+    it("should parse NIP-C0", () => {
+      const tree = createTree("NIP-C0 defines something");
+      const transformer = nipReferences();
+      transformer(tree);
+
+      const nips = getNodesOfType<NipNode>(tree, "nip");
+      expect(nips).toHaveLength(1);
+      expect(nips[0].number).toBe("C0");
+    });
+
+    it("should parse NIP-A0", () => {
+      const tree = createTree("Check NIP-A0");
+      const transformer = nipReferences();
+      transformer(tree);
+
+      const nips = getNodesOfType<NipNode>(tree, "nip");
+      expect(nips).toHaveLength(1);
+      expect(nips[0].number).toBe("A0");
+    });
+
+    it("should handle mixed decimal and hex NIPs", () => {
+      const tree = createTree("NIP-01, NIP-C7, and NIP-19 together");
+      const transformer = nipReferences();
+      transformer(tree);
+
+      const nips = getNodesOfType<NipNode>(tree, "nip");
+      expect(nips).toHaveLength(3);
+      expect(nips[0].number).toBe("01");
+      expect(nips[1].number).toBe("C7");
+      expect(nips[2].number).toBe("19");
+    });
+
+    it("should normalize mixed case hex to uppercase", () => {
+      const tree = createTree("nip-c7 NIP-C7 nip-C7 NIP-c7");
+      const transformer = nipReferences();
+      transformer(tree);
+
+      const nips = getNodesOfType<NipNode>(tree, "nip");
+      expect(nips).toHaveLength(4);
+      expect(nips.every((n) => n.number === "C7")).toBe(true);
+    });
+  });
 });

src/lib/nip-transformer.ts

@@ -6,15 +6,36 @@ import type { Root, Content } from "applesauce-content/nast";
  */
 export interface NipNode {
   type: "nip";
-  /** The NIP number (e.g., "01", "19", "30") */
+  /** The NIP number/identifier (e.g., "01", "19", "C7") */
   number: string;
-  /** The raw matched text (e.g., "NIP-01", "nip-19") */
+  /** The raw matched text (e.g., "NIP-01", "nip-19", "NIP-C7") */
   raw: string;
 }
 
-// Match NIP-xx patterns (case insensitive, 1-3 digits)
-// Supports: NIP-01, NIP-1, nip-19, NIP-100, etc.
-const NIP_PATTERN = /\bNIP-(\d{1,3})\b/gi;
+// Match NIP-xx patterns (case insensitive)
+// Supports both decimal (NIP-01, NIP-19, NIP-100) and hex (NIP-C7, NIP-C0, NIP-A0)
+// Pattern: 1-3 hex characters (which includes pure decimal)
+const NIP_PATTERN = /\bNIP-([0-9A-Fa-f]{1,3})\b/gi;
+
+/**
+ * Check if a NIP identifier is purely decimal
+ */
+function isDecimalNip(nip: string): boolean {
+  return /^\d+$/.test(nip);
+}
+
+/**
+ * Normalize a NIP identifier:
+ * - Decimal NIPs: pad to 2 digits (1 -> 01, 19 -> 19)
+ * - Hex NIPs: uppercase (c7 -> C7)
+ */
+function normalizeNip(nip: string): string {
+  if (isDecimalNip(nip)) {
+    return nip.padStart(2, "0");
+  }
+  // Hex NIP - uppercase it
+  return nip.toUpperCase();
+}
 
 /**
  * Transformer that finds NIP-xx references and converts them to nip nodes.
@@ -26,8 +47,7 @@ export function nipReferences() {
       [
         NIP_PATTERN,
         (full, number) => {
-          // Normalize to 2 digits with leading zero for consistency
-          const normalized = number.padStart(2, "0");
+          const normalized = normalizeNip(number);
           // Cast to Content since we're extending with a custom node type
           return {
             type: "nip",