feat: implement mpp draft spec

package.json

@@ -54,6 +54,11 @@
       "require": "./dist/cjs/x402.cjs",
       "types": "./dist/types/x402.d.ts"
     },
+    "./mpp": {
+      "import": "./dist/esm/mpp.js",
+      "require": "./dist/cjs/mpp.cjs",
+      "types": "./dist/types/mpp.d.ts"
+    },
     "./lnurl": {
       "import": "./dist/esm/lnurl.js",
       "require": "./dist/cjs/lnurl.cjs",

rollup.config.js

@@ -22,6 +22,7 @@ const entries = [
   { name: "402", input: "src/402/index.ts" },
   { name: "l402", input: "src/402/l402/index.ts" },
   { name: "x402", input: "src/402/x402/index.ts" },
+  { name: "mpp", input: "src/402/mpp/index.ts" },
   { name: "lnurl", input: "src/lnurl/index.ts" },
   { name: "podcasting2", input: "src/podcasting2/index.ts" },
 ];

src/402/fetch402.ts

@@ -2,6 +2,7 @@ import { KVStorage, NoStorage, Wallet } from "./utils";
 import { buildX402PaymentSignature } from "./x402/utils";
 import { HEADER_KEY, handleL402Payment } from "./l402/l402";
 import { handleX402Payment } from "./x402/x402";
+import { handleMppChargePayment } from "./mpp/mpp";
 
 const noStorage = new NoStorage();
 
@@ -59,10 +60,19 @@ export const fetch402 = async (
   headers.set("Accept-Authenticate", HEADER_KEY);
   const initResp = await fetch(url, fetchArgs);
 
-  const l402Header = initResp.headers.get("www-authenticate");
-  if (l402Header) {
+  const wwwAuthHeader = initResp.headers.get("www-authenticate");
+  if (wwwAuthHeader) {
+    if (wwwAuthHeader.trimStart().toLowerCase().startsWith("payment")) {
+      return handleMppChargePayment(
+        wwwAuthHeader,
+        url,
+        fetchArgs,
+        headers,
+        wallet,
+      );
+    }
     return handleL402Payment(
-      l402Header,
+      wwwAuthHeader,
       url,
       fetchArgs,
       headers,

src/402/mpp/index.ts

@@ -0,0 +1,2 @@
+export * from "./mpp";
+export * from "./utils";