fee bumping

1 files changed, 54 insertions, 0 deletions

diff --git a/lib/p2a.ts b/lib/p2a.ts
new file mode 100644
index 00000000..6e256f20
--- /dev/null
+++ b/lib/p2a.ts
@@ -0,0 +1,54 @@
+import config from "$config";
+import { bech32m } from "@scure/base";
+
+export const P2A_VALUE = 240;
+export const P2A_SCRIPT = "51024e73"; // OP_1 OP_PUSHBYTES_2 0x4e73
+export const CHILD_VSIZE = 152;
+
+const P2A_WITNESS_PROGRAM = new Uint8Array([0x4e, 0x73]);
+const P2A_WITNESS_VERSION = 1;
+
+const P2A_ADDRESSES: Record<string, string> = {
+  mainnet: "bc1pfeessrawgf",
+  testnet: "tb1pfeessrawgf",
+  signet: "tb1pfeessrawgf",
+  regtest: "bcrt1pfeessrawgf",
+};
+
+const BECH32M_PREFIXES: Record<string, string> = {
+  mainnet: "bc",
+  testnet: "tb",
+  signet: "tb",
+  regtest: "bcrt",
+};
+
+function verifyP2AAddresses() {
+  for (const [network, expected] of Object.entries(P2A_ADDRESSES)) {
+    const prefix = BECH32M_PREFIXES[network];
+    const words = [P2A_WITNESS_VERSION, ...bech32m.toWords(P2A_WITNESS_PROGRAM)];
+    const encoded = bech32m.encode(prefix, words);
+    if (encoded !== expected) {
+      throw new Error(`P2A address mismatch for ${network}: got ${encoded}, expected ${expected}`);
+    }
+  }
+}
+
+verifyP2AAddresses();
+
+export function getP2AAddress(): string {
+  const network = config.bitcoin.network || "mainnet";
+  return P2A_ADDRESSES[network];
+}
+
+export function isP2AOutput(scriptPubKeyHex: string): boolean {
+  return scriptPubKeyHex === P2A_SCRIPT;
+}
+
+export function calculateBumpReserve(
+  userRate: number,
+  fastestRate: number,
+  parentVsize: number,
+): number {
+  if (userRate >= fastestRate) return 0;
+  return Math.ceil((fastestRate - userRate) * parentVsize + fastestRate * CHILD_VSIZE);
+}