ts: CPI events parsing

ts/packages/anchor/src/coder/borsh/event.ts

@@ -4,8 +4,19 @@ import * as base64 from "../../utils/bytes/base64.js";
 import { Idl } from "../../idl.js";
 import { IdlCoder } from "./idl.js";
 import { EventCoder } from "../index.js";
+import BN from "bn.js";
+import { PublicKey } from "@solana/web3.js";
+import { decode as bs58Decode } from "../../utils/bytes/bs58.js";
 
 export class BorshEventCoder implements EventCoder {
+  /**
+   * CPI event discriminator.
+   * https://github.com/coral-xyz/anchor/blob/v0.29.0/lang/src/event.rs
+   */
+  private static eventIxTag: BN = new BN("1d9acb512ea545e4", "hex");
+
+  private address: string;
+
   /**
    * Maps account type identifier to a layout.
    */
@@ -42,6 +53,8 @@ export class BorshEventCoder implements EventCoder {
         ev.name,
       ])
     );
+
+    this.address = idl.address;
   }
 
   public decode(log: string): {
@@ -70,4 +83,26 @@ export class BorshEventCoder implements EventCoder {
     const data = layout.decode(logArr.slice(8));
     return { data, name: eventName };
   }
+
+  get idlAddress(): PublicKey {
+    return new PublicKey(this.address);
+  }
+
+  public static isCPIEventData(buffer: Buffer): boolean {
+    return buffer
+      .subarray(0, 8)
+      .equals(BorshEventCoder.eventIxTag.toBuffer("le"));
+  }
+
+  public decodeCpi(ixInputData: string): {
+    name: string;
+    data: any;
+  } | null {
+    const ixInputBufferData = bs58Decode(ixInputData);
+    if (BorshEventCoder.isCPIEventData(ixInputBufferData)) {
+      const eventData = base64.encode(ixInputBufferData.subarray(8));
+      return this.decode(eventData);
+    }
+    return null;
+  }
 }

ts/packages/anchor/src/utils/events.ts

@@ -0,0 +1,36 @@
+import {
+  CompiledInnerInstruction,
+  VersionedTransactionResponse,
+} from "@solana/web3.js";
+import { BorshEventCoder } from "src/coder";
+import { Idl } from "src/idl";
+import { IdlEvents } from "src/program";
+
+// https://github.com/coral-xyz/anchor/blob/v0.29.0/tests/events/tests/events.ts#L61-L62
+export function parseCpiEvents(
+  eventDecoder: BorshEventCoder,
+  transactionResponse: VersionedTransactionResponse
+): { name: string; data: any }[] {
+  const events: { name: string; data: any }[] = [];
+  const inner: CompiledInnerInstruction[] =
+    transactionResponse?.meta?.innerInstructions ?? [];
+  const idlProgramId = eventDecoder.idlAddress;
+  for (let i = 0; i < inner.length; i++) {
+    for (let j = 0; j < inner[i].instructions.length; j++) {
+      const ix = inner[i].instructions[j];
+      const programPubkey =
+        transactionResponse?.transaction.message.staticAccountKeys[
+          ix.programIdIndex
+        ];
+      if (programPubkey === undefined || !programPubkey.equals(idlProgramId)) {
+        // we are at instructions that does not match the linked program
+        continue;
+      }
+      const event = eventDecoder.decodeCpi(ix.data);
+      if (event) {
+        events.push(event);
+      }
+    }
+  }
+  return events;
+}

ts/packages/anchor/src/utils/index.ts

@@ -5,3 +5,4 @@ export * as bytes from "./bytes/index.js";
 export * as token from "./token.js";
 export * as features from "./features.js";
 export * as registry from "./registry.js";
+export * as events from "./events.js";