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event.ts
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event.ts
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import { PublicKey } from "@solana/web3.js";
import * as assert from "assert";
import { IdlEvent, IdlEventField } from "../idl.js";
import { Coder } from "../coder/index.js";
import { DecodeType } from "./namespace/types.js";
import Provider from "../provider.js";
const PROGRAM_LOG = "Program log: ";
const PROGRAM_DATA = "Program data: ";
const PROGRAM_LOG_START_INDEX = PROGRAM_LOG.length;
const PROGRAM_DATA_START_INDEX = PROGRAM_DATA.length;
// Deserialized event.
export type Event<
E extends IdlEvent = IdlEvent,
Defined = Record<string, never>
> = {
name: E["name"];
data: EventData<E["fields"][number], Defined>;
};
export type EventData<T extends IdlEventField, Defined> = {
[N in T["name"]]: DecodeType<(T & { name: N })["type"], Defined>;
};
type EventCallback = (event: any, slot: number) => void;
export class EventManager {
/**
* Program ID for event subscriptions.
*/
private _programId: PublicKey;
/**
* Network and wallet provider.
*/
private _provider: Provider;
/**
* Event parser to handle onLogs callbacks.
*/
private _eventParser: EventParser;
/**
* Maps event listener id to [event-name, callback].
*/
private _eventCallbacks: Map<number, [string, EventCallback]>;
/**
* Maps event name to all listeners for the event.
*/
private _eventListeners: Map<string, Array<number>>;
/**
* The next listener id to allocate.
*/
private _listenerIdCount: number;
/**
* The subscription id from the connection onLogs subscription.
*/
private _onLogsSubscriptionId: number | undefined;
constructor(programId: PublicKey, provider: Provider, coder: Coder) {
this._programId = programId;
this._provider = provider;
this._eventParser = new EventParser(programId, coder);
this._eventCallbacks = new Map();
this._eventListeners = new Map();
this._listenerIdCount = 0;
}
public addEventListener(
eventName: string,
callback: (event: any, slot: number) => void
): number {
let listener = this._listenerIdCount;
this._listenerIdCount += 1;
// Store the listener into the event map.
if (!(eventName in this._eventCallbacks)) {
this._eventListeners.set(eventName, []);
}
this._eventListeners.set(
eventName,
(this._eventListeners.get(eventName) ?? []).concat(listener)
);
// Store the callback into the listener map.
this._eventCallbacks.set(listener, [eventName, callback]);
// Create the subscription singleton, if needed.
if (this._onLogsSubscriptionId !== undefined) {
return listener;
}
this._onLogsSubscriptionId = this._provider!.connection.onLogs(
this._programId,
(logs, ctx) => {
if (logs.err) {
return;
}
this._eventParser.parseLogs(logs.logs, (event) => {
const allListeners = this._eventListeners.get(event.name);
if (allListeners) {
allListeners.forEach((listener) => {
const listenerCb = this._eventCallbacks.get(listener);
if (listenerCb) {
const [, callback] = listenerCb;
callback(event.data, ctx.slot);
}
});
}
});
}
);
return listener;
}
public async removeEventListener(listener: number): Promise<void> {
// Get the callback.
const callback = this._eventCallbacks.get(listener);
if (!callback) {
throw new Error(`Event listener ${listener} doesn't exist!`);
}
const [eventName] = callback;
// Get the listeners.
let listeners = this._eventListeners.get(eventName);
if (!listeners) {
throw new Error(`Event listeners don't exist for ${eventName}!`);
}
// Update both maps.
this._eventCallbacks.delete(listener);
listeners = listeners.filter((l) => l !== listener);
if (listeners.length === 0) {
this._eventListeners.delete(eventName);
}
// Kill the websocket connection if all listeners have been removed.
if (this._eventCallbacks.size == 0) {
assert.ok(this._eventListeners.size === 0);
if (this._onLogsSubscriptionId !== undefined) {
await this._provider!.connection.removeOnLogsListener(
this._onLogsSubscriptionId
);
this._onLogsSubscriptionId = undefined;
}
}
}
}
export class EventParser {
private coder: Coder;
private programId: PublicKey;
constructor(programId: PublicKey, coder: Coder) {
this.coder = coder;
this.programId = programId;
}
// Each log given, represents an array of messages emitted by
// a single transaction, which can execute many different programs across
// CPI boundaries. However, the subscription is only interested in the
// events emitted by *this* program. In achieving this, we keep track of the
// program execution context by parsing each log and looking for a CPI
// `invoke` call. If one exists, we know a new program is executing. So we
// push the programId onto a stack and switch the program context. This
// allows us to track, for a given log, which program was executing during
// its emission, thereby allowing us to know if a given log event was
// emitted by *this* program. If it was, then we parse the raw string and
// emit the event if the string matches the event being subscribed to.
public parseLogs(logs: string[], callback: (log: Event) => void) {
const logScanner = new LogScanner(logs);
const execution = new ExecutionContext();
let log = logScanner.next();
while (log !== null) {
let [event, newProgram, didPop] = this.handleLog(execution, log);
if (event) {
callback(event);
}
if (newProgram) {
execution.push(newProgram);
}
if (didPop) {
execution.pop();
}
log = logScanner.next();
}
}
// Main log handler. Returns a three element array of the event, the
// next program that was invoked for CPI, and a boolean indicating if
// a program has completed execution (and thus should be popped off the
// execution stack).
private handleLog(
execution: ExecutionContext,
log: string
): [Event | null, string | null, boolean] {
// Executing program is this program.
if (
execution.stack.length > 0 &&
execution.program() === this.programId.toString()
) {
return this.handleProgramLog(log);
}
// Executing program is not this program.
else {
return [null, ...this.handleSystemLog(log)];
}
}
// Handles logs from *this* program.
private handleProgramLog(
log: string
): [Event | null, string | null, boolean] {
// This is a `msg!` log or a `sol_log_data` log.
if (log.startsWith(PROGRAM_LOG) || log.startsWith(PROGRAM_DATA)) {
const logStr = log.startsWith(PROGRAM_LOG)
? log.slice(PROGRAM_LOG_START_INDEX)
: log.slice(PROGRAM_DATA_START_INDEX);
const event = this.coder.events.decode(logStr);
return [event, null, false];
}
// System log.
else {
return [null, ...this.handleSystemLog(log)];
}
}
// Handles logs when the current program being executing is *not* this.
private handleSystemLog(log: string): [string | null, boolean] {
// System component.
const logStart = log.split(":")[0];
// Did the program finish executing?
if (logStart.match(/^Program (.*) success/g) !== null) {
return [null, true];
// Recursive call.
} else if (
logStart.startsWith(`Program ${this.programId.toString()} invoke`)
) {
return [this.programId.toString(), false];
}
// CPI call.
else if (logStart.includes("invoke")) {
return ["cpi", false]; // Any string will do.
} else {
return [null, false];
}
}
}
// Stack frame execution context, allowing one to track what program is
// executing for a given log.
class ExecutionContext {
stack: string[] = [];
program(): string {
assert.ok(this.stack.length > 0);
return this.stack[this.stack.length - 1];
}
push(newProgram: string) {
this.stack.push(newProgram);
}
pop() {
assert.ok(this.stack.length > 0);
this.stack.pop();
}
}
class LogScanner {
constructor(public logs: string[]) {}
next(): string | null {
if (this.logs.length === 0) {
return null;
}
let l = this.logs[0];
this.logs = this.logs.slice(1);
return l;
}
}