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background.ts
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background.ts
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import type {RequestMessage} from './src/PortMessage';
import type {InternalPacket} from './src/types-internal';
import type {DeliveryReceipt} from './src/utils/delivery-logger';
import type {EndpointFingerprint} from './src/utils/endpoint-fingerprint';
import type {Runtime} from 'webextension-polyfill';
import browser from 'webextension-polyfill';
import {createBroadcastEventRuntime} from './src/BroadcastEventRuntime';
import {createMessageRuntime} from './src/MessageRuntime';
import {PortMessage} from './src/PortMessage';
import {initTransportAPI} from './src/TransportAPI';
import {InternalBroadcastEvent} from './src/types-internal';
import {decodeConnectionArgs} from './src/utils/connection-args';
import {createDeliveryLogger} from './src/utils/delivery-logger';
import {createFingerprint} from './src/utils/endpoint-fingerprint';
import {
deserializeEndpoint,
serializeEndpoint,
} from './src/utils/endpoint-utils';
import {internalPacketTypeRouter} from './src/utils/internalPacketTypeRouter';
interface PortConnection {
port: Runtime.Port;
fingerprint: EndpointFingerprint;
}
export function initPegasusTransport(): void {
const pendingResponses = createDeliveryLogger();
const connMap = new Map<string, PortConnection>();
const oncePortConnectedCbs = new Map<string, Set<() => void>>();
const onceSessionEndCbs = new Map<EndpointFingerprint, Set<() => void>>();
const oncePortConnected = (endpointName: string, cb: () => void) => {
oncePortConnectedCbs.set(
endpointName,
(oncePortConnectedCbs.get(endpointName) || new Set()).add(cb),
);
return () => {
const su = oncePortConnectedCbs.get(endpointName);
if (su?.delete(cb) && su?.size === 0) {
oncePortConnectedCbs.delete(endpointName);
}
};
};
const onceSessionEnded = (
sessionFingerprint: EndpointFingerprint,
cb: () => void,
) => {
onceSessionEndCbs.set(
sessionFingerprint,
(onceSessionEndCbs.get(sessionFingerprint) || new Set()).add(cb),
);
};
const notifyEndpoint = (endpoint: string) => ({
withFingerprint: (fingerprint: EndpointFingerprint) => {
const nextChain = <T>(v: T) => ({and: () => v});
const notifications = {
aboutIncomingMessage: (message: InternalPacket) => {
const recipient = connMap.get(endpoint);
if (recipient == null) {
throw new Error('Unable to find recipient endpoint');
}
PortMessage.toExtensionContext(recipient.port, {
message,
status: 'incoming',
});
return nextChain(notifications);
},
aboutMessageUndeliverability: (
resolvedDestination: string,
message: InternalPacket,
) => {
const sender = connMap.get(endpoint);
if (sender?.fingerprint === fingerprint) {
PortMessage.toExtensionContext(sender.port, {
message,
resolvedDestination,
status: 'undeliverable',
});
}
return nextChain(notifications);
},
aboutSessionEnded: (endedSessionFingerprint: EndpointFingerprint) => {
const conn = connMap.get(endpoint);
if (conn?.fingerprint === fingerprint) {
PortMessage.toExtensionContext(conn.port, {
fingerprint: endedSessionFingerprint,
status: 'terminated',
});
}
return nextChain(notifications);
},
aboutSuccessfulDelivery: (receipt: DeliveryReceipt) => {
const sender = connMap.get(endpoint);
if (sender == null) {
throw new Error('Unable to find sender endpoint');
}
PortMessage.toExtensionContext(sender.port, {
receipt,
status: 'delivered',
});
return nextChain(notifications);
},
whenDeliverableTo: (targetEndpoint: string) => {
const notifyDeliverability = () => {
const origin = connMap.get(endpoint);
if (
origin?.fingerprint === fingerprint &&
connMap.has(targetEndpoint)
) {
PortMessage.toExtensionContext(origin.port, {
deliverableTo: targetEndpoint,
status: 'deliverable',
});
return true;
}
};
if (!notifyDeliverability()) {
const unsub = oncePortConnected(
targetEndpoint,
notifyDeliverability,
);
onceSessionEnded(fingerprint, unsub);
}
return nextChain(notifications);
},
};
return notifications;
},
});
const sessFingerprint = createFingerprint();
const messageRuntime = createMessageRuntime(
'background',
async (message) => {
if (
message.origin.context === 'background' &&
['content-script', 'devtools'].includes(message.destination.context) &&
!message.destination.tabId
) {
throw new TypeError(
'When sending messages from background page, use @tabId syntax to target specific tab',
);
}
const resolvedSender = serializeEndpoint({
...message.origin,
...(message.origin.context === 'window' && {context: 'content-script'}),
});
const resolvedDestination = serializeEndpoint({
...message.destination,
...(message.destination.context === 'window' && {
context: 'content-script',
}),
tabId: message.destination.tabId || message.origin.tabId,
});
// downstream endpoints are agnostic of these attributes, presence of these attrs will make them think the message is not intended for them
message.destination.tabId = null;
message.destination.frameId = undefined;
// TODO: fix "as" type casting below
const dest = () => connMap.get(resolvedDestination) as PortConnection;
const sender = () => connMap.get(resolvedSender) as PortConnection;
const deliver = () => {
notifyEndpoint(resolvedDestination)
.withFingerprint(dest().fingerprint)
.aboutIncomingMessage(message);
const receipt: DeliveryReceipt = {
from: {
endpointId: resolvedSender,
fingerprint: sender()?.fingerprint,
},
message,
to: dest().fingerprint,
};
if (message.messageType === 'message') {
pendingResponses.add(receipt);
}
if (message.messageType === 'reply') {
pendingResponses.remove(message.id);
}
if (sender()) {
notifyEndpoint(resolvedSender)
.withFingerprint(sender().fingerprint)
.aboutSuccessfulDelivery(receipt);
}
};
if (dest()?.port) {
deliver();
} else if (message.messageType === 'message') {
if (message.origin.context === 'background') {
oncePortConnected(resolvedDestination, deliver);
} else if (sender()) {
notifyEndpoint(resolvedSender)
.withFingerprint(sender().fingerprint)
.aboutMessageUndeliverability(resolvedDestination, message)
.and()
.whenDeliverableTo(resolvedDestination);
}
}
},
async (message) => {
const resolvedSender = serializeEndpoint({
...message.origin,
...(message.origin.context === 'window' && {context: 'content-script'}),
});
const sender = connMap.get(resolvedSender);
if (sender == null) {
throw new Error('Unable to find sender endpoint');
}
const receipt: DeliveryReceipt = {
from: {
endpointId: resolvedSender,
fingerprint: sender.fingerprint,
},
message,
to: sessFingerprint,
};
notifyEndpoint(resolvedSender)
.withFingerprint(sender.fingerprint)
.aboutSuccessfulDelivery(receipt);
},
);
browser.runtime.onConnect.addListener((incomingPort) => {
const connArgs = decodeConnectionArgs(incomingPort.name);
if (!connArgs) {
return;
}
// all other contexts except 'content-script' are aware of, and pass their identity as name
connArgs.endpointName ||= serializeEndpoint({
context: 'content-script',
frameId: incomingPort.sender?.frameId,
tabId: incomingPort.sender?.tab?.id ?? null,
});
// literal tab id in case of content script, however tab id of inspected page in case of devtools context
const {tabId: linkedTabId, frameId: linkedFrameId} = deserializeEndpoint(
connArgs.endpointName,
);
connMap.set(connArgs.endpointName, {
fingerprint: connArgs.fingerprint,
port: incomingPort,
});
oncePortConnectedCbs.get(connArgs.endpointName)?.forEach((cb) => cb());
oncePortConnectedCbs.delete(connArgs.endpointName);
onceSessionEnded(connArgs.fingerprint, () => {
const rogueMsgs = pendingResponses
.entries()
.filter((pendingMessage) => pendingMessage.to === connArgs.fingerprint);
pendingResponses.remove(rogueMsgs);
rogueMsgs.forEach((rogueMessage) => {
if (rogueMessage.from.endpointId === 'background') {
messageRuntime.endTransaction(rogueMessage.message.transactionId);
} else {
notifyEndpoint(rogueMessage.from.endpointId)
.withFingerprint(rogueMessage.from.fingerprint)
.aboutSessionEnded(connArgs.fingerprint);
}
});
});
incomingPort.onDisconnect.addListener(() => {
// sometimes previous content script's onDisconnect is called *after* the fresh content-script's
// onConnect. So without this fingerprint equality check, we would remove the new port from map
if (
connMap.get(connArgs.endpointName)?.fingerprint === connArgs.fingerprint
) {
connMap.delete(connArgs.endpointName);
}
onceSessionEndCbs.get(connArgs.fingerprint)?.forEach((cb) => cb());
onceSessionEndCbs.delete(connArgs.fingerprint);
});
incomingPort.onMessage.addListener((msg: RequestMessage) => {
if (msg.type === 'sync') {
const allActiveSessions = [...connMap.values()].map(
(conn) => conn.fingerprint,
);
const stillPending = msg.pendingResponses.filter((fp) =>
allActiveSessions.includes(fp.to),
);
pendingResponses.add(...stillPending);
msg.pendingResponses
.filter(
(deliveryReceipt) =>
!allActiveSessions.includes(deliveryReceipt.to),
)
.forEach((deliveryReceipt) =>
notifyEndpoint(connArgs.endpointName)
.withFingerprint(connArgs.fingerprint)
.aboutSessionEnded(deliveryReceipt.to),
);
msg.pendingDeliveries.forEach((intendedDestination) =>
notifyEndpoint(connArgs.endpointName)
.withFingerprint(connArgs.fingerprint)
.whenDeliverableTo(intendedDestination),
);
return;
}
if (msg.type === 'deliver' && msg.message?.origin?.context) {
// origin tab ID is resolved from the port identifier (also prevent "MITM attacks" of extensions)
msg.message.origin.tabId = linkedTabId;
msg.message.origin.frameId = linkedFrameId;
internalPacketTypeRouter(msg.message, {eventRuntime, messageRuntime});
}
});
});
let undeliveredEvents: InternalBroadcastEvent[] | undefined = [];
// PersistentPort usually reconnects within 500ms
setTimeout(() => {
Promise.all(
(undeliveredEvents as InternalBroadcastEvent[]).map(routeEvent),
).catch((err) => {
console.error('Error while tying to deliver undelivered events:', err);
});
undeliveredEvents = undefined;
}, 500);
const routeEvent = async (event: InternalBroadcastEvent) => {
// Background SW just resumed it's work and there are no connections yet
// so we need to queue the event for later delivery
if (connMap.size === 0 && undeliveredEvents !== undefined) {
undeliveredEvents.push(event);
return;
}
connMap.forEach((port, endpoint) => {
notifyEndpoint(endpoint)
.withFingerprint(port.fingerprint)
.aboutIncomingMessage(event);
});
// So background listeners receive events from other contexts
if (event.origin.context !== 'background') {
eventRuntime.handleEvent(event);
}
};
const eventRuntime = createBroadcastEventRuntime('background', routeEvent);
initTransportAPI({
browser: browser,
emitBroadcastEvent: eventRuntime.emitBroadcastEvent,
onBroadcastEvent: eventRuntime.onBroadcastEvent,
onMessage: messageRuntime.onMessage,
sendMessage: messageRuntime.sendMessage,
});
}