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| import { Network } from '@tao.js/core';
// for backwards compatibility
const MAX_SAFE_INTEGER = Math.pow(2, 53) - 1;
let transceiverId = 0;
function newTransceiverId() {
return (transceiverId = ++transceiverId % MAX_SAFE_INTEGER);
}
let signalId = 0;
function newSignalId() {
return (signalId = ++signalId % MAX_SAFE_INTEGER);
}
function transceiverControl(transceiverId, resolve, reject) {
return { transceiverId, signal: { id: newSignalId(), resolve, reject } };
}
/**
* Like a Transponder, a Transceiver converts Signals on a Network to Promises.
* Unlike a Transponder, a Transceiver allows the handlers attached to it to control
* the behavior of the Promise.
*
* If a Handler returns an AppCtx, then it will be chained like a standard handler.
*
* If a Handler returns something other than an AppCtx it will behave as the following:
* - returning truthy value from an InterceptHandler will REJECT the Promise
* - returning any value not `null` or `undefined` from an AsyncHandler or InlineHandler
* it will be used to RESOLVE the Promise
* - throwing an Error in any Handler will REJECT the Promise
*
* A signal to a Promise can only happen once, so the first thing that happens
* will conclude the Promise despite other handlers that may be continue to be
* called depending on how you set up your Handlers
*
* @export
* @class Transceiver
*/
export default class Transceiver {
constructor(network, id, timeoutMs = 0, promise = Promise) {
this._transceiverId =
typeof id === 'function'
? id(newTransceiverId())
: id || newTransceiverId();
this._signals = new Network();
this._signals.use(this.handleSignalAppCon);
this._network =
typeof network.use === 'function' ? network : network._network;
this._timeoutMs = timeoutMs;
this._promise = promise;
this._cloneWithId = typeof id === 'function' ? id : undefined;
}
setCtx = ({ t, term, a, action, o, orient }, data) => {
const transceiverId = this._transceiverId;
const timeoutMs = this._timeoutMs;
const promise = this._promise;
return new promise((resolve, reject) => {
if (timeoutMs) {
setTimeout(() => {
reject(`reached timeout of: ${timeoutMs}ms`);
}, timeoutMs);
}
this._network.setCtxControl(
{ t, term, a, action, o, orient },
data,
transceiverControl(transceiverId, resolve, reject),
this.forwardAppCtx
);
});
};
setAppCtx = ac => {
const transceiverId = this._transceiverId;
const timeoutMs = this._timeoutMs;
const promise = this._promise;
return new promise((resolve, reject) => {
if (timeoutMs) {
setTimeout(() => {
reject(`reached timeout of: ${timeoutMs}ms`);
}, timeoutMs);
}
this._network.setAppCtxControl(
ac,
transceiverControl(transceiverId, resolve, reject),
this.forwardAppCtx
);
});
};
forwardAppCtx = (ac, control) => {
if (control.transceiverId === this._transceiverId) {
this._signals.setAppCtxControl(ac, control, this.forwardAppCtx);
}
this._network.setAppCtxControl(ac, control, this.forwardAppCtx);
};
handleSignalAppCon = (handler, ac, forwardAppCtx, control) => {
if (
control.transceiverId === this._transceiverId &&
control.signal &&
!control.signalled
) {
try {
this.captureSignal(handler, ac, forwardAppCtx, control).catch(
handleErr => {
if (!control.signalled) {
control.signalled = true;
control.signal.reject(handleErr);
}
}
);
} catch (handleErr) {
if (!control.signalled) {
control.signalled = true;
control.signal.reject(handleErr);
}
}
}
// ALERT: handler will have already handled the AppCon before now
// return handler.handleAppCon(ac, forwardAppCtx, control);
};
// TODO: refactor AppCtxHandlers to allow an override of behavior
captureSignal = async (handler, ac, setAppCtx, control) => {
const { t, a, o, data } = ac;
/*
* Intercept Handlers
* always occur first
* have the ability to prevent other handlers from firing on this AC
* optionally can return a single AC that will be set as the new AC instead of the incoming AC
*
* If handler returns truthy value that is not an AppCtx then it will
* be used to REJECT a signal promise that is part of the message
* control
*/
for (let interceptH of handler.interceptHandlers) {
// using the decorator pattern to call these?
let intercepted = await interceptH({ t, a, o }, data);
if (!intercepted) {
continue;
}
if (intercepted instanceof AppCtx) {
try {
setAppCtx(intercepted, control);
} catch (interceptErr) {
if (!control.signalled) {
control.signalled = true;
control.signal.reject(interceptErr);
}
}
} else if (!control.signalled) {
control.signalled = true;
control.signal.reject(intercepted);
}
return;
}
/*
* Async Handlers
* designed to kick off asynchronous handling of an AC outside of the current
* control loop
* fire if all Intercept Handlers don't intercept the fired AC
* work inside of their own execution context
* can return an AC that will be set as a context inside the async exec ctx
* TODO: look into how redux-sagas is implemented and may be a way to use
* generators instead of Promises
* TODO: would ServiceWorkers make sense for this? tao-sw package
*
* If handler returns anything that is not an AppCtx then it will
* be used to RESOLVE a signal promise that is part of the message
* control
* If handler or chained handlers throw anything then it will be
* used to REJECT a signal promise that is part of the message
* control
*/
for (let asyncH of handler.asyncHandlers) {
(() => {
Promise.resolve(asyncH({ t, a, o }, data))
.then(nextAc => {
if (nextAc != null) {
if (nextAc instanceof AppCtx) {
setAppCtx(nextAc, control);
} else if (!control.signalled) {
control.signalled = true;
control.signal.resolve(nextAc);
}
}
})
.catch(asyncErr => {
if (!control.signalled) {
control.signalled = true;
control.signal.reject(asyncErr);
}
});
})();
}
/*
* Inline Handlers
* fire if all Intercept Handlers don't intercept the fired AC
* fired after all Async handlers are fired off
* work inside the same execution context as the caller
* can return an AC that will be set immediately in the TAO
* TODO: should these returns be spooled up then iterated to allow
* all handlers to handle this context before any new ones are set?
* YES: currently implemented that way
*
* If handler returns anything that is not an AppCtx then it will
* be used to RESOLVE a signal promise that is part of the message
* control
* If handler or chained handlers throw anything then it will be
* used to REJECT a signal promise that is part of the message
* control
*/
const nextSpool = [];
let firstResolve = null;
for (let inlineH of handler.inlineHandlers) {
let nextInlineAc = await inlineH({ t, a, o }, data);
if (nextInlineAc != null) {
if (nextInlineAc instanceof AppCtx) {
nextSpool.push(nextInlineAc);
} else if (!firstResolve) {
firstResolve = nextInlineAc;
}
}
}
if (!control.signalled && firstResolve) {
control.signalled = true;
control.signal.resolve(firstResolve);
}
if (nextSpool.length) {
for (let nextAc of nextSpool) {
try {
setAppCtx(nextAc, control);
} catch (inlineErr) {
if (!control.signalled) {
control.signalled = true;
control.signal.reject(inlineErr);
}
}
}
}
};
addSignalHandler = ({ t, term, a, action, o, orient }, handler) => {
this._signals.addInlineHandler({ t, term, a, action, o, orient }, handler);
};
addInterceptHandler({ t, term, a, action, o, orient }, handler) {
this._signals.addInterceptHandler(
{ t, term, a, action, o, orient },
handler
);
}
addAsyncHandler({ t, term, a, action, o, orient }, handler) {
this._signals.addAsyncHandler({ t, term, a, action, o, orient }, handler);
}
addInlineHandler({ t, term, a, action, o, orient }, handler) {
this._signals.addInlineHandler({ t, term, a, action, o, orient }, handler);
}
removeInterceptHandler({ t, term, a, action, o, orient }, handler) {
this._signals.removeInterceptHandler(
{ t, term, a, action, o, orient },
handler
);
}
removeAsyncHandler({ t, term, a, action, o, orient }, handler) {
this._signals.removeAsyncHandler(
{ t, term, a, action, o, orient },
handler
);
}
removeInlineHandler({ t, term, a, action, o, orient }, handler) {
this._signals.removeInlineHandler(
{ t, term, a, action, o, orient },
handler
);
}
}
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