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979bf48 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 | "use strict";
Object.defineProperty(exports, "__esModule", {
value: true
});
Object.defineProperty(exports, "Batcher", {
enumerable: true,
get: function() {
return Batcher;
}
});
const _detachedpromise = require("./detached-promise");
class Batcher {
constructor(cacheKeyFn, /**
* A function that will be called to schedule the wrapped function to be
* executed. This defaults to a function that will execute the function
* immediately.
*/ schedulerFn = (fn)=>fn()){
this.cacheKeyFn = cacheKeyFn;
this.schedulerFn = schedulerFn;
this.pending = new Map();
}
static create(options) {
return new Batcher(options == null ? void 0 : options.cacheKeyFn, options == null ? void 0 : options.schedulerFn);
}
/**
* Wraps a function in a promise that will be resolved or rejected only once
* for a given key. This will allow multiple calls to the function to be
* made, but only one will be executed at a time. The result of the first
* call will be returned to all callers.
*
* @param key the key to use for the cache
* @param fn the function to wrap
* @returns a promise that resolves to the result of the function
*/ async batch(key, fn) {
const cacheKey = this.cacheKeyFn ? await this.cacheKeyFn(key) : key;
if (cacheKey === null) {
return fn({
resolve: (value)=>Promise.resolve(value),
key
});
}
const pending = this.pending.get(cacheKey);
if (pending) return pending;
const { promise, resolve, reject } = new _detachedpromise.DetachedPromise();
this.pending.set(cacheKey, promise);
this.schedulerFn(async ()=>{
try {
const result = await fn({
resolve,
key
});
// Resolving a promise multiple times is a no-op, so we can safely
// resolve all pending promises with the same result.
resolve(result);
} catch (err) {
reject(err);
} finally{
this.pending.delete(cacheKey);
}
});
return promise;
}
}
//# sourceMappingURL=batcher.js.map |