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create "catchTalkback" callbag operator

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Tangent Wantwight 2020-05-02 21:09:38 -04:00
parent 70946d450a
commit 633611056e
1 changed files with 25 additions and 0 deletions
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25
src/Utilities/Callbag.ts
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@ -189,3 +189,28 @@ export function map<I, O, TB>(f: (input: I) => O): (source: Callbag<TB, I>) => C
};
}
/**
* Intercepts talkback data sent to a source and provides them to a closure instead.
* Does not disconnect signals; they are sent upstream as normal.
*/
export function catchTalkback<T, TB>(talkbackHandler: (data: TB) => void): (source: Source<T>) => Callbag<TB, T> {
return (source: Source<T>) => (type: START | DATA | END, data?: Callbag<T, TB> | TB) => {
if (type !== 0) return;
let sourceTalkback: Callbag<void, unknown> | undefined;
const sink = data as Callbag<T, TB>;
source(0, (type: START | DATA | END, data?: Callbag<void, unknown> | T) => {
if (type === 0) {
sourceTalkback = data as Callbag<void, unknown>;
sink(0, (type: START | DATA | END, data?: Callbag<T, TB> | TB) => {
if (type === 1) {
talkbackHandler(data as TB);
} else {
sourceTalkback?.(type as 0 & 1 & 2, data);
}
});
} else {
sink(type as 1 & 2, data);
}
});
};
}