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/**
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* Hachette feature initialization promise
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*
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* Copyright (C) 2021 Wojtek Kosior
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* Redistribution terms are gathered in the `copyright' file.
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*/
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/*
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* This module provides an easy way to wrap an async function into a promise
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* so that it only gets executed once.
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*/
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async function assign_result(state, result_producer)
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{
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state.result = await result_producer();
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state.ready = true;
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for (let cb of state.waiting)
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setTimeout(cb, 0, state.result);
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state.waiting = undefined;
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}
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async function get_result(state)
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{
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if (state.ready)
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return state.result;
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return new Promise((resolve, reject) => state.waiting.push(resolve));
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}
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function make_once(result_producer)
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{
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let state = {waiting : [], ready : false, result : undefined};
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assign_result(state, result_producer);
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return () => get_result(state);
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}
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/*
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* EXPORTS_START
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* EXPORT make_once
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* EXPORTS_END
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*/
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