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36 lines
1.4 KiB
JavaScript
36 lines
1.4 KiB
JavaScript
/** The boot contract: one fetch that tells the page how to start.
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*
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* Both scripts on the page read it, so it is fetched once and shared. A server
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* that predates the contract answers 404, and the page starts the way it always
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* did: a blank questionnaire.
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*/
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let bootPromise = null;
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export function getBoot() {
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bootPromise ??= fetch('/boot.json')
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.then((response) => (response.ok ? response.json() : null))
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.catch(() => null)
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.then((data) => ({
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mode: data?.mode === 'doc' ? 'doc' : 'questionnaire',
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prior: data?.prior && typeof data.prior === 'object' && !Array.isArray(data.prior) ? data.prior : null,
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priorSource: data?.priorSource || null,
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doc: data?.doc || null,
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}));
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return bootPromise;
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}
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/* Restoring a previous run happens inside the questionnaire, which owns the
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state being restored. The document waits on this before it renders, so it
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never reads a form that is still half filled. It resolves either way: a run
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with nothing to restore is ready immediately. */
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let settle;
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export const hydrationReady = new Promise((resolve) => { settle = resolve; });
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/* The attribute is the observable half: it drives the note on the start screen
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and gives anything watching the page one thing to wait for. */
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export function markHydrated(source) {
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document.body.dataset.hydrated = source || 'none';
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settle(source || null);
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}
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