58 lines
1.9 KiB
TypeScript
58 lines
1.9 KiB
TypeScript
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/**
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* Sequential journal navigation — the "previous / next entry" pair at the foot
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* of a journal entry, mirroring `albumNav.ts` (#483) for the journal (#591).
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*
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* `siblings` must already be filtered to what the current visitor may see —
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* a draft, or a password-protected entry they have not unlocked, must never
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* appear here even as a name-only link (GHSA-fvgv-97g3-wjr7 was exactly this
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* class of leak for the index and page metadata).
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*
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* Neighbours are not wrapped around, for the same reason as albums: reaching
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* the end of the journal should feel like an ending, not send the reader back
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* to its start with no sign that they have been round.
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*/
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export interface JournalNavCandidate {
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slug: string;
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title: string;
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}
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export interface JournalNavLink {
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href: string;
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title: string;
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}
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export interface JournalNavPair {
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prev?: JournalNavLink;
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next?: JournalNavLink;
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}
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/**
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* The neighbours of `currentSlug` within `siblings`, in that list's own order
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* (publication order, newest first, same as `/journal` and `listJournalEntries()`).
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*
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* Returns an empty pair when the entry is not in the list, or when it is the
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* only one — both cases mean there is nothing to offer, and the caller renders
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* nothing.
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*/
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export function journalNeighbours(
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siblings: readonly JournalNavCandidate[],
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currentSlug: string,
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): JournalNavPair {
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const index = siblings.findIndex((e) => e.slug === currentSlug);
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if (index === -1 || siblings.length < 2) return {};
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const link = (entry: JournalNavCandidate): JournalNavLink => ({
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href: `/journal/${entry.slug}`,
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title: entry.title,
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});
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const previous = index > 0 ? siblings[index - 1] : undefined;
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const following = index < siblings.length - 1 ? siblings[index + 1] : undefined;
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return {
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...(previous ? { prev: link(previous) } : {}),
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...(following ? { next: link(following) } : {}),
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};
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}
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