66 lines
2.2 KiB
TypeScript
66 lines
2.2 KiB
TypeScript
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/**
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* Sequential album navigation — the "previous / next album" pair at the foot of
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* an album detail page, so a visitor drifting through the portfolio is not
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* dropped at a dead end (#483).
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*
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* The order deliberately comes from whatever list the visitor just came
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* through — the surrounding subpage, or the standalone album list — rather than
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* from a separate ordering of its own. A "next" that disagreed with the grid
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* the visitor was looking at a moment ago would be worse than no control.
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*
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* Neighbours are not wrapped around: the first album has no previous and the
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* last has no next. Wrapping would guarantee a link in every position, but it
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* also sends someone who reaches the end of a sequence back to its start with
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* no sign that they have been round.
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*/
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/** The fields of an album this module needs. Structural, so `ImmichAlbum` fits. */
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export interface AlbumNavCandidate {
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id: string;
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slug: string;
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albumName: string;
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}
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export interface AlbumNavLink {
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href: string;
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name: string;
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}
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export interface AlbumNavPair {
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prev?: AlbumNavLink;
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next?: AlbumNavLink;
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}
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/**
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* The neighbours of `currentId` within `siblings`, in that list's own order.
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*
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* `basePath` is the prefix the album slugs hang off: `''` for standalone albums
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* (`/album-slug`) or `/subpage-slug` for albums inside a subpage.
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*
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* Returns an empty pair when the album 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 albumNeighbours(
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siblings: readonly AlbumNavCandidate[],
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currentId: string,
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basePath = '',
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): AlbumNavPair {
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const index = siblings.findIndex((a) => a.id === currentId);
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if (index === -1 || siblings.length < 2) return {};
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const href = (album: AlbumNavCandidate) => `${basePath}/${album.slug}`;
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const link = (album: AlbumNavCandidate): AlbumNavLink => ({
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href: href(album),
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name: album.albumName,
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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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