53 lines
2.8 KiB
TypeScript
53 lines
2.8 KiB
TypeScript
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import type { VaultNote } from './models';
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// Stay below the shared tool fitter's 8,000-character string limit.
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export const MAX_NOTE_READ_CHARS = 6000;
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/** Bounded reads use JavaScript (UTF-16) offsets, including for literal search. */
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export function readVaultNote(note: VaultNote, params: Record<string, unknown>) {
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const offset = params.offset ?? 0;
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const maxChars = params.maxChars ?? MAX_NOTE_READ_CHARS;
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const query = params.query;
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if (typeof offset !== 'number' || !Number.isSafeInteger(offset) || offset < 0 || offset > note.content.length) {
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return { ok: false, error: 'offset must be an integer within the note content.' };
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}
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if (typeof maxChars !== 'number' || !Number.isSafeInteger(maxChars) || maxChars < 2) {
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return { ok: false, error: 'maxChars must be an integer of at least 2 (capped at 6000).' };
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}
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if (query !== undefined && (typeof query !== 'string' || query.length === 0 || query.length > 200)) {
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return { ok: false, error: 'query must be a nonempty literal string of at most 200 characters.' };
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}
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if (params.expectedUpdatedAt !== undefined && params.expectedUpdatedAt !== note.updatedAt) {
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return { ok: false, error: 'The note changed. Restart reading from offset 0 without expectedUpdatedAt.' };
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}
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const splitsPair = (position: number) => position > 0
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&& /[\uD800-\uDBFF]/.test(note.content[position - 1] ?? '')
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&& /[\uDC00-\uDFFF]/.test(note.content[position] ?? '');
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if (splitsPair(offset)) return { ok: false, error: 'offset splits a Unicode character. Use the returned nextOffset.' };
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const matchOffset = typeof query === 'string' ? note.content.indexOf(query, offset) : undefined;
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let start = matchOffset === undefined ? offset : matchOffset < 0 ? note.content.length : matchOffset;
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if (splitsPair(start)) start -= 1;
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let end = Math.min(note.content.length, start + Math.min(maxChars, MAX_NOTE_READ_CHARS));
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if (splitsPair(end)) end -= 1;
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let nextOffset: number | null = end < note.content.length ? end : null;
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if (matchOffset !== undefined) {
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// Advance past the match start, not the excerpt, so nearby/overlapping hits remain discoverable.
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let searchFrom = matchOffset + 1;
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if (splitsPair(searchFrom)) searchFrom += 1;
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nextOffset = matchOffset >= 0 && searchFrom < note.content.length ? searchFrom : null;
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}
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return {
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ok: true,
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// Large optional metadata must not defeat the body limit.
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note: { id: note.id, title: Array.from(note.title).slice(0, 120).join(''),
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content: note.content.slice(start, end), createdAt: note.createdAt, updatedAt: note.updatedAt },
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offset: start,
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endOffset: end,
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totalChars: note.content.length,
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nextOffset,
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hasMore: nextOffset !== null,
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...(matchOffset === undefined ? {} : { matchOffset: matchOffset < 0 ? null : matchOffset }),
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};
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}
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