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https://github.com/docmost/docmost.git
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add cursor pagination function
This commit is contained in:
Philipinho
@@ -0,0 +1,337 @@
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// source: https://github.com/charlie-hadden/kysely-paginate/blob/main/src/cursor.ts - MIT
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import {
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OrderByDirectionExpression,
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ReferenceExpression,
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SelectQueryBuilder,
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StringReference,
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} from "kysely";
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type SortField<DB, TB extends keyof DB, O> =
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| {
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expression:
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| (StringReference<DB, TB> & keyof O & string)
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| (StringReference<DB, TB> & `${string}.${keyof O & string}`);
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direction: OrderByDirectionExpression;
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key?: keyof O & string;
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}
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| {
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expression: ReferenceExpression<DB, TB>;
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direction: OrderByDirectionExpression;
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key: keyof O & string;
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};
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type ExtractSortFieldKey<
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DB,
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TB extends keyof DB,
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O,
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T extends SortField<DB, TB, O>,
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> = T["key"] extends keyof O & string
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? T["key"]
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: T["expression"] extends keyof O & string
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? T["expression"]
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: T["expression"] extends `${string}.${infer K}`
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? K extends keyof O & string
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? K
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: never
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: never;
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type Fields<DB, TB extends keyof DB, O> = ReadonlyArray<
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Readonly<SortField<DB, TB, O>>
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>;
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type FieldNames<DB, TB extends keyof DB, O, T extends Fields<DB, TB, O>> = {
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[TIndex in keyof T]: ExtractSortFieldKey<DB, TB, O, T[TIndex]>;
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};
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type EncodeCursorValues<
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DB,
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TB extends keyof DB,
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O,
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T extends Fields<DB, TB, O>,
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> = {
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[TIndex in keyof T]: [
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ExtractSortFieldKey<DB, TB, O, T[TIndex]>,
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O[ExtractSortFieldKey<DB, TB, O, T[TIndex]>],
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];
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};
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export type CursorEncoder<
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DB,
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TB extends keyof DB,
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O,
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T extends Fields<DB, TB, O>,
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> = (values: EncodeCursorValues<DB, TB, O, T>) => string;
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type DecodedCursor<DB, TB extends keyof DB, O, T extends Fields<DB, TB, O>> = {
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[TField in ExtractSortFieldKey<DB, TB, O, T[number]>]: string;
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};
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export type CursorDecoder<
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DB,
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TB extends keyof DB,
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O,
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T extends Fields<DB, TB, O>,
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> = (
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cursor: string,
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fields: FieldNames<DB, TB, O, T>,
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) => DecodedCursor<DB, TB, O, T>;
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type ParsedCursorValues<
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DB,
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TB extends keyof DB,
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O,
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T extends Fields<DB, TB, O>,
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> = {
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[TField in ExtractSortFieldKey<DB, TB, O, T[number]>]: O[TField];
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};
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export type CursorParser<
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DB,
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TB extends keyof DB,
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O,
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T extends Fields<DB, TB, O>,
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> = (cursor: DecodedCursor<DB, TB, O, T>) => ParsedCursorValues<DB, TB, O, T>;
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type CursorPaginationResultRow<
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TRow,
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TCursorKey extends string | boolean | undefined,
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> = TRow & {
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[K in TCursorKey extends undefined
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? never
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: TCursorKey extends false
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? never
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: TCursorKey extends true
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? "$cursor"
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: TCursorKey]: string;
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};
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export type CursorPaginationResult<
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TRow,
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TCursorKey extends string | boolean | undefined,
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> = {
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startCursor: string | undefined;
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endCursor: string | undefined;
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hasNextPage?: boolean;
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hasPrevPage?: boolean;
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rows: CursorPaginationResultRow<TRow, TCursorKey>[];
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};
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export async function executeWithCursorPagination<
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DB,
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TB extends keyof DB,
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O,
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const TFields extends Fields<DB, TB, O>,
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TCursorKey extends string | boolean | undefined = undefined,
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>(
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qb: SelectQueryBuilder<DB, TB, O>,
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opts: {
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perPage: number;
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after?: string;
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before?: string;
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cursorPerRow?: TCursorKey;
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fields: TFields;
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encodeCursor?: CursorEncoder<DB, TB, O, TFields>;
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decodeCursor?: CursorDecoder<DB, TB, O, TFields>;
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parseCursor:
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| CursorParser<DB, TB, O, TFields>
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| { parse: CursorParser<DB, TB, O, TFields> };
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},
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): Promise<CursorPaginationResult<O, TCursorKey>> {
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const encodeCursor = opts.encodeCursor ?? defaultEncodeCursor;
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const decodeCursor = opts.decodeCursor ?? defaultDecodeCursor;
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const parseCursor =
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typeof opts.parseCursor === "function"
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? opts.parseCursor
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: opts.parseCursor.parse;
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const fields = opts.fields.map((field) => {
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let key = field.key;
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if (!key && typeof field.expression === "string") {
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const expressionParts = field.expression.split(".");
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key = (expressionParts[1] ?? expressionParts[0]) as
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| (keyof O & string)
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| undefined;
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}
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if (!key) throw new Error("missing key");
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return { ...field, key };
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});
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function generateCursor(row: O): string {
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const cursorFieldValues = fields.map(({ key }) => [
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key,
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row[key],
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]) as EncodeCursorValues<DB, TB, O, TFields>;
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return encodeCursor(cursorFieldValues);
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}
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const fieldNames = fields.map((field) => field.key) as FieldNames<
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DB,
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TB,
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O,
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TFields
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>;
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function applyCursor(
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qb: SelectQueryBuilder<DB, TB, O>,
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encoded: string,
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defaultDirection: "asc" | "desc",
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) {
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const decoded = decodeCursor(encoded, fieldNames);
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const cursor = parseCursor(decoded);
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return qb.where(({ and, or, eb }) => {
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let expression;
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for (let i = fields.length - 1; i >= 0; --i) {
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// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
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const field = fields[i]!;
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const comparison = field.direction === defaultDirection ? ">" : "<";
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const value = cursor[field.key as keyof typeof cursor];
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const conditions = [eb(field.expression, comparison, value)];
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if (expression) {
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conditions.push(and([eb(field.expression, "=", value), expression]));
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}
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expression = or(conditions);
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}
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if (!expression) {
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throw new Error("Error building cursor expression");
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}
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return expression;
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});
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}
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if (opts.after) qb = applyCursor(qb, opts.after, "asc");
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if (opts.before) qb = applyCursor(qb, opts.before, "desc");
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const reversed = !!opts.before && !opts.after;
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for (const { expression, direction } of fields) {
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qb = qb.orderBy(
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expression,
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reversed ? (direction === "asc" ? "desc" : "asc") : direction,
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);
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}
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const rows = await qb.limit(opts.perPage + 1).execute();
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const hasNextPage = reversed ? undefined : rows.length > opts.perPage;
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const hasPrevPage = !reversed ? undefined : rows.length > opts.perPage;
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// If we fetched an extra row to determine if we have a next page, that
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// shouldn't be in the returned results
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if (rows.length > opts.perPage) rows.pop();
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if (reversed) rows.reverse();
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const startRow = rows[0];
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const endRow = rows[rows.length - 1];
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const startCursor = startRow ? generateCursor(startRow) : undefined;
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const endCursor = endRow ? generateCursor(endRow) : undefined;
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return {
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startCursor,
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endCursor,
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hasNextPage,
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hasPrevPage,
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rows: rows.map((row) => {
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if (opts.cursorPerRow) {
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const cursorKey =
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typeof opts.cursorPerRow === "string" ? opts.cursorPerRow : "$cursor";
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// eslint-disable-next-line @typescript-eslint/no-unsafe-member-access, @typescript-eslint/no-explicit-any
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(row as any)[cursorKey] = generateCursor(row);
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}
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return row as CursorPaginationResultRow<O, TCursorKey>;
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}),
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};
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}
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export function defaultEncodeCursor<
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DB,
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TB extends keyof DB,
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O,
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T extends Fields<DB, TB, O>,
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>(values: EncodeCursorValues<DB, TB, O, T>) {
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const cursor = new URLSearchParams();
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for (const [key, value] of values) {
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switch (typeof value) {
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case "string":
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cursor.set(key, value);
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break;
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case "number":
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case "bigint":
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cursor.set(key, value.toString(10));
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break;
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case "object": {
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if (value instanceof Date) {
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cursor.set(key, value.toISOString());
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break;
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}
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}
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// eslint-disable-next-line no-fallthrough
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default:
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throw new Error(`Unable to encode '${key.toString()}'`);
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}
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}
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return Buffer.from(cursor.toString(), "utf8").toString("base64url");
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}
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export function defaultDecodeCursor<
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DB,
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TB extends keyof DB,
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O,
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T extends Fields<DB, TB, O>,
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>(
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cursor: string,
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fields: FieldNames<DB, TB, O, T>,
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): DecodedCursor<DB, TB, O, T> {
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let parsed;
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try {
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parsed = [
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...new URLSearchParams(
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Buffer.from(cursor, "base64url").toString("utf8"),
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).entries(),
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];
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} catch {
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throw new Error("Unparsable cursor");
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}
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if (parsed.length !== fields.length) {
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throw new Error("Unexpected number of fields");
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}
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for (let i = 0; i < fields.length; i++) {
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const field = parsed[i];
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const expectedName = fields[i];
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if (!field) {
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throw new Error("Unable to find field");
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}
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if (field[0] !== expectedName) {
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throw new Error("Unexpected field name");
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}
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}
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return Object.fromEntries(parsed) as DecodedCursor<DB, TB, O, T>;
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}
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