97 lines
2.2 KiB
JavaScript
97 lines
2.2 KiB
JavaScript
import {iterateCursor} from "./utils.js";
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export default class QueryTarget {
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constructor(target) {
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this._target = target;
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}
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reduce(range, reducer, initialValue) {
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return this._reduce(range, reducer, initialValue, "next");
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}
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reduceReverse(range, reducer, initialValue) {
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return this._reduce(range, reducer, initialValue, "next");
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}
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selectLimit(range, amount) {
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return this._selectLimit(range, amount, "next");
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}
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selectLimitReverse(range, amount) {
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return this._selectLimit(range, amount, "prev");
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}
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selectWhile(range, predicate) {
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return this._selectWhile(range, predicate, "next");
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}
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selectWhileReverse(range, predicate) {
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return this._selectWhile(range, predicate, "prev");
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}
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async selectAll(range, direction) {
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const cursor = this._target.openCursor(range, direction);
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const results = [];
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await iterateCursor(cursor, (value) => {
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results.push(value);
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return true;
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});
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return results;
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}
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selectFirst(range) {
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return this._find(range, () => true, "next");
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}
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selectLast(range) {
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return this._find(range, () => true, "prev");
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}
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find(range, predicate) {
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return this._find(range, predicate, "next");
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}
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findReverse(range, predicate) {
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return this._find(range, predicate, "prev");
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}
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_reduce(range, reducer, initialValue, direction) {
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let reducedValue = initialValue;
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const cursor = this._target.openCursor(range, direction);
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return iterateCursor(cursor, (value) => {
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reducedValue = reducer(reducedValue, value);
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return true;
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});
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}
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_selectLimit(range, amount, direction) {
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return this._selectWhile(range, (results) => {
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return results.length === amount;
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}, direction);
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}
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async _selectWhile(range, predicate, direction) {
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const cursor = this._target.openCursor(range, direction);
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const results = [];
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await iterateCursor(cursor, (value) => {
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results.push(value);
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return predicate(results);
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});
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return results;
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}
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async _find(range, predicate, direction) {
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const cursor = this._target.openCursor(range, direction);
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let result;
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const found = await iterateCursor(cursor, (value) => {
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const found = predicate(value);
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if (found) {
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result = value;
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}
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return found;
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});
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if (found) {
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return result;
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}
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}
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} |