fast-check/lib/arbitrary/_internals/SubarrayArbitrary.js

Property based testing framework for JavaScript (like QuickCheck)

import { Arbitrary } from '../../check/arbitrary/definition/Arbitrary.js';
import { Value } from '../../check/arbitrary/definition/Value.js';
import { makeLazy } from '../../stream/LazyIterableIterator.js';
import { Stream } from '../../stream/Stream.js';
import { safeMap, safePush, safeSlice, safeSort, safeSplice } from '../../utils/globals.js';
import { isSubarrayOf } from './helpers/IsSubarrayOf.js';
import { IntegerArbitrary } from './IntegerArbitrary.js';
const safeMathFloor = Math.floor;
const safeMathLog = Math.log;
const safeArrayIsArray = Array.isArray;
export class SubarrayArbitrary extends Arbitrary {
    constructor(originalArray, isOrdered, minLength, maxLength) {
        super();
        this.originalArray = originalArray;
        this.isOrdered = isOrdered;
        this.minLength = minLength;
        this.maxLength = maxLength;
        if (minLength < 0 || minLength > originalArray.length)
            throw new Error('fc.*{s|S}ubarrayOf expects the minimal length to be between 0 and the size of the original array');
        if (maxLength < 0 || maxLength > originalArray.length)
            throw new Error('fc.*{s|S}ubarrayOf expects the maximal length to be between 0 and the size of the original array');
        if (minLength > maxLength)
            throw new Error('fc.*{s|S}ubarrayOf expects the minimal length to be inferior or equal to the maximal length');
        this.lengthArb = new IntegerArbitrary(minLength, maxLength);
        this.biasedLengthArb =
            minLength !== maxLength
                ? new IntegerArbitrary(minLength, minLength + safeMathFloor(safeMathLog(maxLength - minLength) / safeMathLog(2)))
                : this.lengthArb;
    }
    generate(mrng, biasFactor) {
        const lengthArb = biasFactor !== undefined && mrng.nextInt(1, biasFactor) === 1 ? this.biasedLengthArb : this.lengthArb;
        const size = lengthArb.generate(mrng, undefined);
        const sizeValue = size.value;
        const remainingElements = safeMap(this.originalArray, (_v, idx) => idx);
        const ids = [];
        for (let index = 0; index !== sizeValue; ++index) {
            const selectedIdIndex = mrng.nextInt(0, remainingElements.length - 1);
            safePush(ids, remainingElements[selectedIdIndex]);
            safeSplice(remainingElements, selectedIdIndex, 1);
        }
        if (this.isOrdered) {
            safeSort(ids, (a, b) => a - b);
        }
        return new Value(safeMap(ids, (i) => this.originalArray[i]), size.context);
    }
    canShrinkWithoutContext(value) {
        if (!safeArrayIsArray(value)) {
            return false;
        }
        if (!this.lengthArb.canShrinkWithoutContext(value.length)) {
            return false;
        }
        return isSubarrayOf(this.originalArray, value);
    }
    shrink(value, context) {
        if (value.length === 0) {
            return Stream.nil();
        }
        return this.lengthArb
            .shrink(value.length, context)
            .map((newSize) => {
            return new Value(safeSlice(value, value.length - newSize.value), newSize.context);
        })
            .join(value.length > this.minLength
            ? makeLazy(() => this.shrink(safeSlice(value, 1), undefined)
                .filter((newValue) => this.minLength <= newValue.value.length + 1)
                .map((newValue) => new Value([value[0], ...newValue.value], undefined)))
            : Stream.nil());
    }
}