Overlapping Intervals

A simple library for searching for genereic overlapping intervals.

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Table of Contents

• Installation
• Explanation
  • Intervals
• Usage
  • Overlaps between two intervals
  • Overlaps between Arrays or in a single Array
• Custom Implementation
• Contributing
• License

Installation

To install the package, you can use npm or yarn or pnpm:

npm i -S overlapping_intervals

yarn add overlapping_intervals

pnpm add overlapping_intervals

Explanation

Intervals

• Exclusive Intervals

gantt
    title Exclusive Interval using DateStrategy
    dateFormat  YYYY-MM-DD
    section Section
    Interval A           :a1, 2022-01-01, 1d
    Interval B      :2022-01-03  , 1d

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• Inclusive Intervals

gantt
    title Inclusive Interval using DateStrategy
    dateFormat  YYYY-MM-DD
    section Section
    Interval A           :a1, 2022-01-01, 1d
    Interval B      :2022-01-02  , 1d

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Usage

Overlaps between two intervals

You can use the available Strategies or use a custom implementation:

1. DateStrategy
2. NumberStrategy

import { DateStrategy, NumberStrategy, isOverlapping } from 'overlapping_intervals';

const areDatesOverlapping = isOverlapping<Date>(
  { start: new Date(2020, 0, 1), end: new Date(2020, 0, 2) },
  { start: new Date(2020, 0, 2) },
  false,
  DateStrategy
);

console.log(areDatesOverlapping); // outputs false

const areNumbersOverlapping = isOverlapping<number>(
  {
    start: 1,
    end: 2,
  },
  {
    start: 1.5,
    end: 3,
  },
  true,
  NumberStrategy
);

console.log(areNumbersOverlapping); // outputs true

Overlaps between Arrays or in a single Array

You can use the available methods or use a custom implementation:

1. OverlappingDatesSearch
2. OverlappingNumbersSearch

import { OverlappingDatesSearch, Interval } from 'overlapping_intervals';

const group1a: Interval<Date>[] = [
  {
    start: new Date('2022-01-01T00:00:00.000Z'),
    end: new Date('2022-01-05T00:00:00.000Z'),
  },
  {
    start: new Date('2022-01-07T00:00:00.000Z'),
    end: new Date('2022-01-08T00:00:00.000Z'),
  },
  {
    start: new Date('2022-01-09T00:00:00.000Z'),
    end: new Date('2022-01-18T00:00:00.000Z'),
  },
];

const group1b: Interval<Date>[] = [{ start: new Date('2019-02-01T00:00:00.000Z') }];

const overlapsBetweenArrays = OverlappingDatesSearch.findOverlaps(group1a, group1b, false);

const overlapsInArrayA = OverlappingDatesSearch.findOverlaps(
  group1a,
  [] /* pass an empty array*/,
  false
); // check overlapsInArrayA[1] for possible overlaps

// returns a tuple [overlaps between A and B, overlaps in array A, overlaps in array B, has any overlap been found]

Custom Implementation

• Strategy

import { IntervalComparisonStrategy, Interval, isOverlapping } from 'overlapping_intervals';

const isValidNumber = (n?: string): boolean => {
  if (n === undefined && n === null) {
    return false;
  }

  return !Number.isNaN(+(n ?? ''));
};

export class StringIntervalComparisonStrategy implements IntervalComparisonStrategy<string> {
  isOverlapping(a: Interval<string>, b: Interval<string>, exclusive: boolean): boolean {
    const [from1, to1, from2, to2] = [a.start, a.end, b.start, b.end];

    if (!isValidNumber(from1) || !isValidNumber(from2)) {
      throw Error('Please pass valid string numbers in start method');
    }

    if (!exclusive) {
      return (
        (isValidNumber(to2) ? +from1 < +(to2 as string) : true) &&
        (isValidNumber(to1) ? +(to1 as string) > +from2 : true)
      );
    }
    return (
      (isValidNumber(to2) ? +from1 <= +(to2 as string) : true) &&
      (isValidNumber(to1) ? +(to1 as string) >= +from2 : true)
    );
  }
}

// passing the new string strategy enables us to use the isOverlapping Method

export const StringStrategy = new StringIntervalComparisonStrategy();

console.log(
  isOverlapping(
    {
      start: '1',
      end: '3',
    },
    {
      start: '4',
      end: '6',
    },
    false,
    StringStrategy
  )
);

• Finding Overlaps in Array

import { LineSweepOverlapStrategy } from 'overlapping_intervals';

export const stringEndTimesComparison = (a: Interval<string>, b: Interval<string>): number => {
  return +(a?.end ?? `${Number.MAX_SAFE_INTEGER}`) - +(b?.end ?? `${Number.MAX_SAFE_INTEGER}`);
};

export const stringSortFn = (a: Interval<string>, b: Interval<string>): number => {
  return +a.start - +b.start;
};

const OverlappingStringsSearch = new LineSweepOverlapStrategy(
  StringStrategy, // defined in previous example
  stringEndTimesComparison,
  stringSortFn
);

console.log(
  OverlappingStringsSearch.findOverlaps(
    [
      {
        start: '1',
        end: '2',
      },
      {
        start: '2',
        end: '3',
      },
    ],
    [
      {
        start: '4',
        end: '5',
      },
      {
        start: '4.5',
        end: '5.5',
      },
    ],
    false
  )
);

// Outputs [ [], [], [ { start: '4', end: '5' } ], true ] => meaning overlap has been found in B

Contributing

We use Commitizen for standardizing commit messages. Please use pnpm run cm instead of git commit to commit your changes.

This project also uses ESLint to maintain code quality. Please make sure to run pnpm run lint and fix any linting errors before committing your changes.

After your changes are done, create a PR and I'll review and merge your PR <3!

License

This project is licensed under the MIT License.

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