Distribute.ts

import { orderBy, sum } from 'lodash';

export interface ILatLon {
  /** 0 - 180 */
  latitude: number
  /** 0 - 360 */
  longitude: number
}

export const distribute = (sites: ILatLon[], center: ILatLon, goalPercentages: number[]) => {
  // Round sumOfGoal to 2dp to allow for fractions in goalPercentages
  const sumOfGoals = Math.round(sum(goalPercentages) * 100) / 100;
  if (sumOfGoals !== 100) {
    throw new Error(`Goal percentages must sum to 100. Got ${sumOfGoals}`)
  }

  // Order sites based on their distance from the center point
  const orderedSites = orderBy(sites, [site => {
    const latDiff = center.latitude - site.latitude;
    const lonDiff = center.longitude - site.longitude;
    const latLonMagntitude = Math.pow(Math.pow(latDiff, 2) + Math.pow(lonDiff, 2), 0.5);
    return latLonMagntitude
  }], ['asc']);

  // Initialise empty buckets for every goalPercentage
  const buckets: ILatLon[][] = goalPercentages.map(() => [])

  // Iterate over sites and push them into a bucket based on the goalPercentage */
  orderedSites.forEach((site, siteIdx) => {
    // Abuse array.some to iterate until we return true
    goalPercentages.some((goalPercentage, bucketIdx) => {
      let breakLoop = false;
      const bucket = buckets[bucketIdx];
      const percentageCurrentlyInBucket = (bucket.length / (siteIdx + 1)) * 100;
      if (percentageCurrentlyInBucket < goalPercentage) {
        bucket.push(site)
        breakLoop = true
      }
      return breakLoop
    })
  })

  return buckets
}

////////////////////


describe('distribute', () => {
  const sites = [
    {
      latitude: 90,
      longitude: 180,
    },
    {
      latitude: 90,
      longitude: 179,
    },
    {
      latitude: 90,
      longitude: 178,
    },
    {
      latitude: 90,
      longitude: 177,
    },
    {
      latitude: 90,
      longitude: 176,
    },
    {
      latitude: 90,
      longitude: 175,
    },
    {
      latitude: 90,
      longitude: 174,
    },
    {
      latitude: 90,
      longitude: 173,
    },
    {
      latitude: 90,
      longitude: 172,
    },
    {
      latitude: 90,
      longitude: 171,
    },
    {
      latitude: 90,
      longitude: 170,
    },
  ];

  it('it distributes among 2 media evenly', () => {
    const center = {
      latitude: 0,
      longitude: 0,
    };
    const goalPercentages = [50, 50];
    const result = distribute(sites, center, goalPercentages);
    expect(result).toMatchInlineSnapshot(`
      Array [
        Array [
          Object {
            "latitude": 90,
            "longitude": 170,
          },
          Object {
            "latitude": 90,
            "longitude": 172,
          },
          Object {
            "latitude": 90,
            "longitude": 174,
          },
          Object {
            "latitude": 90,
            "longitude": 176,
          },
          Object {
            "latitude": 90,
            "longitude": 178,
          },
          Object {
            "latitude": 90,
            "longitude": 180,
          },
        ],
        Array [
          Object {
            "latitude": 90,
            "longitude": 171,
          },
          Object {
            "latitude": 90,
            "longitude": 173,
          },
          Object {
            "latitude": 90,
            "longitude": 175,
          },
          Object {
            "latitude": 90,
            "longitude": 177,
          },
          Object {
            "latitude": 90,
            "longitude": 179,
          },
        ],
      ]
    `);
  });

  it('it distributes among 2 media but will assign none to the second if too few sites', () => {
    const center = {
      latitude: 0,
      longitude: 0,
    };
    const goalPercentages = [99, 1];
    const result = distribute(sites, center, goalPercentages);
    expect(result).toMatchInlineSnapshot(`
      Array [
        Array [
          Object {
            "latitude": 90,
            "longitude": 170,
          },
          Object {
            "latitude": 90,
            "longitude": 171,
          },
          Object {
            "latitude": 90,
            "longitude": 172,
          },
          Object {
            "latitude": 90,
            "longitude": 173,
          },
          Object {
            "latitude": 90,
            "longitude": 174,
          },
          Object {
            "latitude": 90,
            "longitude": 175,
          },
          Object {
            "latitude": 90,
            "longitude": 176,
          },
          Object {
            "latitude": 90,
            "longitude": 177,
          },
          Object {
            "latitude": 90,
            "longitude": 178,
          },
          Object {
            "latitude": 90,
            "longitude": 179,
          },
          Object {
            "latitude": 90,
            "longitude": 180,
          },
        ],
        Array [],
      ]
    `);
  });

  it('it distributes among 3 media unevenly', () => {
    const center = {
      latitude: 0,
      longitude: 0,
    };
    const goalPercentages = [50, 10, 40];
    const result = distribute(sites, center, goalPercentages);
    expect(result).toMatchInlineSnapshot(`
      Array [
        Array [
          Object {
            "latitude": 90,
            "longitude": 170,
          },
          Object {
            "latitude": 90,
            "longitude": 172,
          },
          Object {
            "latitude": 90,
            "longitude": 174,
          },
          Object {
            "latitude": 90,
            "longitude": 176,
          },
          Object {
            "latitude": 90,
            "longitude": 178,
          },
          Object {
            "latitude": 90,
            "longitude": 180,
          },
        ],
        Array [
          Object {
            "latitude": 90,
            "longitude": 171,
          },
        ],
        Array [
          Object {
            "latitude": 90,
            "longitude": 173,
          },
          Object {
            "latitude": 90,
            "longitude": 175,
          },
          Object {
            "latitude": 90,
            "longitude": 177,
          },
          Object {
            "latitude": 90,
            "longitude": 179,
          },
        ],
      ]
    `);
  });

  it('it distributes among 3 media evenly', () => {
    const center = {
      latitude: 0,
      longitude: 0,
    };
    const goalPercentages = [33.333, 33.333, 33.333];
    const result = distribute(sites, center, goalPercentages);
    expect(result).toMatchInlineSnapshot(`
      Array [
        Array [
          Object {
            "latitude": 90,
            "longitude": 170,
          },
          Object {
            "latitude": 90,
            "longitude": 173,
          },
          Object {
            "latitude": 90,
            "longitude": 176,
          },
          Object {
            "latitude": 90,
            "longitude": 179,
          },
        ],
        Array [
          Object {
            "latitude": 90,
            "longitude": 171,
          },
          Object {
            "latitude": 90,
            "longitude": 174,
          },
          Object {
            "latitude": 90,
            "longitude": 177,
          },
          Object {
            "latitude": 90,
            "longitude": 180,
          },
        ],
        Array [
          Object {
            "latitude": 90,
            "longitude": 172,
          },
          Object {
            "latitude": 90,
            "longitude": 175,
          },
          Object {
            "latitude": 90,
            "longitude": 178,
          },
        ],
      ]
    `);
  });

  it('if there are more goal percentages than sites, the last will be empty', () => {
    const center = {
      latitude: 0,
      longitude: 0,
    };
    const goalPercentages = new Array(12).fill(100 / 12);
    const result = distribute(sites, center, goalPercentages);
    expect(result).toMatchInlineSnapshot(`
      Array [
        Array [
          Object {
            "latitude": 90,
            "longitude": 170,
          },
        ],
        Array [
          Object {
            "latitude": 90,
            "longitude": 171,
          },
        ],
        Array [
          Object {
            "latitude": 90,
            "longitude": 172,
          },
        ],
        Array [
          Object {
            "latitude": 90,
            "longitude": 173,
          },
        ],
        Array [
          Object {
            "latitude": 90,
            "longitude": 174,
          },
        ],
        Array [
          Object {
            "latitude": 90,
            "longitude": 175,
          },
        ],
        Array [
          Object {
            "latitude": 90,
            "longitude": 176,
          },
        ],
        Array [
          Object {
            "latitude": 90,
            "longitude": 177,
          },
        ],
        Array [
          Object {
            "latitude": 90,
            "longitude": 178,
          },
        ],
        Array [
          Object {
            "latitude": 90,
            "longitude": 179,
          },
        ],
        Array [
          Object {
            "latitude": 90,
            "longitude": 180,
          },
        ],
        Array [],
      ]
    `);
  });

  it('throws an error if percentages do not equal 100 (rounded to 2 DP)', () => {
    const center = {
      latitude: 0,
      longitude: 0,
    };
    const goalPercentages = [33.333, 33.333, 33];

    expect(() => distribute(sites, center, goalPercentages)).toThrowError();
  });
});