perfect-postcode/frontend/src/lib/external-search.ts

import type { FeatureFilters } from '../types';

export interface HexagonLocation {
  lat: number;
  lon: number;
  resolution: number;
  postcode?: string;
  isPostcode?: boolean;
}

const PROPERTY_TYPE_MAP: Record<
  string,
  { rightmove: string; onthemarket: string; zoopla: string }
> = {
  House: { rightmove: 'detached,semi-detached,terraced', onthemarket: 'property', zoopla: '' },
  Detached: { rightmove: 'detached', onthemarket: 'detached', zoopla: 'detached' },
  'Semi-Detached': {
    rightmove: 'semi-detached',
    onthemarket: 'semi-detached',
    zoopla: 'semi_detached',
  },
  'Mid-Terrace': { rightmove: 'terraced', onthemarket: 'terraced', zoopla: 'terraced' },
  'End-Terrace': { rightmove: 'terraced', onthemarket: 'terraced', zoopla: 'terraced' },
  'Enclosed Mid-Terrace': { rightmove: 'terraced', onthemarket: 'terraced', zoopla: 'terraced' },
  'Enclosed End-Terrace': { rightmove: 'terraced', onthemarket: 'terraced', zoopla: 'terraced' },
  'Flats/Maisonettes': { rightmove: 'flat', onthemarket: 'flats', zoopla: 'flat' },
  Bungalow: { rightmove: 'bungalow', onthemarket: 'bungalow', zoopla: 'bungalow' },
  'Park home': { rightmove: 'park-home', onthemarket: 'property', zoopla: '' },
};

export const H3_RADIUS_MILES: Record<number, number> = {
  4: 15,
  5: 6,
  6: 3,
  7: 1,
  8: 0.5,
  9: 1,
  10: 1,
  11: 1,
  12: 1,
};

const RIGHTMOVE_RADII = [0.25, 0.5, 1, 3, 5, 10, 15, 20, 30, 40];
const OTM_RADII = [0.25, 0.5, 1, 3, 5, 10, 15, 20, 30, 40];
const ZOOPLA_RADII = [0.25, 0.5, 1, 3, 5, 10, 15, 20, 25, 30];

// Rightmove only accepts these specific price values
const RIGHTMOVE_PRICES = [
  50000, 60000, 70000, 80000, 90000, 100000, 110000, 120000, 125000, 130000, 140000, 150000,
  160000, 170000, 175000, 180000, 190000, 200000, 210000, 220000, 230000, 240000, 250000, 260000,
  270000, 280000, 290000, 300000, 325000, 350000, 375000, 400000, 425000, 450000, 475000, 500000,
  550000, 600000, 650000, 700000, 800000, 900000, 1000000, 1250000, 1500000, 1750000, 2000000,
  2500000, 3000000, 4000000, 5000000, 7500000, 10000000, 15000000, 20000000,
];

function nearestRadius(target: number, allowed: number[]): number {
  return allowed.reduce((best, r) => (Math.abs(r - target) < Math.abs(best - target) ? r : best));
}

/** Snap minPrice down and maxPrice up so Rightmove doesn't ignore them */
function snapRightmovePrice(value: number, direction: 'floor' | 'ceil'): number {
  if (direction === 'floor') {
    // Largest supported value <= target
    for (let i = RIGHTMOVE_PRICES.length - 1; i >= 0; i--) {
      if (RIGHTMOVE_PRICES[i] <= value) return RIGHTMOVE_PRICES[i];
    }
    return RIGHTMOVE_PRICES[0];
  }
  // Smallest supported value >= target
  for (const p of RIGHTMOVE_PRICES) {
    if (p >= value) return p;
  }
  return RIGHTMOVE_PRICES[RIGHTMOVE_PRICES.length - 1];
}

interface SearchUrlOptions {
  location: HexagonLocation;
  filters: FeatureFilters;
  rightmoveLocationId?: string;
}

export function buildPropertySearchUrls({
  location,
  filters,
  rightmoveLocationId,
}: SearchUrlOptions): { rightmove: string | null; onthemarket: string; zoopla: string } | null {
  const { postcode, resolution, isPostcode } = location;
  if (!postcode) return null;

  const radiusMiles = isPostcode ? 0.25 : (H3_RADIUS_MILES[resolution] ?? 1);

  const priceFilter = filters['Last known price'];
  const minPrice =
    Array.isArray(priceFilter) && typeof priceFilter[0] === 'number' ? priceFilter[0] : undefined;
  const maxPrice =
    Array.isArray(priceFilter) && typeof priceFilter[1] === 'number' ? priceFilter[1] : undefined;

  const propertyTypes = filters['Property type'];
  const selectedTypes =
    Array.isArray(propertyTypes) && typeof propertyTypes[0] === 'string'
      ? (propertyTypes as string[])
      : [];

  const bedroomFilter = filters['Bedrooms'];
  const minBedrooms =
    Array.isArray(bedroomFilter) && typeof bedroomFilter[0] === 'number' ? bedroomFilter[0] : undefined;
  const maxBedrooms =
    Array.isArray(bedroomFilter) && typeof bedroomFilter[1] === 'number' ? bedroomFilter[1] : undefined;

  const bathroomFilter = filters['Bathrooms'];
  const minBathrooms =
    Array.isArray(bathroomFilter) && typeof bathroomFilter[0] === 'number' ? bathroomFilter[0] : undefined;
  const maxBathrooms =
    Array.isArray(bathroomFilter) && typeof bathroomFilter[1] === 'number' ? bathroomFilter[1] : undefined;

  const tenureFilter = filters['Leasehold/Freehold'];
  const selectedTenures =
    Array.isArray(tenureFilter) && typeof tenureFilter[0] === 'string'
      ? (tenureFilter as string[])
      : [];

  // Rightmove — requires locationIdentifier from typeahead API
  let rightmove: string | null = null;
  if (rightmoveLocationId) {
    const rmParams = new URLSearchParams();
    rmParams.set('searchLocation', postcode);
    rmParams.set('useLocationIdentifier', 'true');
    rmParams.set('locationIdentifier', rightmoveLocationId);
    rmParams.set('radius', String(nearestRadius(radiusMiles, RIGHTMOVE_RADII)));
    if (minPrice !== undefined) rmParams.set('minPrice', String(snapRightmovePrice(minPrice, 'floor')));
    if (maxPrice !== undefined) rmParams.set('maxPrice', String(snapRightmovePrice(maxPrice, 'ceil')));
    if (minBedrooms !== undefined) rmParams.set('minBedrooms', String(Math.floor(minBedrooms)));
    if (maxBedrooms !== undefined) rmParams.set('maxBedrooms', String(Math.ceil(maxBedrooms)));
    if (minBathrooms !== undefined) rmParams.set('minBathrooms', String(Math.floor(minBathrooms)));
    if (maxBathrooms !== undefined) rmParams.set('maxBathrooms', String(Math.ceil(maxBathrooms)));
    if (selectedTypes.length > 0) {
      const rmTypes = [
        ...new Set(
          selectedTypes.flatMap((t) => {
            const mapped = PROPERTY_TYPE_MAP[t]?.rightmove;
            return mapped ? mapped.split(',') : [];
          })
        ),
      ];
      if (rmTypes.length > 0) rmParams.set('propertyTypes', rmTypes.join(','));
    }
    if (selectedTenures.length > 0) {
      const rmTenures = selectedTenures.map((t) => (t === 'Freehold' ? 'FREEHOLD' : 'LEASEHOLD'));
      rmParams.set('tenureTypes', rmTenures.join(','));
    }
    rmParams.set('_includeSSTC', 'on');
    rightmove = `https://www.rightmove.co.uk/property-for-sale/find.html?${rmParams.toString()}`;
  }

  // OnTheMarket — postcode slug in URL path (e.g. "SW1A 1AA" → "sw1a-1aa")
  const otmSlug = postcode.toLowerCase().replace(/\s+/g, '-');
  const otmParams = new URLSearchParams();
  otmParams.set('radius', String(nearestRadius(radiusMiles, OTM_RADII)));
  if (minPrice !== undefined) otmParams.set('min-price', String(Math.round(minPrice)));
  if (maxPrice !== undefined) otmParams.set('max-price', String(Math.round(maxPrice)));
  if (selectedTypes.length > 0) {
    const otmTypes = [
      ...new Set(selectedTypes.map((t) => PROPERTY_TYPE_MAP[t]?.onthemarket).filter(Boolean)),
    ];
    for (const ot of otmTypes) {
      otmParams.append('prop-types', ot!);
    }
  }
  otmParams.set('view', 'map-list');
  const onthemarket = `https://www.onthemarket.com/for-sale/property/${otmSlug}/?${otmParams.toString()}`;

  // Zoopla
  const zParams = new URLSearchParams();
  zParams.set('q', postcode);
  zParams.set('search_source', 'for-sale');
  zParams.set('radius', String(nearestRadius(radiusMiles, ZOOPLA_RADII)));
  if (minPrice !== undefined) zParams.set('price_min', String(Math.round(minPrice)));
  if (maxPrice !== undefined) zParams.set('price_max', String(Math.round(maxPrice)));
  if (selectedTypes.length > 0) {
    const zTypes = [
      ...new Set(selectedTypes.map((t) => PROPERTY_TYPE_MAP[t]?.zoopla).filter(Boolean)),
    ];
    for (const zt of zTypes) {
      zParams.append('property_sub_type', zt!);
    }
  }
  const zoopla = `https://www.zoopla.co.uk/for-sale/property/?${zParams.toString()}`;

  return { rightmove, onthemarket, zoopla };
}