scripts/build-roads.mjs

// Fetch real Bengaluru roads (primary/secondary/trunk/tertiary) ONCE from the
// OpenStreetMap Overpass API and cache them as a static GeoJSON FeatureCollection
// of LineStrings, so the runtime never depends on the flaky public Overpass
// instance. Writes to public/ (fetchable) and src/data/ (bundled import).
//
// Run: node scripts/build-roads.mjs
import { writeFileSync, mkdirSync } from 'fs'

const OVERPASS_ENDPOINTS = [
  'https://overpass-api.de/api/interpreter',
  'https://overpass.kumi.systems/api/interpreter',
  'https://maps.mail.ru/osm/tools/overpass/api/interpreter',
]

// Bengaluru bbox (south, west, north, east).
const QUERY =
  'data=[out:json][timeout:60];way["highway"~"primary|secondary|trunk|tertiary"](12.85,77.48,13.08,77.72);out geom;'

function widthForHighway(highway) {
  switch (highway) {
    case 'trunk':
    case 'primary':
      return 14
    case 'secondary':
      return 9
    case 'tertiary':
      return 8
    default:
      return 8
  }
}

async function fetchRoads() {
  let lastErr
  for (const url of OVERPASS_ENDPOINTS) {
    try {
      console.log(`Fetching roads from ${url} ...`)
      const res = await fetch(url, {
        method: 'POST',
        headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
        body: QUERY,
      })
      console.log(`  → HTTP ${res.status}`)
      if (!res.ok) {
        lastErr = new Error(`Overpass HTTP ${res.status} @ ${url}`)
        continue
      }
      const json = await res.json()
      const ways = (json.elements ?? []).filter(
        (w) => w.type === 'way' && Array.isArray(w.geometry) && w.geometry.length >= 2,
      )
      console.log(`  → ${ways.length} ways returned`)
      return ways
    } catch (err) {
      console.warn(`  → failed: ${err.message}`)
      lastErr = err
    }
  }
  throw lastErr ?? new Error('All Overpass endpoints failed')
}

const ways = await fetchRoads()

const features = ways.map((way) => {
  const highway = way.tags?.highway ?? 'road'
  return {
    type: 'Feature',
    properties: {
      id: way.id,
      name: way.tags?.name ?? way.tags?.ref ?? 'Unnamed road',
      highway,
      widthMeters: widthForHighway(highway),
    },
    geometry: {
      type: 'LineString',
      // GeoJSON order is [lng, lat].
      coordinates: way.geometry.map((p) => [p.lon, p.lat]),
    },
  }
})

const fc = { type: 'FeatureCollection', features }

// Sanity print: first 3 segments' first coordinate.
for (let i = 0; i < Math.min(3, features.length); i++) {
  console.log(
    `sample ${i}: ${features[i].properties.name} first=[${features[i].geometry.coordinates[0].join(', ')}]`,
  )
}

mkdirSync('public', { recursive: true })
writeFileSync('public/bengaluru-roads.geojson', JSON.stringify(fc))
writeFileSync('src/data/bengaluru-roads.geojson', JSON.stringify(fc))
console.log(`Wrote ${features.length} road features.`)