pmtiles_adapter.js

import fs from 'node:fs';
import { PMTiles, FetchSource } from 'pmtiles';
import { isValidHttpUrl } from './utils.js';

class PMTilesFileSource {
  constructor(fd) {
    this.fd = fd;
  }
  getKey() {
    return this.fd;
  }
  async getBytes(offset, length) {
    const buffer = Buffer.alloc(length);
    await readFileBytes(this.fd, buffer, offset);
    const ab = buffer.buffer.slice(
      buffer.byteOffset,
      buffer.byteOffset + buffer.byteLength,
    );
    return { data: ab };
  }
}

/**
 *
 * @param fd
 * @param buffer
 * @param offset
 */
async function readFileBytes(fd, buffer, offset) {
  return new Promise((resolve, reject) => {
    fs.read(fd, buffer, 0, buffer.length, offset, (err) => {
      if (err) {
        return reject(err);
      }
      resolve();
    });
  });
}

/**
 *
 * @param FilePath
 */
export function openPMtiles(FilePath) {
  let pmtiles = undefined;

  if (isValidHttpUrl(FilePath)) {
    const source = new FetchSource(FilePath);
    pmtiles = new PMTiles(source);
  } else {
    const fd = fs.openSync(FilePath, 'r');
    const source = new PMTilesFileSource(fd);
    pmtiles = new PMTiles(source);
  }
  return pmtiles;
}

/**
 *
 * @param pmtiles
 */
export async function getPMtilesInfo(pmtiles) {
  const header = await pmtiles.getHeader();
  const metadata = await pmtiles.getMetadata();

  //Add missing metadata from header
  metadata['format'] = getPmtilesTileType(header.tileType).type;
  metadata['minzoom'] = header.minZoom;
  metadata['maxzoom'] = header.maxZoom;

  if (header.minLon && header.minLat && header.maxLon && header.maxLat) {
    metadata['bounds'] = [
      header.minLon,
      header.minLat,
      header.maxLon,
      header.maxLat,
    ];
  } else {
    metadata['bounds'] = [-180, -85.05112877980659, 180, 85.0511287798066];
  }

  if (header.centerZoom) {
    metadata['center'] = [
      header.centerLon,
      header.centerLat,
      header.centerZoom,
    ];
  } else {
    metadata['center'] = [
      header.centerLon,
      header.centerLat,
      parseInt(metadata['maxzoom']) / 2,
    ];
  }

  return metadata;
}

/**
 *
 * @param pmtiles
 * @param z
 * @param x
 * @param y
 */
export async function getPMtilesTile(pmtiles, z, x, y) {
  const header = await pmtiles.getHeader();
  const tileType = getPmtilesTileType(header.tileType);
  let zxyTile = await pmtiles.getZxy(z, x, y);
  if (zxyTile && zxyTile.data) {
    zxyTile = Buffer.from(zxyTile.data);
  } else {
    zxyTile = undefined;
  }
  return { data: zxyTile, header: tileType.header };
}

/**
 *
 * @param typenum
 */
function getPmtilesTileType(typenum) {
  let head = {};
  let tileType;
  switch (typenum) {
    case 0:
      tileType = 'Unknown';
      break;
    case 1:
      tileType = 'pbf';
      head['Content-Type'] = 'application/x-protobuf';
      break;
    case 2:
      tileType = 'png';
      head['Content-Type'] = 'image/png';
      break;
    case 3:
      tileType = 'jpeg';
      head['Content-Type'] = 'image/jpeg';
      break;
    case 4:
      tileType = 'webp';
      head['Content-Type'] = 'image/webp';
      break;
    case 5:
      tileType = 'avif';
      head['Content-Type'] = 'image/avif';
      break;
  }
  return { type: tileType, header: head };
}