tileserver-gl/src/contour.js

import sharp from 'sharp';
import mlcontour from '../node_modules/maplibre-contour/dist/index.mjs';
import { getPMtilesTile } from './pmtiles_adapter.js';

/**
 * Manages local DEM (Digital Elevation Model) data using maplibre-contour.
 */
export class LocalDemManager {
  /**
   * Creates a new LocalDemManager instance.
   * @param {string} encoding - The encoding type for the DEM data.
   * @param {number} maxzoom - The maximum zoom level for the DEM data.
   * @param {object} source - The source object that contains either pmtiles or mbtiles.
   * @param {'pmtiles' | 'mbtiles'} sourceType - The type of data source
   * @param {Function} [GetTileFunction] - the function that returns a tile from the pmtiles object.
   * @param {Function} [extractZXYFromUrlTrimFunction] - The function to extract the zxy from the url.
   */
  constructor(
    encoding,
    maxzoom,
    source,
    sourceType,
    GetTileFunction,
    extractZXYFromUrlTrimFunction,
  ) {
    this.encoding = encoding;
    this.maxzoom = maxzoom;
    this.source = source;
    this.sourceType = sourceType;
    this._getTile = GetTileFunction;
    this._extractZXYFromUrlTrim = extractZXYFromUrlTrimFunction;

    this.manager = new mlcontour.LocalDemManager({
      demUrlPattern: '/{z}/{x}/{y}',
      cacheSize: 100,
      encoding: this.encoding,
      maxzoom: this.maxzoom,
      timeoutMs: 10000,
      decodeImage: this.getImageData.bind(this),
      getTile: this.getTileFunction.bind(this),
    });
  }

  get getTileFunction() {
    return this._getTile ? this._getTile.bind(this) : this.GetTile.bind(this);
  }

  get extractZXYFromUrlTrim() {
    return this._extractZXYFromUrlTrim
      ? this._extractZXYFromUrlTrim.bind(this)
      : this._extractZXYFromUrlTrimFunction.bind(this);
  }

  /**
   * Processes image data from a blob.
   * @param {Blob} blob - The image data as a Blob.
   * @param {AbortController} abortController - An AbortController to cancel the image processing.
   * @returns {Promise<any>} - A Promise that resolves with the processed image data, or null if aborted.
   * @throws If an error occurs during image processing.
   */
  async getImageData(blob, abortController) {
    try {
      if (Boolean(abortController?.signal?.aborted)) return null;

      const buffer = await blob.arrayBuffer();
      const image = sharp(Buffer.from(buffer));
      await image.metadata();

      if (Boolean(abortController?.signal?.aborted)) return null;

      const { data, info } = await image
        .raw()
        .toBuffer({ resolveWithObject: true });
      if (Boolean(abortController?.signal?.aborted)) return null;

      const parsed = mlcontour.decodeParsedImage(
        info.width,
        info.height,
        this.encoding,
        data,
      );
      if (Boolean(abortController?.signal?.aborted)) return null;

      return parsed;
    } catch (error) {
      console.error('Error processing image:', error);
      throw error;
    }
  }

  /**
   * Fetches a tile using the provided url and abortController
   * @param {string} url - The url that should be used to fetch the tile.
   * @param {AbortController} abortController - An AbortController to cancel the request.
   * @returns {Promise<{data: Blob, expires: undefined, cacheControl: undefined}>} A promise that resolves with the response data.
   * @throws If an error occurs fetching or processing the tile.
   */
  async GetTile(url, abortController) {
    console.log(url);
    const $zxy = this.extractZXYFromUrlTrim(url);
    if (!$zxy) {
      throw new Error(`Could not extract zxy from $`);
    }
    if (abortController.signal.aborted) {
      return null;
    }

    try {
      let data;
      if (this.sourceType === 'pmtiles') {
        let zxyTile;
        if (getPMtilesTile) {
          zxyTile = await getPMtilesTile(
            this.source,
            $zxy.z,
            $zxy.x,
            $zxy.y,
            abortController,
          );
        } else {
          if (abortController.signal.aborted) {
            console.log('pmtiles aborted in default');
            return null;
          }
          zxyTile = {
            data: new Uint8Array([$zxy.z, $zxy.x, $zxy.y]),
          };
        }

        if (!zxyTile || !zxyTile.data) {
          throw new Error(`No tile returned for $`);
        }
        data = zxyTile.data;
      } else {
        data = await new Promise((resolve, reject) => {
          this.source.getTile($zxy.z, $zxy.x, $zxy.y, (err, tileData) => {
            if (err) {
              return /does not exist/.test(err.message)
                ? resolve(null)
                : reject(err);
            }
            resolve(tileData);
          });
        });
      }

      if (data == null) {
        return null;
      }

      if (!data) {
        throw new Error(`No tile returned for $`);
      }

      const blob = new Blob([data]);
      return {
        data: blob,
        expires: undefined,
        cacheControl: undefined,
      };
    } catch (error) {
      if (error.name === 'AbortError') {
        console.log('fetch cancelled');
        return null;
      }
      throw error;
    }
  }

  /**
   * Default implementation for extracting z,x,y from a url
   * @param {string} url - The url to extract from
   * @returns {{z: number, x: number, y:number} | null} Returns the z,x,y of the url, or null if can't extract
   */
  _extractZXYFromUrlTrimFunction(url) {
    const lastSlashIndex = url.lastIndexOf('/');
    if (lastSlashIndex === -1) {
      return null;
    }

    const segments = url.split('/');
    if (segments.length <= 3) {
      return null;
    }

    const ySegment = segments[segments.length - 1];
    const xSegment = segments[segments.length - 2];
    const zSegment = segments[segments.length - 3];

    const lastDotIndex = ySegment.lastIndexOf('.');
    const cleanedYSegment =
      lastDotIndex === -1 ? ySegment : ySegment.substring(0, lastDotIndex);

    const z = parseInt(zSegment, 10);
    const x = parseInt(xSegment, 10);
    const y = parseInt(cleanedYSegment, 10);

    if (isNaN(z) || isNaN(x) || isNaN(y)) {
      return null;
    }

    return { z, x, y };
  }

  /**
   * Get the underlying maplibre-contour LocalDemManager
   * @returns {mlcontour.LocalDemManager} the underlying maplibre-contour LocalDemManager
   */
  getManager() {
    return this.manager;
  }
}