xprov/app.js

const DEFAULT_CENTER = [-8.65, 39.55];
const API_CAPABILITIES = "/api/capabilities";
const API_WMS = "/api/wms";
const PARCEL_LAYER_NAME = "xpro:parcelas";

const els = {
  status: document.getElementById("status"),
  layerList: document.getElementById("layer-list"),
  layerCount: document.getElementById("layer-count"),
  parcelSearchForm: document.getElementById("parcel-search-form"),
  parcelSearchInput: document.getElementById("parcel-search-input"),
  parcelSearchStatus: document.getElementById("parcel-search-status"),
  backgroundSelect: document.getElementById("background-select"),
};

const softBasemapLayer = new ol.layer.Tile({
  source: new ol.source.XYZ({
    url: "https://{a-d}.basemaps.cartocdn.com/light_nolabels/{z}/{x}/{y}.png",
    attributions:
      '© <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors © <a href="https://carto.com/attributions">CARTO</a>',
  }),
});

const openStreetMapLayer = new ol.layer.Tile({
  visible: false,
  source: new ol.source.OSM(),
});

// Use one WMS image for the viewport so GeoServer can de-conflict parcel
// labels across the whole map, rather than placing the same label per tile.
const wmsSource = new ol.source.ImageWMS({
  url: API_WMS,
  params: {
    LAYERS: "",
    FORMAT: "image/png",
    TRANSPARENT: true,
  },
  ratio: 1,
  crossOrigin: "anonymous",
});

const wmsLayer = new ol.layer.Image({
  opacity: 0.8,
  visible: false,
  source: wmsSource,
});

const parcelSearchSource = new ol.source.Vector();
const parcelSearchLayer = new ol.layer.Vector({
  source: parcelSearchSource,
  style: new ol.style.Style({
    stroke: new ol.style.Stroke({ color: "#d9582b", width: 3 }),
    fill: new ol.style.Fill({ color: "rgba(255, 201, 82, 0.22)" }),
  }),
});

const map = new ol.Map({
  target: "map",
  layers: [softBasemapLayer, openStreetMapLayer, wmsLayer, parcelSearchLayer],
  view: new ol.View({
    center: ol.proj.fromLonLat(DEFAULT_CENTER),
    zoom: 7,
  }),
});

let availableLayers = [];
let selectedLayers = [];

els.parcelSearchForm.addEventListener("submit", searchParcela);
els.backgroundSelect.addEventListener("change", syncBackground);

loadLayers();

async function searchParcela(event) {
  event.preventDefault();

  const parcelNumber = els.parcelSearchInput.value.trim();
  if (!parcelNumber) {
    updateParcelSearchStatus("Enter a parcel number to search.", "error");
    return;
  }

  updateParcelSearchStatus("Searching for parcel…");
  parcelSearchSource.clear();

  try {
    const params = new URLSearchParams({
      service: "WFS",
      version: "2.0.0",
      request: "GetFeature",
      typeNames: PARCEL_LAYER_NAME,
      outputFormat: "application/json",
      srsName: "EPSG:3857",
      CQL_FILTER: `cod_parcela = '${escapeCqlLiteral(parcelNumber)}'`,
    });
    const response = await fetch(`${API_WMS}?${params}`);

    if (!response.ok) {
      throw new Error(`Search failed with status ${response.status}.`);
    }

    const featureCollection = await response.json();
    const features = new ol.format.GeoJSON().readFeatures(featureCollection, {
      featureProjection: "EPSG:3857",
    });

    if (!features.length) {
      updateParcelSearchStatus(`No parcel found with number “${parcelNumber}”.`, "error");
      return;
    }

    parcelSearchSource.addFeatures(features);
    map.getView().fit(parcelSearchSource.getExtent(), {
      padding: [64, 64, 64, 64],
      duration: 500,
      maxZoom: features.length === 1 ? 19 : 16,
    });

    updateParcelSearchStatus(
      features.length === 1
        ? `Found parcel ${parcelNumber}.`
        : `Found ${features.length} parcels numbered ${parcelNumber}.`,
      "success",
    );
  } catch (error) {
    console.error(error);
    updateParcelSearchStatus(error.message || "Unable to search for that parcel.", "error");
  }
}

async function loadLayers() {
  updateStatus("Loading WMS layers...");

  try {
    const capabilities = await loadCapabilities();
    availableLayers = extractLayers(capabilities);
    selectedLayers = availableLayers.map((layer) => layer.name);

    renderLayerList();
    syncSelectedLayers();
    fitToLayerExtent(availableLayers[0]);

    updateStatus(`Showing ${availableLayers.length} layer(s) from GeoServer.`, "success");
  } catch (error) {
    console.error(error);
    updateStatus(error.message || "Unable to load the WMS service.", "error");
    availableLayers = [];
    selectedLayers = [];
    renderLayerList();
    syncSelectedLayers();
  }
}

async function loadCapabilities() {
  const url = new URL(API_CAPABILITIES, window.location.origin);

  const response = await fetch(url);

  if (!response.ok) {
    throw new Error(`GeoServer connection failed with status ${response.status}.`);
  }

  return response.text();
}

function extractLayers(xmlText) {
  const parser = new DOMParser();
  const xml = parser.parseFromString(xmlText, "text/xml");
  const capabilityNode = firstChildByName(xml.documentElement, "Capability");
  const rootLayerNode = firstChildByName(capabilityNode, "Layer");
  const nodes = collectNamedLayers(rootLayerNode);

  return nodes
    .map((layerNode) => {
      const name = textFromChild(layerNode, "Name");
      const title = textFromChild(layerNode, "Title") || name;
      const bbox = firstChildByName(layerNode, "EX_GeographicBoundingBox");
      const extent = bbox
        ? [
            Number(textFromChild(bbox, "westBoundLongitude")),
            Number(textFromChild(bbox, "southBoundLatitude")),
            Number(textFromChild(bbox, "eastBoundLongitude")),
            Number(textFromChild(bbox, "northBoundLatitude")),
          ]
        : null;

      return { name, title, extent };
    })
    .filter((layer) => layer.name);
}

function renderLayerList() {
  els.layerCount.textContent = String(availableLayers.length);

  if (!availableLayers.length) {
    els.layerList.className = "layer-list empty";
    els.layerList.textContent = "No published layers were returned by the service.";
    return;
  }

  els.layerList.className = "layer-list";
  els.layerList.replaceChildren();

  availableLayers.forEach((layer) => {
    const label = document.createElement("label");
    label.className = "layer-item";

    const checkbox = document.createElement("input");
    checkbox.type = "checkbox";
    checkbox.checked = selectedLayers.includes(layer.name);
    checkbox.addEventListener("change", () => {
      selectedLayers = checkbox.checked
        ? [...new Set([...selectedLayers, layer.name])]
        : selectedLayers.filter((name) => name !== layer.name);
      syncSelectedLayers();
      if (checkbox.checked) {
        fitToLayerExtent(layer);
      }
    });

    const meta = document.createElement("div");
    meta.className = "layer-meta";

    const title = document.createElement("span");
    title.className = "layer-title";
    title.textContent = layer.title;

    const name = document.createElement("span");
    name.className = "layer-name";
    name.textContent = layer.name;

    meta.append(title, name);
    label.append(checkbox, meta);
    els.layerList.append(label);
  });
}

function syncSelectedLayers() {
  const orderedSelectedLayers = availableLayers
    .map((layer) => layer.name)
    .filter((name) => selectedLayers.includes(name));

  wmsLayer.setVisible(selectedLayers.length > 0);
  wmsSource.updateParams({
    LAYERS: [...orderedSelectedLayers].reverse().join(","),
    _: Date.now(),
  });
}

function fitToLayerExtent(layer) {
  if (!layer?.extent || layer.extent.some((value) => Number.isNaN(value))) {
    return;
  }

  const projectedExtent = ol.proj.transformExtent(layer.extent, "EPSG:4326", "EPSG:3857");
  map.getView().fit(projectedExtent, {
    padding: [40, 40, 40, 40],
    duration: 500,
    maxZoom: 18,
  });
}

function childElementsByName(node, localName) {
  return [...(node?.children || [])].filter((child) => child.localName === localName);
}

function firstChildByName(node, localName) {
  return childElementsByName(node, localName)[0] || null;
}

function textFromChild(node, localName) {
  return firstChildByName(node, localName)?.textContent?.trim() || "";
}

function collectNamedLayers(node) {
  return childElementsByName(node, "Layer").flatMap((layerNode) => {
    const children = collectNamedLayers(layerNode);
    return textFromChild(layerNode, "Name") ? [layerNode, ...children] : children;
  });
}

function updateStatus(message, tone) {
  els.status.textContent = message;
  els.status.className = tone ? `status ${tone}` : "status";
}

function updateParcelSearchStatus(message, tone) {
  els.parcelSearchStatus.textContent = message;
  els.parcelSearchStatus.className = tone ? `status ${tone}` : "status";
}

function escapeCqlLiteral(value) {
  return value.replaceAll("'", "''");
}

function syncBackground() {
  const useOpenStreetMap = els.backgroundSelect.value === "openstreetmap";
  softBasemapLayer.setVisible(!useOpenStreetMap);
  openStreetMapLayer.setVisible(useOpenStreetMap);
}