chore: split public and src

public/utils/pathUtils.js

@@ -0,0 +1,235 @@
+"use strict";
+
+// get continuous paths (isolines) for all cells at once based on getType(cellId) comparison
+function getIsolines(graph, getType, options = {polygons: false, fill: false, halo: false, waterGap: false}) {
+  const {cells, vertices} = graph;
+  const isolines = {};
+
+  const checkedCells = new Uint8Array(cells.i.length);
+  const addToChecked = cellId => (checkedCells[cellId] = 1);
+  const isChecked = cellId => checkedCells[cellId] === 1;
+
+  for (const cellId of cells.i) {
+    if (isChecked(cellId) || !getType(cellId)) continue;
+    addToChecked(cellId);
+
+    const type = getType(cellId);
+    const ofSameType = cellId => getType(cellId) === type;
+    const ofDifferentType = cellId => getType(cellId) !== type;
+
+    const onborderCell = cells.c[cellId].find(ofDifferentType);
+    if (onborderCell === undefined) continue;
+
+    // check if inner lake. Note there is no shoreline for grid features
+    const feature = graph.features[cells.f[onborderCell]];
+    if (feature.type === "lake" && feature.shoreline?.every(ofSameType)) continue;
+
+    const startingVertex = cells.v[cellId].find(v => vertices.c[v].some(ofDifferentType));
+    if (startingVertex === undefined) throw new Error(`Starting vertex for cell ${cellId} is not found`);
+
+    const vertexChain = connectVertices({vertices, startingVertex, ofSameType, addToChecked, closeRing: true});
+    if (vertexChain.length < 3) continue;
+
+    addIsoline(type, vertices, vertexChain);
+  }
+
+  return isolines;
+
+  function addIsoline(type, vertices, vertexChain) {
+    if (!isolines[type]) isolines[type] = {};
+
+    if (options.polygons) {
+      if (!isolines[type].polygons) isolines[type].polygons = [];
+      isolines[type].polygons.push(vertexChain.map(vertexId => vertices.p[vertexId]));
+    }
+
+    if (options.fill) {
+      if (!isolines[type].fill) isolines[type].fill = "";
+      isolines[type].fill += getFillPath(vertices, vertexChain);
+    }
+
+    if (options.waterGap) {
+      if (!isolines[type].waterGap) isolines[type].waterGap = "";
+      const isLandVertex = vertexId => vertices.c[vertexId].every(i => cells.h[i] >= 20);
+      isolines[type].waterGap += getBorderPath(vertices, vertexChain, isLandVertex);
+    }
+
+    if (options.halo) {
+      if (!isolines[type].halo) isolines[type].halo = "";
+      const isBorderVertex = vertexId => vertices.c[vertexId].some(i => cells.b[i]);
+      isolines[type].halo += getBorderPath(vertices, vertexChain, isBorderVertex);
+    }
+  }
+}
+
+function getFillPath(vertices, vertexChain) {
+  const points = vertexChain.map(vertexId => vertices.p[vertexId]);
+  const firstPoint = points.shift();
+  return `M${firstPoint} L${points.join(" ")} Z`;
+}
+
+function getBorderPath(vertices, vertexChain, discontinue) {
+  let discontinued = true;
+  let lastOperation = "";
+  const path = vertexChain.map(vertexId => {
+    if (discontinue(vertexId)) {
+      discontinued = true;
+      return "";
+    }
+
+    const operation = discontinued ? "M" : "L";
+    discontinued = false;
+    lastOperation = operation;
+
+    const command = operation === "L" && operation === lastOperation ? "" : operation;
+    return ` ${command}${vertices.p[vertexId]}`;
+  });
+
+  return path.join("").trim();
+}
+
+// get single path for an non-continuous array of cells
+function getVertexPath(cellsArray) {
+  const {cells, vertices} = pack;
+
+  const cellsObj = Object.fromEntries(cellsArray.map(cellId => [cellId, true]));
+  const ofSameType = cellId => cellsObj[cellId];
+  const ofDifferentType = cellId => !cellsObj[cellId];
+
+  const checkedCells = new Uint8Array(cells.c.length);
+  const addToChecked = cellId => (checkedCells[cellId] = 1);
+  const isChecked = cellId => checkedCells[cellId] === 1;
+
+  let path = "";
+
+  for (const cellId of cellsArray) {
+    if (isChecked(cellId)) continue;
+
+    const onborderCell = cells.c[cellId].find(ofDifferentType);
+    if (onborderCell === undefined) continue;
+
+    const feature = pack.features[cells.f[onborderCell]];
+    if (feature.type === "lake" && feature.shoreline) {
+      if (feature.shoreline.every(ofSameType)) continue; // inner lake
+    }
+
+    const startingVertex = cells.v[cellId].find(v => vertices.c[v].some(ofDifferentType));
+    if (startingVertex === undefined) throw new Error(`Starting vertex for cell ${cellId} is not found`);
+
+    const vertexChain = connectVertices({vertices, startingVertex, ofSameType, addToChecked, closeRing: true});
+    if (vertexChain.length < 3) continue;
+
+    path += getFillPath(vertices, vertexChain);
+  }
+
+  return path;
+}
+
+function getPolesOfInaccessibility(graph, getType) {
+  const isolines = getIsolines(graph, getType, {polygons: true});
+
+  const poles = Object.entries(isolines).map(([id, isoline]) => {
+    const multiPolygon = isoline.polygons.sort((a, b) => b.length - a.length);
+    const [x, y] = polylabel(multiPolygon, 20);
+    return [id, [rn(x), rn(y)]];
+  });
+
+  return Object.fromEntries(poles);
+}
+
+function connectVertices({vertices, startingVertex, ofSameType, addToChecked, closeRing}) {
+  const MAX_ITERATIONS = vertices.c.length;
+  const chain = []; // vertices chain to form a path
+
+  let next = startingVertex;
+  for (let i = 0; i === 0 || next !== startingVertex; i++) {
+    const previous = chain.at(-1);
+    const current = next;
+    chain.push(current);
+
+    const neibCells = vertices.c[current];
+    if (addToChecked) neibCells.filter(ofSameType).forEach(addToChecked);
+
+    const [c1, c2, c3] = neibCells.map(ofSameType);
+    const [v1, v2, v3] = vertices.v[current];
+
+    if (v1 !== previous && c1 !== c2) next = v1;
+    else if (v2 !== previous && c2 !== c3) next = v2;
+    else if (v3 !== previous && c1 !== c3) next = v3;
+
+    if (next >= vertices.c.length) {
+      ERROR && console.error("ConnectVertices: next vertex is out of bounds");
+      break;
+    }
+
+    if (next === current) {
+      ERROR && console.error("ConnectVertices: next vertex is not found");
+      break;
+    }
+
+    if (i === MAX_ITERATIONS) {
+      ERROR && console.error("ConnectVertices: max iterations reached", MAX_ITERATIONS);
+      break;
+    }
+  }
+
+  if (closeRing) chain.push(startingVertex);
+  return chain;
+}
+
+/**
+ * Finds the shortest path between two cells using a cost-based pathfinding algorithm.
+ * @param {number} start - The ID of the starting cell.
+ * @param {(id: number) => boolean} isExit - A function that returns true if the cell is the exit cell.
+ * @param {(current: number, next: number) => number} getCost - A function that returns the path cost from current cell to the next cell. Must return `Infinity` for impassable connections.
+ * @returns {number[] | null} An array of cell IDs of the path from start to exit, or null if no path is found or start and exit are the same.
+ */
+function findPath(start, isExit, getCost) {
+  if (isExit(start)) return null;
+
+  const from = [];
+  const cost = [];
+  const queue = new FlatQueue();
+  queue.push(start, 0);
+
+  while (queue.length) {
+    const currentCost = queue.peekValue();
+    const current = queue.pop();
+
+    for (const next of pack.cells.c[current]) {
+      if (isExit(next)) {
+        from[next] = current;
+        return restorePath(next, start, from);
+      }
+
+      const nextCost = getCost(current, next);
+      if (nextCost === Infinity) continue; // impassable cell
+      const totalCost = currentCost + nextCost;
+
+      if (totalCost >= cost[next]) continue; // has cheaper path
+      from[next] = current;
+      cost[next] = totalCost;
+      queue.push(next, totalCost);
+    }
+  }
+
+  return null;
+}
+
+// supplementary function for findPath
+function restorePath(exit, start, from) {
+  const pathCells = [];
+
+  let current = exit;
+  let prev = exit;
+
+  while (current !== start) {
+    pathCells.push(current);
+    prev = from[current];
+    current = prev;
+  }
+
+  pathCells.push(current);
+
+  return pathCells.reverse();
+}