Determines which geographical divisions are in a Viewport intersect with the given BBOX.
此脚本不应直接安装。它是供其他脚本使用的外部库，要使用该库请加入元指令 // @require https://update.gf.qytechs.cn/scripts/542477/1623829/wmeGisLBBOX.js
// ==UserScript==
// @name wmeGisLBBOX
// @namespace https://github.com/JS55CT/
// @author JS55CT
// @description Determines which geographical divisions are in a Viewport intersect with the given BBOX.
// @version 2026.07.13.00
// @license MIT
// @grant GM_xmlhttpRequest
// @connect github.io
// @match *://this-library-is-not-supposed-to-run.com/*
// @contributionURL https://github.com/WazeDev/Thank-The-Authors
// ==/UserScript==
var wmeGisLBBOX = (function () {
// Constructor for the wmeGisLBBOX class
const funcName = "wmeGisLBBOX";
const BASE_URL = `https://WazeDev.github.io/wmeGisLBBOX/`;
const BASE_URL_BBOX = `${BASE_URL}BBOX%20JSON/`;
const BASE_URL_GEOJSON = `${BASE_URL}GEOJSON/`;
function wmeGisLBBOX() {
// Ensure class instantiation with 'new'
if (!(this instanceof wmeGisLBBOX)) {
return new wmeGisLBBOX();
}
this.cache = {}; // Cache for storing fetched JSON / geoJSON data
}
/**
* Fetches JSON data from a specified URL, utilizing caching to store and reuse fetched data.
*
* This function makes an HTTP GET request to retrieve data from a given URL and employs caching
* to improve efficiency by storing previously fetched results. It uses `GM_xmlhttpRequest` for
* cross-domain requests when running in a userscript environment.
*
* Process Overview:
* 1. Checks the cache for existing data associated with the URL.
* 2. If cached data is available, returns it immediately.
* 3. If no cache is found, performs an HTTP request to fetch the data.
* 4. On successful fetch, parses the JSON, stores it in cache, and resolves with the data.
* 5. Handles errors, rejecting the Promise with an appropriate error message if the fetch fails.
*
* @param {string} url - The URL from which to fetch JSON data.
* @returns {Promise<Object>} - A Promise resolving to the parsed JSON data.
**/
wmeGisLBBOX.prototype.fetchJsonWithCache = function (url) {
if (this.cache[url]) {
return Promise.resolve(this.cache[url]);
}
// Fetch data using GM_xmlhttpRequest
return new Promise((resolve, reject) => {
GM_xmlhttpRequest({
method: "GET",
url: url,
onload: (response) => {
if (response.status >= 200 && response.status < 300) {
// Parse and store fetched data in cache
const data = JSON.parse(response.responseText);
this.cache[url] = data;
resolve(data);
} else {
reject(new Error(`${funcName}: Failed to fetch data from ${url}, status: ${response.status}`));
}
},
onerror: (error) => {
reject(new Error(`${funcName}: Failed to fetch data from ${url}, error: ${error}`));
},
});
});
};
/**
* Determines whether two bounding boxes intersect.
*
* This function checks for intersection between two bounding boxes `bbox1` and `bbox2`
* by evaluating both latitude and longitude overlapping scenarios. Special handling is included
* to manage cases where bounding boxes wrap the antimeridian (180 degrees longitude).
*
* Process Overview:
* 1. Checks latitude intersection by evaluating if latitude ranges overlap.
* 2. Checks longitude intersection, considering whether a bounding box wraps the antimeridian.
* 3. Returns true if both latitude and longitude intersections occur; false otherwise.
*
* Longitude Intersection Scenarios:
* - Standard check if neither bounding box wraps the antimeridian.
* - Special checks for when one or both bounding boxes wrap the antimeridian.
*
* @param {Object} bbox1 - The first bounding box with properties minLat, maxLat, minLon, maxLon.
* @param {Object} bbox2 - The second bounding box with properties minLat, maxLat, minLon, maxLon.
* @returns {boolean} - True if the bounding boxes intersect, false otherwise.
**/
function checkIntersection(bbox1, bbox2) {
// Check for Latitude Intersection
const latIntersects = !(bbox1.maxLat < bbox2.minLat || bbox1.minLat > bbox2.maxLat);
if (!latIntersects) {
return false;
}
// Check for Longitude Intersection
const bbox1Wraps = bbox1.minLon > bbox1.maxLon;
const bbox2Wraps = bbox2.minLon > bbox2.maxLon;
let lonIntersects = false;
if (!bbox1Wraps && !bbox2Wraps) {
// Neither box wraps the antimeridian - standard overlap check
lonIntersects = !(bbox1.maxLon < bbox2.minLon || bbox1.minLon > bbox2.maxLon);
} else if (bbox1Wraps && !bbox2Wraps) {
// bbox1 wraps and bbox2 does not
const separated = bbox1.maxLon < bbox2.minLon && bbox1.minLon > bbox2.maxLon;
lonIntersects = !separated;
} else if (!bbox1Wraps && bbox2Wraps) {
// bbox2 wraps and bbox1 does not
const separated = bbox2.maxLon < bbox1.minLon && bbox2.minLon > bbox1.maxLon;
lonIntersects = !separated;
} else {
lonIntersects = true; // Both boxes wrap the antimeridian
}
return lonIntersects; // Return true if both latitude and longitude intersect
}
/**
* Identifies countries intersecting with the specified viewport bounding box.
*
* This function fetches a list of countries defined by their bounding boxes,
* checks for intersection with the current viewport, and returns details for
* countries that intersect.
*
* Process Overview:
* 1. Fetches country bounding box data from a specified JSON URL.
* 2. Iterates over country data, checking each one's bounding boxes against the viewport.
* 3. Collects information on countries that intersect, including ISO codes and names.
*
* viewportBbox: {minLon: number, minLat: number, maxLon: number, maxLat: number}
*
* Error Handling:
* - Logs errors during the fetch process and returns an empty array if issues occur.
*
* @param {Object} viewportBbox - The bounding box defining the current viewport.
* @returns {Array} - An array of objects representing countries intersecting with the viewport.
**/
wmeGisLBBOX.prototype.getIntersectingCountries = async function (viewportBbox) {
const url = `${BASE_URL_BBOX}COUNTRIES_BBOX_ESPG4326.json`;
return this.fetchJsonWithCache(url)
.then((COUNTRY_DATA) => {
const intersectingCountries = Object.keys(COUNTRY_DATA).flatMap((code) => {
const countryData = COUNTRY_DATA[code];
for (const bbox of countryData.bbox) {
if (checkIntersection(bbox, viewportBbox)) {
return [
{
ISO_ALPHA2: countryData["ISO_ALPHA2"],
ISO_ALPHA3: countryData["ISO_ALPHA3"],
name: countryData["name"],
Sub_level: countryData["Sub_level"],
source: "BBOX",
},
];
}
}
return [];
});
return intersectingCountries;
})
.catch((error) => {
console.error(`${funcName}: Error fetching country data:`, error);
return [];
});
};
/**
* Fetches and augments country data with subdivision information.
*
* This asynchronous function retrieves base country information and then
* iteratively fetches additional subdivision data for each country, augmenting
* the country data with its respective subdivisions.
*
* @returns {Object} - A comprehensive data object containing country details and
* corresponding first-level subdivisions.
*
* Process Overview:
* 1. Fetches country data from a static JSON file.
* 2. Iterates through each country and retrieves its subdivision JSON data.
* 3. Adds the fetched subdivisions data to the country information structure.
*
* Error Handling:
* - Logs an error if fetching either the country or subdivision data fails.
* - Returns an empty object if the initial fetch fails.
*
* URLs:
* - Subdivision Data: Dynamic URL based on country ISO_ALPHA3 code from the base URL.
**/
wmeGisLBBOX.prototype.getCountriesAndSubsJson = async function () {
const url = `${BASE_URL_BBOX}COUNTRIES_BBOX_ESPG4326.json`;
const funcName = "getCountriesAndSubsJson";
try {
// Fetch the country data
const COUNTRY_DATA = await this.fetchJsonWithCache(url);
if (!COUNTRY_DATA) {
console.warn(`${funcName}: No country data found.`);
return {};
}
// Iterate over each country to fetch and add subdivision data
for (const countryCode in COUNTRY_DATA) {
if (COUNTRY_DATA.hasOwnProperty(countryCode)) {
// Fetch the first-level subdivision data for the country
const isoAlpha3 = COUNTRY_DATA[countryCode].ISO_ALPHA3;
const subL1Url = `${BASE_URL_BBOX}${isoAlpha3}/${isoAlpha3}_BBOX_ESPG4326.json`;
try {
const subL1Data = await this.fetchJsonWithCache(subL1Url);
if (!subL1Data) {
COUNTRY_DATA[countryCode].subL1 = {}; // Initialize as empty object if no data is found
} else {
// Add subdivisions to the country data
COUNTRY_DATA[countryCode].subL1 = subL1Data;
}
} catch (subError) {
COUNTRY_DATA[countryCode].subL1 = {}; // Safely initialize as empty object in case of error
}
}
}
return COUNTRY_DATA;
} catch (error) {
console.warn(`${funcName}: Error fetching country data:`, error);
return {};
}
};
/**
* Cleans intersecting country data by pruning empty subdivisions across different levels.
*
* This function processes country data that intersects with a given geographic area,
* handling hierarchical subdivision structures and removing any empty or null subdivisions.
* It dynamically adapts to the subdivision level identified for each country.
*
* Process Overview:
* 1. Iterates through intersecting country data.
* 2. Applies cleaning logic based on subdivision levels (subLevel) present.
* 3. Specifically handles multi-level subdivisions, including special logic for deep levels.
* 4. Recursively prunes subdivisions that lack content, ensuring only relevant data remains.
*
* Cleaning Logic by Subdivision Level:
* - Sub_Level = 1: Retains countries and sub-level 1 if they contain valid subdivisions.
* - Sub_Level = 2: Further inspects sub-level 2; if empty, removes it and reveals sub-level 1 if needed.
* - Sub_Level = 3: Examines sub-level 3 within applicable countries, removing them if empty and ensuring sub-level 2 remains relevant.
* - Undetected or Sub_Level = 0: Completely removes countries with unidentified subdivisions.
*
* @param {Object} intersectingCountries - Object containing intersecting country data.
*
* Modifications:
* - Directly alters the `intersectingCountries` object by removing empty subdivisions.
* - Ensures structural integrity by retaining populated subdivisions and appropriate country entries.
*/
wmeGisLBBOX.prototype.cleanIntersectingData = function (intersectingCountries) {
for (const countryName in intersectingCountries) {
const country = intersectingCountries[countryName];
const subLevel = country.Sub_level || 0; // Default to 0 if Sub_level is not provided
// Handle Sub_level = 0: Return the country directly
if (subLevel === 0) {
continue; // This means we should retain the country as is without further checks
}
// Proceed with cleanup based on sub-level hierarchy
if (subLevel >= 3) {
for (const sub1Name in country.subL1) {
const subL1 = country.subL1[sub1Name];
for (const sub2Name in subL1.subL2) {
const subL2 = subL1.subL2[sub2Name];
if (!subL2.subL3 || Object.keys(subL2.subL3).length === 0) {
delete subL1.subL2[sub2Name];
}
}
}
}
if (subLevel >= 2) {
for (const sub1Name in country.subL1) {
const subL1 = country.subL1[sub1Name];
if (!subL1.subL2 || Object.keys(subL1.subL2).length === 0) {
delete country.subL1[sub1Name];
}
}
}
if (subLevel >= 1) {
if (!country.subL1 || Object.keys(country.subL1).length === 0) {
delete intersectingCountries[countryName];
}
}
}
};
/**
* Fetches GeoJSON data for a specified region and checks for intersection with a given viewport.
*
* This asynchronous function retrieves GeoJSON data based on the specified country, subdivision,
* and sub-subdivision codes. It then checks whether the geometries in the GeoJSON intersect
* with the provided viewport bounding box, returning intersection results or the full GeoJSON data.
*
* Process Overview:
* 1. Constructs the URL for the GeoJSON file based on provided codes.
* 2. Fetches the GeoJSON data using the constructed URL.
* 3. Defines the viewport area as a polygon using the specified bounding box coordinates.
* 4. Iterates through GeoJSON features, checking if their geometries intersect with the viewport.
* 5. Returns either the full GeoJSON data or a boolean indicating intersection presence based on a flag.
*
* Supported Geometry Types:
* - Polygon: Directly checks for intersection with the viewport polygon.
* - MultiPolygon: Iterates through component polygons to check for intersection.
* - Logs a warning if any unsupported geometry types are encountered.
*
* Error Handling:
* - Logs an error message if fetching or processing the GeoJSON fails, returns `false`.
*
* viewportBbox: {minLon: number, minLat: number, maxLon: number, maxLat: number}
*
* @param {string} countyCode - The country code corresponding to the GeoJSON data.
* @param {string} subCode - The subdivision code for the GeoJSON data.
* @param {string} subSubCode - The sub-subdivision code for the GeoJSON data.
* @param {Object} viewportBbox - The bounding box of the viewport.
* @param {boolean} [returnGeoJson=false] - Flag to determine if the full GeoJSON data should be returned.
* @returns {boolean|Object} - Returns true or false for intersection presence, or the full GeoJSON data.
**/
wmeGisLBBOX.prototype.fetchAndCheckGeoJsonIntersection = async function (countyCode, subCode, subSubCode, viewportBbox, returnGeoJson = false) {
const url = `${BASE_URL_GEOJSON}${countyCode}/${subCode}/${countyCode}-${subCode}-${subSubCode}_EPSG4326.geojson`;
try {
const geoJsonData = await this.fetchJsonWithCache(url);
// Define the viewport as a polygon.
const viewportPolygon = [
[viewportBbox.minLon, viewportBbox.minLat],
[viewportBbox.minLon, viewportBbox.maxLat],
[viewportBbox.maxLon, viewportBbox.maxLat],
[viewportBbox.maxLon, viewportBbox.minLat],
[viewportBbox.minLon, viewportBbox.minLat],
];
// Iterate through each feature in the GeoJSON data
for (const feature of geoJsonData.features) {
const featureGeometry = feature.geometry;
// Check if the geometry type is Polygon or MultiPolygon
if (featureGeometry.type === "Polygon") {
for (const polygon of featureGeometry.coordinates) {
if (hasIntersection(polygon, viewportPolygon)) {
return returnGeoJson ? geoJsonData : true; // Return the GeoJSON data or intersection boolean
}
}
} else if (featureGeometry.type === "MultiPolygon") {
for (const multiPolygon of featureGeometry.coordinates) {
for (const polygon of multiPolygon) {
if (hasIntersection(polygon, viewportPolygon)) {
return returnGeoJson ? geoJsonData : true; // Return the GeoJSON data or intersection boolean
}
}
}
} else {
console.warn(`${funcName}: Unsupported geometry type:`, featureGeometry.type);
continue; // Skip unsupported geometry types
}
}
return false; // No intersection found
} catch (error) {
console.error(`${funcName}: Error fetching or processing GeoJSON from ${url}:`, error);
return false;
}
};
/**
* Identifies US states and counties that intersect with the given viewport bounding box.
*
* This asynchronous function fetches state and county bounding box data, identifies which states
* and counties intersect with a specified viewport, and optionally checks for more precise
* intersections using GeoJSON data.
*
* Process Overview:
* 1. Retrieves bounding box data for US states.
* 2. Checks each state's bounding box against the viewport for intersections.
* 3. For intersecting states, fetches county bounding box data and identifies intersecting counties.
* 4. If `highPrecision` is true, uses GeoJSON data to refine intersection checks.
* 5. Constructs an object that maps intersecting states to their respective intersecting counties and subdivisions.
*
* Optional Features:
* - High precision mode uses GeoJSON data to confirm intersections and update data sources.
* - Supports returning GeoJSON data if intersections occur and `returnGeoJson` is true.
*
* viewportBbox: {minLon: number, minLat: number, maxLon: number, maxLat: number}
*
* Error Handling:
* - Logs a message if fetching or processing bounding box or GeoJSON data fails.
*
* @param {Object} viewportBbox - The bounding box of the viewport.
* @param {boolean} [highPrecision=false] - Flag to activate high precision intersection checks using GeoJSON.
* @param {boolean} [returnGeoJson=false] - Flag to indicate if GeoJSON data should be returned when intersecting.
* @returns {Object} - A structured object detailing intersecting states, counties, and subdivisions.
**/
wmeGisLBBOX.prototype.getIntersectingStatesAndCounties = async function (viewportBbox, highPrecision = false, returnGeoJson = false) {
const STATES_URL = `${BASE_URL_BBOX}USA/USA_BBOX_ESPG4326.json`;
const intersectingRegions = {};
try {
const US_States = await this.fetchJsonWithCache(STATES_URL);
for (const stateCode in US_States) {
const stateData = US_States[stateCode];
if (checkIntersection(stateData.bbox, viewportBbox)) {
const intersectingCounties = {};
const countiesUrl = `${BASE_URL_BBOX}USA/USA-${stateCode}_BBOX_ESPG4326.json`;
const countiesData = await this.fetchJsonWithCache(countiesUrl);
for (const countyEntry of countiesData) {
const countyName = Object.keys(countyEntry)[0];
const countyData = countyEntry[countyName];
if (checkIntersection(countyData.bbox, viewportBbox)) {
const intersectingSubCounties = countyData.subdivisions
.filter((sub) => sub.bbox && checkIntersection(sub.bbox, viewportBbox))
.reduce((acc, sub) => {
acc[sub.name] = {
subL3_num: sub.sub_num,
source: "BBOX",
};
return acc;
}, {});
if (Object.keys(intersectingSubCounties).length > 0) {
let source = "BBOX";
let geoJsonData = null;
if (highPrecision) {
const intersectsGeoJson = await this.fetchAndCheckGeoJsonIntersection("USA", stateCode, countyData.sub_num, viewportBbox, returnGeoJson);
if (returnGeoJson && intersectsGeoJson) {
geoJsonData = intersectsGeoJson;
source = "GEOJSON";
} else if (intersectsGeoJson) {
source = "GEOJSON";
} else {
continue;
}
}
intersectingCounties[countyName] = {
subL2_num: countyData.sub_num,
subL3: intersectingSubCounties,
source: source,
};
if (geoJsonData) {
intersectingCounties[countyName].geoJsonData = geoJsonData;
}
}
}
}
if (Object.keys(intersectingCounties).length > 0) {
let stateSource = "BBOX";
if (highPrecision) {
const anyCountyWithGeoJson = Object.values(intersectingCounties).some((county) => county.source === "GEOJSON");
if (anyCountyWithGeoJson) {
stateSource = "GEOJSON";
}
}
intersectingRegions[stateData.name] = {
subL1_id: stateData.sub_id,
subL1_num: stateData.sub_num,
subL2: intersectingCounties,
source: stateSource,
};
}
}
}
} catch (error) {
console.error(`${funcName}: Failed to fetch or process data:`, error);
}
return intersectingRegions;
};
/**
* Retrieves and identifies subdivisions that intersect with a given viewport bounding box.
*
* This asynchronous function fetches hierarchical subdivision data for a specified country based
* on the subdivisions level (`Sub_level`). It checks for intersections at both first and second subdivision levels
* (if applicable) and returns structured data detailing the intersecting areas.
*
* Process Overview:
* 1. Constructs the URL for the country's first-level subdivision data.
* 2. Fetches and checks first-level subdivisions for intersection with the viewport.
* 3. For intersecting first-level subdivisions and if `Sub_level` is 2, constructs URLs for second-level data.
* 4. Checks second-level subdivisions for intersection and integrate results into the output.
* 5. Builds and returns a comprehensive object of intersecting subdivisions.
*
* Parameters:
* - `viewportBbox`: {minLon: number, minLat: number, maxLon: number, maxLat: number}
* Represents the geographic viewport for intersection checks.
*
* Error Handling:
* - Logs warnings if no first-level or second-level data are found.
* - Logs errors for issues with fetching or processing subdivisions.
*
* @param {Object} countryObj - An object containing details about the country, including ISO code and Sub_level.
* @param {Object} viewportBbox - The bounding box of the viewport to check against.
* @returns {Object} - An object containing details of intersecting subdivisions, organized by hierarchy.
*/
wmeGisLBBOX.prototype.getIntersectingSubdivisions = async function (countryObj, viewportBbox) {
const subdivisionsResult = {};
const countryCode = countryObj.ISO_ALPHA3;
const subL1Url = `${BASE_URL_BBOX}${countryCode}/${countryCode}_BBOX_ESPG4326.json`;
const funcName = "getIntersectingSubdivisions";
try {
// Check Sub_Level to decide how to handle subdivisions
if (!countryObj.Sub_level) {
return subdivisionsResult; // Return {} if Sub_Level is 0 or undefined
}
if (countryObj.Sub_level >= 1) {
// Fetch first-level subdivision data
const subL1Data = await this.fetchJsonWithCache(subL1Url);
if (!subL1Data) {
console.warn(`${funcName}: No first-level subdivision data found for country code: ${countryCode}`);
return subdivisionsResult;
}
for (const subdivisionID in subL1Data) {
const subdivision = subL1Data[subdivisionID];
// Check intersection for first-level subdivisions
if (checkIntersection(subdivision.bbox, viewportBbox)) {
const subdivisionName = subdivision["name"];
// Initialize data for this subdivision
subdivisionsResult[subdivisionName] = {
subL1_num: subdivision["sub_num"],
subL1_id: subdivisionID,
source: "BBOX",
subL2: {}, // Placeholder for second-level subdivisions
};
// If Sub_Level is 2, fetch second-level subdivision data
if (countryObj.Sub_level === 2) {
const subL2Url = `${BASE_URL_BBOX}${countryCode}/${countryCode}-${subdivisionID}_BBOX_ESPG4326.json`;
try {
const subL2Data = await this.fetchJsonWithCache(subL2Url);
if (!subL2Data) {
console.warn(`${funcName}: No second-level subdivision data found for ${subdivisionName} (${subdivisionID}) in country: ${countryCode}`);
} else {
// Process second-level subdivisions
for (const subsubDivision of subL2Data) {
const subsubID = Object.keys(subsubDivision)[0];
const subsub = subsubDivision[subsubID];
// Check intersection for second-level subdivisions
if (checkIntersection(subsub.bbox, viewportBbox)) {
const subsubName = subsub["name"];
// Add intersecting second-level subdivisions
subdivisionsResult[subdivisionName].subL2[subsubName] = {
subL2_num: subsub["sub_num"],
source: "BBOX",
};
}
}
}
} catch (subError) {
console.warn(`${funcName}: Error fetching second-level data for ${subdivisionName} (${subdivisionID}) in country: ${countryCode} - ${subError.message}`);
}
} // End of Sub_Level 2 check
}
}
}
} catch (error) {
console.error(`${funcName}: Error fetching or processing subdivisions for country code ${countryCode} - ${error.message}`);
}
return subdivisionsResult;
};
/**
* Determines regions within the viewport by identifying intersecting countries and their subdivisions.
*
* This asynchronous function analyzes a given viewport bounding box to determine which countries
* and internal subdivisions, such as states and counties, are visible. It accommodates the USA
* specifically and uses different handling for other countries.
*
* Process Overview:
* 1. Fetches countries that intersect with the viewport.
* 2. If no intersecting countries are found, logs a warning.
* 3. For the USA, retrieves intersecting states and counties; for other countries, retrieves subdivisions.
* 4. Cleans up intersecting data to ensure only relevant information is retained.
* 5. Constructs a results object that maps visible countries to their intersecting subdivisions.
*
* Features:
* - Supports high precision checks using GeoJSON data if specified.
* - Integration of subdivision logic for both the USA and other countries.
*
* viewportBbox: {minLon: number, minLat: number, maxLon: number, maxLat: number}
*
* Error Handling:
* - Logs errors encountered during the fetching and processing of intersecting regions.
*
* @param {Object} viewportBbox - The bounding box defining the current viewport.
* @param {boolean} [highPrecision=false] - Flag to use high precision intersection checks.
* @param {boolean} [returnGeoJson=false] - Flag to determine if GeoJSON data should be returned.
* @returns {Object} - Structured results identifying regions within the viewport.
**/
wmeGisLBBOX.prototype.whatsInView = async function (viewportBbox, highPrecision = false, returnGeoJson = false) {
const results = {};
const funcName = "whatsInView";
try {
const countries = await this.getIntersectingCountries(viewportBbox);
if (!countries || Object.keys(countries).length === 0) {
console.warn(`${funcName}: Viewport does not intersect with any known countries.`);
return results;
}
for (const countryCode in countries) {
const country = countries[countryCode];
// Handle the case when Sub_level is 0
if (country.Sub_level === 0) {
results[country.name] = {
ISO_ALPHA2: country.ISO_ALPHA2,
ISO_ALPHA3: country.ISO_ALPHA3,
Sub_level: country.Sub_level,
source: country.source,
subL1: {}, // Leave subL1 empty when Sub_level is 0
};
continue;
}
if (country.ISO_ALPHA3 === "USA") {
const statesAndCounties = await this.getIntersectingStatesAndCounties(viewportBbox, highPrecision, returnGeoJson);
if (statesAndCounties && Object.keys(statesAndCounties).length > 0) {
results[country.name] = {
ISO_ALPHA2: country.ISO_ALPHA2,
ISO_ALPHA3: country.ISO_ALPHA3,
Sub_level: country.Sub_level,
subL1: statesAndCounties,
};
this.cleanIntersectingData(results);
}
} else {
const subdivisions = await this.getIntersectingSubdivisions(country, viewportBbox);
if (subdivisions && Object.keys(subdivisions).length > 0) {
results[country.name] = {
ISO_ALPHA2: country.ISO_ALPHA2,
ISO_ALPHA3: country.ISO_ALPHA3,
Sub_level: country.Sub_level,
subL1: subdivisions,
};
this.cleanIntersectingData(results);
}
}
}
} catch (error) {
console.error(`${funcName}: Error during finding intersecting regions:`, error);
}
return results;
};
/**
* Determines if a given point is inside a polygon using the ray-casting algorithm.
*
* This function checks whether a point, defined by its coordinates, is inside a polygon.
* The polygon is represented by an array of vertices (points), and the function uses the
* ray-casting technique to toggle the state whenever the ray crosses a polygon edge.
*
* Process Overview:
* 1. Iterates over each edge of the polygon using vertex pairs (xi, yi) and (xj, yj).
* 2. Uses logical conditions to check if a horizontal ray extending from the point intersects
* with the polygon's edge.
* 3. Toggles 'inside' state whenever an intersection is detected, flipping between true and false.
* 4. Returns the final 'inside' state, indicating whether the point lies within the polygon.
*
* @param {Array} point - An array [x, y] representing the coordinates of the point to test.
* @param {Array} vs - An array of vertices, where each vertex is represented as [x, y].
* @returns {boolean} - True if the point is inside the polygon, false otherwise.
**/
function isPointInPolygon(point, vs) {
const [x, y] = point;
let inside = false;
for (let i = 0, j = vs.length - 1; i < vs.length; j = i++) {
const [xi, yi] = vs[i];
const [xj, yj] = vs[j];
const intersect = yi > y !== yj > y && x < ((xj - xi) * (y - yi)) / (yj - yi) + xi;
if (intersect) inside = !inside;
}
return inside;
}
/**
* Calculates the intersection point, if any, between two line segments defined by endpoints.
*
* This function checks whether two line segments, one defined by (p1, p2) and the other by (q1, q2),
* intersect. The method utilizes linear algebra to derive intersection coordinates and subsequently
* verifies that the intersection falls within the bounds of both segments.
*
* Process Overview:
* 1. Computes coefficients for the line equations using segment endpoints.
* 2. Determines if the lines are parallel (denominator = 0), in which case no intersection exists.
* 3. Calculates potential intersection coordinates using determinant-based formulae.
* 4. Verifies if the intersection coordinates lie within the bounds of both line segments.
* 5. Returns the intersection point if valid, or null if no intersection exists within segment limits.
*
* @param {Array} p1 - [x, y] coordinates of the first endpoint of the first segment.
* @param {Array} p2 - [x, y] coordinates of the second endpoint of the first segment.
* @param {Array} q1 - [x, y] coordinates of the first endpoint of the second segment.
* @param {Array} q2 - [x, y] coordinates of the second endpoint of the second segment.
* @returns {Array|null} - [x, y] coordinates of the intersection point, or null if no intersection.
**/
function segmentIntersection(p1, p2, q1, q2) {
// Calculate coefficients
const a1 = p2[1] - p1[1];
const b1 = p1[0] - p2[0];
const c1 = a1 * p1[0] + b1 * p1[1];
const a2 = q2[1] - q1[1];
const b2 = q1[0] - q2[0];
const c2 = a2 * q1[0] + b2 * q1[1];
const denominator = a1 * b2 - a2 * b1;
if (denominator === 0) {
return null; // Parallel lines
}
const intersectX = (b2 * c1 - b1 * c2) / denominator;
const intersectY = (a1 * c2 - a2 * c1) / denominator;
// Check if the intersection is within the bounds of the line segments
const withinBounds = (value, end1, end2) => Math.min(end1, end2) <= value && value <= Math.max(end1, end2);
if (withinBounds(intersectX, p1[0], p2[0]) && withinBounds(intersectY, p1[1], p2[1]) && withinBounds(intersectX, q1[0], q2[0]) && withinBounds(intersectY, q1[1], q2[1])) {
return [intersectX, intersectY];
}
return null; // Intersection point is not within the line segments
}
/**
* Checks for intersection between two polygons.
*
* This function determines if two polygons intersect by examining:
* 1. If any edges from `polygon1` intersect with any edges from `polygon2`.
* 2. If any point from `polygon1` is contained within `polygon2`.
* 3. If any point from `polygon2` is contained within `polygon1`.
*
* The function uses helper methods `segmentIntersection` to check edge intersections
* and `isPointInPolygon` to evaluate point containment.
*
* Process Overview:
* - Iterates over edges of both polygons, checking for intersection using the `segmentIntersection` function.
* - Verifies point containment using the `isPointInPolygon` function to see if any point from one polygon is inside the other.
* - Returns true if any intersection or containment is found; otherwise, returns false.
*
* @param {Array} polygon1 - An array of points defining the first polygon, where each point is an {x, y} object.
* @param {Array} polygon2 - An array of points defining the second polygon, where each point is an {x, y} object.
* @returns {boolean} - True if an intersection or containment is found between the polygons, false otherwise.
**/
function hasIntersection(polygon1, polygon2) {
// Check each edge of polygon1 against each edge of polygon2
for (let i = 0; i < polygon1.length - 1; i++) {
for (let j = 0; j < polygon2.length - 1; j++) {
const intersection = segmentIntersection(polygon1[i], polygon1[i + 1], polygon2[j], polygon2[j + 1]);
if (intersection) {
return true; // An intersection is found
}
}
}
// Check if any point of polygon1 is inside polygon2
for (const point of polygon1) {
if (isPointInPolygon(point, polygon2)) {
return true; // A contained point is found
}
}
// Check if any point of polygon2 is inside polygon1
for (const point of polygon2) {
if (isPointInPolygon(point, polygon1)) {
return true; // A contained point is found
}
}
return false; // No intersection found
}
return wmeGisLBBOX;
})();
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