polylabel 0.1.11

/**
 * Wraps a GeoJSON {@link Geometry} in a GeoJSON {@link Feature}.
 *
 * @name feature
 * @param {Geometry} geometry input geometry
 * @param {Object} properties properties
 * @returns {FeatureCollection} a FeatureCollection of input features
 * @example
 * var geometry = {
 *      "type": "Point",
 *      "coordinates": [
 *        67.5,
 *        32.84267363195431
 *      ]
 *    }
 *
 * var feature = turf.feature(geometry);
 *
 * //=feature
 */
function feature(geometry, properties) {
    return {
        type: 'Feature',
        properties: properties || {},
        geometry: geometry
    };
}

module.exports.feature = feature;

/**
 * Takes coordinates and properties (optional) and returns a new {@link Point} feature.
 *
 * @name point
 * @param {Array<number>} coordinates longitude, latitude position (each in decimal degrees)
 * @param {Object=} properties an Object that is used as the {@link Feature}'s
 * properties
 * @returns {Feature<Point>} a Point feature
 * @example
 * var pt1 = turf.point([-75.343, 39.984]);
 *
 * //=pt1
 */
module.exports.point = function (coordinates, properties) {
    if (!Array.isArray(coordinates)) throw new Error('Coordinates must be an array');
    if (coordinates.length < 2) throw new Error('Coordinates must be at least 2 numbers long');
    return feature({
        type: 'Point',
        coordinates: coordinates.slice()
    }, properties);
};

/**
 * Takes an array of LinearRings and optionally an {@link Object} with properties and returns a {@link Polygon} feature.
 *
 * @name polygon
 * @param {Array<Array<Array<number>>>} coordinates an array of LinearRings
 * @param {Object=} properties a properties object
 * @returns {Feature<Polygon>} a Polygon feature
 * @throws {Error} throw an error if a LinearRing of the polygon has too few positions
 * or if a LinearRing of the Polygon does not have matching Positions at the
 * beginning & end.
 * @example
 * var polygon = turf.polygon([[
 *  [-2.275543, 53.464547],
 *  [-2.275543, 53.489271],
 *  [-2.215118, 53.489271],
 *  [-2.215118, 53.464547],
 *  [-2.275543, 53.464547]
 * ]], { name: 'poly1', population: 400});
 *
 * //=polygon
 */
module.exports.polygon = function (coordinates, properties) {

    if (!coordinates) throw new Error('No coordinates passed');

    for (var i = 0; i < coordinates.length; i++) {
        var ring = coordinates[i];
        if (ring.length < 4) {
            throw new Error('Each LinearRing of a Polygon must have 4 or more Positions.');
        }
        for (var j = 0; j < ring[ring.length - 1].length; j++) {
            if (ring[ring.length - 1][j] !== ring[0][j]) {
                throw new Error('First and last Position are not equivalent.');
            }
        }
    }

    return feature({
        type: 'Polygon',
        coordinates: coordinates
    }, properties);
};

/**
 * Creates a {@link LineString} based on a
 * coordinate array. Properties can be added optionally.
 *
 * @name lineString
 * @param {Array<Array<number>>} coordinates an array of Positions
 * @param {Object=} properties an Object of key-value pairs to add as properties
 * @returns {Feature<LineString>} a LineString feature
 * @throws {Error} if no coordinates are passed
 * @example
 * var linestring1 = turf.lineString([
 *	[-21.964416, 64.148203],
 *	[-21.956176, 64.141316],
 *	[-21.93901, 64.135924],
 *	[-21.927337, 64.136673]
 * ]);
 * var linestring2 = turf.lineString([
 *	[-21.929054, 64.127985],
 *	[-21.912918, 64.134726],
 *	[-21.916007, 64.141016],
 * 	[-21.930084, 64.14446]
 * ], {name: 'line 1', distance: 145});
 *
 * //=linestring1
 *
 * //=linestring2
 */
module.exports.lineString = function (coordinates, properties) {
    if (!coordinates) {
        throw new Error('No coordinates passed');
    }
    return feature({
        type: 'LineString',
        coordinates: coordinates
    }, properties);
};

/**
 * Takes one or more {@link Feature|Features} and creates a {@link FeatureCollection}.
 *
 * @name featureCollection
 * @param {Feature[]} features input features
 * @returns {FeatureCollection} a FeatureCollection of input features
 * @example
 * var features = [
 *  turf.point([-75.343, 39.984], {name: 'Location A'}),
 *  turf.point([-75.833, 39.284], {name: 'Location B'}),
 *  turf.point([-75.534, 39.123], {name: 'Location C'})
 * ];
 *
 * var fc = turf.featureCollection(features);
 *
 * //=fc
 */
module.exports.featureCollection = function (features) {
    return {
        type: 'FeatureCollection',
        features: features
    };
};

/**
 * Creates a {@link Feature<MultiLineString>} based on a
 * coordinate array. Properties can be added optionally.
 *
 * @name multiLineString
 * @param {Array<Array<Array<number>>>} coordinates an array of LineStrings
 * @param {Object=} properties an Object of key-value pairs to add as properties
 * @returns {Feature<MultiLineString>} a MultiLineString feature
 * @throws {Error} if no coordinates are passed
 * @example
 * var multiLine = turf.multiLineString([[[0,0],[10,10]]]);
 *
 * //=multiLine
 *
 */
module.exports.multiLineString = function (coordinates, properties) {
    if (!coordinates) {
        throw new Error('No coordinates passed');
    }
    return feature({
        type: 'MultiLineString',
        coordinates: coordinates
    }, properties);
};

/**
 * Creates a {@link Feature<MultiPoint>} based on a
 * coordinate array. Properties can be added optionally.
 *
 * @name multiPoint
 * @param {Array<Array<number>>} coordinates an array of Positions
 * @param {Object=} properties an Object of key-value pairs to add as properties
 * @returns {Feature<MultiPoint>} a MultiPoint feature
 * @throws {Error} if no coordinates are passed
 * @example
 * var multiPt = turf.multiPoint([[0,0],[10,10]]);
 *
 * //=multiPt
 *
 */
module.exports.multiPoint = function (coordinates, properties) {
    if (!coordinates) {
        throw new Error('No coordinates passed');
    }
    return feature({
        type: 'MultiPoint',
        coordinates: coordinates
    }, properties);
};


/**
 * Creates a {@link Feature<MultiPolygon>} based on a
 * coordinate array. Properties can be added optionally.
 *
 * @name multiPolygon
 * @param {Array<Array<Array<Array<number>>>>} coordinates an array of Polygons
 * @param {Object=} properties an Object of key-value pairs to add as properties
 * @returns {Feature<MultiPolygon>} a multipolygon feature
 * @throws {Error} if no coordinates are passed
 * @example
 * var multiPoly = turf.multiPolygon([[[[0,0],[0,10],[10,10],[10,0],[0,0]]]]);
 *
 * //=multiPoly
 *
 */
module.exports.multiPolygon = function (coordinates, properties) {
    if (!coordinates) {
        throw new Error('No coordinates passed');
    }
    return feature({
        type: 'MultiPolygon',
        coordinates: coordinates
    }, properties);
};

/**
 * Creates a {@link Feature<GeometryCollection>} based on a
 * coordinate array. Properties can be added optionally.
 *
 * @name geometryCollection
 * @param {Array<{Geometry}>} geometries an array of GeoJSON Geometries
 * @param {Object=} properties an Object of key-value pairs to add as properties
 * @returns {Feature<GeometryCollection>} a GeoJSON GeometryCollection Feature
 * @example
 * var pt = {
 *     "type": "Point",
 *       "coordinates": [100, 0]
 *     };
 * var line = {
 *     "type": "LineString",
 *     "coordinates": [ [101, 0], [102, 1] ]
 *   };
 * var collection = turf.geometryCollection([pt, line]);
 *
 * //=collection
 */
module.exports.geometryCollection = function (geometries, properties) {
    return feature({
        type: 'GeometryCollection',
        geometries: geometries
    }, properties);
};

var factors = {
    miles: 3960,
    nauticalmiles: 3441.145,
    degrees: 57.2957795,
    radians: 1,
    inches: 250905600,
    yards: 6969600,
    meters: 6373000,
    metres: 6373000,
    kilometers: 6373,
    kilometres: 6373,
    feet: 20908792.65
};

/*
 * Convert a distance measurement from radians to a more friendly unit.
 *
 * @name radiansToDistance
 * @param {number} distance in radians across the sphere
 * @param {string} [units=kilometers] can be degrees, radians, miles, or kilometers
 * inches, yards, metres, meters, kilometres, kilometers.
 * @returns {number} distance
 */
module.exports.radiansToDistance = function (radians, units) {
    var factor = factors[units || 'kilometers'];
    if (factor === undefined) {
        throw new Error('Invalid unit');
    }
    return radians * factor;
};

/*
 * Convert a distance measurement from a real-world unit into radians
 *
 * @name distanceToRadians
 * @param {number} distance in real units
 * @param {string} [units=kilometers] can be degrees, radians, miles, or kilometers
 * inches, yards, metres, meters, kilometres, kilometers.
 * @returns {number} radians
 */
module.exports.distanceToRadians = function (distance, units) {
    var factor = factors[units || 'kilometers'];
    if (factor === undefined) {
        throw new Error('Invalid unit');
    }
    return distance / factor;
};

/*
 * Convert a distance measurement from a real-world unit into degrees
 *
 * @name distanceToRadians
 * @param {number} distance in real units
 * @param {string} [units=kilometers] can be degrees, radians, miles, or kilometers
 * inches, yards, metres, meters, kilometres, kilometers.
 * @returns {number} degrees
 */
module.exports.distanceToDegrees = function (distance, units) {
    var factor = factors[units || 'kilometers'];
    if (factor === undefined) {
        throw new Error('Invalid unit');
    }
    return (distance / factor) * 57.2958;
};