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handle longitudes + snap start/stop to axis values (subsetByValue)
Snapping start/stop values to axis values increases the chance of using a cached request in certain subsetting scenarios.
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| // COPIED FROM covjson-reader -> DRY!!!!! | ||
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| const OPENGIS_CRS_PREFIX = 'http://www.opengis.net/def/crs/' | ||
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| /** 3D WGS84 in lat-lon-height order */ | ||
| const EPSG4979 = OPENGIS_CRS_PREFIX + '/EPSG/0/4979' | ||
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| /** 2D WGS84 in lat-lon order */ | ||
| const EPSG4326 = OPENGIS_CRS_PREFIX + '/EPSG/0/4326' | ||
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| /** 2D WGS84 in lon-lat order */ | ||
| const CRS84 = OPENGIS_CRS_PREFIX + '/OGC/1.3/CRS84' | ||
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| /** CRSs in which position is specified by geodetic latitude and longitude */ | ||
| const EllipsoidalCRSs = [EPSG4979, EPSG4326, CRS84] | ||
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| /** Position of longitude axis */ | ||
| const LongitudeAxisIndex = { | ||
| [EPSG4979]: 1, | ||
| [EPSG4326]: 1, | ||
| [CRS84]: 0 | ||
| } | ||
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| /** | ||
| * Returns a function which converts an arbitrary longitude to the | ||
| * longitude extent used in the coverage domain. | ||
| * This only supports primitive axes since this is what subsetByValue supports. | ||
| * The longitude extent is extended to 360 degrees if the actual extent is smaller. | ||
| * The extension is done equally on both sides of the extent. | ||
| * | ||
| * For example, the domain may have longitudes within [0,360]. | ||
| * An input longitude of -70 is converted to 290. | ||
| * All longitudes within [0,360] are returned unchanged. | ||
| * | ||
| * If the domain has longitudes within [10,50] then the | ||
| * extended longitude range is [-150,210] (-+180 from the middle point). | ||
| * An input longitude of -170 is converted to 190. | ||
| * All longitudes within [-150,210] are returned unchanged. | ||
| * | ||
| * @ignore | ||
| */ | ||
| export function getLongitudeWrapper (domain, axisName) { | ||
| // for primitive axes, the axis identifier = component identifier | ||
| if (!isLongitudeAxis(domain, axisName)) { | ||
| throw new Error(`'${axisName}' is not a longitude axis`) | ||
| } | ||
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| let vals = domain.axes.get(axisName).values | ||
| let lon_min = vals[0] | ||
| let lon_max = vals[vals.length-1] | ||
| if (lon_min > lon_max) { | ||
| [lon_min,lon_max] = [lon_max,lon_min] | ||
| } | ||
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| let x_mid = (lon_max + lon_min) / 2 | ||
| let x_min = x_mid - 180 | ||
| let x_max = x_mid + 180 | ||
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| return lon => { | ||
| if (x_min <= lon && lon <= x_max) { | ||
| // directly return to avoid introducing rounding errors | ||
| return lon | ||
| } else { | ||
| return ((lon - x_min) % 360 + 360) % 360 + x_min | ||
| } | ||
| } | ||
| } | ||
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| /** | ||
| * Return whether the given domain axis represents longitudes. | ||
| * | ||
| * @ignore | ||
| */ | ||
| export function isLongitudeAxis (domain, axisName) { | ||
| let ref = getReferenceObject(domain, [axisName]) | ||
| if (!ref) { | ||
| return false | ||
| } | ||
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| let crsId = ref.system.id | ||
| // TODO should support unknown CRSs with embedded axis information | ||
| if (EllipsoidalCRSs.indexOf(crsId) === -1) { | ||
| // this also covers the case when there is no ID property | ||
| return false | ||
| } | ||
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| let compIdx = ref.components.indexOf(axisName) | ||
| let isLongitude = LongitudeAxisIndex[crsId] === compIdx | ||
| return isLongitude | ||
| } | ||
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| /** | ||
| * Returns true if the given axis has ISO8601 date strings | ||
| * as axis values. | ||
| */ | ||
| export function isISODateAxis (domain, axisName) { | ||
| let val = domain.axes.get(axisName).values[0] | ||
| if (typeof val !== 'string') { | ||
| return false | ||
| } | ||
| return !isNaN(new Date(val).getTime()) | ||
| } | ||
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| /** | ||
| * Return the reference system connection object for the given domain component, | ||
| * or undefined if none exists. | ||
| */ | ||
| function getReferenceObject (domain, component) { | ||
| let ref = domain.referencing.find(ref => ref.components.indexOf(component) !== -1) | ||
| return ref | ||
| } |