001// License: GPL. For details, see LICENSE file. 002package org.openstreetmap.josm.plugins.streetside.utils.api; 003 004import java.text.ParseException; 005import java.text.SimpleDateFormat; 006import java.util.Collection; 007import java.util.HashSet; 008import java.util.Locale; 009import java.util.function.Function; 010 011import javax.json.JsonArray; 012import javax.json.JsonNumber; 013import javax.json.JsonObject; 014import javax.json.JsonValue; 015 016import org.openstreetmap.josm.data.coor.LatLon; 017import org.openstreetmap.josm.tools.Logging; 018 019public final class JsonStreetsideDecoder { 020 private JsonStreetsideDecoder() { 021 // Private constructor to avoid instantiation 022 } 023 024 /** 025 * Parses a given {@link JsonObject} as a GeoJSON FeatureCollection into a {@link Collection} 026 * of the desired Java objects. The method, which converts the GeoJSON features into Java objects 027 * is given as a parameter to this method. 028 * @param <T> feature type 029 * @param json the {@link JsonObject} to be parsed 030 * @param featureDecoder feature decoder which transforms JSON objects to Java objects 031 * @return a {@link Collection} which is parsed from the given {@link JsonObject}, which contains GeoJSON. 032 * Currently a {@link HashSet} is used, but please don't rely on it, this could change at any time without 033 * prior notice. The return value will not be <code>null</code>. 034 */ 035 public static <T> Collection<T> decodeFeatureCollection(final JsonObject json, Function<JsonObject, T> featureDecoder) { 036 final Collection<T> result = new HashSet<>(); 037 if ( 038 json != null && "FeatureCollection".equals(json.getString("type", null)) && json.containsKey("features") 039 ) { 040 final JsonValue features = json.get("features"); 041 for (int i = 0; features instanceof JsonArray && i < ((JsonArray) features).size(); i++) { 042 final JsonValue val = ((JsonArray) features).get(i); 043 if (val instanceof JsonObject) { 044 final T feature = featureDecoder.apply((JsonObject) val); 045 if (feature != null) { 046 result.add(feature); 047 } 048 } 049 } 050 } 051 return result; 052 } 053 054 /** 055 * Decodes a {@link JsonArray} of exactly size 2 to a {@link LatLon} instance. 056 * The first value in the {@link JsonArray} is treated as longitude, the second one as latitude. 057 * @param json the {@link JsonArray} containing the two numbers 058 * @return the decoded {@link LatLon} instance, or <code>null</code> if the parameter is 059 * not a {@link JsonArray} of exactly size 2 containing two {@link JsonNumber}s. 060 */ 061 static LatLon decodeLatLon(final JsonArray json) { 062 final double[] result = decodeDoublePair(json); 063 if (result != null) { 064 return new LatLon(result[1], result[0]); 065 } 066 return null; 067 } 068 069 /** 070 * Decodes a pair of double values, which are stored in a {@link JsonArray} of exactly size 2. 071 * @param json the {@link JsonArray} containing the two values 072 * @return a double array which contains the two values in the same order, or <code>null</code> 073 * if the parameter was not a {@link JsonArray} of exactly size 2 containing two {@link JsonNumber}s 074 */ 075 @SuppressWarnings("PMD.ReturnEmptyArrayRatherThanNull") 076 static double[] decodeDoublePair(final JsonArray json) { 077 if ( 078 json != null && 079 json.size() == 2 && 080 json.get(0) instanceof JsonNumber && 081 json.get(1) instanceof JsonNumber 082 ) { 083 return new double[]{json.getJsonNumber(0).doubleValue(), json.getJsonNumber(1).doubleValue()}; 084 } 085 return null; 086 } 087 088 /** 089 * Decodes a timestamp formatted as a {@link String} to the equivalent UNIX epoch timestamp 090 * (number of milliseconds since 1970-01-01T00:00:00.000+0000). 091 * @param timestamp the timestamp formatted according to the format <code>yyyy-MM-dd'T'HH:mm:ss.SSSX</code> 092 * @return the point in time as a {@link Long} value representing the UNIX epoch time, or <code>null</code> if the 093 * parameter does not match the required format (this also triggers a warning via 094 * {@link Logging#warn(Throwable)}), or the parameter is <code>null</code>. 095 */ 096 static Long decodeTimestamp(final String timestamp) { 097 if (timestamp != null) { 098 try { 099 return new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSX", Locale.UK).parse(timestamp).getTime(); 100 } catch (ParseException e) { 101 StackTraceElement calledBy = e.getStackTrace()[Math.min(e.getStackTrace().length - 1, 2)]; 102 Logging.log(Logging.LEVEL_WARN,String.format( 103 "Could not decode time from the timestamp `%s` (called by %s.%s:%d)", 104 timestamp, calledBy.getClassName(), calledBy.getMethodName(), calledBy.getLineNumber() 105 ), e); 106 } 107 } 108 return null; 109 } 110}