001 package edu.nrao.sss.astronomy;
002
003 import java.io.BufferedReader;
004 import java.io.IOException;
005 import java.io.InputStreamReader;
006 import java.io.UnsupportedEncodingException;
007 import java.net.MalformedURLException;
008 import java.net.URL;
009 import java.net.URLEncoder;
010 import java.text.SimpleDateFormat;
011 import java.util.Date;
012
013 import edu.nrao.sss.measure.ArcUnits;
014 import edu.nrao.sss.measure.Latitude;
015 import edu.nrao.sss.measure.Longitude;
016 import edu.nrao.sss.util.SourceNotFoundException;
017
018 /**
019 * IMCE's SkyBot Resolver source locator.
020 * <p>
021 * This locator sends a CGI query to IMCE
022 * (<a href="http://www.imcce.fr/imcce_en.html">Institut de Mechanique
023 * Celeste et de Calcul des Ephemerides</a>) and parses the response.
024 * The web address for the query is
025 * <a href="http://www.imcce.fr/webservices/skybot/skybotresolver_query.php">
026 * http://www.imcce.fr/webservices/skybot/skybotresolver_query.php</a>.
027 * </p>
028 * <p>
029 * <b>Version Info:</b>
030 * <table style="margin-left:2em">
031 * <tr><td>$Revision: 555 $</td></tr>
032 * <tr><td>$Date: 2007-04-24 09:05:24 -0600 (Tue, 24 Apr 2007) $</td></tr>
033 * <tr><td>$Author: dharland $</td></tr>
034 * </table></p>
035 *
036 * @author David M. Harland
037 * @since 2007-04-18
038 */
039 public class SkyBotResolver
040 implements SourceLocator
041 {
042 private static final String CGI_SCRIPT =
043 "http://www.imcce.fr/webservices/skybot/skybotresolver_query.php";
044
045 private static final String CONST_PARAMS = "?-out=object&-mime=text";
046
047 private static final String QUERY_BASE = CGI_SCRIPT + CONST_PARAMS;
048
049 private static final char PARAM_DELIM = '&';
050
051 private static final String ENCODING = "UTF-8";
052
053 private static final String COMMENT_TOKEN = "#";
054
055 private static final SimpleDateFormat DATE_FORMATTER =
056 new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
057
058 private static final int RA_POS = 2;
059 private static final int DEC_POS = 3;
060
061 //============================================================================
062 //
063 //============================================================================
064
065 /* (non-Javadoc)
066 * @see SourceLocator#findPosition(java.lang.String, java.util.Date)
067 */
068 public SkyPosition findPosition(String sourceName, Date time)
069 throws SourceNotFoundException
070 {
071 String skybotQuery = buildQuery(sourceName, time);
072
073 BufferedReader page = getPageReader(skybotQuery);
074
075 return getPositionFrom(page);
076 }
077
078 /* (non-Javadoc)
079 * SourceLocator#findPosition(java.lang.String)
080 */
081 public SkyPosition findPosition(String sourceName)
082 throws SourceNotFoundException
083 {
084 String skybotQuery = buildQuery(sourceName);
085
086 BufferedReader page = getPageReader(skybotQuery);
087
088 return getPositionFrom(page);
089 }
090
091 //============================================================================
092 //
093 //============================================================================
094
095 /** Builds a query string based on name of body and time of "now". */
096 private String buildQuery(String bodyName)
097 throws SourceNotFoundException
098 {
099 return buildQuery(bodyName, "now");
100 }
101
102 /** Builds a query string based on name of body and time. */
103 private String buildQuery(String bodyName, Date time)
104 throws SourceNotFoundException
105 {
106 return buildQuery(bodyName, DATE_FORMATTER.format(time));
107 }
108
109 /** Builds a query string using the two parameters. */
110 private String buildQuery(String bodyName, String dateText)
111 throws SourceNotFoundException
112 {
113 StringBuilder query = new StringBuilder(QUERY_BASE);
114
115 try
116 {
117 //Date
118 query.append(PARAM_DELIM)
119 .append("-ep=")
120 .append(URLEncoder.encode(dateText, ENCODING));
121
122 //Body name
123 query.append(PARAM_DELIM)
124 .append("-obj=")
125 .append(URLEncoder.encode(bodyName, ENCODING));
126 }
127 catch (UnsupportedEncodingException uee)
128 {
129 throw new SourceNotFoundException(
130 "Problem encoding date and/or name parameters for use in URL.", uee);
131 }
132
133 return query.toString();
134 }
135
136 /** Turns the text into a URL then into a BufferedReader. */
137 private BufferedReader getPageReader(String skybotAddress)
138 throws SourceNotFoundException
139 {
140 try
141 {
142 URL skybot = new URL(skybotAddress);
143
144 return new BufferedReader(new InputStreamReader(skybot.openStream()));
145 }
146 catch (MalformedURLException mue)
147 {
148 throw new SourceNotFoundException("Problem with this URL: " +
149 skybotAddress, mue);
150 }
151 catch (IOException ioe)
152 {
153 throw new SourceNotFoundException("Problem opening query results.", ioe);
154 }
155 }
156
157 /** Reads the page, looking for position information. */
158 private SkyPosition getPositionFrom(BufferedReader page)
159 throws SourceNotFoundException
160 {
161 try
162 {
163 confirmFlagLine(page.readLine(), page);
164
165 page.readLine(); //Skip "ticket" line
166
167 confirmColumnHeadings(page.readLine());
168
169 SkyPosition position = makePosition(page.readLine());
170
171 page.close();
172
173 return position;
174 }
175 catch (IOException ioe)
176 {
177 throw new SourceNotFoundException("Problem reading query results.", ioe);
178 }
179 catch (IllegalArgumentException iae)
180 {
181 throw new SourceNotFoundException("Unexpected results format.", iae);
182 }
183 }
184
185 /**
186 * Makes sure line contains "flag" and that value is not 0 or -1.
187 * 0 = source-not-found; -1 = error.
188 */
189 private void confirmFlagLine(String line, BufferedReader page)
190 throws SourceNotFoundException
191 {
192 if (!line.contains("flag"))
193 throw new IllegalArgumentException("First line did not contain 'flag'.");
194
195 int flag = Integer.parseInt(line.substring(line.indexOf(": ")+2));
196
197 if (flag < 1)
198 {
199 String explanation = "";
200
201 while (true)
202 {
203 try {
204 line = page.readLine();
205 }
206 catch (IOException ex) {
207 throw new SourceNotFoundException("Problem reading query results."
208 , ex);
209 }
210 if (line == null)
211 break;
212
213 if (!line.startsWith(COMMENT_TOKEN))
214 {
215 explanation = line;
216 break;
217 }
218 }
219
220 throw new IllegalArgumentException(explanation);
221 }
222 }
223
224 /** Confirms that we understand the data in the results line. */
225 private void confirmColumnHeadings(String line)
226 {
227 String[] columns = line.split(",");
228
229 if (!columns[RA_POS].contains("RA(h)"))
230 throw new IllegalArgumentException(
231 "Expected RA, in hours, in column " + RA_POS + " of " + line);
232
233 if (!columns[DEC_POS].contains("DE(deg)"))
234 throw new IllegalArgumentException(
235 "Expected RA, in hours, in column " + DEC_POS + " of " + line);
236 }
237
238 /**
239 * Parses skyBotLine and returns a sky position using the portion
240 * of the line that represents the RA and Dec.
241 */
242 private SkyPosition makePosition(String skyBotLine)
243 {
244 SimpleSkyPosition position =
245 new SimpleSkyPosition(CelestialCoordinateSystem.EQUATORIAL, Epoch.J2000);
246
247 String[] tokens = skyBotLine.split("\\|");
248
249 if (tokens.length != 7)
250 throw new IllegalArgumentException(skyBotLine);
251
252 position.setLongitude(Longitude.parse(tokens[RA_POS] +
253 ArcUnits.HOUR.getSymbol()));
254
255 position.setLatitude(Latitude.parse(tokens[DEC_POS] +
256 ArcUnits.DEGREE.getSymbol()));
257 return position;
258 }
259
260 //============================================================================
261 //
262 //============================================================================
263 /*
264 public static void main(String[] args) throws Exception
265 {
266 SkyBotResolver locator = new SkyBotResolver();
267
268 String[] bodies = {"mars", "pluto", "ida", "ceres", "lunch", ""};
269
270 for (int b=0; b < bodies.length; b++)
271 {
272 try
273 {
274 SkyPosition position = locator.findPosition(bodies[b]);
275
276 System.out.print(bodies[b] + ": ");
277 System.out.print(position.getLongitude().toStringHms());
278 System.out.print(", ");
279 System.out.println(position.getLatitude().toStringDms());
280 }
281 catch (SourceNotFoundException ex)
282 {
283 System.out.println(ex.getMessage() + " " + ex.getCause().getMessage());
284 }
285 }
286
287 Calendar cal = Calendar.getInstance();
288
289 for (int day=1; day <= 10; day++)
290 {
291 Date time = cal.getTime();
292
293 SkyPosition position = locator.findPosition("Mars", time);
294
295 System.out.print(time + ": ");
296 System.out.print(position.getLongitude().toStringHms());
297 System.out.print(", ");
298 System.out.println(position.getLatitude().toStringDms());
299
300 cal.add(Calendar.DATE, 1);
301 }
302 }
303 */
304 }