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package org.openstack4j.openstack.common;

import java.io.IOException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.deser.std.StdDeserializer;

/**
 * The date formats returned from the OpenStack telemetry APIs can be returned in multiple formats like:
 * "yyyy-MM-dd'T'HH:mm:ss" or "yyyy-MM-dd'T'HH:mm:ss.SSSSSS". This cannot be parsed correctly with a SimpleDateFormat,
 * so the formats must be normalized. This date deserializer normalizes the date into "yyyy-MM-dd'T'HH:mm:ss.SSS" and
 * then parses it into a Date.
 *
 * @author pdube
 */
public class TelemetryDateDeserializer extends StdDeserializer {
   private static final String MILLIS_DATE_FORMAT = "yyyy-MM-dd'T'HH:mm:ss.SSS";

   public TelemetryDateDeserializer() {
      this(null);
   }

   public TelemetryDateDeserializer(Class vc) {
      super(vc);
   }

   @Override
   public Date deserialize(JsonParser jsonParser, DeserializationContext ctxt)
         throws IOException, JsonProcessingException {
      String date = jsonParser.getText();
      SimpleDateFormat sdf = new SimpleDateFormat(MILLIS_DATE_FORMAT);
      sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
      try {
         return sdf.parse(getParseableDate(date));
      } catch (ParseException e) {
         throw new JsonParseException(jsonParser, "Could not process telemetry date", e);
      }
   }

   /**
    * Modifies the date string to have the expected date format ("yyyy-MM-dd'T'HH:mm:ss.SSS")
    * 
    * @param date
    * @return the date with the correct format
    */
   private String getParseableDate(String date) {
      // e.g. [ "2017-06-20 13:00:00" , "395000" ] or [] if no decimal
      String[] sdate = date.split("\\.");
      if (sdate.length > 1) {
         return sdate[0] + "." + getExpectedDecimals(sdate[1]);
      }
      return date + ".000";
   }

   private String getExpectedDecimals(String decimals) {
      return (decimals + "000").substring(0, 3);
   }

}