package wjhk.jupload2.filedata.helper;

 import java.util.HashMap;

 import java.util.Map;

 import wjhk.jupload2.exception.JUploadException;

 import wjhk.jupload2.policies.UploadPolicy;

 /**

  * this class is used to parse the

  * {@link UploadPolicy#PROP_TARGET_PICTURE_FORMAT} parameter and provide easy

  * access to the conversions

  * <ul>

  * <li>all file extensions are case-insensitive</li>

  * <li>jpg and jpeg are distinct!</li>

  * </ul>

  * expected format example: {@code "png,bmp:jpg;gif:png;"}

  * 

  * @see UploadPolicy

  */

 public class ImageFileConversionInfo {

     private static final String FORMAT_SEPARATOR = ",";

     private static final String RELATION_SEPARATOR = ";";

     private static final String RELATION_ASSIGNMENT = ":";

     /**

      * will only contain strings in lower-case formats

      * <ul>

      * <li>key: source format</li>

      * <li>value: target format</li>

      * </ul>

      */

     private Map<String, String> formatRelations = new HashMap<String, String>();

     /**

      * will build a new ImageFileConversionInfo object for the given

      * conversionList.

      * 

      * @param conversionList e.g. {@code "png,bmp:jpg;gif:png;"}, may be empty

      *            or {@code null}

      * @throws JUploadException if the conversionList is erroneous

      */

     public ImageFileConversionInfo(String conversionList)

             throws JUploadException {

         parseConversionList(conversionList);

     }

     /**

      * returns the target format (in lowercase) for the given sourceFormat or

      * {@code null} if no conversion is necessary (or if sourceFormat is {@code

      * null})

      * 

      * @param sourceFormat format of the source file (case does not matter):

      *            e.g. jpg, JpeG, png, ..

      * @return the target format (in lowercase) for the given sourceFormat or

      *         {@code null} if no conversion is necessary (or if sourceFormat is

      *         {@code null})

      */

     public String getTargetFormatOrNull(String sourceFormat) {

         if (sourceFormat == null) {

             return null;

         }

         String mapValue = this.formatRelations.get(sourceFormat.toLowerCase());

         return mapValue;

     }

     /**

      * returns the target format for the given sourceFormat.

      * <ul>

      * <li>the case of the sourceFormat does not matter</li>

      * <li>the returned format will always be lower-case</li>

      * <li>if a conversion is necessary the target format will be returned: e.g.

      * if "bmp" should be converted to a "png": "png" will be returned</li>

      * <li>if no conversion is necessary, the sourceFormat (in lower-case) will

      * be returned</li>

      * <li>if sourceFormat is {@code null}, {@code null} will be returned</li>

      * </ul>

      * 

      * @param sourceFormat format of the source file (case does not matter):

      *            e.g. jpg, JpeG, png, ..

      * @return the target format for the given sourceFormat (see details in the

      *         method description)

      */

     public String getTargetFormat(String sourceFormat) {

         if (sourceFormat == null) {

             return null;

         }

         String targetFormatOrNull = getTargetFormatOrNull(sourceFormat);

         if (targetFormatOrNull == null) {

             return sourceFormat.toLowerCase();

         }

         return targetFormatOrNull;

     }

     /**

      * will parse the conversion list and fill formatRelations with entries.<br />

      * see description of {@link UploadPolicy} for expected format.

      * 

      * @param conversionList the conversion list to parse

      * @throws JUploadException if problems parsing the conversionList occured

      */

     private void parseConversionList(String conversionList)

             throws JUploadException {

         if (conversionList == null || conversionList.equals("")) {

             return;

         }

         /*

          * example: conversionList="Png,bmp:JPG;gif:png"

          */

         /*

          * if the conversion list does not end with the relation separator, we

          * add it to keep the parsing logic simpler

          */

         if (!conversionList.endsWith(RELATION_SEPARATOR)) {

             conversionList += RELATION_SEPARATOR;

         }

         /*

          * example: conversionList="Png,bmp:JPG;gif:png;"

          */

         String[] relations = conversionList.split(RELATION_SEPARATOR);

         for (String relation : relations) {

             /*

              * example: relation="Png,bmp:JPG"

              */

             String[] assignmentDetails = relation.split(RELATION_ASSIGNMENT);

             if (assignmentDetails.length != 2) {

                 throw new JUploadException("Invalid format: relation '"

                         + relation + "' should contain exatly one '"

                         + RELATION_ASSIGNMENT + "'");

             }

             String sourceFormatList = assignmentDetails[0];

             /*

              * example: sourceFormatList="Png,bmp"

              */

             String targetFormat = assignmentDetails[1].toLowerCase();

             /*

              * example: targetFormat="jpg"

              */

             String[] sourceFormats = sourceFormatList.split(FORMAT_SEPARATOR);

             for (String sourceFormat : sourceFormats) {

                 /*

                  * example: sourceFormat="Png"

                  */

                 String lcSourceFormat = sourceFormat.toLowerCase();

                 /*

                  * example: lcSourceFormat="png"

                  */

                 if (lcSourceFormat.equals(targetFormat)) {

                     throw new JUploadException("format '" + sourceFormat

                             + "' is assigned to itself");

                 }

                 String putResult = this.formatRelations.put(lcSourceFormat,

                         targetFormat);

                 if (putResult != null) {

                     throw new JUploadException("format '" + lcSourceFormat

                             + "' is assigned to multiple target formats: '"

                             + targetFormat + "', '" + putResult + "'");

                 }

             }

         }

     }

     /**

      * @see java.lang.Object#toString()

      */

     @Override

     public String toString() {

         StringBuilder sb = new StringBuilder("ImageFileConversionInfo (");

         for (Map.Entry<String, String> formatRelation : this.formatRelations

                 .entrySet()) {

             sb.append(formatRelation.getKey());

             sb.append("-->");

             sb.append(formatRelation.getValue());

             sb.append(";");

         }

         sb.append(")");

         return sb.toString();

     }

 }