/** @return The previous page. */
private <T> Page<T> queryPreviousPage(
int rowsPerPage,
String currentStartKey,
String currentStartKeyDocId,
String startKey,
String startKeyDocId,
Class<T> classOfT) {
// set view query params
limit(rowsPerPage + 1);
includeDocs(true);
descending(true); // read backward
startKey(currentStartKey);
startKeyDocId(currentStartKeyDocId);
// init page, query view
final Page<T> page = new Page<T>();
final List<T> pageList = new ArrayList<T>();
final ViewResult<String, String, T> vr = queryView(String.class, String.class, classOfT);
final List<ViewResult<String, String, T>.Rows> rows = vr.getRows();
final int resultRows = rows.size();
final int offset = vr.getOffset();
final long totalRows = vr.getTotalRows();
Collections.reverse(rows); // fix order
// holds page params
final JsonObject currentKeys = new JsonObject();
final JsonObject jsonNext = new JsonObject();
final JsonObject jsonPrev = new JsonObject();
currentKeys.addProperty(CURRENT_START_KEY, rows.get(0).getKey());
currentKeys.addProperty(CURRENT_START_KEY_DOC_ID, rows.get(0).getId());
for (int i = 0; i < resultRows; i++) {
// set keys for the next page
if (i == resultRows - 1) { // last element (i.e rowsPerPage + 1)
if (resultRows >= rowsPerPage) { // if not last page
page.setHasNext(true);
jsonNext.addProperty(START_KEY, rows.get(i).getKey());
jsonNext.addProperty(START_KEY_DOC_ID, rows.get(i).getId());
jsonNext.add(CURRENT_KEYS, currentKeys);
jsonNext.addProperty(ACTION, NEXT);
page.setNextParam(Base64.encodeBase64URLSafeString(jsonNext.toString().getBytes()));
continue;
}
}
pageList.add(rows.get(i).getDoc());
}
// set keys for the previous page
if (offset != (totalRows - rowsPerPage - 1)) { // if not first page
page.setHasPrevious(true);
jsonPrev.addProperty(START_KEY, currentStartKey);
jsonPrev.addProperty(START_KEY_DOC_ID, currentStartKeyDocId);
jsonPrev.add(CURRENT_KEYS, currentKeys);
jsonPrev.addProperty(ACTION, PREVIOUS);
page.setPreviousParam(Base64.encodeBase64URLSafeString(jsonPrev.toString().getBytes()));
}
// calculate paging display info
page.setResultList(pageList);
page.setTotalResults(totalRows);
page.setResultFrom((int) totalRows - (offset + rowsPerPage));
final int resultTo = (int) totalRows - offset - 1;
page.setResultTo(resultTo);
page.setPageNumber(resultTo / rowsPerPage);
return page;
}
/** @return The next page. */
private <T> Page<T> queryNextPage(
int rowsPerPage,
String currentStartKey,
String currentStartKeyDocId,
String startKey,
String startKeyDocId,
Class<T> classOfT) {
// set view query params
limit(rowsPerPage + 1);
includeDocs(true);
if (startKey != null) {
startKey(startKey);
startKeyDocId(startKeyDocId);
}
// init page, query view
final Page<T> page = new Page<T>();
final List<T> pageList = new ArrayList<T>();
final ViewResult<String, String, T> vr = queryView(String.class, String.class, classOfT);
final List<ViewResult<String, String, T>.Rows> rows = vr.getRows();
final int resultRows = rows.size();
final int offset = vr.getOffset();
final long totalRows = vr.getTotalRows();
// holds page params
final JsonObject currentKeys = new JsonObject();
final JsonObject jsonNext = new JsonObject();
final JsonObject jsonPrev = new JsonObject();
currentKeys.addProperty(CURRENT_START_KEY, rows.get(0).getKey());
currentKeys.addProperty(CURRENT_START_KEY_DOC_ID, rows.get(0).getId());
for (int i = 0; i < resultRows; i++) {
// set keys for the next page
if (i == resultRows - 1) { // last element (i.e rowsPerPage + 1)
if (resultRows > rowsPerPage) { // if not last page
page.setHasNext(true);
jsonNext.addProperty(START_KEY, rows.get(i).getKey());
jsonNext.addProperty(START_KEY_DOC_ID, rows.get(i).getId());
jsonNext.add(CURRENT_KEYS, currentKeys);
jsonNext.addProperty(ACTION, NEXT);
page.setNextParam(Base64.encodeBase64URLSafeString(jsonNext.toString().getBytes()));
continue; // exclude
}
}
pageList.add(rows.get(i).getDoc());
}
// set keys for the previous page
if (offset != 0) { // if not first page
page.setHasPrevious(true);
jsonPrev.addProperty(START_KEY, currentStartKey);
jsonPrev.addProperty(START_KEY_DOC_ID, currentStartKeyDocId);
jsonPrev.add(CURRENT_KEYS, currentKeys);
jsonPrev.addProperty(ACTION, PREVIOUS);
page.setPreviousParam(Base64.encodeBase64URLSafeString(jsonPrev.toString().getBytes()));
}
// calculate paging display info
page.setResultList(pageList);
page.setTotalResults(totalRows);
page.setResultFrom(offset + 1);
final int resultTo =
rowsPerPage > resultRows
? resultRows
: rowsPerPage; // fix when rowsPerPage exceeds returned rows
page.setResultTo(offset + resultTo);
page.setPageNumber((int) Math.ceil(page.getResultFrom() / Double.valueOf(rowsPerPage)));
return page;
}