com.crushpaper.ResultsPaginator.java Source code

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Here is the source code for com.crushpaper.ResultsPaginator.java

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/*
Copyright 2015 CrushPaper.com.
    
This file is part of CrushPaper.
    
CrushPaper is free software: you can redistribute it and/or modify
it under the terms of version 3 of the GNU Affero General Public
License as published by the Free Software Foundation.
    
CrushPaper is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Affero General Public License for more details.
    
You should have received a copy of the GNU Affero General Public License
along with CrushPaper.  If not, see <http://www.gnu.org/licenses/>.
 */
package com.crushpaper;

import java.util.Map;

import org.apache.commons.lang3.StringEscapeUtils;

import com.crushpaper.Servlet.RequestAndResponse;

/**
 * Contains the logic for deciding which list items should be included in a
 * page.
 */
public class ResultsPaginator {
    ResultsPaginator(RequestAndResponse requestAndResponse, String noMatchesText, StringBuilder result,
            ServletText servletText) {
        this.requestAndResponse = requestAndResponse;
        this.noMatchesText = noMatchesText;
        this.result = result;
        this.servletText = servletText;

        start = getStartForPagination(requestAndResponse);
        end = start + getPageSizeForPagination();
        resultNumber = start;
    }

    /**
     * Returns the next action the iterator should take. 0 means break.
     * Otherwise it is the 1 based index of the result.
     */
    int next() {
        ++resultNumber;
        if (resultNumber > end) {
            return 0;
        }

        anyMatches = true;

        return resultNumber;
    }

    /**
     * The iterator should call this when it has finished iterating to print out
     * the right message.
     */
    public void done() {
        if (resultNumber == (end + 1)) {
            getPreviousAndNextLinksForPagination(start != 0, true, requestAndResponse, result);
        } else if (start == 0 && !anyMatches) {
            result.append(noMatchesText);
        } else if (start != 0 && !anyMatches) {
            result.append(servletText.sentenceNoMoreResults());
        } else if (start != 0) {
            getPreviousAndNextLinksForPagination(true, false, requestAndResponse, result);
        }
    }

    /** Returns true if there would be more results. */
    public boolean hasMore() {
        return resultNumber == (end + 1);
    }

    /**
     * Returns the name of the URL parameter that contains the start of the page
     * for pagination.
     */
    private String startParameterNameForPagination() {
        return "start";
    }

    /** Returns the page size for the pagination of the results. */
    private int getPageSizeForPagination() {
        return 20;
    }

    /** Returns the starting point for the pagination of the results. */
    private int getStartForPagination(RequestAndResponse requestAndResponse) {
        String start = requestAndResponse.getParameter(startParameterNameForPagination());
        if (start == null) {
            return 0;
        }

        try {
            return Integer.parseInt(start);
        } catch (Exception e) {
            return 0;
        }
    }

    /** Returns the HTML for the next link in pagination. */
    private void getPreviousAndNextLinksForPagination(boolean includePreviousLink, boolean includeNextLink,
            RequestAndResponse requestAndResponse, StringBuilder result) {
        StringBuilder baseUrl = new StringBuilder();
        baseUrl.append(StringEscapeUtils.escapeHtml4(requestAndResponse.getRequestURI()));

        int start = getStartForPagination(requestAndResponse) + getPageSizeForPagination();

        boolean addedQuestionMark = false;
        java.util.Map<java.lang.String, java.lang.String[]> parameters = requestAndResponse.getParameterMap();
        for (Map.Entry<String, String[]> entry : parameters.entrySet()) {
            String key = entry.getKey();

            if (key == null || key.equals(startParameterNameForPagination()) || key.equals("time"))
                continue;

            for (String value : entry.getValue()) {
                if (!addedQuestionMark) {
                    baseUrl.append("?");
                    addedQuestionMark = true;
                } else {
                    baseUrl.append("&");
                }

                baseUrl.append(StringEscapeUtils.escapeHtml4(key));
                baseUrl.append("=");
                baseUrl.append(StringEscapeUtils.escapeHtml4(value));
            }
        }

        if (!addedQuestionMark) {
            baseUrl.append("?");
        } else {
            baseUrl.append("&");
        }

        baseUrl.append(startParameterNameForPagination());
        baseUrl.append("=");

        result.append("<table width=\"100%\"><tr><td>");

        if (includePreviousLink) {
            result.append("<a onclick=\"replacePaneForLink(event, '" + servletText.pageTitleGetPreviousPage()
                    + "', true); return false;\" class=\"previousLink\" href=\"");

            result.append(baseUrl.toString());
            result.append(start - getPageSizeForPagination() * 2);

            result.append("\">");
            result.append(servletText.linkPrevious());
            result.append("</a>");
        }

        if (includeNextLink) {
            result.append("<a onclick=\"replacePaneForLink(event, '" + servletText.pageTitleGetNextPage()
                    + "', true); return false;\" class=\"nextLink\" href=\"");

            result.append(baseUrl.toString());
            result.append(start);

            result.append("\">");
            result.append(servletText.linkNext());
            result.append("</a>");
        }

        result.append("</td></tr></table>");
    }

    /**
     * Returns the starting position of the query. This is a multiple of the
     * page size.
     */
    public int getStartPosition() {
        return start;
    }

    /**
     * Returns the number of results that should be returned by a query for this
     * page. This is the page size + 1 so that it can be determined if a next
     * link should be included.
     */
    public int getMaxResults() {
        return getPageSizeForPagination() + 1;
    }

    RequestAndResponse requestAndResponse;
    StringBuilder result;
    private String noMatchesText;
    ServletText servletText;

    private int resultNumber, start, end;
    private boolean anyMatches;
}