ChatPaginator.java

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package org.bukkit.util;

import org.bukkit.ChatColor;

import java.util.LinkedList;
import java.util.List;

public class ChatPaginator {
    public static final int GUARANTEED_NO_WRAP_CHAT_PAGE_WIDTH = 55; // Will never wrap, even with the largest characters
    public static final int AVERAGE_CHAT_PAGE_WIDTH = 65; // Will typically not wrap using an average character distribution
    public static final int UNBOUNDED_PAGE_WIDTH = Integer.MAX_VALUE;
    public static final int OPEN_CHAT_PAGE_HEIGHT = 20; // The height of an expanded chat window
    public static final int CLOSED_CHAT_PAGE_HEIGHT = 10; // The height of the default chat window
    public static final int UNBOUNDED_PAGE_HEIGHT = Integer.MAX_VALUE;

    public static ChatPage paginate(String unpaginatedString, int pageNumber) {
        return  paginate(unpaginatedString, pageNumber, GUARANTEED_NO_WRAP_CHAT_PAGE_WIDTH, CLOSED_CHAT_PAGE_HEIGHT);
    }

    public static ChatPage paginate(String unpaginatedString, int pageNumber, int lineLength, int pageHeight) {
        String[] lines = wordWrap(unpaginatedString, lineLength);

        int totalPages = lines.length / pageHeight + (lines.length % pageHeight == 0 ? 0 : 1);
        int actualPageNumber = pageNumber <= totalPages ? pageNumber : totalPages;

        int from = (actualPageNumber - 1) * pageHeight;
        int to = from + pageHeight <= lines.length  ? from + pageHeight : lines.length;
        String[] selectedLines = Java15Compat.Arrays_copyOfRange(lines, from, to);

        return new ChatPage(selectedLines, actualPageNumber, totalPages);
    }

    public static String[] wordWrap(String rawString, int lineLength) {
        // A null string is a single line
        if (rawString == null) {
            return new String[] {""};
        }

        // A string shorter than the lineWidth is a single line
        if (rawString.length() <= lineLength && !rawString.contains("\n")) {
            return new String[] {rawString};
        }

        char[] rawChars = (rawString + ' ').toCharArray(); // add a trailing space to trigger pagination
        StringBuilder word = new StringBuilder();
        StringBuilder line = new StringBuilder();
        List<String> lines = new LinkedList<String>();
        int lineColorChars = 0;

        for (int i = 0; i < rawChars.length; i++) {
            char c = rawChars[i];

            // skip chat color modifiers
            if (c == ChatColor.COLOR_CHAR) {
                word.append(ChatColor.getByChar(rawChars[i + 1]));
                lineColorChars += 2;
                i++; // Eat the next character as we have already processed it
                continue;
            }

            if (c == ' ' || c == '\n') {
                if (line.length() == 0 && word.length() > lineLength) { // special case: extremely long word begins a line
                    for (String partialWord : word.toString().split("(?<=\\G.{" + lineLength + "})")) {
                        lines.add(partialWord);
                    }
                } else if (line.length() + word.length() - lineColorChars == lineLength) { // Line exactly the correct length...newline
                    line.append(word);
                    lines.add(line.toString());
                    line = new StringBuilder();
                    lineColorChars = 0;
                } else if (line.length() + 1 + word.length() - lineColorChars > lineLength) { // Line too long...break the line
                    for (String partialWord : word.toString().split("(?<=\\G.{" + lineLength + "})")) {
                        lines.add(line.toString());
                        line = new StringBuilder(partialWord);
                    }
                    lineColorChars = 0;
                } else {
                    if (line.length() > 0) {
                        line.append(' ');
                    }
                    line.append(word);
                }
                word = new StringBuilder();

                if (c == '\n') { // Newline forces the line to flush
                    lines.add(line.toString());
                    line = new StringBuilder();
                }
            } else {
                word.append(c);
            }
        }

        if(line.length() > 0) { // Only add the last line if there is anything to add
            lines.add(line.toString());
        }

        // Iterate over the wrapped lines, applying the last color from one line to the beginning of the next
        if (lines.get(0).length() == 0 || lines.get(0).charAt(0) != ChatColor.COLOR_CHAR) {
            lines.set(0, ChatColor.WHITE + lines.get(0));
        }
        for (int i = 1; i < lines.size(); i++) {
            final String pLine = lines.get(i-1);
            final String subLine = lines.get(i);

            char color = pLine.charAt(pLine.lastIndexOf(ChatColor.COLOR_CHAR) + 1);
            if (subLine.length() == 0 || subLine.charAt(0) != ChatColor.COLOR_CHAR) {
                lines.set(i, ChatColor.getByChar(color) + subLine);
            }
        }

        return lines.toArray(new String[lines.size()]);
    }

    public static class ChatPage {

        private String[] lines;
        private int pageNumber;
        private int totalPages;

        public ChatPage(String[] lines, int pageNumber, int totalPages) {
            this.lines = lines;
            this.pageNumber = pageNumber;
            this.totalPages = totalPages;
        }

        public int getPageNumber() {
            return pageNumber;
        }

        public int getTotalPages() {
            return totalPages;
        }

        public String[] getLines() {

            return lines;
        }
    }
}