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Jython is an implementation of the high-level, dynamic, object-oriented language Python written in 100% Pure Java, and seamlessly integrated with the Java platform. It thus allows you to run Python on any Java platform.

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/**
 * Copyright 2009, Google Inc.  All rights reserved.
 * Licensed to PSF under a Contributor Agreement.
 */
package org.python.indexer.demos;

import org.python.indexer.StyleRun;

import java.util.ArrayList;
import java.util.List;
import java.util.HashSet;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;

/**
 * Turns a list of {@link StyleRun}s into HTML spans.
 */
class StyleApplier {

    // Empirically, adding the span tags multiplies length by 6 or more.
    private static final int SOURCE_BUF_MULTIPLIER = 6;

    private SortedSet tags = new TreeSet();

    private StringBuilder buffer;  // html output buffer

    private String source;  // input source code
    private String path;  // input source path, for logging

    // Current offset into the source being copied into the html buffer.
    private int sourceOffset = 0;

    abstract class Tag implements Comparable{
        int offset;
        StyleRun style;
        public int compareTo(Tag other) {
            if (this == other) {
                return 0;
            }
            if (this.offset < other.offset) {
                return -1;
            }
            if (other.offset < this.offset) {
                return 1;
            }
            return this.hashCode() - other.hashCode();
        }
        void insert() {
            // Copy source code up through this tag.
            if (offset > sourceOffset) {
                copySource(sourceOffset, offset);
            }
        }
    }

    class StartTag extends Tag {
        public StartTag(StyleRun style) {
            offset = style.start();
            this.style = style;
        }
        @Override
        void insert() {
            super.insert();
            switch (style.type) {
                case ANCHOR:
                    buffer.append("");
        }
    }

    class EndTag extends Tag {
        public EndTag(StyleRun style) {
            offset = style.end();
            this.style = style;
        }
        @Override
        void insert() {
            super.insert();
            switch (style.type) {
                case ANCHOR:
                case LINK:
                    buffer.append("");
                    break;
                default:
                    buffer.append("");
                    break;
            }
        }
    }

    public StyleApplier(String path, String src, List runs) {
        this.path = path;
        source = src;
        for (StyleRun run : runs) {
            tags.add(new StartTag(run));
            tags.add(new EndTag(run));
        }
    }

    /**
     * @return the html
     */
    public String apply() {
        buffer = new StringBuilder(source.length() * SOURCE_BUF_MULTIPLIER);
        int lastStart = -1;
        for (Tag tag : tags) {
            tag.insert();
        }
        // Copy in remaining source beyond last tag.
        if (sourceOffset < source.length()) {
            copySource(sourceOffset, source.length());
        }
        return buffer.toString();
    }

    /**
     * Copies code from the input source to the output html.
     * @param beg the starting source offset
     * @param end the end offset, or -1 to go to end of file
     */
    private void copySource(int beg, int end) {
        // Be robust if the analyzer gives us bad offsets.
        try {
            String src = escape((end == -1)
                                ? source.substring(beg)
                                : source.substring(beg, end));
            buffer.append(src);
        } catch (RuntimeException x) {
            System.err.println("Warning: " + x);
        }
        sourceOffset = end;
    }

    private String escape(String s) {
        return s.replace("&", "&")
                .replace("'", "'")
                .replace("\"", """)
                .replace("<", "<")
                .replace(">", ">");
    }

    private String toCSS(StyleRun style) {
        return style.type.toString().toLowerCase().replace("_", "-");
    }
}