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//
//  ========================================================================
//  Copyright (c) 1995-2022 Mort Bay Consulting Pty Ltd and others.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package com.signalfx.shaded.jetty.http.pathmap;

import java.util.HashMap;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import com.signalfx.shaded.jetty.util.log.Log;
import com.signalfx.shaded.jetty.util.log.Logger;

public class RegexPathSpec extends AbstractPathSpec
{
    private static final Logger LOG = Log.getLogger(UriTemplatePathSpec.class);

    private static final Map FORBIDDEN_ESCAPED = new HashMap<>();

    static
    {
        FORBIDDEN_ESCAPED.put('s', "any whitespace");
        FORBIDDEN_ESCAPED.put('n', "newline");
        FORBIDDEN_ESCAPED.put('r', "carriage return");
        FORBIDDEN_ESCAPED.put('t', "tab");
        FORBIDDEN_ESCAPED.put('f', "form-feed");
        FORBIDDEN_ESCAPED.put('b', "bell");
        FORBIDDEN_ESCAPED.put('e', "escape");
        FORBIDDEN_ESCAPED.put('c', "control char");
    }

    private final String _declaration;
    private final PathSpecGroup _group;
    private final int _pathDepth;
    private final int _specLength;
    private final Pattern _pattern;

    public RegexPathSpec(String regex)
    {
        String declaration;
        if (regex.startsWith("regex|"))
            declaration = regex.substring("regex|".length());
        else
            declaration = regex;
        int specLength = declaration.length();
        // build up a simple signature we can use to identify the grouping
        boolean inTextList = false;
        boolean inQuantifier = false;
        StringBuilder signature = new StringBuilder();

        int pathDepth = 0;
        char last = 0;
        for (int i = 0; i < declaration.length(); i++)
        {
            char c = declaration.charAt(i);
            switch (c)
            {
                case '^': // ignore anchors
                case '$': // ignore anchors
                case '\'': // ignore escaping
                case '(': // ignore grouping
                case ')': // ignore grouping
                    break;
                case '+': // single char quantifier
                case '?': // single char quantifier
                case '*': // single char quantifier
                case '|': // alternate match token
                case '.': // any char token
                    signature.append('g'); // glob
                    break;
                case '{':
                    inQuantifier = true;
                    break;
                case '}':
                    inQuantifier = false;
                    break;
                case '[':
                    inTextList = true;
                    break;
                case ']':
                    inTextList = false;
                    signature.append('g'); // glob
                    break;
                case '/':
                    if (!inTextList && !inQuantifier)
                        pathDepth++;
                    break;
                default:
                    if (!inTextList && !inQuantifier && Character.isLetterOrDigit(c))
                    {
                        if (last == '\\') // escaped
                        {
                            String forbiddenReason = FORBIDDEN_ESCAPED.get(c);
                            if (forbiddenReason != null)
                            {
                                throw new IllegalArgumentException(String.format("%s does not support \\%c (%s) for \"%s\"",
                                    this.getClass().getSimpleName(), c, forbiddenReason, declaration));
                            }
                            switch (c)
                            {
                                case 'S': // any non-whitespace
                                case 'd': // any digits
                                case 'D': // any non-digits
                                case 'w': // any word
                                case 'W': // any non-word
                                    signature.append('g'); // glob
                                    break;
                                default:
                                    signature.append('l'); // literal (exact)
                                    break;
                            }
                        }
                        else // not escaped
                        {
                            signature.append('l'); // literal (exact)
                        }
                    }
                    break;
            }
            last = c;
        }
        Pattern pattern = Pattern.compile(declaration);

        // Figure out the grouping based on the signature
        String sig = signature.toString();

        PathSpecGroup group;
        if (Pattern.matches("^l*$", sig))
            group = PathSpecGroup.EXACT;
        else if (Pattern.matches("^l*g+", sig))
            group = PathSpecGroup.PREFIX_GLOB;
        else if (Pattern.matches("^g+l+.*", sig))
            group = PathSpecGroup.SUFFIX_GLOB;
        else
            group = PathSpecGroup.MIDDLE_GLOB;

        _declaration = declaration;
        _group = group;
        _pathDepth = pathDepth;
        _specLength = specLength;
        _pattern = pattern;

        if (LOG.isDebugEnabled())
        {
            LOG.debug("Creating RegexPathSpec[{}] (signature: [{}], group: {})",
                _declaration, sig, _group);
        }
    }

    protected Matcher getMatcher(String path)
    {
        int idx = path.indexOf('?');
        if (idx >= 0)
        {
            // match only non-query part
            return _pattern.matcher(path.substring(0, idx));
        }
        else
        {
            // match entire path
            return _pattern.matcher(path);
        }
    }

    @Override
    public int getSpecLength()
    {
        return _specLength;
    }

    @Override
    public PathSpecGroup getGroup()
    {
        return _group;
    }

    @Override
    public int getPathDepth()
    {
        return _pathDepth;
    }

    @Override
    public String getPathInfo(String path)
    {
        // Path Info only valid for PREFIX_GLOB types
        if (_group == PathSpecGroup.PREFIX_GLOB)
        {
            Matcher matcher = getMatcher(path);
            if (matcher.matches())
            {
                if (matcher.groupCount() >= 1)
                {
                    String pathInfo = matcher.group(1);
                    if ("".equals(pathInfo))
                        return "/";
                    else
                        return pathInfo;
                }
            }
        }
        return null;
    }

    @Override
    public String getPathMatch(String path)
    {
        Matcher matcher = getMatcher(path);
        if (matcher.matches())
        {
            if (_group == PathSpecGroup.PREFIX_GLOB && matcher.groupCount() >= 1)
            {
                int idx = matcher.start(1);
                if (idx > 0)
                {
                    if (path.charAt(idx - 1) == '/')
                        idx--;
                    return path.substring(0, idx);
                }
            }
            return path;
        }
        return null;
    }

    @Override
    public String getDeclaration()
    {
        return _declaration;
    }

    @Override
    public String getPrefix()
    {
        return null;
    }

    @Override
    public String getSuffix()
    {
        return null;
    }

    public Pattern getPattern()
    {
        return _pattern;
    }

    @Override
    public boolean matches(final String path)
    {
        return getMatcher(path).matches();
    }

    @Override
    public MatchedPath matched(String path)
    {
        Matcher matcher = getMatcher(path);
        if (matcher.matches())
        {
            return new RegexMatchedPath(this, path, matcher);
        }
        return null;
    }

    private class RegexMatchedPath implements MatchedPath
    {
        private final RegexPathSpec pathSpec;
        private final String path;
        private final Matcher matcher;

        public RegexMatchedPath(RegexPathSpec regexPathSpec, String path, Matcher matcher)
        {
            this.pathSpec = regexPathSpec;
            this.path = path;
            this.matcher = matcher;
        }

        @Override
        public String getPathMatch()
        {
            try
            {
                String p = matcher.group("name");
                if (p != null)
                {
                    return p;
                }
            }
            catch (IllegalArgumentException ignore)
            {
                // ignore if group name not found.
            }

            if (pathSpec.getGroup() == PathSpecGroup.PREFIX_GLOB && matcher.groupCount() >= 1)
            {
                int idx = matcher.start(1);
                if (idx > 0)
                {
                    if (this.path.charAt(idx - 1) == '/')
                        idx--;
                    return this.path.substring(0, idx);
                }
            }

            // default is the full path
            return this.path;
        }

        @Override
        public String getPathInfo()
        {
            try
            {
                String p = matcher.group("info");
                if (p != null)
                {
                    return p;
                }
            }
            catch (IllegalArgumentException ignore)
            {
                // ignore if group info not found.
            }

            // Path Info only valid for PREFIX_GLOB
            if (pathSpec.getGroup() == PathSpecGroup.PREFIX_GLOB && matcher.groupCount() >= 1)
            {
                String pathInfo = matcher.group(1);
                if ("".equals(pathInfo))
                    return "/";
                else
                    return pathInfo;
            }

            // default is null
            return null;
        }

        @Override
        public String toString()
        {
            return getClass().getSimpleName() + "[" +
                "pathSpec=" + pathSpec +
                ", path=\"" + path + "\"" +
                ", matcher=" + matcher +
                ']';
        }
    }
}