/*
    * Copyright (C) 2009-2010, Google Inc. and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
    * SPDX-License-Identifier: BSD-3-Clause
    */
  
  package org.eclipse.jgit.http.server.glue;
  
  import static javax.servlet.http.HttpServletResponse.SC_NOT_FOUND;
  import static org.eclipse.jgit.http.server.glue.MetaFilter.REGEX_GROUPS;
  
  import java.io.IOException;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  import javax.servlet.Filter;
  import javax.servlet.ServletException;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  /**
   * Selects requests by matching the URI against a regular expression.
   * <p>
   * The pattern is bound and matched against the path info of the servlet
   * request, as this class assumes it is invoked by {@link MetaServlet}.
   * <p>
   * If there are capture groups in the regular expression, the matched ranges of
   * the capture groups are stored as an array of modified HttpServetRequests,
   * into the request attribute {@link MetaFilter#REGEX_GROUPS}. Using a capture
   * group that may not capture, e.g. {@code "(/foo)?"}, will cause an error at
   * request handling time.
   * <p>
   * Each servlet request has been altered to have its {@code getServletPath()}
   * method return the original path info up to the beginning of the corresponding
   * capture group, and its {@code getPathInfo()} method return the matched text.
   * A {@link RegexGroupFilter} can be applied in the pipeline to switch the
   * current HttpServletRequest to reference a different capture group before
   * running additional filters, or the final servlet.
   * <p>
   * Note that for {@code getPathInfo()} to start with a leading "/" as described
   * in the servlet documentation, capture groups must actually capture the
   * leading "/".
   * <p>
   * This class dispatches the remainder of the pipeline using the first capture
   * group as the current request, making {@code RegexGroupFilter} required only
   * to access capture groups beyond the first.
   */
  class RegexPipeline extends UrlPipeline {
  	static class Binder extends ServletBinderImpl {
  		private final Pattern pattern;
  
  		Binder(String p) {
  			pattern = Pattern.compile(p);
  		}
  
  		Binder(Pattern p) {
  			pattern = p;
  		}
  
  		@Override
  		UrlPipeline create() {
  			return new RegexPipeline(pattern, getFilters(), getServlet());
  		}
  	}
  
  	private final Pattern pattern;
  
  	RegexPipeline(final Pattern pattern, final Filter[] filters,
  			final HttpServlet servlet) {
  		super(filters, servlet);
  		this.pattern = pattern;
  	}
  
  	@Override
  	boolean match(HttpServletRequest req) {
  		final String pathInfo = req.getPathInfo();
  		return pathInfo != null && pattern.matcher(pathInfo).matches();
  	}
  
  	@Override
  	void service(HttpServletRequest req, HttpServletResponse rsp)
  			throws ServletException, IOException {
  		final String reqInfo = req.getPathInfo();
  		if (reqInfo == null) {
  			rsp.sendError(SC_NOT_FOUND);
  			return;
  		}
  
  		final Matcher cur = pattern.matcher(reqInfo);
  		if (!cur.matches()) {
  			rsp.sendError(SC_NOT_FOUND);
  			return;
  		}
  
 		final String reqPath = req.getServletPath();
 		final Object old = req.getAttribute(REGEX_GROUPS);
 		try {
 			if (1 <= cur.groupCount()) {
 				// If there are groups extract every capture group and
 				// build a request for them so RegexGroupFilter can pick
 				// a different capture group later. Continue using the
 				// first capture group as the path info.
 				WrappedRequest[] groups = new WrappedRequest[cur.groupCount()];
 				for (int groupId = 1; groupId <= cur.groupCount(); groupId++) {
 					final int s = cur.start(groupId);
 					final String path, info;
 
 					path = reqPath + reqInfo.substring(0, s);
 					info = cur.group(groupId);
 					groups[groupId - 1] = new WrappedRequest(req, path, info);
 				}
 				req.setAttribute(REGEX_GROUPS, groups);
 				super.service(groups[0], rsp);
 
 			} else {
 				// No capture groups were present, service the whole request.
 				final String path = reqPath + reqInfo;
 				final String info = null;
 				super.service(new WrappedRequest(req, path, info), rsp);
 			}
 		} finally {
 			if (old != null)
 				req.setAttribute(REGEX_GROUPS, old);
 			else
 				req.removeAttribute(REGEX_GROUPS);
 		}
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public String toString() {
 		return "Pipeline[regex: " + pattern + " ]";
 	}
 }