/*
 * 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;

import java.io.File;
import java.text.MessageFormat;
import java.util.LinkedList;
import java.util.List;

import javax.servlet.Filter;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.eclipse.jgit.http.server.glue.ErrorServlet;
import org.eclipse.jgit.http.server.glue.MetaFilter;
import org.eclipse.jgit.http.server.glue.RegexGroupFilter;
import org.eclipse.jgit.http.server.glue.ServletBinder;
import org.eclipse.jgit.http.server.resolver.AsIsFileService;
import org.eclipse.jgit.http.server.resolver.DefaultReceivePackFactory;
import org.eclipse.jgit.http.server.resolver.DefaultUploadPackFactory;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.transport.resolver.FileResolver;
import org.eclipse.jgit.transport.resolver.ReceivePackFactory;
import org.eclipse.jgit.transport.resolver.RepositoryResolver;
import org.eclipse.jgit.transport.resolver.UploadPackFactory;
import org.eclipse.jgit.util.StringUtils;

/**
 * Handles Git repository access over HTTP.
 * <p>
 * Applications embedding this filter should map a directory path within the
 * application to this filter. For a servlet version, see
 * {@link org.eclipse.jgit.http.server.GitServlet}.
 * <p>
 * Applications may wish to add additional repository action URLs to this
 * servlet by taking advantage of its extension from
 * {@link org.eclipse.jgit.http.server.glue.MetaFilter}. Callers may register
 * their own URL suffix translations through {@link #serve(String)}, or their
 * regex translations through {@link #serveRegex(String)}. Each translation
 * should contain a complete filter pipeline which ends with the HttpServlet
 * that should handle the requested action.
 */
public class GitFilter extends MetaFilter {
	private volatile boolean initialized;

	private RepositoryResolver<HttpServletRequest> resolver;

	private AsIsFileService asIs = new AsIsFileService();

	private UploadPackFactory<HttpServletRequest> uploadPackFactory = new DefaultUploadPackFactory();

	private UploadPackErrorHandler uploadPackErrorHandler;

	private ReceivePackFactory<HttpServletRequest> receivePackFactory = new DefaultReceivePackFactory();

	private ReceivePackErrorHandler receivePackErrorHandler;

	private final List<Filter> uploadPackFilters = new LinkedList<>();

	private final List<Filter> receivePackFilters = new LinkedList<>();

	/**
	 * New servlet that will load its base directory from {@code web.xml}.
	 * <p>
	 * The required parameter {@code base-path} must be configured to point to
	 * the local filesystem directory where all served Git repositories reside.
	 */
	public GitFilter() {
		// Initialized above by field declarations.
	}

	/**
	 * New servlet configured with a specific resolver.
	 *
	 * @param resolver
	 *            the resolver to use when matching URL to Git repository. If
	 *            null the {@code base-path} parameter will be looked for in the
	 *            parameter table during init, which usually comes from the
	 *            {@code web.xml} file of the web application.
	 */
	public void setRepositoryResolver(RepositoryResolver<HttpServletRequest> resolver) {
		assertNotInitialized();
		this.resolver = resolver;
	}

	/**
	 * Set AsIsFileService
	 *
	 * @param f
	 *            the filter to validate direct access to repository files
	 *            through a dumb client. If {@code null} then dumb client
	 *            support is completely disabled.
	 */
	public void setAsIsFileService(AsIsFileService f) {
		assertNotInitialized();
		this.asIs = f != null ? f : AsIsFileService.DISABLED;
	}

	/**
	 * Set upload-pack factory
	 *
	 * @param f
	 *            the factory to construct and configure an
	 *            {@link org.eclipse.jgit.transport.UploadPack} session when a
	 *            fetch or clone is requested by a client.
	 */
	@SuppressWarnings("unchecked")
	public void setUploadPackFactory(UploadPackFactory<HttpServletRequest> f) {
		assertNotInitialized();
		this.uploadPackFactory = f != null ? f : (UploadPackFactory<HttpServletRequest>)UploadPackFactory.DISABLED;
	}

	/**
	 * Set a custom error handler for git-upload-pack.
	 *
	 * @param h
	 *            A custom error handler for git-upload-pack.
	 */
	public void setUploadPackErrorHandler(UploadPackErrorHandler h) {
		assertNotInitialized();
		this.uploadPackErrorHandler = h;
	}

	/**
	 * Add upload-pack filter
	 *
	 * @param filter
	 *            filter to apply before any of the UploadPack operations. The
	 *            UploadPack instance is available in the request attribute
	 *            {@link org.eclipse.jgit.http.server.ServletUtils#ATTRIBUTE_HANDLER}.
	 */
	public void addUploadPackFilter(Filter filter) {
		assertNotInitialized();
		uploadPackFilters.add(filter);
	}

	/**
	 * Set the receive-pack factory
	 *
	 * @param f
	 *            the factory to construct and configure a
	 *            {@link org.eclipse.jgit.transport.ReceivePack} session when a
	 *            push is requested by a client.
	 */
	@SuppressWarnings("unchecked")
	public void setReceivePackFactory(ReceivePackFactory<HttpServletRequest> f) {
		assertNotInitialized();
		this.receivePackFactory = f != null ? f : (ReceivePackFactory<HttpServletRequest>)ReceivePackFactory.DISABLED;
	}

	/**
	 * Set a custom error handler for git-receive-pack.
	 *
	 * @param h
	 *            A custom error handler for git-receive-pack.
	 */
	public void setReceivePackErrorHandler(ReceivePackErrorHandler h) {
		assertNotInitialized();
		this.receivePackErrorHandler = h;
	}

	/**
	 * Add receive-pack filter
	 *
	 * @param filter
	 *            filter to apply before any of the ReceivePack operations. The
	 *            ReceivePack instance is available in the request attribute
	 *            {@link org.eclipse.jgit.http.server.ServletUtils#ATTRIBUTE_HANDLER}.
	 */
	public void addReceivePackFilter(Filter filter) {
		assertNotInitialized();
		receivePackFilters.add(filter);
	}

	private void assertNotInitialized() {
		if (initialized)
			throw new IllegalStateException(HttpServerText.get().alreadyInitializedByContainer);
	}

	/** {@inheritDoc} */
	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		super.init(filterConfig);

		if (resolver == null) {
			File root = getFile(filterConfig, "base-path");
			boolean exportAll = getBoolean(filterConfig, "export-all");
			setRepositoryResolver(new FileResolver<>(root, exportAll));
		}

		initialized = true;

		if (uploadPackFactory != UploadPackFactory.DISABLED) {
			ServletBinder b = serve("*/" + GitSmartHttpTools.UPLOAD_PACK);
			b = b.through(new UploadPackServlet.Factory(uploadPackFactory));
			for (Filter f : uploadPackFilters)
				b = b.through(f);
			b.with(new UploadPackServlet(uploadPackErrorHandler));
		}

		if (receivePackFactory != ReceivePackFactory.DISABLED) {
			ServletBinder b = serve("*/" + GitSmartHttpTools.RECEIVE_PACK);
			b = b.through(new ReceivePackServlet.Factory(receivePackFactory));
			for (Filter f : receivePackFilters)
				b = b.through(f);
			b.with(new ReceivePackServlet(receivePackErrorHandler));
		}

		ServletBinder refs = serve("*/" + Constants.INFO_REFS);
		if (uploadPackFactory != UploadPackFactory.DISABLED) {
			refs = refs.through(new UploadPackServlet.InfoRefs(
					uploadPackFactory, uploadPackFilters));
		}
		if (receivePackFactory != ReceivePackFactory.DISABLED) {
			refs = refs.through(new ReceivePackServlet.InfoRefs(
					receivePackFactory, receivePackFilters));
		}
		if (asIs != AsIsFileService.DISABLED) {
			refs = refs.through(new IsLocalFilter());
			refs = refs.through(new AsIsFileFilter(asIs));
			refs.with(new InfoRefsServlet());
		} else
			refs.with(new ErrorServlet(HttpServletResponse.SC_NOT_ACCEPTABLE));

		if (asIs != AsIsFileService.DISABLED) {
			final IsLocalFilter mustBeLocal = new IsLocalFilter();
			final AsIsFileFilter enabled = new AsIsFileFilter(asIs);

			serve("*/" + Constants.HEAD)//
					.through(mustBeLocal)//
					.through(enabled)//
					.with(new TextFileServlet(Constants.HEAD));

			final String info_alternates = Constants.OBJECTS + "/" + Constants.INFO_ALTERNATES;
			serve("*/" + info_alternates)//
					.through(mustBeLocal)//
					.through(enabled)//
					.with(new TextFileServlet(info_alternates));

			final String http_alternates = Constants.OBJECTS + "/" + Constants.INFO_HTTP_ALTERNATES;
			serve("*/" + http_alternates)//
					.through(mustBeLocal)//
					.through(enabled)//
					.with(new TextFileServlet(http_alternates));

			serve("*/objects/info/packs")//
					.through(mustBeLocal)//
					.through(enabled)//
					.with(new InfoPacksServlet());

			serveRegex("^/(.*)/objects/([0-9a-f]{2}/[0-9a-f]{38})$")//
					.through(mustBeLocal)//
					.through(enabled)//
					.through(new RegexGroupFilter(2))//
					.with(new ObjectFileServlet.Loose());

			serveRegex("^/(.*)/objects/(pack/pack-[0-9a-f]{40}\\.pack)$")//
					.through(mustBeLocal)//
					.through(enabled)//
					.through(new RegexGroupFilter(2))//
					.with(new ObjectFileServlet.Pack());

			serveRegex("^/(.*)/objects/(pack/pack-[0-9a-f]{40}\\.idx)$")//
					.through(mustBeLocal)//
					.through(enabled)//
					.through(new RegexGroupFilter(2))//
					.with(new ObjectFileServlet.PackIdx());
		}
	}

	private static File getFile(FilterConfig cfg, String param)
			throws ServletException {
		String n = cfg.getInitParameter(param);
		if (n == null || "".equals(n))
			throw new ServletException(MessageFormat.format(HttpServerText.get().parameterNotSet, param));

		File path = new File(n);
		if (!path.exists())
			throw new ServletException(MessageFormat.format(HttpServerText.get().pathForParamNotFound, path, param));
		return path;
	}

	private static boolean getBoolean(FilterConfig cfg, String param)
			throws ServletException {
		String n = cfg.getInitParameter(param);
		if (n == null)
			return false;
		try {
			return StringUtils.toBoolean(n);
		} catch (IllegalArgumentException err) {
			throw new ServletException(MessageFormat.format(
					HttpServerText.get().invalidBoolean, param, n), err);
		}
	}

	/** {@inheritDoc} */
	@Override
	protected ServletBinder register(ServletBinder binder) {
		if (resolver == null)
			throw new IllegalStateException(HttpServerText.get().noResolverAvailable);
		binder = binder.through(new NoCacheFilter());
		binder = binder.through(new RepositoryFilter(resolver));
		return binder;
	}
}