/*
 * Copyright (C) 2015, Sasa Zivkov <sasa.zivkov@sap.com>
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 * - Neither the name of the Eclipse Foundation, Inc. nor the
 *   names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior
 *   written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.eclipse.jgit.lfs.server;

import static java.nio.charset.StandardCharsets.UTF_8;
import static org.apache.http.HttpStatus.SC_FORBIDDEN;
import static org.apache.http.HttpStatus.SC_NOT_FOUND;
import static org.apache.http.HttpStatus.SC_OK;
import static org.apache.http.HttpStatus.SC_SERVICE_UNAVAILABLE;
import static org.apache.http.HttpStatus.SC_UNPROCESSABLE_ENTITY;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.Reader;
import java.io.Writer;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.eclipse.jgit.lfs.errors.LfsException;
import org.eclipse.jgit.lfs.errors.LfsRepositoryNotFound;
import org.eclipse.jgit.lfs.errors.LfsRepositoryReadOnly;
import org.eclipse.jgit.lfs.errors.LfsValidationError;

import com.google.gson.FieldNamingPolicy;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

/**
 * LFS protocol handler implementing the LFS batch API [1]
 *
 * [1] https://github.com/github/git-lfs/blob/master/docs/api/v1/http-v1-batch.md
 *
 * @since 4.3
 */
public abstract class LfsProtocolServlet extends HttpServlet {

	private static final long serialVersionUID = 1L;

	private static final String CONTENTTYPE_VND_GIT_LFS_JSON = "application/vnd.git-lfs+json"; //$NON-NLS-1$

	private Gson gson = createGson();

	/**
	 * Get the large file repository for the given request and path.
	 *
	 * @param request
	 *            the request
	 * @param path
	 *            the path
	 *
	 * @return the large file repository storing large files or null if the
	 *         request is not supported.
	 * @throws LfsException
	 * @since 4.5
	 */
	protected abstract LargeFileRepository getLargeFileRepository(
			LfsRequest request, String path) throws LfsException;

	/**
	 * LFS request.
	 *
	 * @since 4.5
	 */
	protected static class LfsRequest {
		private String operation;

		private List<LfsObject> objects;

		/**
		 * Get the LFS operation.
		 *
		 * @return the operation
		 */
		public String getOperation() {
			return operation;
		}

		/**
		 * Get the LFS objects.
		 *
		 * @return the objects
		 */
		public List<LfsObject> getObjects() {
			return objects;
		}
	}

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse res)
			throws ServletException, IOException {
		Writer w = new BufferedWriter(
				new OutputStreamWriter(res.getOutputStream(), UTF_8));

		Reader r = new BufferedReader(new InputStreamReader(req.getInputStream(), UTF_8));
		LfsRequest request = gson.fromJson(r, LfsRequest.class);
		String path = req.getPathInfo();

		LargeFileRepository repo = null;
		try {
			repo = getLargeFileRepository(request, path);
		} catch (LfsValidationError e) {
			sendError(res, SC_UNPROCESSABLE_ENTITY, e.getMessage());
			return;
		} catch (LfsRepositoryNotFound e) {
			sendError(res, SC_NOT_FOUND, e.getMessage());
			return;
		} catch (LfsRepositoryReadOnly e) {
			sendError(res, SC_FORBIDDEN, e.getMessage());
			return;
		} catch (LfsException e) {
			sendError(res, SC_SERVICE_UNAVAILABLE, e.getMessage());
			return;
		}
		if (repo == null) {
			res.setStatus(SC_SERVICE_UNAVAILABLE);
			return;
		}

		res.setStatus(SC_OK);
		res.setContentType(CONTENTTYPE_VND_GIT_LFS_JSON);
		TransferHandler handler = TransferHandler
				.forOperation(request.operation, repo, request.objects);
		gson.toJson(handler.process(), w);
		w.flush();
	}

	static class Error {
		String message;

		Error(String m) {
			this.message = m;
		}
	}

	private void sendError(HttpServletResponse rsp, int status, String message)
			throws IOException {
		rsp.setStatus(status);
		PrintWriter writer = rsp.getWriter();
		gson.toJson(new Error(message), writer);
		writer.flush();
		writer.close();
		rsp.flushBuffer();
	}

	private Gson createGson() {
		GsonBuilder gb = new GsonBuilder()
				.setFieldNamingPolicy(
						FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES)
				.setPrettyPrinting().disableHtmlEscaping();
		return gb.create();
	}
}