/* ###
 * IP: GHIDRA
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package pdb.symbolserver;

import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URI;
import java.net.http.HttpRequest;
import java.net.http.HttpRequest.BodyPublishers;
import java.net.http.HttpResponse;
import java.net.http.HttpResponse.BodyHandlers;
import java.time.Duration;

import ghidra.net.HttpClients;
import ghidra.util.Msg;
import ghidra.util.task.TaskMonitor;

/**
 * A {@link SymbolServer} that is accessed via HTTP.
 * <p>
 * 
 */
public class HttpSymbolServer extends AbstractSymbolServer {
	private static final String GHIDRA_USER_AGENT = "Ghidra_HttpSymbolServer_client";
	private static final int HTTP_STATUS_OK = HttpURLConnection.HTTP_OK;
	private static final int HTTP_REQUEST_TIMEOUT_MS = 10000; // 10 seconds
	
	/**
	 * Predicate that tests if the location string is an instance of a HttpSymbolServer location.
	 * 
	 * @param locationString symbol server location string
	 * @return boolean true if the string should be handled by the HttpSymbolServer class 
	 */
	public static boolean isHttpSymbolServerLocation(String locationString) {
		return locationString.startsWith("http://") || locationString.startsWith("https://");
	}
	
	private final URI serverURI;

	/**
	 * Creates a new instance of a HttpSymbolServer.
	 * 
	 * @param serverURI URI / URL of the symbol server 
	 */
	public HttpSymbolServer(URI serverURI) {
		String path = serverURI.getPath();
		this.serverURI =
			path.endsWith("/") ? serverURI : serverURI.resolve(serverURI.getPath() + "/");
	}

	@Override
	public String getName() {
		return serverURI.toString();
	}

	@Override
	public boolean isValid(TaskMonitor monitor) {
		// NOTE: checking a http symbolserver's state by testing the
		// existence of a file is not 100% universally correct, as different
		// webserver implementations will handle this differently, but
		// no better options are apparent.
		// Just getting any HTTP response, including a 404 not found, isn't a
		// good indication that the symbol server is valid as it could be
		// a missing subtree of a parent web site.
		return exists("", monitor) || exists(PINGME_FILENAME, monitor);
	}

	private HttpRequest.Builder request(String str) {
		return HttpRequest.newBuilder(serverURI.resolve(str))
				.timeout(Duration.ofMillis(HTTP_REQUEST_TIMEOUT_MS))
				.setHeader("User-Agent", GHIDRA_USER_AGENT);
	}

	@Override
	public boolean exists(String filename, TaskMonitor monitor) {
		try {
			HttpRequest request = request(filename).method("HEAD", BodyPublishers.noBody()).build();

			Msg.debug(this,
				logPrefix() + ": Checking exist for [" + filename + "]: " + request.toString());
			HttpResponse<Void> response =
				HttpClients.getHttpClient().send(request, BodyHandlers.discarding());
			int statusCode = response.statusCode();
			Msg.debug(this, logPrefix() + ": Response: " + response.statusCode());

			return statusCode == HTTP_STATUS_OK;
		}
		catch (InterruptedException | IOException e) {
			// ignore, return false
			return false;
		}
	}

	@Override
	public SymbolServerInputStream getFileStream(String filename, TaskMonitor monitor)
			throws IOException {
		try {
			HttpRequest request = request(filename).GET().build();
			Msg.debug(this,
				logPrefix() + ": Getting file [" + filename + "]: " + request.toString());
			HttpResponse<InputStream> response =
				HttpClients.getHttpClient().send(request, BodyHandlers.ofInputStream());
			int statusCode = response.statusCode();
			Msg.debug(this, logPrefix() + ": Http response: " + response.statusCode());
			if (statusCode == HTTP_STATUS_OK) {
				long contentLen = response.headers().firstValueAsLong("Content-Length").orElse(-1);
				return new SymbolServerInputStream(response.body(), contentLen);
			}
			throw new IOException("Unable to get file: " + statusCode);
		}
		catch (InterruptedException e) {
			throw new IOException("Http get interrupted");
		}
	}

	@Override
	public String getFileLocation(String filename) {
		return serverURI.resolve(filename).toString();
	}

	@Override
	public boolean isLocal() {
		return false;
	}

	@Override
	public String toString() {
		return String.format("HttpSymbolServer: [ url: %s, storageLevel: %d]", serverURI.toString(),
			storageLevel);
	}

	private String logPrefix() {
		return getClass().getSimpleName() + "[" + serverURI + "]";
	}

}