//License: GPL. See README for details.
package org.openstreetmap.josm.io;

import static org.openstreetmap.josm.tools.I18n.tr;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StringReader;
import java.io.StringWriter;
import java.net.ConnectException;
import java.net.HttpURLConnection;
import java.net.SocketTimeoutException;
import java.net.URL;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Properties;

import javax.xml.parsers.SAXParserFactory;

import org.openstreetmap.josm.Main;
import org.openstreetmap.josm.data.osm.Changeset;
import org.openstreetmap.josm.data.osm.OsmPrimitive;
import org.openstreetmap.josm.data.osm.OsmPrimitiveType;
import org.openstreetmap.josm.data.osm.visitor.CreateOsmChangeVisitor;
import org.openstreetmap.josm.gui.progress.ProgressMonitor;
import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

/**
 * Class that encapsulates the communications with the OSM API.
 *
 * All interaction with the server-side OSM API should go through this class.
 *
 * It is conceivable to extract this into an interface later and create various
 * classes implementing the interface, to be able to talk to various kinds of servers.
 *
 */
public class OsmApi extends OsmConnection {
    /** max number of retries to send a request in case of HTTP 500 errors or timeouts */
    static public final int DEFAULT_MAX_NUM_RETRIES = 5;

    /** the collection of instantiated OSM APIs */
    private static HashMap<String, OsmApi> instances = new HashMap<String, OsmApi>();

    /**
     * replies the {@see OsmApi} for a given server URL
     *
     * @param serverUrl  the server URL
     * @return the OsmApi
     * @throws IllegalArgumentException thrown, if serverUrl is null
     *
     */
    static public OsmApi getOsmApi(String serverUrl) {
        OsmApi api = instances.get(serverUrl);
        if (api == null) {
            api = new OsmApi(serverUrl);
            instances.put(serverUrl,api);
        }
        return api;
    }
    /**
     * replies the {@see OsmApi} for the URL given by the preference <code>osm-server.url</code>
     *
     * @return the OsmApi
     * @exception IllegalStateException thrown, if the preference <code>osm-server.url</code> is not set
     *
     */
    static public OsmApi getOsmApi() {
        String serverUrl = Main.pref.get("osm-server.url", "http://api.openstreetmap.org/api");
        if (serverUrl == null)
            throw new IllegalStateException(tr("preference ''{0}'' missing. Can't initialize OsmApi", "osm-server.url"));
        return getOsmApi(serverUrl);
    }

    /** the server URL */
    private String serverUrl;

    /**
     * Object describing current changeset
     */
    private Changeset changeset;

    /**
     * API version used for server communications
     */
    private String version = null;

    /** the api capabilities */
    private Capabilities capabilities = new Capabilities();

    /**
     * true if successfully initialized
     */
    private boolean initialized = false;

    private StringWriter swriter = new StringWriter();
    private OsmWriter osmWriter = new OsmWriter(new PrintWriter(swriter), true, null);

    /**
     * A parser for the "capabilities" response XML
     */
    private class CapabilitiesParser extends DefaultHandler {
        @Override
        public void startDocument() throws SAXException {
            capabilities.clear();
        }

        @Override public void startElement(String namespaceURI, String localName, String qName, Attributes atts) throws SAXException {
            for (int i=0; i< qName.length(); i++) {
                capabilities.put(qName, atts.getQName(i), atts.getValue(i));
            }
        }
    }

    /**
     * creates an OSM api for a specific server URL
     *
     * @param serverUrl the server URL. Must not be null
     * @exception IllegalArgumentException thrown, if serverUrl is null
     */
    protected OsmApi(String serverUrl)  {
        if (serverUrl == null)
            throw new IllegalArgumentException(tr("parameter '{0}' must not be null", "serverUrl"));
        this.serverUrl = serverUrl;
    }

    /**
     * Returns the OSM protocol version we use to talk to the server.
     * @return protocol version, or null if not yet negotiated.
     */
    public String getVersion() {
        return version;
    }

    /**
     * Returns true if the negotiated version supports changesets.
     * @return true if the negotiated version supports changesets.
     */
    public boolean hasChangesetSupport() {
        return ((version != null) && (version.compareTo("0.6")>=0));
    }

    /**
     * Initializes this component by negotiating a protocol version with the server.
     *
     * @exception OsmApiInitializationException thrown, if an exception occurs
     */
    public void initialize() throws OsmApiInitializationException {
        if (initialized)
            return;
        initAuthentication();
        try {
            String s = sendRequest("GET", "capabilities", null);
            InputSource inputSource = new InputSource(new StringReader(s));
            SAXParserFactory.newInstance().newSAXParser().parse(inputSource, new CapabilitiesParser());
            if (capabilities.supportsVersion("0.6")) {
                version = "0.6";
            } else if (capabilities.supportsVersion("0.5")) {
                version = "0.5";
            } else {
                System.err.println(tr("This version of JOSM is incompatible with the configured server."));
                System.err.println(tr("It supports protocol versions 0.5 and 0.6, while the server says it supports {0} to {1}.",
                        capabilities.get("version", "minimum"), capabilities.get("version", "maximum")));
                initialized = false;
            }
            System.out.println(tr("Communications with {0} established using protocol version {1}",
                    serverUrl,
                    version));
            osmWriter.setVersion(version);
            initialized = true;
        } catch (Exception ex) {
            initialized = false;
            throw new OsmApiInitializationException(ex);
        }
    }

    /**
     * Makes an XML string from an OSM primitive. Uses the OsmWriter class.
     * @param o the OSM primitive
     * @param addBody true to generate the full XML, false to only generate the encapsulating tag
     * @return XML string
     */
    private String toXml(OsmPrimitive o, boolean addBody) {
        swriter.getBuffer().setLength(0);
        osmWriter.setWithBody(addBody);
        osmWriter.setChangeset(changeset);
        osmWriter.header();
        o.visit(osmWriter);
        osmWriter.footer();
        osmWriter.out.flush();
        return swriter.toString();
    }

    /**
     * Returns the base URL for API requests, including the negotiated version number.
     * @return base URL string
     */
    public String getBaseUrl() {
        StringBuffer rv = new StringBuffer(serverUrl);
        if (version != null) {
            rv.append("/");
            rv.append(version);
        }
        rv.append("/");
        // this works around a ruby (or lighttpd) bug where two consecutive slashes in
        // an URL will cause a "404 not found" response.
        int p; while ((p = rv.indexOf("//", 6)) > -1) { rv.delete(p, p + 1); }
        return rv.toString();
    }

    /**
     * Creates an OSM primitive on the server. The OsmPrimitive object passed in
     * is modified by giving it the server-assigned id.
     *
     * @param osm the primitive
     * @throws OsmTransferException if something goes wrong
     */
    public void createPrimitive(OsmPrimitive osm) throws OsmTransferException {
        initialize();
        String ret = "";
        try {
            ret = sendRequest("PUT", OsmPrimitiveType.from(osm).getAPIName()+"/create", toXml(osm, true));
            osm.id = Long.parseLong(ret.trim());
            osm.version = 1;
        } catch(NumberFormatException e){
            throw new OsmTransferException(tr("unexpected format of id replied by the server, got ''{0}''", ret));
        }
    }

    /**
     * Modifies an OSM primitive on the server. For protocols greater than 0.5,
     * the OsmPrimitive object passed in is modified by giving it the server-assigned
     * version.
     *
     * @param osm the primitive
     * @throws OsmTransferException if something goes wrong
     */
    public void modifyPrimitive(OsmPrimitive osm) throws OsmTransferException {
        initialize();
        if (version.equals("0.5")) {
            // legacy mode does not return the new object version.
            sendRequest("PUT", OsmPrimitiveType.from(osm).getAPIName()+"/" + osm.id, toXml(osm, true));
        } else {
            String ret = null;
            // normal mode (0.6 and up) returns new object version.
            try {
                ret = sendRequest("PUT", OsmPrimitiveType.from(osm).getAPIName()+"/" + osm.id, toXml(osm, true));
                osm.version = Integer.parseInt(ret.trim());
            } catch(NumberFormatException e) {
                throw new OsmTransferException(tr("unexpected format of new version of modified primitive ''{0}'', got ''{1}''", osm.id, ret));
            }
        }
    }

    /**
     * Deletes an OSM primitive on the server.
     * @param osm the primitive
     * @throws OsmTransferException if something goes wrong
     */
    public void deletePrimitive(OsmPrimitive osm) throws OsmTransferException {
        initialize();
        // legacy mode does not require payload. normal mode (0.6 and up) requires payload for version matching.
        sendRequest("DELETE", OsmPrimitiveType.from(osm).getAPIName()+"/" + osm.id, version.equals("0.5") ? null : toXml(osm, false));
    }

    /**
     * Creates a new changeset on the server to use for subsequent calls.
     * @param comment the "commit comment" for the new changeset
     * @throws OsmTransferException signifying a non-200 return code, or connection errors
     */
    public void createChangeset(String comment, ProgressMonitor progressMonitor) throws OsmTransferException {
        progressMonitor.beginTask((tr("Opening changeset...")));
        try {
            changeset = new Changeset();
            Properties sysProp = System.getProperties();
            Object ua = sysProp.get("http.agent");
            changeset.put("created_by", (ua == null) ? "JOSM" : ua.toString());
            changeset.put("comment", comment);
            createPrimitive(changeset);
        } finally {
            progressMonitor.finishTask();
        }
    }

    /**
     * Closes a changeset on the server.
     *
     * @throws OsmTransferException if something goes wrong.
     */
    public void stopChangeset(ProgressMonitor progressMonitor) throws OsmTransferException {
        progressMonitor.beginTask(tr("Closing changeset..."));
        try {
            initialize();
            sendRequest("PUT", "changeset" + "/" + changeset.id + "/close", null);
            changeset = null;
        } finally {
            progressMonitor.finishTask();
        }
    }

    /**
     * Uploads a list of changes in "diff" form to the server.
     *
     * @param list the list of changed OSM Primitives
     * @return list of processed primitives
     * @throws OsmTransferException if something is wrong
     */
    public Collection<OsmPrimitive> uploadDiff(final Collection<OsmPrimitive> list, ProgressMonitor progressMonitor) throws OsmTransferException {

        progressMonitor.beginTask("", list.size() * 2);
        try {
            if (changeset == null)
                throw new OsmTransferException(tr("No changeset present for diff upload"));

            initialize();
            final ArrayList<OsmPrimitive> processed = new ArrayList<OsmPrimitive>();

            CreateOsmChangeVisitor duv = new CreateOsmChangeVisitor(changeset, OsmApi.this);

            progressMonitor.subTask(tr("Preparing..."));
            for (OsmPrimitive osm : list) {
                osm.visit(duv);
                progressMonitor.worked(1);
            }
            progressMonitor.indeterminateSubTask(tr("Uploading..."));

            String diff = duv.getDocument();
            try {
                String diffresult = sendRequest("POST", "changeset/" + changeset.id + "/upload", diff);
                DiffResultReader.parseDiffResult(diffresult, list, processed, duv.getNewIdMap(),
                        progressMonitor.createSubTaskMonitor(ProgressMonitor.ALL_TICKS, false));
            } catch(OsmTransferException e) {
                throw e;
            } catch(Exception e) {
                throw new OsmTransferException(e);
            }

            return processed;
        } finally {
            progressMonitor.finishTask();
        }
    }



    private void sleepAndListen() throws OsmTransferCancelledException {
        System.out.print(tr("Waiting 10 seconds ... "));
        for(int i=0; i < 10; i++) {
            if (cancel || isAuthCancelled())
                throw new OsmTransferCancelledException();
            try {
                Thread.sleep(1000);
            } catch (InterruptedException ex) {}
        }
        System.out.println(tr("OK - trying again."));
    }

    /**
     * Replies the max. number of retries in case of 5XX errors on the server
     * 
     * @return the max number of retries
     */
    protected int getMaxRetries() {
        int ret = Main.pref.getInteger("osm-server.max-num-retries", DEFAULT_MAX_NUM_RETRIES);
        return Math.max(ret,0);
    }

    /**
     * Generic method for sending requests to the OSM API.
     *
     * This method will automatically re-try any requests that are answered with a 5xx
     * error code, or that resulted in a timeout exception from the TCP layer.
     *
     * @param requestMethod The http method used when talking with the server.
     * @param urlSuffix The suffix to add at the server url, not including the version number,
     *    but including any object ids (e.g. "/way/1234/history").
     * @param requestBody the body of the HTTP request, if any.
     *
     * @return the body of the HTTP response, if and only if the response code was "200 OK".
     * @exception OsmTransferException if the HTTP return code was not 200 (and retries have
     *    been exhausted), or rewrapping a Java exception.
     */
    private String sendRequest(String requestMethod, String urlSuffix,
            String requestBody) throws OsmTransferException {

        StringBuffer responseBody = new StringBuffer();

        int retries = getMaxRetries();

        while(true) { // the retry loop
            try {
                URL url = new URL(new URL(getBaseUrl()), urlSuffix, new MyHttpHandler());
                System.out.print(requestMethod + " " + url + "... ");
                activeConnection = (HttpURLConnection)url.openConnection();
                activeConnection.setConnectTimeout(15000);
                activeConnection.setRequestMethod(requestMethod);
                addAuth(activeConnection);

                if (requestMethod.equals("PUT") || requestMethod.equals("POST") || requestMethod.equals("DELETE")) {
                    activeConnection.setDoOutput(true);
                    activeConnection.setRequestProperty("Content-type", "text/xml");
                    OutputStream out = activeConnection.getOutputStream();

                    // It seems that certain bits of the Ruby API are very unhappy upon
                    // receipt of a PUT/POST message withtout a Content-length header,
                    // even if the request has no payload.
                    // Since Java will not generate a Content-length header unless
                    // we use the output stream, we create an output stream for PUT/POST
                    // even if there is no payload.
                    if (requestBody != null) {
                        BufferedWriter bwr = new BufferedWriter(new OutputStreamWriter(out, "UTF-8"));
                        bwr.write(requestBody);
                        bwr.flush();
                    }
                    out.close();
                }

                activeConnection.connect();
                System.out.println(activeConnection.getResponseMessage());
                int retCode = activeConnection.getResponseCode();

                if (retCode >= 500) {
                    if (retries-- > 0) {
                        sleepAndListen();
                        int maxRetries = getMaxRetries();
                        System.out.println(tr("Starting retry {0} of {1}.", maxRetries - retries,maxRetries));
                        continue;
                    }
                }

                // populate return fields.
                responseBody.setLength(0);

                // If the API returned an error code like 403 forbidden, getInputStream
                // will fail with an IOException.
                InputStream i = null;
                try {
                    i = activeConnection.getInputStream();
                } catch (IOException ioe) {
                    i = activeConnection.getErrorStream();
                }
                BufferedReader in = new BufferedReader(new InputStreamReader(i));

                String s;
                while((s = in.readLine()) != null) {
                    responseBody.append(s);
                    responseBody.append("\n");
                }
                String errorHeader = null;
                // Look for a detailed error message from the server
                if (activeConnection.getHeaderField("Error") != null) {
                    errorHeader = activeConnection.getHeaderField("Error");
                    System.err.println("Error header: " + errorHeader);
                } else if (retCode != 200 && responseBody.length()>0) {
                    System.err.println("Error body: " + responseBody);
                }
                activeConnection.disconnect();

                if (retCode != 200)
                    throw new OsmApiException(
                            retCode,
                            errorHeader == null? null : errorHeader.trim(),
                                    responseBody == null ? null : responseBody.toString().trim()
                    );

                return responseBody.toString();
            } catch (UnknownHostException e) {
                throw new OsmTransferException(e);
            } catch (SocketTimeoutException e) {
                if (retries-- > 0) {
                    continue;
                }
                throw new OsmTransferException(e);
            } catch (ConnectException e) {
                if (retries-- > 0) {
                    continue;
                }
                throw new OsmTransferException(e);
            } catch (Exception e) {
                if (e instanceof OsmTransferException) throw (OsmTransferException) e;
                throw new OsmTransferException(e);
            }
        }
    }

    /**
     * returns the API capabilities; null, if the API is not initialized yet
     *
     * @return the API capabilities
     */
    public Capabilities getCapabilities() {
        return capabilities;
    }
}