package com.nimbusds.oauth2.sdk.http;


import java.io.*;
import java.net.*;
import java.util.Enumeration;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;

import net.jcip.annotations.ThreadSafe;

import net.minidev.json.JSONObject;

import com.nimbusds.oauth2.sdk.ParseException;
import com.nimbusds.oauth2.sdk.util.JSONObjectUtils;
import com.nimbusds.oauth2.sdk.util.URLUtils;


/**
 * HTTP request with support for the parameters required to construct an 
 * {@link com.nimbusds.oauth2.sdk.Request OAuth 2.0 request message}.
 *
 * <p>Supported HTTP methods:
 *
 * <ul>
 *     <li>{@link Method#GET HTTP GET}
 *     <li>{@link Method#POST HTTP POST}
 *     <li>{@link Method#POST HTTP PUT}
 *     <li>{@link Method#POST HTTP DELETE}
 * </ul>
 *
 * <p>Supported request headers:
 *
 * <ul>
 *     <li>Content-Type
 *     <li>Authorization
 *     <li>Accept
 *     <li>Etc.
 * </ul>
 *
 * <p>Supported timeouts:
 *
 * <ul>
 *     <li>On HTTP connect
 *     <li>On HTTP response read
 * </ul>
 */
@ThreadSafe
public class HTTPRequest extends HTTPMessage {


        /**
         * Enumeration of the HTTP methods used in OAuth 2.0 requests.
         */
        public static enum Method {
        
                /**
                 * HTTP GET.
                 */
                GET,
                
                
                /**
                 * HTTP POST.
                 */
                POST,
                
                
                /**
                 * HTTP PUT.
                 */
                PUT,
                
                
                /**
                 * HTTP DELETE.
                 */
                DELETE
        }
        
        
        /**
         * The request method.
         */
        private final Method method;


        /**
         * The request URL.
         */
        private final URL url;
        
        
        /**
         * The query string / post body.
         */
        private String query = null;


        /**
         * The HTTP connect timeout, in milliseconds. Zero implies none.
         */
        private int connectTimeout = 0;


        /**
         * The HTTP response read timeout, in milliseconds. Zero implies none.

         */
        private int readTimeout = 0;
        
        
        /**
         * Creates a new minimally specified HTTP request.
         *
         * @param method The HTTP request method. Must not be {@code null}.
         * @param url    The HTTP request URL. Must not be {@code null}.
         */
        public HTTPRequest(final Method method, final URL url) {
        
                if (method == null)
                        throw new IllegalArgumentException("The HTTP method must not be null");
                
                this.method = method;


                if (url == null)
                        throw new IllegalArgumentException("The HTTP URL must not be null");

                this.url = url;
        }


        /**
         * Reconstructs the request URL string for the specified servlet
         * request. The host part is always the local IP address. The query
         * string and fragment is always omitted.
         *
         * @param request The servlet request. Must not be {@code null}.
         *
         * @return The reconstructed request URL string.
         */
        private static String reconstructRequestURLString(final HttpServletRequest request) {

                StringBuilder sb = new StringBuilder("http");

                if (request.isSecure())
                        sb.append('s');

                sb.append("://");

                String localAddress = request.getLocalAddr();

                if (localAddress.contains(".")) {
                        // IPv3 address
                        sb.append(localAddress);
                } else if (localAddress.contains(":")) {
                        // IPv6 address, see RFC 2732
                        sb.append('[');
                        sb.append(localAddress);
                        sb.append(']');
                } else {
                        // Don't know what to do
                }

                if (! request.isSecure() && request.getLocalPort() != 80) {
                        // HTTP plain at port other than 80
                        sb.append(':');
                        sb.append(request.getLocalPort());
                }

                if (request.isSecure() && request.getLocalPort() != 443) {
                        // HTTPS at port other than 443 (default TLS)
                        sb.append(':');
                        sb.append(request.getLocalPort());
                }

                String path = request.getRequestURI();

                if (path != null)
                        sb.append(path);

                return sb.toString();
        }
        
        
        /**
         * Creates a new HTTP request from the specified HTTP servlet request.
         *
         * @param sr The servlet request. Must not be {@code null}.
         *
         * @throws IllegalArgumentException The the servlet request method is
         *                                  not GET, POST, PUT or DELETE or the
         *                                  content type header value couldn't
         *                                  be parsed.
         * @throws IOException              For a POST or PUT body that
         *                                  couldn't be read due to an I/O
         *                                  exception.
         */
        public HTTPRequest(final HttpServletRequest sr)
                throws IOException {

                this(sr, -1);
        }

        /**
         * Creates a new HTTP request from the specified HTTP servlet request.
         *
         * @param sr              The servlet request. Must not be
         *                        {@code null}.
         * @param maxEntityLength The maximum entity length to accept, -1 for
         *                        no limit.
         *
         * @throws IllegalArgumentException The the servlet request method is
         *                                  not GET, POST, PUT or DELETE or the
         *                                  content type header value couldn't
         *                                  be parsed.
         * @throws IOException              For a POST or PUT body that
         *                                  couldn't be read due to an I/O
         *                                  exception.
         */
        public HTTPRequest(final HttpServletRequest sr,
                           final long maxEntityLength)
                throws IOException {
        
                method = HTTPRequest.Method.valueOf(sr.getMethod().toUpperCase());

                String urlString = reconstructRequestURLString(sr);

                try {
                        url = new URL(urlString);

                } catch (MalformedURLException e) {

                        throw new IllegalArgumentException("Invalid request URL: " + e.getMessage() + ": " + urlString, e);
                }
                
                try {
                        setContentType(sr.getContentType());
                
                } catch (ParseException e) {
                        
                        throw new IllegalArgumentException("Invalid Content-Type header value: " + e.getMessage(), e);
                }
                
                Enumeration<String> headerNames = sr.getHeaderNames();

                while (headerNames.hasMoreElements()) {
                        final String headerName = headerNames.nextElement();
                        setHeader(headerName, sr.getHeader(headerName));
                }
                
                if (method.equals(Method.GET) || method.equals(Method.DELETE)) {
                
                        setQuery(sr.getQueryString());

                } else if (method.equals(Method.POST) || method.equals(Method.PUT)) {
                
                        // read body
                        StringBuilder body = new StringBuilder(256);

                        BufferedReader reader = sr.getReader();

                        char[] cbuf = new char[256];

                        int readChars;

                        while ((readChars = reader.read(cbuf)) != -1) {

                                body.append(cbuf, 0, readChars);

                                if (maxEntityLength > 0 && body.length() > maxEntityLength) {
                                        throw new IOException("Request entity body is too large, limit is " + maxEntityLength + " chars");
                                }
                        }
                        
                        reader.close();
                        
                        setQuery(body.toString());
                }
        }
        
        
        /**
         * Gets the request method.
         *
         * @return The request method.
         */
        public Method getMethod() {
        
                return method;
        }


        /**
         * Gets the request URL.
         *
         * @return The request URL.
         */
        public URL getURL() {

                return url;
        }
        
        
        /**
         * Ensures this HTTP request has the specified method.
         *
         * @param expectedMethod The expected method. Must not be {@code null}.
         *
         * @throws ParseException If the method doesn't match the expected.
         */
        public void ensureMethod(final Method expectedMethod)
                throws ParseException {
                
                if (method != expectedMethod)
                        throw new ParseException("The HTTP request method must be " + expectedMethod);
        }
        
        
        /**
         * Gets the {@code Authorization} header value.
         *
         * @return The {@code Authorization} header value, {@code null} if not 
         *         specified.
         */
        public String getAuthorization() {
        
                return getHeader("Authorization");
        }
        
        
        /**
         * Sets the {@code Authorization} header value.
         *
         * @param authz The {@code Authorization} header value, {@code null} if 
         *              not specified.
         */
        public void setAuthorization(final String authz) {
        
                setHeader("Authorization", authz);
        }


        /**
         * Gets the {@code Accept} header value.
         *
         * @return The {@code Accept} header value, {@code null} if not
         *         specified.
         */
        public String getAccept() {

                return getHeader("Accept");
        }


        /**
         * Sets the {@code Accept} header value.
         *
         * @param accept The {@code Accept} header value, {@code null} if not
         *               specified.
         */
        public void setAccept(final String accept) {

                setHeader("Accept", accept);
        }
        
        
        /**
         * Gets the raw (undecoded) query string if the request is HTTP GET or
         * the entity body if the request is HTTP POST.
         *
         * <p>Note that the '?' character preceding the query string in GET
         * requests is not included in the returned string.
         *
         * <p>Example query string (line breaks for clarity):
         *
         * <pre>
         * response_type=code
         * &amp;client_id=s6BhdRkqt3
         * &amp;state=xyz
         * &amp;redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb
         * </pre>
         *
         * @return For HTTP GET requests the URL query string, for HTTP POST 
         *         requests the body. {@code null} if not specified.
         */
        public String getQuery() {
        
                return query;
        }
        
        
        /**
         * Sets the raw (undecoded) query string if the request is HTTP GET or
         * the entity body if the request is HTTP POST.
         *
         * <p>Note that the '?' character preceding the query string in GET
         * requests must not be included.
         *
         * <p>Example query string (line breaks for clarity):
         *
         * <pre>
         * response_type=code
         * &amp;client_id=s6BhdRkqt3
         * &amp;state=xyz
         * &amp;redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb
         * </pre>
         *
         * @param query For HTTP GET requests the URL query string, for HTTP 
         *              POST requests the body. {@code null} if not specified.
         */
        public void setQuery(final String query) {
        
                this.query = query;
        }


        /**
         * Ensures this HTTP response has a specified query string or entity
         * body.
         *
         * @throws ParseException If the query string or entity body is missing
         *                        or empty.
         */
        private void ensureQuery()
                throws ParseException {
                
                if (query == null || query.trim().isEmpty())
                        throw new ParseException("Missing or empty HTTP query string / entity body");
        }
        
        
        /**
         * Gets the request query as a parameter map. The parameters are 
         * decoded according to {@code application/x-www-form-urlencoded}.
         *
         * @return The request query parameters, decoded. If none the map will
         *         be empty.
         */
        public Map<String,String> getQueryParameters() {
        
                return URLUtils.parseParameters(query);
        }


        /**
         * Gets the request query or entity body as a JSON Object.
         *
         * @return The request query or entity body as a JSON object.
         *
         * @throws ParseException If the Content-Type header isn't 
         *                        {@code application/json}, the request query
         *                        or entity body is {@code null}, empty or 
         *                        couldn't be parsed to a valid JSON object.
         */
        public JSONObject getQueryAsJSONObject()
                throws ParseException {

                ensureContentType(CommonContentTypes.APPLICATION_JSON);

                ensureQuery();

                return JSONObjectUtils.parseJSONObject(query);
        }


        /**
         * Gets the HTTP connect timeout.
         *
         * @return The HTTP connect read timeout, in milliseconds. Zero implies
         *         no timeout.
         */
        public int getConnectTimeout() {

                return connectTimeout;
        }


        /**
         * Sets the HTTP connect timeout.
         *
         * @param connectTimeout The HTTP connect timeout, in milliseconds.
         *                       Zero implies no timeout. Must not be negative.
         */
        public void setConnectTimeout(final int connectTimeout) {

                if (connectTimeout < 0) {
                        throw new IllegalArgumentException("The HTTP connect timeout must be zero or positive");
                }

                this.connectTimeout = connectTimeout;
        }


        /**
         * Gets the HTTP response read timeout.
         *
         * @return The HTTP response read timeout, in milliseconds. Zero
         *         implies no timeout.
         */
        public int getReadTimeout() {

                return readTimeout;
        }


        /**
         * Sets the HTTP response read timeout.
         *
         * @param readTimeout The HTTP response read timeout, in milliseconds.
         *                    Zero implies no timeout. Must not be negative.
         */
        public void setReadTimeout(final int readTimeout) {

                if (readTimeout < 0) {
                        throw new IllegalArgumentException("The HTTP response read timeout must be zero or positive");
                }

                this.readTimeout = readTimeout;
        }


        /**
         * Returns an established HTTP URL connection for this HTTP request.
         *
         * @return The HTTP URL connection, with the request sent and ready to
         *         read the response.
         *
         * @throws IOException If the HTTP request couldn't be made, due to a
         *                     network or other error.
         */
        public HttpURLConnection toHttpURLConnection()
                throws IOException {

                URL finalURL = url;

                if (query != null && (method.equals(HTTPRequest.Method.GET) || method.equals(Method.DELETE))) {

                        // Append query string
                        StringBuilder sb = new StringBuilder(url.toString());
                        sb.append('?');
                        sb.append(query);

                        try {
                                finalURL = new URL(sb.toString());

                        } catch (MalformedURLException e) {

                                throw new IOException("Couldn't append query string: " + e.getMessage(), e);
                        }
                }

                HttpURLConnection conn = (HttpURLConnection)finalURL.openConnection();

                for (Map.Entry<String,String> header: getHeaders().entrySet()) {
                        conn.setRequestProperty(header.getKey(), header.getValue());
                }

                conn.setRequestMethod(method.name());
                conn.setConnectTimeout(connectTimeout);
                conn.setReadTimeout(readTimeout);

                if (method.equals(HTTPRequest.Method.POST) || method.equals(Method.PUT)) {

                        conn.setDoOutput(true);

                        if (getContentType() != null)
                                conn.setRequestProperty("Content-Type", getContentType().toString());

                        if (query != null) {
                                OutputStreamWriter writer = new OutputStreamWriter(conn.getOutputStream());
                                writer.write(query);
                                writer.close();
                        }
                }

                return conn;
        }


        /**
         * Sends this HTTP request to the request URL and retrieves the 
         * resulting HTTP response.
         *
         * @return The resulting HTTP response.
         *
         * @throws IOException If the HTTP request couldn't be made, due to a 
         *                     network or other error.
         */
        public HTTPResponse send()
                throws IOException {

                HttpURLConnection conn = toHttpURLConnection();

                int statusCode;

                BufferedReader reader;

                try {
                        // Open a connection, then send method and headers
                        reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));

                        // The next step is to get the status
                        statusCode = conn.getResponseCode();

                } catch (IOException e) {

                        // HttpUrlConnection will throw an IOException if any
                        // 4XX response is sent. If we request the status
                        // again, this time the internal status will be
                        // properly set, and we'll be able to retrieve it.
                        statusCode = conn.getResponseCode();

                        if (statusCode == -1) {
                                // Rethrow IO exception
                                throw e;
                        } else {
                                // HTTP status code indicates the response got
                                // through, read the content but using error stream
                                InputStream errStream = conn.getErrorStream();

                                if (errStream != null) {
                                        // We have useful HTTP error body
                                        reader = new BufferedReader(new InputStreamReader(errStream));
                                } else {
                                        // No content, set to empty string
                                        reader = new BufferedReader(new StringReader(""));
                                }
                        }
                }

                StringBuilder body = new StringBuilder();

                try {
                        String line;

                        while ((line = reader.readLine()) != null) {
                                body.append(line);
                                body.append(System.getProperty("line.separator"));
                        }

                        reader.close();

                } finally {
                        conn.disconnect();
                }


                HTTPResponse response = new HTTPResponse(statusCode);

                String location = conn.getHeaderField("Location");

                if (location != null) {

                        try {
                                response.setLocation(new URI(location));

                        } catch (URISyntaxException e) {
                                throw new IOException("Couldn't parse Location header: " + e.getMessage(), e);
                        }
                }


                try {
                        response.setContentType(conn.getContentType());

                } catch (ParseException e) {

                        throw new IOException("Couldn't parse Content-Type header: " + e.getMessage(), e);
                }


                response.setCacheControl(conn.getHeaderField("Cache-Control"));

                response.setPragma(conn.getHeaderField("Pragma"));

                response.setWWWAuthenticate(conn.getHeaderField("WWW-Authenticate"));

                String bodyContent = body.toString();

                if (! bodyContent.isEmpty())
                        response.setContent(bodyContent);


                return response;
        }
}