package com.nimbusds.oauth2.sdk.http;


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

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>
 *
 * <p>HTTP 3xx redirection: follow (default) / don't follow
 */
@ThreadSafe
public class HTTPRequest extends HTTPMessage {


        /**
         * Enumeration of the HTTP methods used in OAuth 2.0 requests.
         */
        public 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 fragment.
         */
        private String fragment = 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;


        /**
         * Controls HTTP 3xx redirections.
         */
        private boolean followRedirects = true;
        
        
        /**
         * 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;
        }
        
        
        /**
         * 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.parse(query);
        }


        /**
         * Gets the raw (undecoded) request fragment.
         *
         * @return The request fragment, {@code null} if not specified.
         */
        public String getFragment() {

                return fragment;
        }


        /**
         * Sets the raw (undecoded) request fragment.
         *
         * @param fragment The request fragment, {@code null} if not specified.
         */
        public void setFragment(final String fragment) {

                this.fragment = fragment;
        }


        /**
         * 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;
        }


        /**
         * Gets the boolean setting whether HTTP redirects (requests with
         * response code 3xx) should be automatically followed.
         *
         * @return {@code true} if HTTP redirects are automatically followed,
         *         else {@code false}.
         */
        public boolean getFollowRedirects() {

                return followRedirects;
        }


        /**
         * Sets whether HTTP redirects (requests with response code 3xx) should
         * be automatically followed.
         *
         * @param follow Whether or not to follow HTTP redirects.
         */
        public void setFollowRedirects(final boolean follow) {

                followRedirects = follow;
        }


        /**
         * 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);
                        }
                }

                if (fragment != null) {

                        // Append raw fragment
                        StringBuilder sb = new StringBuilder(finalURL.toString());
                        sb.append('#');
                        sb.append(fragment);

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

                        } catch (MalformedURLException e) {

                                throw new IOException("Couldn't append raw fragment: " + 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);
                conn.setInstanceFollowRedirects(followRedirects);

                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);

                // Set headers
                for (Map.Entry<String,List<String>> responseHeader: conn.getHeaderFields().entrySet()) {

                        if (responseHeader.getKey() == null) {
                                continue; // skip header
                        }

                        List<String> values = responseHeader.getValue();
                        if (values == null || values.isEmpty() || values.get(0) == null) {
                                continue; // skip header
                        }

                        response.setHeader(responseHeader.getKey(), values.get(0));
                }

                final String bodyContent = body.toString();
                if (! bodyContent.isEmpty())
                        response.setContent(bodyContent);

                return response;
        }
}