package com.nimbusds.oauth2.sdk.http;


import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
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}. This
 * class is thread-safe.
 *
 * <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
 * </ul>
 *
 * @author Vladimir Dzhuvinov
 */
@ThreadSafe
public final 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;
        
        
        /**
         * Specifies an {@code Authorization} header value.
         */
        private String authorization = null;
        
        
        /**
         * The query string / post body.
         */
        private String query = null;
        
        
        /**
         * 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;
        }
        
        
        /**
         * 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 or POST, or the content type
         *                                  header value couldn't be parsed.
         * @throws IOException              For a POST body that couldn't be 
         *                                  read due to an I/O exception.
         */
        public HTTPRequest(final HttpServletRequest sr)
                throws IOException {
        
                method = HTTPRequest.Method.valueOf(sr.getMethod().toUpperCase());

                try {
                        url = new URL(sr.getRequestURL().toString());

                } catch (MalformedURLException e) {

                        throw new IllegalArgumentException("Invalid request URL: " + e.getMessage(), e);
                }
                
                String ct = sr.getContentType();
                
                try {
                        setContentType(sr.getContentType());
                
                } catch (ParseException e) {
                        
                        throw new IllegalArgumentException("Invalid Content-Type header value: " + e.getMessage(), e);
                }
                
                setAuthorization(sr.getHeader("Authorization"));
                
                if (method.equals(Method.GET)) {
                
                        setQuery(sr.getQueryString());

                } else if (method.equals(Method.POST)) {
                
                        // read body
                        
                        StringBuilder body = new StringBuilder(256);
                        
                        BufferedReader reader = sr.getReader();
                        
                        String line;
                        
                        while ((line = reader.readLine()) != null) {
                        
                                body.append(line);
                                body.append(System.getProperty("line.separator"));
                        }
                        
                        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 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) {
        
                authorization = authz;
        }
        
        
        /**
         * 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.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);
        }


        /**
         * 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 {

                URL finalURL;

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

                        // Append query string

                        try {
                                finalURL = new URL(url.toString() + "?" + query);

                        } catch (MalformedURLException e) {

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

                } else {

                        finalURL = url;
                }

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

                if (authorization != null)
                        conn.setRequestProperty("Authorization", authorization);

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

                        conn.setDoOutput(true);
                        
                        conn.setRequestProperty("Content-Type", CommonContentTypes.APPLICATION_URLENCODED.toString());

                        if (query != null) {

                                OutputStreamWriter writer = new OutputStreamWriter(conn.getOutputStream());
                                writer.write(query);
                                writer.flush(); 
                        }
                }


                BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
       
                StringBuilder body = new StringBuilder();

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


                HTTPResponse response = new HTTPResponse(conn.getResponseCode());

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

                if (location != null) {

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

                        } catch (MalformedURLException 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;
        }
}