package com.nimbusds.oauth2.sdk;


import java.net.URI;
import java.net.URISyntaxException;
import java.util.LinkedHashMap;
import java.util.Map;

import net.jcip.annotations.Immutable;

import com.nimbusds.oauth2.sdk.id.ClientID;


/**
 * Authorisation code grant. Used in access token requests with an
 * authorisation code.
 *
 * <p>Related specifications:
 *
 * <ul>
 *     <li>OAuth 2.0 (RFC 6749), section 4.1.3.
 * </ul>
 */
@Immutable
public final class AuthorizationCodeGrant extends AuthorizationGrant {


        /**
         * The associated grant type.
         */
        public static final GrantType GRANT_TYPE = GrantType.AUTHORIZATION_CODE;


        /**
         * The authorisation code received from the authorisation server.
         */
        private final AuthorizationCode code;


        /**
         * The conditionally required redirection URI in the initial
         * authorisation request.
         */
        private final URI redirectURI;


        /**
         * The conditionally required client ID.
         */
        private final ClientID clientID;


        /**
         * Creates a new authorisation code grant. This constructor is
         * intended for an authenticated access token requests (doesn't require
         * the client identifier to be specified).
         *
         * @param code        The authorisation code. Must not be {@code null}.
         * @param redirectURI The redirection URI of the original authorisation
         *                    request. Required if the {redirect_uri}
         *                    parameter was included in the authorisation
         *                    request, else {@code null}.
         */
        public AuthorizationCodeGrant(final AuthorizationCode code,
                                      final URI redirectURI) {

                super(GRANT_TYPE);

                if (code == null)
                        throw new IllegalArgumentException("The authorisation code must not be null");

                this.code = code;

                this.redirectURI = redirectURI;

                this.clientID = null;
        }


        /**
         * Creates a new authorisation code grant. This constructor is
         * intended for an unauthenticated access token request and requires
         * the client identifier to be specified.
         *
         * @param code        The authorisation code. Must not be {@code null}.
         * @param redirectURI The redirection URI of the original authorisation
         *                    request, {@code null} if the {@code redirect_uri}
         *                    parameter was not included in the authorisation
         *                    request.
         * @param clientID    The client identifier. Must not be {@code null}.
         */
        public AuthorizationCodeGrant(final AuthorizationCode code,
                                      final URI redirectURI,
                                      final ClientID clientID) {

                super(GrantType.AUTHORIZATION_CODE);

                if (code == null)
                        throw new IllegalArgumentException("The authorisation code must not be null");

                this.code = code;

                this.redirectURI = redirectURI;

                if (clientID == null)
                        throw new IllegalArgumentException("The client identifier must not be null");

                this.clientID = clientID;
        }


        /**
         * Gets the authorisation code.
         *
         * @return The authorisation code.
         */
        public AuthorizationCode getAuthorizationCode() {

                return code;
        }


        /**
         * Gets the redirection URI of the original authorisation request.
         *
         * @return The redirection URI, {@code null} if the
         *         {@code redirect_uri} parameter was not included in the
         *         original authorisation request.
         */
        public URI getRedirectionURI() {

                return redirectURI;
        }


        /**
         * Gets the client identifier.
         *
         * @return The client identifier, {@code null} if not specified
         *         (implies an authenticated access token request).
         */
        public ClientID getClientID() {

                return clientID;
        }


        @Override
        public Map<String,String> toParameters() {

                Map<String,String> params = new LinkedHashMap<String,String>();

                params.put("grant_type", GRANT_TYPE.getValue());

                params.put("code", code.getValue());

                if (redirectURI != null)
                        params.put("redirect_uri", redirectURI.toString());

                if (clientID != null)
                        params.put("client_id", clientID.getValue());

                return params;
        }


        /**
         * Parses an authorisation code grant from the specified parameters.
         *
         * <p>Example:
         *
         * <pre>
         * grant_type=authorization_code
         * code=SplxlOBeZQQYbYS6WxSbIA
         * redirect_uri=https://Fclient.example.com/cb
         * </pre>
         *
         * @param params The parameters.
         *
         * @return The authorisation code grant.
         *
         * @throws ParseException If parsing failed.
         */
        public static AuthorizationCodeGrant parse(final Map<String,String> params)
                throws ParseException {

                // Parse grant type
                String grantTypeString = params.get("grant_type");

                if (grantTypeString == null)
                        throw new ParseException("Missing \"grant_type\" parameter", OAuth2Error.INVALID_REQUEST);

                GrantType grantType = new GrantType(grantTypeString);

                if (! grantType.equals(GRANT_TYPE))
                        throw new ParseException("The \"grant_type\" must be " + GRANT_TYPE, OAuth2Error.INVALID_GRANT);


                // Parse authorisation code
                String codeString = params.get("code");

                if (codeString == null || codeString.trim().isEmpty())
                        throw new ParseException("Missing or empty \"code\" parameter", OAuth2Error.INVALID_REQUEST);

                AuthorizationCode code = new AuthorizationCode(codeString);


                // Parse optional redirection URI
                String redirectURIString = params.get("redirect_uri");

                URI redirectURI = null;

                if (redirectURIString != null) {

                        try {
                                redirectURI = new URI(redirectURIString);

                        } catch (URISyntaxException e) {

                                throw new ParseException("Invalid \"redirect_uri\" parameter: " + e.getMessage(), OAuth2Error.INVALID_REQUEST, e);
                        }
                }


                // Parse optional client ID
                String clientIDString = params.get("client_id");

                ClientID clientID = null;

                if (clientIDString != null && clientIDString.trim().length() > 0)
                        clientID = new ClientID(clientIDString);

                if (clientID == null)
                        return new AuthorizationCodeGrant(code, redirectURI);
                else
                        return new AuthorizationCodeGrant(code, redirectURI, clientID);
        }
}