package com.nimbusds.oauth2.sdk;


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

import com.nimbusds.oauth2.sdk.pkce.CodeVerifier;
import net.jcip.annotations.Immutable;
import org.apache.commons.lang3.StringUtils;


/**
 * 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.
 *     <li>Proof Key for Code Exchange by OAuth Public Clients (RFC 7636).
 * </ul>
 */
@Immutable
public class AuthorizationCodeGrant extends AuthorizationGrant {


        /**
         * The 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 optional authorisation code verifier for PKCE.
         */
        private final CodeVerifier codeVerifier;


        /**
         * Creates a new authorisation code grant.
         *
         * @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) {

                this(code, redirectURI, null);
        }


        /**
         * Creates a new authorisation code grant.
         *
         * @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}.
         * @param codeVerifier The authorisation code verifier for PKCE,
         *                     {@code null} if not specified.
         */
        public AuthorizationCodeGrant(final AuthorizationCode code,
                                      final URI redirectURI,
                                      final CodeVerifier codeVerifier) {

                super(GRANT_TYPE);

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

                this.code = code;

                this.redirectURI = redirectURI;

                this.codeVerifier = codeVerifier;
        }


        /**
         * 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 authorisation code verifier for PKCE.
         *
         * @return The authorisation code verifier, {@code null} if not
         *         specified.
         */
        public CodeVerifier getCodeVerifier() {

                return codeVerifier;
        }


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

                Map<String,String> params = new LinkedHashMap<>();
                params.put("grant_type", GRANT_TYPE.getValue());
                params.put("code", code.getValue());

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

                if (codeVerifier != null)
                        params.put("code_verifier", codeVerifier.getValue());

                return params;
        }


        @Override
        public boolean equals(Object o) {
                if (this == o) return true;
                if (!(o instanceof AuthorizationCodeGrant)) return false;

                AuthorizationCodeGrant codeGrant = (AuthorizationCodeGrant) o;

                if (!code.equals(codeGrant.code)) return false;
                if (redirectURI != null ? !redirectURI.equals(codeGrant.redirectURI) : codeGrant.redirectURI != null)
                        return false;
                return codeVerifier != null ? codeVerifier.equals(codeGrant.codeVerifier) : codeGrant.codeVerifier == null;

        }


        @Override
        public int hashCode() {
                int result = code.hashCode();
                result = 31 * result + (redirectURI != null ? redirectURI.hashCode() : 0);
                result = 31 * result + (codeVerifier != null ? codeVerifier.hashCode() : 0);
                return result;
        }


        /**
         * 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) {
                        String msg = "Missing \"grant_type\" parameter";
                        throw new ParseException(msg, OAuth2Error.INVALID_REQUEST.appendDescription(": " + msg));
                }

                if (! GrantType.parse(grantTypeString).equals(GRANT_TYPE)) {
                        String msg = "The \"grant_type\" must be \"" + GRANT_TYPE + "\"";
                        throw new ParseException(msg, OAuth2Error.UNSUPPORTED_GRANT_TYPE.appendDescription(": " + msg));
                }

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

                if (codeString == null || codeString.trim().isEmpty()) {
                        String msg = "Missing or empty \"code\" parameter";
                        throw new ParseException(msg, OAuth2Error.INVALID_REQUEST.appendDescription(": " + msg));
                }

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


                // Parse optional code verifier
                String codeVerifierString = params.get("code_verifier");

                CodeVerifier codeVerifier = null;

                if (StringUtils.isNotBlank(codeVerifierString)) {

                        try {
                                codeVerifier = new CodeVerifier(codeVerifierString);
                        } catch (IllegalArgumentException e) {
                                // Illegal code verifier
                                throw new ParseException(e.getMessage(), e);
                        }
                }

                return new AuthorizationCodeGrant(code, redirectURI, codeVerifier);
        }
}