package org.gcube.common.keycloak;

import static org.gcube.common.keycloak.model.OIDCConstants.AUDIENCE_PARAMETER;
import static org.gcube.common.keycloak.model.OIDCConstants.CLIENT_CREDENTIALS_GRANT_TYPE;
import static org.gcube.common.keycloak.model.OIDCConstants.CLIENT_ID_PARAMETER;
import static org.gcube.common.keycloak.model.OIDCConstants.CLIENT_SECRET_PARAMETER;
import static org.gcube.common.keycloak.model.OIDCConstants.GRANT_TYPE_PARAMETER;
import static org.gcube.common.keycloak.model.OIDCConstants.PERMISSION_PARAMETER;
import static org.gcube.common.keycloak.model.OIDCConstants.REFRESH_TOKEN_GRANT_TYPE;
import static org.gcube.common.keycloak.model.OIDCConstants.REFRESH_TOKEN_PARAMETER;
import static org.gcube.common.keycloak.model.OIDCConstants.TOKEN_PARAMETER;
import static org.gcube.common.keycloak.model.OIDCConstants.UMA_TOKEN_GRANT_TYPE;
import static org.gcube.common.keycloak.model.OIDCConstants.PASSWORD_GRANT_TYPE;
import static org.gcube.common.keycloak.model.OIDCConstants.USERNAME_PARAMETER;
import static org.gcube.common.keycloak.model.OIDCConstants.PASSWORD_PARAMETER;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;
import java.util.Arrays;
import java.util.Base64;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

import org.gcube.common.gxrest.request.GXHTTPStringRequest;
import org.gcube.common.gxrest.response.inbound.GXInboundResponse;
import org.gcube.common.keycloak.model.ModelUtils;
import org.gcube.common.keycloak.model.TokenIntrospectionResponse;
import org.gcube.common.keycloak.model.TokenResponse;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class DefaultKeycloakClient implements KeycloakClient {

    protected static Logger logger = LoggerFactory.getLogger(KeycloakClient.class);

    protected final static String AUTHORIZATION_HEADER = "Authorization";
    protected final static String D4S_CONTEXT_HEADER_NAME = "X-D4Science-Context";

    public static final String BASE_URL = "https://url.d4science.org/auth/realms/";

    @Override
    public URL getRealmBaseURL(String context) throws KeycloakClientException {
        return getRealmBaseURL(context, DEFAULT_REALM);
    }

    @Override
    public URL getRealmBaseURL(String context, String realm) throws KeycloakClientException {
        String urlString = BASE_URL + realm + "/";
        if (!context.startsWith(PROD_ROOT_SCOPE)) {
            String root = context.split("/")[1];
            urlString = urlString.replace("url", "url." + root.replaceAll("\\.", "-"));
        }
        try {
            return new URL(urlString);
        } catch (MalformedURLException e) {
            // That should be almost impossible
            logger.warn("Cannot create base URL from string: {}", urlString, e);
            return null;
        }
    }

    @Override
    public URL getTokenEndpointURL(URL realmBaseURL) throws KeycloakClientException {
        logger.debug("Constructing token endpoint URL starting from base URL: {}", realmBaseURL);
        try {
            URL tokenURL = null;
            if (realmBaseURL.getPath().endsWith("/")) {
                tokenURL = new URL(realmBaseURL, OPEN_ID_URI_PATH + "/" + TOKEN_URI_PATH);
            } else {
                tokenURL = new URL(realmBaseURL.toString() + "/" + OPEN_ID_URI_PATH + "/" + TOKEN_URI_PATH);
            }
            logger.debug("Constructed token URL is: {}", tokenURL);
            return tokenURL;
        } catch (MalformedURLException e) {
            throw new KeycloakClientException("Cannot constructs toke URL from base URL: " + realmBaseURL, e);
        }
    }

    @Override
    public URL getIntrospectionEndpointURL(URL realmBaseURL) throws KeycloakClientException {
        logger.debug("Constructing introspection URL starting from base URL: {}", realmBaseURL);
        try {
            URL tokenURL = null;
            if (realmBaseURL.getPath().endsWith("/")) {
                tokenURL = new URL(realmBaseURL,
                        OPEN_ID_URI_PATH + "/" + TOKEN_URI_PATH + "/" + TOKEN_INTROSPECT_URI_PATH);
            } else {
                tokenURL = new URL(realmBaseURL.toString() + "/" + OPEN_ID_URI_PATH + "/" + TOKEN_URI_PATH + "/"
                        + TOKEN_INTROSPECT_URI_PATH);
            }
            logger.debug("Constructed introspection URL is: {}", tokenURL);
            return tokenURL;
        } catch (MalformedURLException e) {
            throw new KeycloakClientException("Cannot constructs toke URL from base URL: " + realmBaseURL, e);
        }
    }

    @Override
    public URL computeIntrospectionEndpointURL(URL tokenEndpointURL) throws KeycloakClientException {
        logger.debug("Computing introspection endpoint URL starting from token endpoint URL: {}", tokenEndpointURL);
        try {
            URL introspectionURL = null;
            if (tokenEndpointURL.getPath().endsWith(TOKEN_URI_PATH + "/")) {
                introspectionURL = new URL(tokenEndpointURL, TOKEN_INTROSPECT_URI_PATH);
            } else {
                introspectionURL = new URL(tokenEndpointURL, TOKEN_URI_PATH + "/" + TOKEN_INTROSPECT_URI_PATH);
            }
            logger.debug("Computed introspection URL is: {}", introspectionURL);
            return introspectionURL;
        } catch (MalformedURLException e) {
            throw new KeycloakClientException("Cannot compute introspection URL from token URL: " + tokenEndpointURL,
                    e);
        }
    }

    @Override
    public TokenResponse queryOIDCToken(String context, String clientId, String clientSecret)
            throws KeycloakClientException {

        return queryOIDCTokenWithContext(context, clientId, clientSecret, null);
    }

    @Override
    public TokenResponse queryOIDCTokenWithContext(String context, String clientId, String clientSecret,
            String audience) throws KeycloakClientException {

        return queryOIDCTokenWithContext(getTokenEndpointURL(getRealmBaseURL(context)), clientId, clientSecret,
                audience);
    }

    @Override
    public TokenResponse queryOIDCTokenOfUser(String context, String clientId, String clientSecret, String username,
            String password) throws KeycloakClientException {

        return queryOIDCTokenOfUserWithContext(context, clientId, clientSecret, username, password, null);
    }

    @Override
    public TokenResponse queryOIDCTokenOfUserWithContext(String context, String clientId, String clientSecret,
            String username, String password, String audience) throws KeycloakClientException {

        return queryOIDCTokenOfUserWithContext(getTokenEndpointURL(getRealmBaseURL(context)), clientId, clientSecret,
                username, password, null);
    }

    @Override
    public TokenResponse queryOIDCToken(URL tokenURL, String clientId, String clientSecret)
            throws KeycloakClientException {

        return queryOIDCTokenWithContext(tokenURL, clientId, clientSecret, null);
    }

    @Override
    public TokenResponse queryOIDCTokenWithContext(URL tokenURL, String clientId, String clientSecret,
            String audience) throws KeycloakClientException {

        return queryOIDCTokenWithContext(tokenURL, constructBasicAuthenticationHeader(clientId, clientSecret),
                audience);
    }

    protected String constructBasicAuthenticationHeader(String clientId, String clientSecret) {
        return "Basic " + Base64.getEncoder().encodeToString((clientId + ":" + clientSecret).getBytes());
    }

    @Override
    public TokenResponse queryOIDCTokenOfUserWithContext(String context, String authorization, String username,
            String password, String audience) throws KeycloakClientException {

        return queryOIDCTokenOfUserWithContext(getTokenEndpointURL(getRealmBaseURL(context)), authorization, username,
                password, audience);
    }

    @Override
    public TokenResponse queryOIDCToken(String context, String authorization) throws KeycloakClientException {
        return queryOIDCTokenWithContext(context, authorization, null);
    }

    @Override
    public TokenResponse queryOIDCTokenWithContext(String context, String authorization, String audience)
            throws KeycloakClientException {
        return queryOIDCTokenWithContext(getTokenEndpointURL(getRealmBaseURL(context)), authorization, audience);
    }

    @Override
    public TokenResponse queryOIDCTokenOfUserWithContext(URL tokenURL, String clientId, String clientSecret,
            String username, String password, String audience) throws KeycloakClientException {

        return queryOIDCTokenOfUserWithContext(tokenURL, constructBasicAuthenticationHeader(clientId, clientSecret),
                username, password, audience);
    }

    @Override
    public TokenResponse queryOIDCTokenOfUserWithContext(URL tokenURL, String authorization, String username,
            String password, String audience) throws KeycloakClientException {

        Map<String, List<String>> params = new HashMap<>();
        params.put(GRANT_TYPE_PARAMETER, Arrays.asList(PASSWORD_GRANT_TYPE));
        params.put(USERNAME_PARAMETER, Arrays.asList(username));
        params.put(PASSWORD_PARAMETER, Arrays.asList(password));

        Map<String, String> headers = new HashMap<>();
        logger.debug("Adding authorization header as: {}", authorization);
        headers.put(AUTHORIZATION_HEADER, authorization);

        if (audience != null) {
            logger.debug("Adding d4s context header as: {}", audience);
            headers.put(D4S_CONTEXT_HEADER_NAME, audience);
        }

        return performRequest(tokenURL, headers, params);
    }

    @Override
    public TokenResponse queryOIDCToken(URL tokenURL, String authorization) throws KeycloakClientException {
        return queryOIDCTokenWithContext(tokenURL, authorization, null);
    }

    @Override
    public TokenResponse queryOIDCTokenWithContext(URL tokenURL, String authorization, String audience)
            throws KeycloakClientException {
        logger.debug("Querying OIDC token from Keycloak server with URL: {}", tokenURL);

        Map<String, List<String>> params = new HashMap<>();
        params.put(GRANT_TYPE_PARAMETER, Arrays.asList(CLIENT_CREDENTIALS_GRANT_TYPE));

        Map<String, String> headers = new HashMap<>();
        logger.debug("Adding authorization header as: {}", authorization);
        headers.put(AUTHORIZATION_HEADER, authorization);

        if (audience != null) {
            logger.debug("Adding d4s context header as: {}", audience);
            headers.put(D4S_CONTEXT_HEADER_NAME, audience);
        }

        return performRequest(tokenURL, headers, params);
    }

    @Override
    public TokenResponse queryUMAToken(String context, TokenResponse oidcTokenResponse, String audience,
            List<String> permissions) throws KeycloakClientException {

        return queryUMAToken(getTokenEndpointURL(getRealmBaseURL(context)), oidcTokenResponse, audience, permissions);
    }

    @Override
    public TokenResponse queryUMAToken(URL tokenURL, TokenResponse oidcTokenResponse, String audience,
            List<String> permissions) throws KeycloakClientException {

        return queryUMAToken(tokenURL, constructBeareAuthenticationHeader(oidcTokenResponse), audience, permissions);
    }

    protected String constructBeareAuthenticationHeader(TokenResponse oidcTokenResponse) {
        return "Bearer " + oidcTokenResponse.getAccessToken();
    }

    @Override
    public TokenResponse queryUMAToken(String context, String clientId, String clientSecret, String audience,
            List<String> permissions) throws KeycloakClientException {

        return queryUMAToken(getTokenEndpointURL(getRealmBaseURL(context)), clientId, clientSecret, audience,
                permissions);
    }

    @Override
    public TokenResponse queryUMAToken(URL tokenURL, String clientId, String clientSecret, String audience,
            List<String> permissions) throws KeycloakClientException {

        return queryUMAToken(tokenURL,
                constructBasicAuthenticationHeader(clientId, clientSecret),
                audience, permissions);
    }

    @Override
    public TokenResponse queryUMAToken(String context, String authorization, String audience,
            List<String> permissions) throws KeycloakClientException {

        return queryUMAToken(getTokenEndpointURL(getRealmBaseURL(context)), authorization, audience, permissions);
    }

    @Override
    public TokenResponse queryUMAToken(URL tokenURL, String authorization, String audience,
            List<String> permissions) throws KeycloakClientException {

        if (audience == null || "".equals(audience)) {
            throw new KeycloakClientException("Audience must be not null nor empty");
        }

        logger.debug("Querying UMA token from Keycloak server with URL: {}", tokenURL);

        Map<String, List<String>> params = new HashMap<>();
        params.put(GRANT_TYPE_PARAMETER, Arrays.asList(UMA_TOKEN_GRANT_TYPE));

        try {
            params.put(AUDIENCE_PARAMETER, Arrays.asList(URLEncoder.encode(checkAudience(audience), "UTF-8")));
            logger.trace("audience is {}", checkAudience(audience));
        } catch (UnsupportedEncodingException e) {
            logger.error("Can't URL encode audience: {}", audience, e);
        }

        Map<String, String> headers = new HashMap<>();
        logger.debug("Adding authorization header as: {}", authorization);
        headers.put(AUTHORIZATION_HEADER, authorization);

        if (permissions != null && !permissions.isEmpty()) {
            params.put(
                    PERMISSION_PARAMETER, permissions.stream().map(s -> {
                        try {
                            return URLEncoder.encode(s, "UTF-8");
                        } catch (UnsupportedEncodingException e) {
                            return "";
                        }
                    }).collect(Collectors.toList()));
        }

        return performRequest(tokenURL, headers, params);
    }

    protected TokenResponse performRequest(URL tokenURL, Map<String, String> headers, Map<String, List<String>> params)
            throws KeycloakClientException {

        if (tokenURL == null) {
            throw new KeycloakClientException("Token URL must be not null");
        }

        if (!headers.containsKey(AUTHORIZATION_HEADER) || "".equals(headers.get(AUTHORIZATION_HEADER))) {
            throw new KeycloakClientException("Authorization must be not null nor empty");
        }
        // Constructing request object
        GXHTTPStringRequest request;
        try {
            String queryString = params.entrySet().stream()
                    .flatMap(p -> p.getValue().stream().map(v -> p.getKey() + "=" + v))
                    .reduce((p1, p2) -> p1 + "&" + p2).orElse("");

            logger.trace("Query string is {}", queryString);

            request = GXHTTPStringRequest.newRequest(tokenURL.toString())
                    .header("Content-Type", "application/x-www-form-urlencoded").withBody(queryString);

            safeSetAsExternalCallForOldAPI(request);

            logger.trace("Adding provided headers: {}", headers);
            for (String headerName : headers.keySet()) {
                request.header(headerName, headers.get(headerName));
            }
        } catch (Exception e) {
            throw new KeycloakClientException("Cannot construct the request object correctly", e);
        }

        GXInboundResponse response;
        try {
            response = request.post();
        } catch (Exception e) {
            throw new KeycloakClientException("Cannot send request correctly", e);
        }
        if (response.isSuccessResponse()) {
            try {
                return response.tryConvertStreamedContentFromJson(TokenResponse.class);
            } catch (Exception e) {
                throw new KeycloakClientException("Cannot construct token response object correctly", e);
            }
        } else {
            String errorBody = "[empty]";
            try {
                errorBody = response.getStreamedContentAsString();
            } catch (IOException e1) {
                // Not interesting case
            }
            throw KeycloakClientException.create("Unable to get token", response.getHTTPCode(),
                    response.getHeaderFields()
                            .getOrDefault("content-type", Collections.singletonList("unknown/unknown")).get(0),
                    errorBody);
        }
    }

    private static String checkAudience(String audience) {
        if (audience.startsWith("/")) {
            try {
                logger.trace("Audience was provided in non URL encoded form, encoding it");
                return URLEncoder.encode(audience, "UTF-8");
            } catch (UnsupportedEncodingException e) {
                logger.error("Cannot URL encode 'audience'", e);
            }
        }
        return audience;
    }

    @Override
    public TokenResponse refreshToken(String context, TokenResponse tokenResponse) throws KeycloakClientException {
        return refreshToken(getTokenEndpointURL(getRealmBaseURL(context)), tokenResponse);
    }

    @Override
    public TokenResponse refreshToken(URL tokenURL, TokenResponse tokenResponse) throws KeycloakClientException {
        return refreshToken(tokenURL, null, null, tokenResponse);
    }

    @Override
    public TokenResponse refreshToken(String context, String clientId, String clientSecret, TokenResponse tokenResponse)
            throws KeycloakClientException {

        return refreshToken(getTokenEndpointURL(getRealmBaseURL(context)), clientId, clientSecret, tokenResponse);
    }

    @Override
    public TokenResponse refreshToken(URL tokenURL, String clientId, String clientSecret, TokenResponse tokenResponse)
            throws KeycloakClientException {

        if (clientId == null) {
            logger.debug("Client id not set, trying to get it from access token info");
            try {
                clientId = ModelUtils.getClientIdFromToken(ModelUtils.getAccessTokenFrom(tokenResponse));
            } catch (Exception e) {
                throw new KeycloakClientException("Cannot construct access token object from token response", e);
            }
        }
        return refreshToken(tokenURL, clientId, clientSecret, tokenResponse.getRefreshToken());
    }

    @Override
    public TokenResponse refreshToken(String context, String clientId, String clientSecret,
            String refreshTokenJWTString)
            throws KeycloakClientException {

        return refreshToken(getTokenEndpointURL(getRealmBaseURL(context)), clientId, clientSecret,
                refreshTokenJWTString);
    }

    @Override
    public TokenResponse refreshToken(URL tokenURL, String clientId, String clientSecret, String refreshTokenJWTString)
            throws KeycloakClientException {

        if (tokenURL == null) {
            throw new KeycloakClientException("Token URL must be not null");
        }

        if (clientId == null || "".equals(clientId)) {
            throw new KeycloakClientException("Client id must be not null nor empty");
        }

        if (refreshTokenJWTString == null || "".equals(clientId)) {
            throw new KeycloakClientException("Refresh token JWT encoded string must be not null nor empty");
        }

        logger.debug("Refreshing token from Keycloak server with URL: {}", tokenURL);

        // Constructing request object
        GXHTTPStringRequest request;
        try {
            Map<String, String> params = new HashMap<>();
            params.put(GRANT_TYPE_PARAMETER, REFRESH_TOKEN_GRANT_TYPE);
            params.put(REFRESH_TOKEN_PARAMETER, refreshTokenJWTString);
            params.put(CLIENT_ID_PARAMETER, URLEncoder.encode(clientId, "UTF-8"));
            if (clientSecret != null && !"".equals(clientSecret)) {
                params.put(CLIENT_SECRET_PARAMETER, URLEncoder.encode(clientSecret, "UTF-8"));
            }

            String queryString = params.entrySet().stream()
                    .map(p -> p.getKey() + "=" + p.getValue())
                    .reduce((p1, p2) -> p1 + "&" + p2).orElse("");

            request = GXHTTPStringRequest.newRequest(tokenURL.toString()).header("Content-Type",
                    "application/x-www-form-urlencoded").withBody(queryString);

            safeSetAsExternalCallForOldAPI(request);
        } catch (Exception e) {
            throw new KeycloakClientException("Cannot construct the request object correctly", e);
        }

        GXInboundResponse response;
        try {
            response = request.post();
        } catch (Exception e) {
            throw new KeycloakClientException("Cannot send request correctly", e);
        }
        if (response.isSuccessResponse()) {
            try {
                return response.tryConvertStreamedContentFromJson(TokenResponse.class);
            } catch (Exception e) {
                throw new KeycloakClientException("Cannot construct token response object correctly", e);
            }
        } else {
            throw KeycloakClientException.create("Unable to refresh token", response.getHTTPCode(),
                    response.getHeaderFields()
                            .getOrDefault("content-type", Collections.singletonList("unknown/unknown")).get(0),
                    response.getMessage());
        }
    }

    @Override
    public TokenIntrospectionResponse introspectAccessToken(String context, String clientId, String clientSecret,
            String accessTokenJWTString) throws KeycloakClientException {

        return introspectAccessToken(getIntrospectionEndpointURL(getRealmBaseURL(context)), clientId, clientSecret,
                accessTokenJWTString);
    }

    @Override
    public TokenIntrospectionResponse introspectAccessToken(URL introspectionURL, String clientId, String clientSecret,
            String accessTokenJWTString) throws KeycloakClientException {

        if (introspectionURL == null) {
            throw new KeycloakClientException("Introspection URL must be not null");
        }

        if (clientId == null || "".equals(clientId)) {
            throw new KeycloakClientException("Client id must be not null nor empty");
        }

        if (clientSecret == null || "".equals(clientSecret)) {
            throw new KeycloakClientException("Client secret must be not null nor empty");
        }

        logger.debug("Verifying access token against Keycloak server with URL: {}", introspectionURL);

        // Constructing request object
        GXHTTPStringRequest request;
        try {
            Map<String, String> params = new HashMap<>();
            params.put(TOKEN_PARAMETER, accessTokenJWTString);

            String queryString = params.entrySet().stream()
                    .map(p -> p.getKey() + "=" + p.getValue())
                    .reduce((p1, p2) -> p1 + "&" + p2).orElse("");

            request = GXHTTPStringRequest.newRequest(introspectionURL.toString()).header("Content-Type",
                    "application/x-www-form-urlencoded").withBody(queryString);

            safeSetAsExternalCallForOldAPI(request);

            request = request.header("Authorization", constructBasicAuthenticationHeader(clientId, clientSecret));
        } catch (Exception e) {
            throw new KeycloakClientException("Cannot construct the request object correctly", e);
        }

        GXInboundResponse response;
        try {
            response = request.post();
        } catch (Exception e) {
            throw new KeycloakClientException("Cannot send request correctly", e);
        }
        if (response.isSuccessResponse()) {
            try {
                return response.tryConvertStreamedContentFromJson(TokenIntrospectionResponse.class);
            } catch (Exception e) {
                throw new KeycloakClientException("Cannot construct introspection response object correctly", e);
            }
        } else {
            throw KeycloakClientException.create("Unable to get token introspection response", response.getHTTPCode(),
                    response.getHeaderFields()
                            .getOrDefault("content-type", Collections.singletonList("unknown/unknown")).get(0),
                    response.getMessage());
        }
    }

    @Override
    public boolean isAccessTokenVerified(String context, String clientId, String clientSecret,
            String accessTokenJWTString) throws KeycloakClientException {

        return isAccessTokenVerified(getIntrospectionEndpointURL(getRealmBaseURL(context)), clientId, clientSecret,
                accessTokenJWTString);
    }

    @Override
    public boolean isAccessTokenVerified(URL introspectionURL, String clientId, String clientSecret,
            String accessTokenJWTString) throws KeycloakClientException {

        return introspectAccessToken(introspectionURL, clientId, clientSecret, accessTokenJWTString).getActive();
    }

    protected void safeSetAsExternalCallForOldAPI(GXHTTPStringRequest request) {
        try {
            logger.trace("Looking for the 'isExternalCall' method in the 'GXHTTPStringRequest' class");
            Method isExetnalCallMethod = request.getClass().getMethod("isExternalCall", boolean.class);
            logger.trace("Method found, is the old gxJRS API. Invoking it with 'true' argument");
            isExetnalCallMethod.invoke(request, true);
        } catch (NoSuchMethodException e) {
            logger.trace("Method not found, is the new gxJRS API");
        } catch (SecurityException | IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
            logger.warn("Cannot invoke 'isExternalCall' method via reflection on 'GXHTTPStringRequest' class", e);
        }
    }

}