package act.security;

/*-
 * #%L
 * ACT Framework
 * %%
 * Copyright (C) 2014 - 2017 ActFramework
 * %%
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * #L%
 */

import act.Act;
import act.app.ActionContext;
import act.app.App;
import act.conf.AppConfig;
import act.util.MissingAuthenticationHandler;
import org.osgl.exception.UnexpectedException;
import org.osgl.http.H;
import org.osgl.inject.BeanSpec;
import org.osgl.util.S;

import java.lang.annotation.*;
import java.lang.reflect.Method;
import java.lang.reflect.Type;

public class CSRF {

    /**
     * Mark a controller class or action handler method that
     * requires the CSRF protection. This can be used
     * to construct the whitelist of CSRF protection resources
     * when the global {@link act.conf.AppConfigKey#CSRF} is
     * disabled
     */
    @Documented
    @Retention(RetentionPolicy.RUNTIME)
    @Target({ElementType.METHOD, ElementType.TYPE})
    public @interface Enable {
    }

    /**
     * Mark a controller class or action handler method that
     * is not subject to CSRF protection. This can be used
     * to construct the blacklist of CSRF protection resources
     * when the global {@link act.conf.AppConfigKey#CSRF} is
     * enabled
     */
    @Documented
    @Retention(RetentionPolicy.RUNTIME)
    @Target({ElementType.METHOD, ElementType.TYPE})
    public @interface Disable {
    }

    public static String token(ActionContext ctx) {
        String paramName = ctx.config().csrfParamName();
        return ctx.renderArg(paramName);
    }

    public static String formField(ActionContext ctx) {
        String paramName = ctx.config().csrfParamName();
        return S.newBuffer("<input type='hidden' name='").a(paramName)
                .a("' value='").a(ctx.renderArg(paramName)).a("'>").toString();
    }

    public static Spec spec(Class controller) {
        return spec(BeanSpec.of(controller, Act.injector()));
    }

    public static Spec spec(Method action) {
        Type type = Method.class;
        Annotation[] annotations = action.getDeclaredAnnotations();
        return spec(BeanSpec.of(type, annotations, Act.injector()));
    }

    private static Spec spec(BeanSpec beanSpec) {
        if (null != beanSpec.getAnnotation(Enable.class)) {
            return new Spec(true);
        } else if (null != beanSpec.getAnnotation(Disable.class)) {
            return new Spec(false);
        }
        return Spec.DEFAULT;
    }


    public static class Spec {

        // The dumb spec does nothing
        public static final Spec DUMB = new Spec() {
            @Override
            public void preCheck(ActionContext context) {
                // do nothing implementation
            }

            @Override
            public void check(ActionContext context, H.Session session) {
                // do nothing implementation
            }

            @Override
            public void setCookieAndRenderArgs(ActionContext context) {
                // do nothing implementation
            }
        };

        // The default spec delegate to global App configuration
        public static final Spec DEFAULT = new Spec();

        private App app;
        private Boolean enabled;
        private String paramName;
        private String headerName;
        private String cookieName;
        private String cookieDomain;
        private CSRFProtector csrfProtector;

        private Spec() {this(null);}

        private Spec(Boolean enabled) {
            this.app = Act.app();
            AppConfig config = app.config();
            boolean globalEnabled = config.csrfEnabled();
            this.enabled = null == enabled ? globalEnabled : enabled;
            if (!this.enabled) {
                return;
            }
            this.paramName = config.csrfParamName();
            this.headerName = config.csrfHeaderName();
            this.cookieName = config.csrfCookieName();
            this.cookieDomain = config.cookieDomain();
            this.csrfProtector = config.csrfProtector();
        }

        private boolean effective() {
            return DUMB != this && DEFAULT != this;
        }

        /**
         * Do sanity check to see if CSRF token is present. This method
         * is called before session resolved
         *
         * @param context the current context
         */
        public void preCheck(ActionContext context) {
            if (!enabled) {
                return;
            }
            H.Method method = context.req().method();
            if (method.safe()) {
                return;
            }
            String token = retrieveCsrfToken(context);
            if (S.blank(token)) {
                raiseCsrfNotVerified(context);
            }
        }

        /**
         * Check CSRF token after session resolved
         * @param context the current context
         */
        public void check(ActionContext context, H.Session session) {
            if (!enabled) {
                return;
            }
            String token = context.csrfPrefetched();
            try {
                if (!csrfProtector.verifyToken(token, session, app)) {
                    context.clearCsrfPrefetched();
                    raiseCsrfNotVerified(context);
                }
            } catch (UnexpectedException e) {
                Act.LOGGER.warn(e, "Error checking CSRF token");
                raiseCsrfNotVerified(context);
            }
        }

        public CSRF.Spec chain(final Spec next) {
            return effective() ? this : next;
        }

        public void setCookieAndRenderArgs(ActionContext context) {
            if (!enabled) {
                return;
            }
            String token = retrieveCsrfToken(context);
            if (S.blank(token)) {
                // this branch is for safe methods
                H.Session session = context.session();
                token = csrfProtector.retrieveToken(session, cookieName, app);
            }
            if (S.blank(token) || justLoggedIn(context)) {
                H.Session session = context.session();
                csrfProtector.clearExistingToken(session, cookieName);
                token = app.encrypt(csrfProtector.generateToken(session, app));
                H.Cookie cookie = new H.Cookie(cookieName, token);
                cookie.secure(context.config().sessionSecure());
                cookie.domain(cookieDomain);
                cookie.path("/");
                context.resp().addCookie(cookie);
                csrfProtector.outputToken(token, cookieName, cookieDomain, context);
            }
            context.renderArg(paramName, token);
        }

        private String retrieveCsrfToken(ActionContext context) {
            String token = context.csrfPrefetched();
            if (S.blank(token)) {
                token = context.req().header(headerName);
            }
            if (S.blank(token)) {
                token = context.paramVal(paramName);
            }
            if (S.notBlank(token)) {
                context.setCsrfPrefetched(token);
            }
            return token;
        }

        private static boolean justLoggedIn(ActionContext context) {
            boolean wasUnauthenticated = context.wasUnauthenticated();
            return wasUnauthenticated && context.isLoggedIn();
        }

        private static void raiseCsrfNotVerified(ActionContext context) {
            context.clearCsrfPrefetched();
            MissingAuthenticationHandler handler = context.csrfFailureHandler();
            handler.handle(context);
        }

    }

}
