/*
 * Copyright 2014 Red Hat, Inc.
 *
 *  All rights reserved. This program and the accompanying materials
 *  are made available under the terms of the Eclipse Public License v1.0
 *  and Apache License v2.0 which accompanies this distribution.
 *
 *  The Eclipse Public License is available at
 *  http://www.eclipse.org/legal/epl-v10.html
 *
 *  The Apache License v2.0 is available at
 *  http://www.opensource.org/licenses/apache2.0.php
 *
 *  You may elect to redistribute this code under either of these licenses.
 */

package io.vertx.ext.web.handler.impl;

import io.vertx.core.AsyncResult;
import io.vertx.core.Future;
import io.vertx.core.Handler;
import io.vertx.core.http.HttpHeaders;
import io.vertx.core.http.HttpMethod;
import io.vertx.core.http.HttpServerRequest;
import io.vertx.ext.web.RoutingContext;
import io.vertx.ext.web.Session;
import io.vertx.ext.web.handler.AuthHandler;
import io.vertx.ext.auth.AuthProvider;
import io.vertx.ext.auth.User;

import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * @author <a href="http://tfox.org">Tim Fox</a>
 */
public abstract class AuthHandlerImpl implements AuthHandler {

  static final String AUTH_PROVIDER_CONTEXT_KEY = "io.vertx.ext.web.handler.AuthHandler.provider";

  static final HttpStatusException FORBIDDEN = new HttpStatusException(403);
  static final HttpStatusException UNAUTHORIZED = new HttpStatusException(401);
  static final HttpStatusException BAD_REQUEST = new HttpStatusException(400);

  protected final String realm;
  protected final AuthProvider authProvider;
  protected final Set<String> authorities = new HashSet<>();

  public AuthHandlerImpl(AuthProvider authProvider) {
    this(authProvider, "");
  }

  public AuthHandlerImpl(AuthProvider authProvider, String realm) {
    this.authProvider = authProvider;
    this.realm = realm;
  }

  @Override
  public AuthHandler addAuthority(String authority) {
    authorities.add(authority);
    return this;
  }

  @Override
  public AuthHandler addAuthorities(Set<String> authorities) {
    this.authorities.addAll(authorities);
    return this;
  }

  @Override
  public void authorize(User user, Handler<AsyncResult<Void>> handler) {
    int requiredcount = authorities.size();
    if (requiredcount > 0) {
      if (user == null) {
        handler.handle(Future.failedFuture(FORBIDDEN));
        return;
      }

      AtomicInteger count = new AtomicInteger();
      AtomicBoolean sentFailure = new AtomicBoolean();

      Handler<AsyncResult<Boolean>> authHandler = res -> {
        if (res.succeeded()) {
          if (res.result()) {
            if (count.incrementAndGet() == requiredcount) {
              // Has all required authorities
              handler.handle(Future.succeededFuture());
            }
          } else {
            if (sentFailure.compareAndSet(false, true)) {
              handler.handle(Future.failedFuture(FORBIDDEN));
            }
          }
        } else {
          handler.handle(Future.failedFuture(res.cause()));
        }
      };
      for (String authority : authorities) {
        if (!sentFailure.get()) {
          user.isAuthorized(authority, authHandler);
        }
      }
    } else {
      // No auth required
      handler.handle(Future.succeededFuture());
    }
  }

  protected String authenticateHeader(RoutingContext context) {
    return null;
  }

  @Override
  public void handle(RoutingContext ctx) {

    if (handlePreflight(ctx)) {
      return;
    }

    User user = ctx.user();
    if (user != null) {
      // proceed to AuthZ
      authorizeUser(ctx, user);
      return;
    }
    // parse the request in order to extract the credentials object
    parseCredentials(ctx, res -> {
      if (res.failed()) {
        processException(ctx, res.cause());
        return;
      }
      // check if the user has been set
      User updatedUser = ctx.user();

      if (updatedUser != null) {
        Session session = ctx.session();
        if (session != null) {
          // the user has upgraded from unauthenticated to authenticated
          // session should be upgraded as recommended by owasp
          session.regenerateId();
        }
        // proceed to AuthZ
        authorizeUser(ctx, updatedUser);
        return;
      }

      // proceed to authN
      getAuthProvider(ctx).authenticate(res.result(), authN -> {
        if (authN.succeeded()) {
          User authenticated = authN.result();
          ctx.setUser(authenticated);
          Session session = ctx.session();
          if (session != null) {
            // the user has upgraded from unauthenticated to authenticated
            // session should be upgraded as recommended by owasp
            session.regenerateId();
          }
          // proceed to AuthZ
          authorizeUser(ctx, authenticated);
        } else {
          String header = authenticateHeader(ctx);
          if (header != null) {
            ctx.response()
              .putHeader("WWW-Authenticate", header);
          }
          // to allow further processing if needed
          processException(ctx, new HttpStatusException(401));
        }
      });
    });
  }

  /**
   * This method is protected so custom auth handlers can override the default
   * error handling
   */
  protected void processException(RoutingContext ctx, Throwable exception) {

    if (exception != null) {
      if (exception instanceof HttpStatusException) {
        final int statusCode = ((HttpStatusException) exception).getStatusCode();
        final String payload = ((HttpStatusException) exception).getPayload();

        switch (statusCode) {
          case 302:
            ctx.response()
              .putHeader(HttpHeaders.LOCATION, payload)
              .setStatusCode(302)
              .end("Redirecting to " + payload + ".");
            return;
          case 401:
            String header = authenticateHeader(ctx);
            if (header != null) {
              ctx.response()
                .putHeader("WWW-Authenticate", header);
            }
            ctx.fail(401);
            return;
          default:
            ctx.fail(statusCode);
            return;
        }
      }
    }

    // fallback 500
    ctx.fail(exception);
  }

  private void authorizeUser(RoutingContext ctx, User user) {
    authorize(user, authZ -> {
      if (authZ.failed()) {
        processException(ctx, authZ.cause());
        return;
      }
      // success, allowed to continue
      ctx.next();
    });
  }

  private boolean handlePreflight(RoutingContext ctx) {
    final HttpServerRequest request = ctx.request();
    // See: https://www.w3.org/TR/cors/#cross-origin-request-with-preflight-0
    // Preflight requests should not be subject to security due to the reason UAs will remove the Authorization header
    if (request.method() == HttpMethod.OPTIONS) {
      // check if there is a access control request header
      final String accessControlRequestHeader = ctx.request().getHeader(HttpHeaders.ACCESS_CONTROL_REQUEST_HEADERS);
      if (accessControlRequestHeader != null) {
        // lookup for the Authorization header
        for (String ctrlReq : accessControlRequestHeader.split(",")) {
          if (ctrlReq.equalsIgnoreCase("Authorization")) {
            // this request has auth in access control, so we can allow preflighs without authentication
            ctx.next();
            return true;
          }
        }
      }
    }

    return false;
  }

  private AuthProvider getAuthProvider(RoutingContext ctx) {
    try {
      AuthProvider provider = ctx.get(AUTH_PROVIDER_CONTEXT_KEY);
      if (provider != null) {
        // we're overruling the configured one for this request
        return provider;
      }
    } catch (RuntimeException e) {
      // bad type, ignore and return default
    }

    return authProvider;
  }
}
