/*
    * Copyright 2017 LINE Corporation
    *
    * LINE Corporation licenses this file to you 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:
    *
    *   https://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.
   */
  
  package com.linecorp.centraldogma.server.internal.api;
  
  import static com.google.common.base.Preconditions.checkArgument;
  import static com.google.common.base.Strings.nullToEmpty;
  import static java.util.Objects.requireNonNull;
  
  import java.util.Locale;
  import java.util.concurrent.CompletionStage;
  import java.util.function.BiFunction;
  import java.util.function.Function;
  import java.util.function.Supplier;
  
  import javax.annotation.Nullable;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import com.fasterxml.jackson.core.JsonProcessingException;
  import com.fasterxml.jackson.databind.JsonNode;
  import com.fasterxml.jackson.databind.node.JsonNodeFactory;
  import com.fasterxml.jackson.databind.node.ObjectNode;
  import com.google.common.collect.ImmutableList;
  import com.google.common.collect.ImmutableMap;
  
  import com.linecorp.armeria.common.HttpResponse;
  import com.linecorp.armeria.common.HttpStatus;
  import com.linecorp.armeria.common.MediaType;
  import com.linecorp.armeria.common.RequestContext;
  import com.linecorp.armeria.common.logging.LogLevel;
  import com.linecorp.armeria.common.util.Exceptions;
  import com.linecorp.armeria.server.HttpResponseException;
  import com.linecorp.centraldogma.common.ShuttingDownException;
  import com.linecorp.centraldogma.internal.Jackson;
  
  /**
   * A utility class which provides common functions for HTTP API.
   */
  //TODO(minwoox) change this class to package-local when the admin API is integrated with HTTP API
  public final class HttpApiUtil {
  
      private static final Logger logger = LoggerFactory.getLogger(HttpApiUtil.class);
      private static final String ERROR_MESSAGE_FORMAT = "{} Returning a {} response: {}";
  
      static final JsonNode unremoveRequest = Jackson.valueToTree(
              ImmutableList.of(
                      ImmutableMap.of("op", "replace",
                                      "path", "/status",
                                      "value", "active")));
  
      /**
       * Throws a newly created {@link HttpResponseException} with the specified {@link HttpStatus} and
       * {@code message}.
       */
      public static <T> T throwResponse(RequestContext ctx, HttpStatus status, String message) {
          throw HttpResponseException.of(newResponse(ctx, status, message));
      }
  
      /**
       * Throws a newly created {@link HttpResponseException} with the specified {@link HttpStatus} and
       * the formatted message.
       */
      public static <T> T throwResponse(RequestContext ctx, HttpStatus status, String format, Object... args) {
          throw HttpResponseException.of(newResponse(ctx, status, format, args));
      }
  
      /**
       * Throws a newly created {@link HttpResponseException} with the specified {@link HttpStatus},
       * {@code cause} and {@code message}.
       */
      public static <T> T throwResponse(RequestContext ctx, HttpStatus status, Throwable cause, String message) {
          throw HttpResponseException.of(newResponse(ctx, status, cause, message));
      }
  
      /**
       * Throws a newly created {@link HttpResponseException} with the specified {@link HttpStatus},
       * {@code cause} and the formatted message.
       */
      public static <T> T throwResponse(RequestContext ctx, HttpStatus status, Throwable cause,
                                        String format, Object... args) {
          throw HttpResponseException.of(newResponse(ctx, status, cause, format, args));
      }
  
      /**
      * Returns a newly created {@link HttpResponse} with the specified {@link HttpStatus} and the formatted
      * message.
      */
     public static HttpResponse newResponse(RequestContext ctx, HttpStatus status,
                                            String format, Object... args) {
         requireNonNull(ctx, "ctx");
         requireNonNull(status, "status");
         requireNonNull(format, "format");
         requireNonNull(args, "args");
         return newResponse(ctx, status, String.format(Locale.ENGLISH, format, args));
     }
 
     /**
      * Returns a newly created {@link HttpResponse} with the specified {@link HttpStatus} and {@code message}.
      */
     public static HttpResponse newResponse(RequestContext ctx, HttpStatus status, String message) {
         requireNonNull(ctx, "ctx");
         requireNonNull(status, "status");
         requireNonNull(message, "message");
         return newResponse0(ctx, status, null, message);
     }
 
     /**
      * Returns a newly created {@link HttpResponse} with the specified {@link HttpStatus} and {@code cause}.
      */
     public static HttpResponse newResponse(RequestContext ctx, HttpStatus status, Throwable cause) {
         requireNonNull(ctx, "ctx");
         requireNonNull(status, "status");
         requireNonNull(cause, "cause");
         return newResponse0(ctx, status, cause, null);
     }
 
     /**
      * Returns a newly created {@link HttpResponse} with the specified {@link HttpStatus}, {@code cause} and
      * the formatted message.
      */
     public static HttpResponse newResponse(RequestContext ctx, HttpStatus status, Throwable cause,
                                            String format, Object... args) {
         requireNonNull(ctx, "ctx");
         requireNonNull(status, "status");
         requireNonNull(cause, "cause");
         requireNonNull(format, "format");
         requireNonNull(args, "args");
 
         return newResponse(ctx, status, cause, String.format(Locale.ENGLISH, format, args));
     }
 
     /**
      * Returns a newly created {@link HttpResponse} with the specified {@link HttpStatus}, {@code cause} and
      * {@code message}.
      */
     public static HttpResponse newResponse(RequestContext ctx, HttpStatus status,
                                            Throwable cause, String message) {
         requireNonNull(ctx, "ctx");
         requireNonNull(status, "status");
         requireNonNull(cause, "cause");
         requireNonNull(message, "message");
 
         return newResponse0(ctx, status, cause, message);
     }
 
     private static HttpResponse newResponse0(RequestContext ctx, HttpStatus status,
                                              @Nullable Throwable cause, @Nullable String message) {
         checkArgument(!status.isContentAlwaysEmpty(),
                       "status: %s (expected: a status with non-empty content)", status);
 
         final ObjectNode node = JsonNodeFactory.instance.objectNode();
         if (cause != null) {
             cause = Exceptions.peel(cause);
             node.put("exception", cause.getClass().getName());
             if (message == null) {
                 message = cause.getMessage();
             }
         }
 
         final String m = nullToEmpty(message);
         node.put("message", m);
 
         final LogLevel logLevel;
         switch (status.codeClass()) {
             case SERVER_ERROR:
                 if (cause != null) {
                     if (!(Exceptions.isStreamCancelling(cause) ||
                           cause instanceof ShuttingDownException)) {
                         logLevel = LogLevel.WARN;
                     } else {
                         logLevel = null;
                     }
                 } else {
                     logLevel = LogLevel.WARN;
                 }
                 break;
             case CLIENT_ERROR:
                 logLevel = LogLevel.DEBUG;
                 break;
             case UNKNOWN:
                 logLevel = LogLevel.WARN;
                 break;
             default:
                 logLevel = null;
         }
 
         // TODO(trustin): Use LogLevel.OFF instead of null and logLevel.log()
         //                once we add LogLevel.OFF and LogLevel.log() with more args.
         if (logLevel != null) {
             if (logLevel == LogLevel.WARN) {
                 if (cause != null) {
                     logger.warn(ERROR_MESSAGE_FORMAT, ctx, status, m, cause);
                 } else {
                     logger.warn(ERROR_MESSAGE_FORMAT, ctx, status, m);
                 }
             } else {
                 if (cause != null) {
                     logger.debug(ERROR_MESSAGE_FORMAT, ctx, status, m, cause);
                 } else {
                     logger.debug(ERROR_MESSAGE_FORMAT, ctx, status, m);
                 }
             }
         }
 
         // TODO(hyangtack) Need to introduce a new field such as 'stackTrace' in order to return
         //                 the stack trace of the cause to the trusted client.
         try {
             return HttpResponse.of(status, MediaType.JSON_UTF_8, Jackson.writeValueAsBytes(node));
         } catch (JsonProcessingException e) {
             // should not reach here
             throw new Error(e);
         }
     }
 
     /**
      * Ensures the specified {@link JsonNode} equals to {@link HttpApiUtil#unremoveRequest}.
      *
      * @throws IllegalArgumentException if the {@code node} does not equal to
      *                                  {@link HttpApiUtil#unremoveRequest}.
      */
     static void checkUnremoveArgument(JsonNode node) {
         checkArgument(unremoveRequest.equals(node),
                       "Unsupported JSON patch: " + node +
                       " (expected: " + unremoveRequest + ')');
     }
 
     /**
      * Ensures the specified {@code status} is valid.
      *
      * @throws IllegalArgumentException if the {@code status} is invalid.
      */
     static void checkStatusArgument(String status) {
         checkArgument("removed".equalsIgnoreCase(status),
                       "invalid status: " + status + " (expected: removed)");
     }
 
     /**
      * Throws the specified {@link Throwable} if it is not {@code null}. This is a special form to be used
      * for {@link CompletionStage#handle(BiFunction)}.
      */
     @SuppressWarnings("unused")
     static Void throwUnsafelyIfNonNull(@Nullable Object unused,
                                        @Nullable Throwable cause) {
         throwUnsafelyIfNonNull(cause);
         return null;
     }
 
     /**
      * Throws the specified {@link Throwable} if it is not {@code null}.
      */
     public static void throwUnsafelyIfNonNull(@Nullable Throwable cause) {
         if (cause != null) {
             Exceptions.throwUnsafely(cause);
         }
     }
 
     /**
      * Returns a {@link BiFunction} for a {@link CompletionStage#handle(BiFunction)} which returns an object
      * if the specified {@link Throwable} is {@code null}. Otherwise, it throws the {@code cause}.
      */
     @SuppressWarnings("unchecked")
     static <T, U> BiFunction<? super T, Throwable, ? extends U> returnOrThrow(Supplier<? super U> supplier) {
         return (unused, cause) -> {
             throwUnsafelyIfNonNull(cause);
             return (U) supplier.get();
         };
     }
 
     /**
      * Returns a {@link BiFunction} for a {@link CompletionStage#handle(BiFunction)} which returns an object
      * applied by the specified {@code function} if the specified {@link Throwable} is {@code null}.
      * Otherwise, it throws the {@code cause}.
      */
     static <T, U> BiFunction<? super T, Throwable, ? extends U> returnOrThrow(
             Function<? super T, ? extends U> function) {
         return (result, cause) -> {
             throwUnsafelyIfNonNull(cause);
             return function.apply(result);
         };
     }
 
     private HttpApiUtil() {}
 }