// Copyright 2016 The Domain Registry Authors. All Rights Reserved.
//
// 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.

package google.registry.flows;

import static google.registry.flows.EppXmlTransformer.marshalWithLenientRetry;
import static google.registry.flows.EppXmlTransformer.unmarshal;
import static google.registry.flows.picker.FlowPicker.getFlowClass;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Joiner;
import com.google.common.collect.ImmutableList;

import google.registry.model.eppcommon.Trid;
import google.registry.model.eppinput.EppInput;
import google.registry.model.eppoutput.EppOutput;
import google.registry.model.eppoutput.EppResponse;
import google.registry.model.eppoutput.Result;
import google.registry.model.eppoutput.Result.Code;
import google.registry.monitoring.whitebox.EppMetrics;
import google.registry.util.Clock;
import google.registry.util.FormattingLogger;

import javax.inject.Inject;

/**
 * An implementation of the EPP command/response protocol.
 *
 * @see "http://tools.ietf.org/html/rfc5730"
 */
public final class EppController {

  private static final FormattingLogger logger = FormattingLogger.getLoggerForCallerClass();

  @Inject Clock clock;
  @Inject EppMetrics metrics;
  @Inject EppController() {}

  /**
   * Read an EPP envelope from the client, find the matching flow, execute it, and return
   * the response marshalled to a byte array.
   */
  public byte[] handleEppCommand(
      SessionMetadata sessionMetadata,
      TransportCredentials credentials,
      byte[] inputXmlBytes) {
    Trid trid = null;
    try {
      EppInput eppInput = unmarshal(EppInput.class, inputXmlBytes);
      trid = Trid.create(eppInput.getCommandWrapper().getClTrid());
      ImmutableList<String> targetIds = eppInput.getTargetIds();
      metrics.setCommandName(eppInput.getCommandName());
      metrics.setClientId(sessionMetadata.getClientId());
      metrics.setPrivilegeLevel(sessionMetadata.isSuperuser() ? "SUPERUSER" : "NORMAL");
      if (!targetIds.isEmpty()) {
        metrics.setEppTarget(Joiner.on(",").join(targetIds));
      }
      FlowRunner flowRunner = new FlowRunner(
          getFlowClass(eppInput),
          eppInput,
          trid,
          sessionMetadata,
          credentials,
          inputXmlBytes,
          metrics,
          clock);
      EppOutput eppOutput = flowRunner.run();
      if (eppOutput.isResponse()) {
        metrics.setEppStatus(eppOutput.getResponse().getResult().getCode());
      }
      return marshalWithLenientRetry(eppOutput);
    } catch (EppException e) {
      // The command failed. Send the client an error message.
      metrics.setEppStatus(e.getResult().getCode());
      return marshalWithLenientRetry(getErrorResponse(clock, e.getResult(), trid));
    } catch (Throwable e) {
      // Something bad and unexpected happened. Send the client a generic error, and log it.
      logger.severe(e, "Unexpected failure");
      metrics.setEppStatus(Code.CommandFailed);
      return marshalWithLenientRetry(
          getErrorResponse(clock, Result.create(Code.CommandFailed), trid));
    } finally {
      metrics.export();
    }
  }

  /** Create a response indicating an Epp failure. */
  @VisibleForTesting
  static EppOutput getErrorResponse(Clock clock, Result result, Trid trid) {
    // Create TRID (without a clTRID) if one hasn't been created yet, as it's necessary to construct
    // a valid response. This can happen if the error occurred before we could even parse out the
    // clTRID (e.g. if a syntax error occurred parsing the supplied XML).
    return EppOutput.create(new EppResponse.Builder()
        .setTrid(trid == null ? Trid.create(null) : trid)
        .setResult(result)
        .setExecutionTime(clock.nowUtc())
        .build());
  }
}