/*-
 * ========================LICENSE_START=================================
 * O-RAN-SC
 * %%
 * Copyright (C) 2020 Nordix Foundation
 * %%
 * 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.
 * ========================LICENSE_END===================================
 */
package org.oransc.policyagent.dmaap;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonObject;

import java.io.IOException;
import java.util.Optional;

import org.onap.dmaap.mr.client.MRBatchingPublisher;
import org.oransc.policyagent.clients.AsyncRestClient;
import org.oransc.policyagent.dmaap.DmaapRequestMessage.Operation;
import org.oransc.policyagent.exceptions.ServiceException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.reactive.function.client.WebClientResponseException;
import reactor.core.publisher.Mono;

/**
 * The class handles incoming requests from DMAAP.
 * <p>
 * That means: invoke a REST call towards this services and to send back a
 * response though DMAAP
 */
public class DmaapMessageHandler {
    private static final Logger logger = LoggerFactory.getLogger(DmaapMessageHandler.class);
    private static Gson gson = new GsonBuilder() //
        .create(); //
    private final MRBatchingPublisher dmaapClient;
    private final AsyncRestClient agentClient;

    public DmaapMessageHandler(MRBatchingPublisher dmaapClient, AsyncRestClient agentClient) {
        this.agentClient = agentClient;
        this.dmaapClient = dmaapClient;
    }

    public void handleDmaapMsg(String msg) {
        this.createTask(msg) //
            .subscribe(message -> logger.debug("handleDmaapMsg: {}", message), //
                throwable -> logger.warn("handleDmaapMsg failure {}", throwable.getMessage()), //
                () -> logger.debug("handleDmaapMsg complete"));
    }

    Mono<String> createTask(String msg) {
        try {
            DmaapRequestMessage dmaapRequestMessage = gson.fromJson(msg, ImmutableDmaapRequestMessage.class);
            return this.invokePolicyAgent(dmaapRequestMessage) //
                .onErrorResume(t -> handleAgentCallError(t, msg, dmaapRequestMessage)) //
                .flatMap(
                    response -> sendDmaapResponse(response.getBody(), dmaapRequestMessage, response.getStatusCode()));
        } catch (Exception e) {
            logger.warn("Received unparsable message from DMAAP: {}", msg);
            return Mono.error(e); // Cannot make any response
        }
    }

    private Mono<ResponseEntity<String>> handleAgentCallError(Throwable t, String originalMessage,
        DmaapRequestMessage dmaapRequestMessage) {
        logger.debug("Agent call failed: {}", t.getMessage());
        HttpStatus status = HttpStatus.NOT_FOUND;
        String errorMessage = t.getMessage();
        if (t instanceof WebClientResponseException) {
            WebClientResponseException exception = (WebClientResponseException) t;
            status = exception.getStatusCode();
            errorMessage = exception.getResponseBodyAsString();
        } else if (t instanceof ServiceException) {
            status = HttpStatus.BAD_REQUEST;
            errorMessage = prepareBadOperationErrorMessage(t, originalMessage);

        }
        return sendDmaapResponse(errorMessage, dmaapRequestMessage, status) //
            .flatMap(notUsed -> Mono.empty());
    }

    private String prepareBadOperationErrorMessage(Throwable t, String originalMessage) {
        String operationParameterStart = "operation\":\"";
        int indexOfOperationStart = originalMessage.indexOf(operationParameterStart) + operationParameterStart.length();
        int indexOfOperationEnd = originalMessage.indexOf("\",\"", indexOfOperationStart);
        String badOperation = originalMessage.substring(indexOfOperationStart, indexOfOperationEnd);
        return t.getMessage().replace("null", badOperation);
    }

    private Mono<ResponseEntity<String>> invokePolicyAgent(DmaapRequestMessage dmaapRequestMessage) {
        DmaapRequestMessage.Operation operation = dmaapRequestMessage.operation();
        String uri = dmaapRequestMessage.url();

        if (operation == Operation.DELETE) {
            return agentClient.deleteForEntity(uri);
        } else if (operation == Operation.GET) {
            return agentClient.getForEntity(uri);
        } else if (operation == Operation.PUT) {
            return agentClient.putForEntity(uri, payload(dmaapRequestMessage));
        } else if (operation == Operation.POST) {
            return agentClient.postForEntity(uri, payload(dmaapRequestMessage));
        } else {
            return Mono.error(new ServiceException("Not implemented operation: " + operation));
        }

    }

    private String payload(DmaapRequestMessage message) {
        Optional<JsonObject> payload = message.payload();
        if (payload.isPresent()) {
            return gson.toJson(payload.get());
        } else {
            logger.warn("Expected payload in message from DMAAP: {}", message);
            return "";
        }
    }

    private Mono<String> sendDmaapResponse(String response, DmaapRequestMessage dmaapRequestMessage,
        HttpStatus status) {
        return createDmaapResponseMessage(dmaapRequestMessage, response, status) //
            .flatMap(this::sendToDmaap) //
            .onErrorResume(this::handleResponseCallError);
    }

    private Mono<String> sendToDmaap(String body) {
        try {
            logger.debug("sendToDmaap: {} ", body);
            dmaapClient.send(body);
            dmaapClient.sendBatchWithResponse();
            return Mono.just("OK");
        } catch (IOException e) {
            return Mono.error(e);
        }
    }

    private Mono<String> handleResponseCallError(Throwable t) {
        logger.debug("Failed to send response to DMaaP: {}", t.getMessage());
        return Mono.empty();
    }

    private Mono<String> createDmaapResponseMessage(DmaapRequestMessage dmaapRequestMessage, String response,
        HttpStatus status) {
        DmaapResponseMessage dmaapResponseMessage = ImmutableDmaapResponseMessage.builder() //
            .status(status.toString()) //
            .message(response == null ? "" : response) //
            .type("response") //
            .correlationId(dmaapRequestMessage.correlationId() == null ? "" : dmaapRequestMessage.correlationId()) //
            .originatorId(dmaapRequestMessage.originatorId() == null ? "" : dmaapRequestMessage.originatorId()) //
            .requestId(dmaapRequestMessage.requestId() == null ? "" : dmaapRequestMessage.requestId()) //
            .timestamp(dmaapRequestMessage.timestamp() == null ? "" : dmaapRequestMessage.timestamp()) //
            .build();
        String str = gson.toJson(dmaapResponseMessage);
        return Mono.just(str);

    }
}