/*
 * SPDX-License-Identifier: Apache-2.0
 *
 * The OpenSearch Contributors require contributions made to
 * this file be licensed under the Apache-2.0 license or a
 * compatible open source license.
 */

package org.opensearch.search.pipeline;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.opensearch.action.search.SearchPhaseContext;
import org.opensearch.action.search.SearchPhaseResults;
import org.opensearch.action.search.SearchRequest;
import org.opensearch.action.search.SearchResponse;
import org.opensearch.common.Nullable;
import org.opensearch.common.io.stream.BytesStreamOutput;
import org.opensearch.core.common.io.stream.NamedWriteableAwareStreamInput;
import org.opensearch.core.common.io.stream.NamedWriteableRegistry;
import org.opensearch.core.common.io.stream.StreamInput;
import org.opensearch.search.SearchPhaseResult;

import java.util.Collections;
import java.util.List;
import java.util.concurrent.TimeUnit;
import java.util.function.LongSupplier;

/**
 * Concrete representation of a search pipeline, holding multiple processors.
 */
class Pipeline {

    public static final String REQUEST_PROCESSORS_KEY = "request_processors";
    public static final String RESPONSE_PROCESSORS_KEY = "response_processors";
    public static final String PHASE_PROCESSORS_KEY = "phase_results_processors";

    private static final Logger logger = LogManager.getLogger(Pipeline.class);

    private final String id;
    private final String description;
    private final Integer version;

    // TODO: Refactor org.opensearch.ingest.CompoundProcessor to implement our generic Processor interface
    // Then these can be CompoundProcessors instead of lists.
    private final List<SearchRequestProcessor> searchRequestProcessors;
    private final List<SearchResponseProcessor> searchResponseProcessors;
    private final List<SearchPhaseResultsProcessor> searchPhaseResultsProcessors;
    private final NamedWriteableRegistry namedWriteableRegistry;
    private final LongSupplier relativeTimeSupplier;

    Pipeline(
        String id,
        @Nullable String description,
        @Nullable Integer version,
        List<SearchRequestProcessor> requestProcessors,
        List<SearchResponseProcessor> responseProcessors,
        List<SearchPhaseResultsProcessor> phaseResultsProcessors,
        NamedWriteableRegistry namedWriteableRegistry,
        LongSupplier relativeTimeSupplier
    ) {
        this.id = id;
        this.description = description;
        this.version = version;
        this.searchRequestProcessors = Collections.unmodifiableList(requestProcessors);
        this.searchResponseProcessors = Collections.unmodifiableList(responseProcessors);
        this.searchPhaseResultsProcessors = Collections.unmodifiableList(phaseResultsProcessors);
        this.namedWriteableRegistry = namedWriteableRegistry;
        this.relativeTimeSupplier = relativeTimeSupplier;
    }

    String getId() {
        return id;
    }

    String getDescription() {
        return description;
    }

    Integer getVersion() {
        return version;
    }

    List<SearchRequestProcessor> getSearchRequestProcessors() {
        return searchRequestProcessors;
    }

    List<SearchResponseProcessor> getSearchResponseProcessors() {
        return searchResponseProcessors;
    }

    List<SearchPhaseResultsProcessor> getSearchPhaseResultsProcessors() {
        return searchPhaseResultsProcessors;
    }

    protected void beforeTransformRequest() {}

    protected void afterTransformRequest(long timeInNanos) {}

    protected void onTransformRequestFailure() {}

    protected void beforeRequestProcessor(Processor processor) {}

    protected void afterRequestProcessor(Processor processor, long timeInNanos) {}

    protected void onRequestProcessorFailed(Processor processor) {}

    protected void beforeTransformResponse() {}

    protected void afterTransformResponse(long timeInNanos) {}

    protected void onTransformResponseFailure() {}

    protected void beforeResponseProcessor(Processor processor) {}

    protected void afterResponseProcessor(Processor processor, long timeInNanos) {}

    protected void onResponseProcessorFailed(Processor processor) {}

    SearchRequest transformRequest(SearchRequest request) throws SearchPipelineProcessingException {
        if (searchRequestProcessors.isEmpty() == false) {
            long pipelineStart = relativeTimeSupplier.getAsLong();
            beforeTransformRequest();
            try {
                try (BytesStreamOutput bytesStreamOutput = new BytesStreamOutput()) {
                    request.writeTo(bytesStreamOutput);
                    try (StreamInput in = bytesStreamOutput.bytes().streamInput()) {
                        try (StreamInput input = new NamedWriteableAwareStreamInput(in, namedWriteableRegistry)) {
                            request = new SearchRequest(input);
                        }
                    }
                }
                for (SearchRequestProcessor processor : searchRequestProcessors) {
                    beforeRequestProcessor(processor);
                    long start = relativeTimeSupplier.getAsLong();
                    try {
                        request = processor.processRequest(request);
                    } catch (Exception e) {
                        onRequestProcessorFailed(processor);
                        if (processor.isIgnoreFailure()) {
                            logger.warn(
                                "The exception from request processor ["
                                    + processor.getType()
                                    + "] in the search pipeline ["
                                    + id
                                    + "] was ignored",
                                e
                            );
                        } else {
                            throw e;
                        }
                    } finally {
                        long took = TimeUnit.NANOSECONDS.toMillis(relativeTimeSupplier.getAsLong() - start);
                        afterRequestProcessor(processor, took);
                    }
                }
            } catch (Exception e) {
                onTransformRequestFailure();
                throw new SearchPipelineProcessingException(e);
            } finally {
                long took = TimeUnit.NANOSECONDS.toMillis(relativeTimeSupplier.getAsLong() - pipelineStart);
                afterTransformRequest(took);
            }
        }
        return request;
    }

    SearchResponse transformResponse(SearchRequest request, SearchResponse response) throws SearchPipelineProcessingException {
        if (searchResponseProcessors.isEmpty() == false) {
            long pipelineStart = relativeTimeSupplier.getAsLong();
            beforeTransformResponse();
            try {
                for (SearchResponseProcessor processor : searchResponseProcessors) {
                    beforeResponseProcessor(processor);
                    long start = relativeTimeSupplier.getAsLong();
                    try {
                        response = processor.processResponse(request, response);
                    } catch (Exception e) {
                        onResponseProcessorFailed(processor);
                        if (processor.isIgnoreFailure()) {
                            logger.warn(
                                "The exception from response processor ["
                                    + processor.getType()
                                    + "] in the search pipeline ["
                                    + id
                                    + "] was ignored",
                                e
                            );
                        } else {
                            throw e;
                        }
                    } finally {
                        long took = TimeUnit.NANOSECONDS.toMillis(relativeTimeSupplier.getAsLong() - start);
                        afterResponseProcessor(processor, took);
                    }
                }
            } catch (Exception e) {
                onTransformResponseFailure();
                throw new SearchPipelineProcessingException(e);
            } finally {
                long took = TimeUnit.NANOSECONDS.toMillis(relativeTimeSupplier.getAsLong() - pipelineStart);
                afterTransformResponse(took);
            }
        }
        return response;
    }

    <Result extends SearchPhaseResult> void runSearchPhaseResultsTransformer(
        SearchPhaseResults<Result> searchPhaseResult,
        SearchPhaseContext context,
        String currentPhase,
        String nextPhase
    ) throws SearchPipelineProcessingException {
        try {
            for (SearchPhaseResultsProcessor searchPhaseResultsProcessor : searchPhaseResultsProcessors) {
                if (currentPhase.equals(searchPhaseResultsProcessor.getBeforePhase().getName())
                    && nextPhase.equals(searchPhaseResultsProcessor.getAfterPhase().getName())) {
                    try {
                        searchPhaseResultsProcessor.process(searchPhaseResult, context);
                    } catch (Exception e) {
                        if (searchPhaseResultsProcessor.isIgnoreFailure()) {
                            logger.warn(
                                "The exception from search phase results processor ["
                                    + searchPhaseResultsProcessor.getType()
                                    + "] in the search pipeline ["
                                    + id
                                    + "] was ignored",
                                e
                            );
                        } else {
                            throw e;
                        }
                    }

                }
            }
        } catch (RuntimeException e) {
            throw new SearchPipelineProcessingException(e);
        }
    }

    static final Pipeline NO_OP_PIPELINE = new Pipeline(
        SearchPipelineService.NOOP_PIPELINE_ID,
        "Pipeline that does not transform anything",
        0,
        Collections.emptyList(),
        Collections.emptyList(),
        Collections.emptyList(),
        null,
        () -> 0L
    );
}