/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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
 *
 *     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 org.apache.nifi.elasticsearch;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.jayway.jsonpath.JsonPath;
import org.apache.nifi.annotation.behavior.DynamicProperty;
import org.apache.nifi.annotation.documentation.CapabilityDescription;
import org.apache.nifi.annotation.documentation.Tags;
import org.apache.nifi.annotation.lifecycle.OnEnabled;
import org.apache.nifi.components.PropertyDescriptor;
import org.apache.nifi.components.ValidationResult;
import org.apache.nifi.controller.ConfigurationContext;
import org.apache.nifi.expression.ExpressionLanguageScope;
import org.apache.nifi.lookup.LookupFailureException;
import org.apache.nifi.lookup.LookupService;
import org.apache.nifi.processor.util.StandardValidators;
import org.apache.nifi.record.path.FieldValue;
import org.apache.nifi.record.path.RecordPath;
import org.apache.nifi.schema.access.SchemaNotFoundException;
import org.apache.nifi.serialization.JsonInferenceSchemaRegistryService;
import org.apache.nifi.serialization.record.MapRecord;
import org.apache.nifi.serialization.record.Record;
import org.apache.nifi.serialization.record.RecordSchema;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.stream.Collectors;
import java.util.stream.Stream;

@CapabilityDescription("Lookup a record from Elasticsearch Server associated with the specified document ID. " +
        "The coordinates that are passed to the lookup must contain the key 'id'.")
@Tags({"lookup", "enrich", "record", "elasticsearch"})
@DynamicProperty(name = "A JSONPath expression", value = "A Record Path expression",
        description = "Retrieves an object using JSONPath from the result document and places it in the return Record at the specified Record Path.")
public class ElasticSearchLookupService extends JsonInferenceSchemaRegistryService implements LookupService<Record> {
    public static final PropertyDescriptor CLIENT_SERVICE = new PropertyDescriptor.Builder()
        .name("el-rest-client-service")
        .displayName("Client Service")
        .description("An ElasticSearch client service to use for running queries.")
        .identifiesControllerService(ElasticSearchClientService.class)
        .required(true)
        .build();
    public static final PropertyDescriptor INDEX = new PropertyDescriptor.Builder()
        .name("el-lookup-index")
        .displayName("Index")
        .description("The name of the index to read from")
        .required(true)
        .expressionLanguageSupported(ExpressionLanguageScope.ENVIRONMENT)
        .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
        .build();

    public static final PropertyDescriptor TYPE = new PropertyDescriptor.Builder()
        .name("el-lookup-type")
        .displayName("Type")
        .description("The type of this document (used by Elasticsearch for indexing and searching)")
        .required(false)
        .expressionLanguageSupported(ExpressionLanguageScope.ENVIRONMENT)
        .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
        .build();

    private ElasticSearchClientService clientService;

    private String index;
    private String type;
    private ObjectMapper mapper;

    private volatile ConcurrentHashMap<String, RecordPath> recordPathMappings;

    private final List<PropertyDescriptor> descriptors;

    public ElasticSearchLookupService() {
        descriptors = Stream.concat(
                super.getSupportedPropertyDescriptors().stream(),
                Stream.of(CLIENT_SERVICE, INDEX, TYPE)
        ).toList();
    }

    @Override
    @OnEnabled
    public void onEnabled(final ConfigurationContext context) {
        clientService = context.getProperty(CLIENT_SERVICE).asControllerService(ElasticSearchClientService.class);
        index = context.getProperty(INDEX).evaluateAttributeExpressions().getValue();
        type  = context.getProperty(TYPE).evaluateAttributeExpressions().getValue();
        mapper = new ObjectMapper();

        final List<PropertyDescriptor> dynamicDescriptors = context.getProperties().keySet().stream()
            .filter(PropertyDescriptor::isDynamic)
            .toList();

        final Map<String, RecordPath> tempRecordPathMappings = new HashMap<>();
        for (final PropertyDescriptor desc : dynamicDescriptors) {
            final String value = context.getProperty(desc).getValue();
            final String name  = desc.getName();
            tempRecordPathMappings.put(name, RecordPath.compile(value));
        }

        recordPathMappings = new ConcurrentHashMap<>(tempRecordPathMappings);

        super.onEnabled(context);
    }

    @Override
    protected List<PropertyDescriptor> getSupportedPropertyDescriptors() {
        return descriptors;
    }

    @Override
    public PropertyDescriptor getSupportedDynamicPropertyDescriptor(final String name) {
        return new PropertyDescriptor.Builder()
            .name(name)
            .addValidator((subject, input, context) -> {
                ValidationResult.Builder builder = new ValidationResult.Builder();
                try {
                    JsonPath.parse(input);
                    builder.valid(true);
                } catch (Exception ex) {
                    builder.explanation(ex.getMessage())
                        .valid(false)
                        .subject(subject);
                }

                return builder.build();
            })
            .dynamic(true)
            .build();
    }

    @Override
    public Optional<Record> lookup(final Map<String, Object> coordinates) throws LookupFailureException {
        final Map<String, String> context = coordinates.entrySet().stream()
            .collect(Collectors.toMap(
                Map.Entry::getKey,
                e -> e.getValue().toString()
            ));
        return lookup(coordinates, context);
    }

    @Override
    public Optional<Record> lookup(final Map<String, Object> coordinates, final Map<String, String> context) throws LookupFailureException {
        validateCoordinates(coordinates);

        try {
            final Record record;
            if (coordinates.containsKey("_id")) {
                record = getById((String)coordinates.get("_id"), context);
            } else {
                record = getByQuery(coordinates, context);
            }

            return record == null ? Optional.empty() : Optional.of(record);
        } catch (Exception ex) {
            getLogger().error("Error during lookup.", ex);
            throw new LookupFailureException(ex);
        }
    }

    private void validateCoordinates(final Map<String, Object> coordinates) throws LookupFailureException {
        final List<String> reasons = new ArrayList<>();

        if (coordinates.containsKey("_id") && !(coordinates.get("_id") instanceof String)) {
            reasons.add("_id was supplied, but it was not a String.");
        }

        if (coordinates.containsKey("_id") && coordinates.size() > 1) {
            reasons.add("When _id is used, it can be the only key used in the lookup.");
        }

        if (!reasons.isEmpty()) {
            final String error = String.join("\n", reasons);
            throw new LookupFailureException(error);
        }
    }

    @SuppressWarnings("unchecked")
    private Record getById(final String _id, final Map<String, String> context) throws IOException, LookupFailureException, SchemaNotFoundException {
        final Map<String, Object> query = new HashMap<String, Object>(){{
            put("query", new HashMap<String, Object>() {{
                put("match", new HashMap<String, String>(){{
                    put("_id", _id);
                }});
            }});
        }};

        final String json = mapper.writeValueAsString(query);

        final SearchResponse response = clientService.search(json, index, type, null);
        if (response.getNumberOfHits() > 1) {
            throw new LookupFailureException(String.format("Expected 1 response, got %d for query %s",
                response.getNumberOfHits(), json));
        } else if (response.getNumberOfHits() == 0) {
            return null;
        }

        final Map<String, Object> source = (Map<String, Object>)response.getHits().get(0).get("_source");

        final RecordSchema toUse = getSchema(context, source, null);

        Record record = new MapRecord(toUse, source);
        if (recordPathMappings.size() > 0) {
            record = applyMappings(record, source);
        }

        return record;
    }

    Map<String, Object> getNested(final String key, final Object value) {
        final String path = key.substring(0, key.lastIndexOf("."));

        return new HashMap<String, Object>(){{
            put("path", path);
            put("query", new HashMap<String, Object>(){{
                put("match", new HashMap<String, Object>(){{
                    put(key, value);
                }});
            }});
        }};
    }

    private Map<String, Object> buildQuery(final Map<String, Object> coordinates) {
        final Map<String, Object> query = new HashMap<String, Object>(){{
            put("bool", new HashMap<String, Object>(){{
                put("must", coordinates.entrySet().stream()
                    .map(e -> new HashMap<String, Object>(){{
                        if (e.getKey().contains(".")) {
                            put("nested", getNested(e.getKey(), e.getValue()));
                        } else {
                            put("match", new HashMap<String, Object>() {{
                                put(e.getKey(), e.getValue());
                            }});
                        }
                    }}).collect(Collectors.toList())
                );
            }});
        }};

        return new HashMap<String, Object>(){{
            put("size", 1);
            put("query", query);
        }};
    }

    @SuppressWarnings("unchecked")
    private Record getByQuery(final Map<String, Object> query, final Map<String, String> context) throws LookupFailureException {
        try {
            final String json = mapper.writeValueAsString(buildQuery(query));

            final SearchResponse response = clientService.search(json, index, type, null);
            if (response.getNumberOfHits() == 0) {
                return null;
            } else {
                final Map<String, Object> source = (Map<String, Object>)response.getHits().get(0).get("_source");
                final RecordSchema toUse = getSchema(context, source, null);
                Record record = new MapRecord(toUse, source);
                if (recordPathMappings.size() > 0) {
                    record = applyMappings(record, source);
                }

                return record;
            }

        } catch (Exception e) {
            throw new LookupFailureException(e);
        }
    }

    private Record applyMappings(final Record record, final Map<String, Object> source) {
        final Record rec = new MapRecord(record.getSchema(), new HashMap<>());

        recordPathMappings.forEach((key, path) -> {
            try {
                final Object o = JsonPath.read(source, key);
                final Optional<FieldValue> first = path.evaluate(rec).getSelectedFields().findFirst();
                first.ifPresent(fieldValue -> fieldValue.updateValue(o));
            } catch (Exception ex) {
                throw new RuntimeException(ex);
            }
        });

        return rec;
    }

    @Override
    public Class<?> getValueType() {
        return Record.class;
    }

    @Override
    public Set<String> getRequiredKeys() {
        return Collections.emptySet();
    }
}
