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/*
 * Copyright (C) 2020 Graylog, Inc.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the Server Side Public License, version 1,
 * as published by MongoDB, Inc.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * Server Side Public License for more details.
 *
 * You should have received a copy of the Server Side Public License
 * along with this program. If not, see
 * .
 */
package org.graylog.plugins.pipelineprocessor.functions.json;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.MissingNode;
import org.graylog.plugins.pipelineprocessor.EvaluationContext;
import org.graylog.plugins.pipelineprocessor.ast.functions.AbstractFunction;
import org.graylog.plugins.pipelineprocessor.ast.functions.FunctionArgs;
import org.graylog.plugins.pipelineprocessor.ast.functions.FunctionDescriptor;
import org.graylog.plugins.pipelineprocessor.ast.functions.ParameterDescriptor;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.inject.Inject;

import java.io.IOException;

import static com.google.common.collect.ImmutableList.of;

public class JsonParse extends AbstractFunction {
    private static final Logger log = LoggerFactory.getLogger(JsonParse.class);
    public static final String NAME = "parse_json";

    private final ObjectMapper objectMapper;
    private final ParameterDescriptor valueParam;

    @Inject
    public JsonParse(ObjectMapper objectMapper) {
        this.objectMapper = objectMapper;
        valueParam = ParameterDescriptor.string("value").description("The string to parse as a JSON tree").build();
    }

    @Override
    public JsonNode evaluate(FunctionArgs args, EvaluationContext context) {
        final String value = valueParam.required(args, context);
        try {
            final JsonNode node = objectMapper.readTree(value);
            if (node == null) {
                throw new IOException("null result");
            }
            return node;
        } catch (IOException e) {
            log.warn("Unable to parse JSON", e);
        }
        return MissingNode.getInstance();
    }

    @Override
    public FunctionDescriptor descriptor() {
        return FunctionDescriptor.builder()
                .name(NAME)
                .returnType(JsonNode.class)
                .params(of(
                        valueParam
                ))
                .description("Parses a string as a JSON tree")
                .build();
    }
}