/*
 * ============LICENSE_START===================================================
 * Copyright (c) 2018 Amdocs
 * ============================================================================
 * 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.onap.pomba.contextbuilder.aai.reader;

import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.jayway.jsonpath.Configuration;
import com.jayway.jsonpath.DocumentContext;
import com.jayway.jsonpath.JsonPath;
import com.jayway.jsonpath.Option;
import com.jayway.jsonpath.ReadContext;
import com.jayway.jsonpath.spi.json.GsonJsonProvider;
import com.jayway.jsonpath.spi.json.JsonProvider;
import com.jayway.jsonpath.spi.mapper.GsonMappingProvider;
import com.jayway.jsonpath.spi.mapper.MappingProvider;
import java.util.ArrayList;
import java.util.EnumSet;
import java.util.List;
import java.util.Set;
import org.onap.pomba.contextbuilder.aai.exception.AuditError;
import org.onap.pomba.contextbuilder.aai.exception.AuditException;

/**
 * Reads JSON objects. Supported by the JayWay JsonPath library.
 */
public class JsonReader {

    private Configuration jsonPathConfig;

    /**
     * Initialize the JSON reader.
     */
    public JsonReader() {
        setJsonProvider();
        this.jsonPathConfig = Configuration.builder().options(Option.SUPPRESS_EXCEPTIONS).build();
    }

    /**
     * Parse the JSON.
     *
     * @param json
     *            the JSON object
     * @return a {@link ReadContext} the parsed JSON.
     * @throws ValidationServiceException
     */
    public DocumentContext parse(String json) throws AuditException {
        DocumentContext document = null;
        try {
            document = JsonPath.using(jsonPathConfig).parse(json);
        } catch (Exception e) {
            throw new AuditException(AuditError.JSON_READER_PARSE_ERROR, e);
        }
        return document;
    }

    /**
     * Gets values from JSON objects.
     *
     * @param json
     *            the JSON object
     * @param path
     *            the path to property values. The format must comply with the JayWay JsonPath definition.
     * @return a List of values found by evaluating the path.
     * @throws ValidationServiceException
     */
    public List<String> get(String json, String path) throws AuditException {
        return getAsList(parse(json), path);
    }

    /**
     * Gets values from JSON objects. Used in combination with {@link JsonReader#parse(String)} it reduces the number of
     * times the JSON document is parsed.
     *
     * @param document
     *            a {@link DocumentContext} object with the parsed JSON
     * @param path
     *            the path to property values. The format must comply with the JayWay JsonPath definition.
     * @return a List of values found by evaluating the path, or an empty list if no values were found
     */
    public List<String> getAsList(DocumentContext document, String path) {
        List<String> result = new ArrayList<>();
        JsonElement jsonElement = document.read(path);
        if (jsonElement != null) {
            if (jsonElement.isJsonPrimitive()) {
                result.add(jsonElement.getAsString());
            } else if (jsonElement.isJsonObject()) {
                result.add(jsonElement.getAsJsonObject().toString());
            } else if (jsonElement.isJsonArray()) {
                for (JsonElement obj : jsonElement.getAsJsonArray()) {
                    Object object = jsonElementToObject(obj);
                    result.add(object == null ? null : object.toString());
                }
            }
        }
        return result;
    }

    /**
     * Get the value(s) from the specified JSON document
     *
     * @param document
     *            a {@link DocumentContext} object with the parsed JSON
     * @param path
     *            the path to property value(s). The format must comply with the JayWay JsonPath definition.
     * @return either all the values found by evaluating the path (e.g. as an array), or a String object (only) where
     *         the path evaluates to a single primitive value
     */
    public Object getObject(DocumentContext document, String path) {
        return jsonElementToObject(document.read(path));
    }

    /**
     * Convert the JSON element to a String or Array where possible, otherwise return the JSON object.
     *
     * @param jsonElement
     * @return the jsonElement converted to a Java Object
     */
    private Object jsonElementToObject(JsonElement jsonElement) {
        if (jsonElement == null) {
            return null;
        } else if (jsonElement.isJsonPrimitive()) {
            return jsonElement.getAsString();
        } else if (jsonElement.isJsonObject()) {
            return jsonElement.getAsJsonObject();
        } else if (jsonElement.isJsonArray()) {
            // Convert to a List for simplified handling within rules
            return jsonArrayToList(jsonElement.getAsJsonArray());
        } else {
            return jsonElement;
        }
    }

    private List<Object> jsonArrayToList(JsonArray jsonArray) {
        List<Object> result = new ArrayList<>();
        for (JsonElement obj : jsonArray) {
            result.add(jsonElementToObject(obj));
        }
        return result;
    }

    /**
     * @param document
     * @param path
     * @return a JsonElement from the document
     */
    public JsonElement getJsonElement(DocumentContext document, String path) {
        return document.read(path);
    }

    private void setJsonProvider() {
        Configuration.setDefaults(new Configuration.Defaults() {
            private final JsonProvider jsonProvider = new GsonJsonProvider();
            private final MappingProvider mappingProvider = new GsonMappingProvider();

            @Override
            public JsonProvider jsonProvider() {
                return jsonProvider;
            }

            @Override
            public MappingProvider mappingProvider() {
                return mappingProvider;
            }

            @Override
            public Set<Option> options() {
                return EnumSet.noneOf(Option.class);
            }
        });
    }
}