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package com.bq.oss.lib.queries.parser;

import java.util.Iterator;

import com.bq.oss.lib.queries.request.Count;
import com.bq.oss.lib.queries.exception.MalformedJsonQueryException;
import com.bq.oss.lib.queries.request.Aggregation;
import com.bq.oss.lib.queries.request.AggregationOperator;
import com.bq.oss.lib.queries.request.Sum;
import com.bq.oss.lib.queries.request.Average;
import com.fasterxml.jackson.databind.JsonNode;

/**
 * @author Rubén Carrasco
 *
 */
public class JacksonAggregationParser implements AggregationParser {

	private final CustomJsonParser jsonParser;

	public JacksonAggregationParser(CustomJsonParser jsonParser) {
		this.jsonParser = jsonParser;
	}

	@Override
	public Aggregation parse(String aggregationString) throws MalformedJsonQueryException {
		JsonNode node = jsonParser.readValueAsTree(aggregationString);
		if (node.isObject()) {
			return getOperationFromNode(node);
		} else {
			throw new MalformedJsonQueryException("Unexpected array");
		}
	}

	private Aggregation getOperationFromNode(JsonNode node) throws MalformedJsonQueryException {
		Iterator fieldNames = node.fieldNames();
		if (fieldNames.hasNext()) {
			String key = fieldNames.next();

			if (fieldNames.hasNext()) {
				throw new MalformedJsonQueryException("Wrong number of fields (Expected one)");
			}

			String textValue = node.get(key).textValue();
			switch (getOperator(key)) {
				case $COUNT:
					return new Count(textValue);
				case $AVG:
					return new Average(textValue);
				case $SUM:
					return new Sum(textValue);
				default:
					return null;
			}

		} else {
			throw new MalformedJsonQueryException("Empty object");
		}
	}

	private AggregationOperator getOperator(String key) throws MalformedJsonQueryException {
		try {
			return AggregationOperator.valueOf(key.toUpperCase());
		} catch (IllegalArgumentException e) {
			throw new MalformedJsonQueryException("Unknown aggregation operator " + key);
		}
	}

}