com.nhl.link.move.runtime.json.JsonRowReader Maven / Gradle / Ivy

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package com.nhl.link.move.runtime.json;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.node.NumericNode;
import com.nhl.link.move.LmRuntimeException;
import com.nhl.link.move.RowReader;
import com.nhl.link.move.runtime.json.query.JsonNodeWrapper;

import java.util.Iterator;
import java.util.List;

class JsonRowReader implements RowReader {

    private final JsonRowAttribute[] header;
	private final JsonNode rootNode;
	private final List items;

	public JsonRowReader(JsonRowAttribute[] header, JsonNode rootNode, List items) {
		this.header = header;
		this.rootNode = rootNode;
		this.items = items;
	}

	@Override
	public void close() {
		// no need to close anything
	}

	@Override
	public JsonRowAttribute[] getHeader() {
		return header;
	}

	@Override
	public Iterator iterator() {
		return new Iterator() {
			private int i = 0;

			@Override
			public boolean hasNext() {
				return i < items.size();
			}

			@Override
			public Object[] next() {
				return fromNode(items.get(i++));
			}

			@Override
			public void remove() {
				throw new UnsupportedOperationException();
			}
		};
	}

	private Object[] fromNode(JsonNodeWrapper node) {

		Object[] row = new Object[header.length];

		for (int i = 0; i < header.length; i++) {
			row[i] = valueFromNode(header[i], node);
		}

		return row;
	}

	private Object valueFromNode(JsonRowAttribute attribute, JsonNodeWrapper node) {

		List result = attribute.getSourceQuery().execute(rootNode, node);
		if (result == null || result.isEmpty()) {
			return null;
		}
		if (result.size() > 1) {
			throw new LmRuntimeException("Attribute query yielded a list of values (total: " + result.size() +
					"). A single value is expected.");
		}
		return extractValue(result.get(0).getNode());
	}

	private Object extractValue(JsonNode node) {
		switch (node.getNodeType()) {
			case ARRAY:
			case POJO:
			case OBJECT: {
				throw new LmRuntimeException("Expected a value node");
			}
			case MISSING:
			case NULL: {
				return null;
			}
			case BINARY:
			case STRING: {
				return node.asText();
			}
			case BOOLEAN: {
				return node.asBoolean();
			}
			case NUMBER: {
				NumericNode numericNode = (NumericNode) node;
				switch (numericNode.numberType()) {
					case INT: {
						return numericNode.intValue();
					}
					case LONG: {
						return numericNode.longValue();
					}
					case FLOAT: {
						return numericNode.floatValue();
					}
					case DOUBLE: {
						return numericNode.doubleValue();
					}
					case BIG_INTEGER: {
						return numericNode.bigIntegerValue();
					}
					case BIG_DECIMAL: {
						return numericNode.decimalValue();
					}
					// intentionally fall through
				}
			}
			default: {
				throw new LmRuntimeException("Unexpected JSON node type: " + node.getNodeType());
			}
		}
	}

}