/**
 * Copyright (c) 2012 - 2018 Data In Motion and others.
 * All rights reserved. 
 * 
 * This program and the accompanying materials are made available under the terms of the 
 * Eclipse Public License v1.0 which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     Data In Motion - initial API and implementation
 */
package org.gecko.whiteboard.graphql.schema;

import java.math.BigDecimal;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

import graphql.AssertException;
import graphql.language.IntValue;
import graphql.language.StringValue;
import graphql.schema.Coercing;
import graphql.schema.CoercingParseLiteralException;
import graphql.schema.CoercingParseValueException;
import graphql.schema.CoercingSerializeException;
import graphql.schema.GraphQLScalarType;

/**
 * 
 * @author jalbert
 * @since 21 Nov 2018
 */
public class GeckoScalars {
    /**
     * This represents the "Boolean" type as defined in the graphql specification : http://facebook.github.io/graphql/#sec-Boolean
     */
    public static final GraphQLScalarType GraphQLDate = new GraphQLScalarType("Date", "Built-in Date with the following pattern yyyy-MM-dd'T'HH:mm:ss.SSSZ an example would look like this: 2018-11-18T13:45:00.000+0100", new Coercing<Date, String>() {

    	private final DateFormat formater = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ");
    	
        private Date convertImpl(Object input) {
            if (input instanceof Date) {
                return (Date) input;
            } else if (input instanceof String) {
            	try {
					return formater.parse(input.toString());
				} catch (ParseException e) {
                    throw new CoercingParseLiteralException("The Date String " + input.toString() + " appeared not to be of the expected format yyyy-MM-dd'T'HH:mm:ss.SSSZ");
				}
            } else if (input instanceof Number) {
                BigDecimal value;
                try {
                    value = new BigDecimal(input.toString());
                } catch (NumberFormatException e) {
                    throw new CoercingParseLiteralException("Internal error: should never happen");
                }
                return new Date(value.longValue());
            } else {
                return null;
            }

        }

        @Override
        public String serialize(Object input) {
            if (!(input instanceof Date)) {
                throw new CoercingSerializeException(
                        "Expected type 'java.util.Date' but was '" + typeName(input) + "'."
                );
            }
            return formater.format(input);
        }

        @Override
        public Date parseValue(Object input) {
            Date result = convertImpl(input);
            if (result == null) {
                throw new CoercingParseValueException(
                        "Expected type 'java.util.Date' but was '" + typeName(input) + "'."
                );
            }
            return result;
        }

        @Override
        public Date parseLiteral(Object input) {
            if (!(input instanceof StringValue || input instanceof IntValue)) {
                throw new CoercingParseLiteralException(
                        "Expected AST type 'StringValue' or 'IntValue' but was '" + typeName(input) + "'."
                );
            }
            if(input instanceof StringValue) {
            	return convertImpl(((StringValue) input).getValue());
            } else {
            	return convertImpl(((IntValue) input).getValue());
            }
        }
    });
    
    private static String typeName(Object input) {
        if (input == null) {
            return "null";
        }

        return input.getClass().getSimpleName();
    }
}