/**
 * @author tschw
 * @author Ben Houston / http://clara.io/
 * @author David Sarno / http://lighthaus.us/
 */

var AnimationUtils = {

	// same as Array.prototype.slice, but also works on typed arrays
	arraySlice: function ( array, from, to ) {

		if ( AnimationUtils.isTypedArray( array ) ) {

			// in ios9 array.subarray(from, undefined) will return empty array
			// but array.subarray(from) or array.subarray(from, len) is correct
			return new array.constructor( array.subarray( from, to !== undefined ? to : array.length ) );

		}

		return array.slice( from, to );

	},

	// converts an array to a specific type
	convertArray: function ( array, type, forceClone ) {

		if ( ! array || // let 'undefined' and 'null' pass
				! forceClone && array.constructor === type ) return array;

		if ( typeof type.BYTES_PER_ELEMENT === 'number' ) {

			return new type( array ); // create typed array

		}

		return Array.prototype.slice.call( array ); // create Array

	},

	isTypedArray: function ( object ) {

		return ArrayBuffer.isView( object ) &&
				! ( object instanceof DataView );

	},

	// returns an array by which times and values can be sorted
	getKeyframeOrder: function ( times ) {

		function compareTime( i, j ) {

			return times[ i ] - times[ j ];

		}

		var n = times.length;
		var result = new Array( n );
		for ( var i = 0; i !== n; ++ i ) result[ i ] = i;

		result.sort( compareTime );

		return result;

	},

	// uses the array previously returned by 'getKeyframeOrder' to sort data
	sortedArray: function ( values, stride, order ) {

		var nValues = values.length;
		var result = new values.constructor( nValues );

		for ( var i = 0, dstOffset = 0; dstOffset !== nValues; ++ i ) {

			var srcOffset = order[ i ] * stride;

			for ( var j = 0; j !== stride; ++ j ) {

				result[ dstOffset ++ ] = values[ srcOffset + j ];

			}

		}

		return result;

	},

	// function for parsing AOS keyframe formats
	flattenJSON: function ( jsonKeys, times, values, valuePropertyName ) {

		var i = 1, key = jsonKeys[ 0 ];

		while ( key !== undefined && key[ valuePropertyName ] === undefined ) {

			key = jsonKeys[ i ++ ];

		}

		if ( key === undefined ) return; // no data

		var value = key[ valuePropertyName ];
		if ( value === undefined ) return; // no data

		if ( Array.isArray( value ) ) {

			do {

				value = key[ valuePropertyName ];

				if ( value !== undefined ) {

					times.push( key.time );
					values.push.apply( values, value ); // push all elements

				}

				key = jsonKeys[ i ++ ];

			} while ( key !== undefined );

		} else if ( value.toArray !== undefined ) {

			// ...assume THREE.Math-ish

			do {

				value = key[ valuePropertyName ];

				if ( value !== undefined ) {

					times.push( key.time );
					value.toArray( values, values.length );

				}

				key = jsonKeys[ i ++ ];

			} while ( key !== undefined );

		} else {

			// otherwise push as-is

			do {

				value = key[ valuePropertyName ];

				if ( value !== undefined ) {

					times.push( key.time );
					values.push( value );

				}

				key = jsonKeys[ i ++ ];

			} while ( key !== undefined );

		}

	}

};


export { AnimationUtils };
