//
//  Vector2D.m
//  ExploringGraphics2
//
//  Copyright TrailsintheSand.com 2008. All rights reserved.
//

#import "Vector2D.h"
#import "Point2D.h"

// Geometry constants
#define PI 3.14159
#define ONEEIGHTYOVERPI 57.29582
#define PIOVERONEEIGHTY  0.01745

@implementation Vector2D

@synthesize angle;
@synthesize length;
@synthesize endPoint;

- (id)init
{
    if (self = [super init])
    {
        angle = 0.0;
        length = 0.0;
        endPoint = [[Point2D alloc] init];
    }
    
    return self;
}

- (id)initWithX:(CGFloat)x Y:(CGFloat)y;
{
    if (self = [super init])
    {
        endPoint = [[Point2D alloc] initWithX:x Y:y];
        
        // Calculate the angle based on the end point
        angle = atan2(-endPoint.Y, endPoint.X) * ONEEIGHTYOVERPI;
        if(angle < 0)
        {
            angle += 360;
        }

        // Calculate the length of the vector
        length = sqrt(endPoint.X * endPoint.X + endPoint.Y * endPoint.Y);
    }
    
    return self;
}

- (void)setAngle:(CGFloat)degrees
{
    angle = degrees;
    double radians = angle * PIOVERONEEIGHTY;
    endPoint.X = length * cos(radians); // could speed these up with a lookup table
    endPoint.Y = -(length * sin(radians));
}

@end