/*

     File: CrumbPath.m 

 Abstract: n/a 

  Version: 1.2 

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*/

#import "CrumbPath.h"

#define INITIAL_POINT_SPACE 1000

#define MINIMUM_DELTA_METERS 10.0

@implementation CrumbPath

@synthesize points, pointCount;

- (id)initWithCenterCoordinate:(CLLocationCoordinate2D)coord

{

    if (self = [super init]) {

        // initialize point storage and place this first coordinate in it

        pointSpace = INITIAL_POINT_SPACE;

        points = malloc(sizeof(MKMapPoint) * pointSpace);

        points[0] = MKMapPointForCoordinate(coord);

        pointCount = 1;

        MKMapRect worldRect = MKMapRectMake(0, 0, MKMapSizeWorld.width, MKMapSizeWorld.height);

        boundingMapRect = worldRect;

        // initialize read-write lock for drawing and updates

        pthread_rwlock_init(&rwLock, NULL);

    }

    return self;

}

- (void)dealloc

{

    free(points);

    pthread_rwlock_destroy(&rwLock);

    [super dealloc];

}

- (CLLocationCoordinate2D)coordinate

{

    return MKCoordinateForMapPoint(points[0]);

}

- (MKMapRect)boundingMapRect

{

    return boundingMapRect;

}

- (void)lockForReading

{

    pthread_rwlock_rdlock(&rwLock);

}

- (void)unlockForReading

{

    pthread_rwlock_unlock(&rwLock);

}

- (MKMapRect)addCoordinate:(CLLocationCoordinate2D)coord

{

    // Acquire the write lock because we are going to be changing the list of points

    pthread_rwlock_wrlock(&rwLock);

    // Convert a CLLocationCoordinate2D to an MKMapPoint

    MKMapPoint newPoint = MKMapPointForCoordinate(coord);

    MKMapPoint prevPoint = points[pointCount - 1];

    // Get the distance between this new point and the previous point.

    CLLocationDistance metersApart = MKMetersBetweenMapPoints(newPoint, prevPoint);

    MKMapRect updateRect = MKMapRectNull;

    if (metersApart > MINIMUM_DELTA_METERS) {

        // Grow the points array if necessary

        if (pointSpace == pointCount) {

            pointSpace *= 2;

            points = realloc(points, pointSpace);

        }    

        // Add the new point to the points array

        points[pointCount] = newPoint;

        pointCount++;

        // Compute MKMapRect bounding prevPoint and newPoint

        double minX = MIN(newPoint.x, prevPoint.x);

        double minY = MIN(newPoint.y, prevPoint.y);

        double maxX = MAX(newPoint.x, prevPoint.x);

        double maxY = MAX(newPoint.y, prevPoint.y);

        updateRect = MKMapRectMake(minX, minY, maxX - minX, maxY - minY);

    }

    pthread_rwlock_unlock(&rwLock);

    return updateRect;

}

@end