package ru.delkom07.geometry;

import ru.delkom07.geometry.obj.LineFunction;

public class LineFunctions {
	
 	/**
 	 * Returns line function of given segment.
 	 * @param p1 - first point of segment.
 	 * @param p2 - second point of segment.
 	 * @return line function of given segment.
 	 * @tested
 	 */
 	public static LineFunction getLineFunction(double[] p1, double[] p2) {
 		final double A = -(p2[1]-p1[1]);  // -(y2-y1)
 		final double B = (p2[0]-p1[0]); // (x2-x1)
 		final double C = -p1[1]*p2[0] + p1[0]*p2[1]; // -y1x2 + x1y2
 		
 		final double k = (p2[1]-p1[1])/(p2[0]-p1[0]); // (y2-y1)/(x2-x1)
 		final double b = (p1[1]*p2[0]-p1[0]*p2[1])/(p2[0]-p1[0]); // (y1x2-x1y2)/(x2-x1)
 		
 		return new LineFunction() {
 			@Override
 			public double value(double x) {
 		 			return k*(double)x + b;
 			}
 			@Override
 			public double getA() {return A;}
 			@Override
 			public double getB() {return B;}
 			@Override
 			public double getC() {return C;}
 			@Override
 			public double getk() {return k;}
 			@Override
 			public double getb() {return b;}
 		};
 	}
 	
 	/**
 	 * Returns perpendicular line function of given segment.
 	 * @param p1 - first point of segment.
 	 * @param p2 - second point of segment.
 	 * @return line function of given segment.
 	 * @tested
 	 */
 	public static LineFunction getNormalLineFunction(double[] p1, double[] p2, double[] pM) {
 		final double k = -(p2[0]-p1[0])/(p2[1]-p1[1]); // -(x2-x1)/(y2-y1)
 		final double b = pM[1]+(-k)*pM[0]; // y0+(x2-x1)/(y2-y1)*x0
 		
 		final double A = k;  
 		final double B = -1; 
 		final double C = b; 
 		
 		return new LineFunction() {
 			@Override
 			public double value(double x) {
 		 			return k*(double)x + b;
 			}
 			@Override
 			public double getA() {return A;}
 			@Override
 			public double getB() {return B;}
 			@Override
 			public double getC() {return C;}
 			@Override
 			public double getk() {return k;}
 			@Override
 			public double getb() {return b;}
 		};
 	}
 	
 	/**
 	 * Returns middle normal line function of given segment.
 	 * @param p1 - first point of segment.
 	 * @param p2 - second point of segment.
 	 * @return middle normal line function of given segment.
 	 * @tested
 	 */
 	public static LineFunction getMiddleNormalLineFunction(double[] p1, double[] p2) {
 		// Middle point
 		double xMdl = (p1[0]+p2[0])/2.0;
 		double yMdl = (p1[1]+p2[1])/2.0;
 		
 		final double k = -(p2[0]-p1[0])/(p2[1]-p1[1]); // -(x2-x1)/(y2-y1)
 		final double b = yMdl+(-k)*xMdl; // y0+(x2-x1)/(y2-y1)*x0
 		
 		final double A = k;  
 		final double B = -1; 
 		final double C = b;
 		
 		return new LineFunction() {
 			@Override
 			public double value(double x) {
 		 			return k*(double)x + b;
 			}
 			@Override
 			public double getA() {return A;}
 			@Override
 			public double getB() {return B;}
 			@Override
 			public double getC() {return C;}
 			@Override
 			public double getk() {return k;}
 			@Override
 			public double getb() {return b;}
 		};
 	}
 	
 	
 	
    /**
     * Calculates distance from point to line.
     * @param point - given point.
     * @param func - function of line.
     * @return distance from point to line.
     * @tested
     */
    private static double distanceFromPointToLine(double[] point, LineFunction func) {
    	double A = func.getA();
    	double B = func.getB();
    	double C = func.getC();
    	
    	double tmp = Math.sqrt(A*A + B*B);
		return Math.abs(A*point[0] + B*point[1] + C) / tmp;
    }
    
    /**
     * Calculates distance from point to line.
     * @param point - given point.
     * @param line - given line.
     * @return distance from point to line.
     * @tested
     */
    private static double distanceFromPointToLine(double[] point, double[] line) {
		double A = (line[3]-line[1]);
		double B = -(line[2]-line[0]);
		double C = (line[1]*line[2] - line[1]*line[0] - line[0]*line[3] + line[0]*line[1]);
		
		double tmp = Math.sqrt(A*A + B*B);
		if(0!=tmp) return Math.abs(A*point[0] + B*point[1] + C) / tmp;
		return SimpleGeometry.distance(point, new double[]{line[0], line[1]});
    }

}