// LabTest.java
//
// Author: Rahul Simha
// Feb, 2008
//
// Simulate a disease test.


public class LabTest {

    double probSick=0.05;           // 5% of population is infected.
    double probSickTestsPos=0.99;   // Pr[Pos|Sick]
    double probWellTestsPos=0.03;   // Pr[Pos|Well]

    boolean isSick;

    public LabTest (double probSick, double probSickTestsPos, double probWellTestsPos)
    {
        this.probSick = probSick;
        this.probSickTestsPos = probSickTestsPos;
        this.probWellTestsPos = probWellTestsPos;
    }
    

    public void nextPatient ()
    {
	if (RandTool.uniform() < probSick) {
	    isSick = true;
	}
	else {
	    isSick = false;
	}
    }

    public boolean isSick ()
    {
	return isSick;
    }

    public boolean testedPositive ()
    {
	if (isSick) {
	    if (RandTool.uniform() < probSickTestsPos) {
		return true;
	    }
	    return false;
	}
	if (RandTool.uniform() < probWellTestsPos) {
	    return true;
	}
	return false;
    }

}