// Amount of time to let the robot run.
#define RUNTIME 30.0
// Direction control flags.
#define LEFT 0
#define RIGHT 1
// Motor power level definitions.
#define HIGH 80
#define MID 60
#define LOW 40

int irRead[5] = {0,0,0,0,0}; // Array used to store the IR sensor readings.
int hit = -1; // Variable used to indicate where a light source has been detected
int oldHit = hit;
int timeup = 0; // Flag used to signal when time has expired.

// Variables used to store the process ID's of the three main processes.
int timerPID;
int lightLocatorPID;
int controlMotorsPID;

// The timer function waits for a specified length of time and then switches the
// timeup flag.
void timer( float t ){
    float startTime = seconds();
    while( seconds() - startTime < t ){  // While time has not expired.
        defer();  // Relinquish control of the processor.
    }
    timeup = 1; // Once time has expired, change the flag, and exit the function.
} // timer( float t )

// The lightLocator function sets the variable hit to an integer representing
// the IR sensor that is detecting the most IR light.
// -1 indicates that no meaningful hit was detected.
// 0 through 4 indicate which sensor has a hit.
void lightLocator() {
    int i;        // A counter index.
    int minRead;  // The lowest IR reading.
    int maxRead;  // The highest IR reading.
    int maxIndex; // The index (sensor number) of the highest IR reading.
    
    while(!timeup){
        // Reset tracking variables.
        minRead = 256;
        maxRead = -1;
        maxIndex = -1;    
        // Loop through each sensor to obtain the readings.
        for(i=0; i<=4; i++){
            irRead[i] = 255 - analog(i); // ****
            
            if( irRead[i]<minRead ){     // ****
                minRead = irRead[i];
            }
            if( irRead[i]>maxRead ){     // ****
                maxIndex = i;
                maxRead = irRead[i];
            }
        }
        // Process the readings to see if a meaningful hit was found.
        if( /* Enter a Boolean statement that recognizes a true hit. */ ){
            hit = maxIndex;
        }
        else{ hit = -1; } // ****
    }
} // lightLocator()


// The controlMotors function controls the motors based on the value of "hit"
// which is continuously updated by lightLocator().
void controlMotors()
{
    while(!timeup){ // As long as time is left, continue updating the motor commands.
        if ( hit != oldHit){ // ****
            oldHit = hit;
            if(hit == -1){ // No hit; what should you do?
                defer();
            }
            if(hit == 0){  // Turn left quickly
                defer();
            }
            if(hit == 1){  // Turn left slowly
                defer();
            }
            if(hit == 2){  // Go forward
                defer();
            }
            if(hit == 3){  // Turn right slowly
                defer();
            }
            if(hit == 4){  // Turn right quickly
                defer();
            }
        }
    }
    // Once time has expired kill the engines and end the function.
    alloff();
} // controlMotors()

// Main simply starts processes for the controlling functions above.
void main()
{
    while(1){
        printf("Press start to  chase light.\n");
        while( !start_button() ){  } // ****
        
        printf("Chasing!!\n");  
        reset_system_time();  // ****
        timeup = 0;           // ****
        
        timerPID = start_process( timer( RUNTIME ) );
        lightLocatorPID = start_process( lightLocator() );
        controlMotorsPID = start_process( controlMotors() );
        
        while(!timeup && !stop_button() ){  // ****
            // Add debugging commands here as needed.
            defer(); 
        }
        
        // ****
        kill_process(controlMotorsPID);
        kill_process(lightLocatorPID);
        kill_process(timerPID);
        alloff();
        beep();
    }
} // main()