// lightapp.cpp - TRAFFIC LIGHT APPLICATION
//
// MODULE INDEX
// NAME                 CONTENTS
// InitApp              Initiate application
// Tick                 Process clock tick
// VehicleWaiting       Process change in vehicle waiting status
//
// MAINTENANCE HISTORY
// DATE         PROGRAMMER AND DETAILS
// 09-11-02     JS      Original
//
//-----------------------------------------------------------------------------

#include <stdio.h>              // Standard input/output
#include <string.h>             // String manipulation
#include <stdlib.h>             // Standard library
#include <errno.h>              // Error codes
#include "lightsys.h"           // Traffic light system declarations

//-----------------------------------------------------------------------------

// TRAFFIC LIGHT CYCLE STRUCTURE

struct Cycle {
        int             cyclePeriod;            // Cycle period
        Colour          cycleNorthColour;       // North facing colour
        Colour          cycleEastColour;        // East facing colour
        Colour          cycleSouthColour;       // South facing colour
        Colour          cycleWestColour;        // West facing colour
};

//-----------------------------------------------------------------------------

// CYCLE TABLE

Cycle cycleArr[] = {
        {30,    GREEN,  RED,    RED,    RED},
        {5,     AMBER,  RED,    RED,    RED},
        {60,    RED,    GREEN,  RED,    RED},
        {5,     RED,    AMBER,  RED,    RED},
        {40,    RED,    RED,    GREEN,  RED},
        {5,     RED,    RED,    AMBER,  RED},
        {50,    RED,    RED,    RED,    GREEN},
        {5,     RED,    RED,    RED,    AMBER}
};
#define CYCLECNT (sizeof(cycleArr)/sizeof(cycleArr[0]))

//-----------------------------------------------------------------------------

// GLOBAL DATA

int             phase;          // Current phase
int             ticksRem;       // Ticks remaining in the current phase
int             northWait;      // Vehicles waiting on the north branch
int             eastWait;       // Vehicles waiting on the east branch
int             southWait;      // Vehicles waiting on the south branch
int             westWait;       // Vehicles waiting on the west branch

//-----------------------------------------------------------------------------

// INITIATE APPLICATION

void
InitApp ()
{
        phase = 0;
        ticksRem = cycleArr[phase].cyclePeriod;
        northWait = 0;
        eastWait = 0;
        southWait = 0;
        westWait = 0;
        Display (
                cycleArr[phase].cycleNorthColour,
                cycleArr[phase].cycleEastColour,
                cycleArr[phase].cycleSouthColour,
                cycleArr[phase].cycleWestColour
        );
}

//-----------------------------------------------------------------------------

// PROCESS CLOCK TICK

void
Tick ()
{
        // Decrement ticks remaining in the current cycle.
        // If no more ticks remain, move to the next phase.

        ticksRem -- ;
        if (ticksRem == 0) {

                // Select the next phase

                phase ++ ;
                if (phase >= CYCLECNT) phase = 0;

                // If the new phase involves a light turning green
                // and no cars are waiting on that branch, but cars
                // are waiting on a branch somewhere, skip the next
                // two phases.

                while (
                        (
                                northWait ||
                                eastWait ||
                                southWait ||
                                westWait
                        ) && (
                                (
                                        ! northWait &&
                                        cycleArr[phase].cycleNorthColour==GREEN
                                ) || (
                                        ! eastWait &&
                                        cycleArr[phase].cycleEastColour==GREEN
                                ) || (
                                        ! southWait &&
                                        cycleArr[phase].cycleSouthColour==GREEN
                                ) || (
                                        ! westWait &&
                                        cycleArr[phase].cycleWestColour==GREEN
                                )
                        )
                ) {
                        phase ++ ;
                        if (phase >= CYCLECNT) phase = 0;
                        phase ++ ;
                        if (phase >= CYCLECNT) phase = 0;
                }

                // Set the ticks remaining in the new phase

                ticksRem = cycleArr[phase].cyclePeriod;

                // Display the new traffic light settings

                Display (
                        cycleArr[phase].cycleNorthColour,
                        cycleArr[phase].cycleEastColour,
                        cycleArr[phase].cycleSouthColour,
                        cycleArr[phase].cycleWestColour
                );
        }
}

//-----------------------------------------------------------------------------

// PROCESS CHANGE IN VEHICLE WAITING STATUS

void
VehicleWaiting (
        int             northNewWait,   // Vehicles waiting on the north branch
        int             eastNewWait,    // Vehicles waiting on the east branch
        int             southNewWait,   // Vehicles waiting on the south branch
        int             westNewWait)    // Vehicles waiting on the west branch
{
        northWait = northNewWait;
        eastWait = eastNewWait;
        southWait = southNewWait;
        westWait = westNewWait;
}