// Purpose.  Bridge design pattern demo
// 
// Discussion.  The motivation is to decouple the Time interface from the
// Time implementation, while still allowing the abstraction and the
// realization to each be modelled with their own inheritance hierarchy.
// The implementation classes below are straight-forward.  The interface
// classes are a little more subtle.  Routinely, a Bridge pattern
// interface hierarchy "hasa" implementation class.  Here the interface
// base class "hasa" a pointer to the implementation base class, and each
// class in the interface hierarchy is responsible for populating the base
// class pointer with the correct concrete implementation class.  Then all
// requests from the client are simply delegated by the interface class to
// the encapsulated implementation class.

#include <iostream.h>
#include <iomanip.h>
#include <string.h>

class TimeImp {
public:
   TimeImp( int hr, int min ) {
      hr_ = hr;  min_ = min; }
   virtual void tell() {
      cout << "time is " << setw(2) << setfill(48) << hr_ << min_ << endl; }
protected:
   int hr_, min_;
};

class CivilianTimeImp : public TimeImp {
public:
   CivilianTimeImp( int hr, int min, int pm ) : TimeImp( hr, min ) {
      if (pm)
         strcpy( whichM_, " PM" );
      else
         strcpy( whichM_, " AM" ); }
   /* virtual */ void tell() {
      cout << "time is " << hr_ << ":" << min_ << whichM_ << endl; }
protected:
   char  whichM_[4];
};

class ZuluTimeImp : public TimeImp {
public:
   ZuluTimeImp( int hr, int min, int zone ) : TimeImp( hr, min ) {
      if (zone == 5)
         strcpy( zone_, " Eastern Standard Time" );
      else if (zone == 6)
         strcpy( zone_, " Central Standard Time" ); }
   /* virtual */ void tell() {
      cout << "time is " << setw(2) << setfill(48) << hr_ << min_ 
         << zone_ << endl; }
protected:
   char  zone_[30];
};

class Time {
public:
   Time() { }
   Time( int hr, int min ) {
      imp_ = new TimeImp( hr, min ); }
   virtual void tell() {
      imp_->tell(); }
protected:
   TimeImp*  imp_;
};

class CivilianTime : public Time {
public:
   CivilianTime( int hr, int min, int pm ) {
      imp_ = new CivilianTimeImp( hr, min, pm ); }
};

class ZuluTime : public Time {
public:
   ZuluTime( int hr, int min, int zone ) {
      imp_ = new ZuluTimeImp( hr, min, zone ); }
};


void main() {
   Time*  times[3];
   times[0] = new Time( 14, 30 );
   times[1] = new CivilianTime( 2, 30, 1 );
   times[2] = new ZuluTime( 14, 30, 6 );
   for (int i=0; i < 3; i++)
      times[i]->tell();
}

// time is 1430
// time is 2:30 PM
// time is 1430 Central Standard Time