//---------------------------------------------------
// Purpose: To demonstrate the implementation and use
//          of finite state machines using 2D arrays.
// Author:  John Gauch
//---------------------------------------------------

#include <iostream>
using namespace std;

// Program constants
const int STATES = 5;
const int INPUTS = 4;

//---------------------------------------------------
// Print the 2D table representing finite state machine
//---------------------------------------------------
void print_table(int table[STATES][INPUTS])
{
   // Print values
   cout << "     ";
   for (int input = 0; input < INPUTS; input++)
      cout << char('a' + input) << "   ";
   cout << endl;

   // Print line
   cout << "   +";
   for (int count = 0; count < INPUTS; count++)
      cout << "---+";
   cout << "\n";

   // Print state table
   for (int state = 0; state < STATES; state++)
   {
      // Print values
      cout << " " << state << " | ";
      for (int input = 0; input < INPUTS; input++)
         cout << table[state][input] << " | ";
      cout << endl;

      // Print line
      cout << "   +";
      for (int count = 0; count < INPUTS; count++)
         cout << "---+";
      cout << "\n";
   }
}

//---------------------------------------------------
// Interactively travese the finite state machine
//---------------------------------------------------
void explore_table(int table[STATES][INPUTS], int start, int end)
{
   // Use state table
   int state = start;
   cout << "state = " << state << endl;
   while (state != end)
   {
      // Get user input
      char dir = ' ';
      int input = INPUTS;
      while (input < 0 || input >= INPUTS)
      {
         cout << "Enter direction ['a'..'" << char('a'+INPUTS-1) << "']: ";
         cin >> dir;
         input = dir - 'a';
      }

      // Move to new state
      state = table[state][input];
      cout << "state = " << state << endl;
   }

   // Print final message
   cout << "You win!\n";
}

//---------------------------------------------------
// Main program
//---------------------------------------------------
int main()
{
   // Define state table
   int start = 0;
   int end = 0;
   int table[STATES][INPUTS] = {
      {1,2,3,4},
      {2,3,4,0},
      {3,4,0,1},
      {4,0,1,2},
      {0,1,2,3} };

   // Print state table
   print_table(table);

   // Explore state table
   cout << "Enter start state: ";
   cin >> start;
   cout << "Enter end state: ";
   cin >> end;
   explore_table(table, start, end);
   return 0;
}