// Program slice.cpp      CS 31 Extended Example       shinnerl@ucla.edu
// For a detailed description, see the accompanying specification.
// Note: "word" means any contiguous sequence of nonspace characters.

#include <iostream>
#include <string>
#include <cstdlib>
#include <cctype>
#include <cassert>
using std::string;
using std::cout;
using std::cin;
using std::endl;
using std::isspace;

void showMenu(){ 

  cout << "\n String Slicer Menu\n"
       << " ------------------\n"
       << " P    PRINT    the phrase to the screen  \n"
       << " S    SLICE    one letter from each word \n"
       << " T    TABULATE all slices in adjacent columns \n"
       << " Q    QUIT     the program" << endl;
}

void showPrompt(){
   cout << "\nPSTQ> ";
}

unsigned skipSpace( const string& s, unsigned i, unsigned length ){
  // Returns "length" when end of string is reached.
  // Else, returns index of next nonspace.
  while ( i < length && isspace( s[i] ) )
    ++i;
  return i;
}

unsigned nextWord( const string& s, unsigned i ){
  // Return the index of the first character of the next word.
  // Return index equal to s.size() if the end of s is reached.
  unsigned l = s.size();
  while ( i < l && !isspace( s[i] ) )  // Skip remaining nonspace.
    ++i;
  i = skipSpace( s, i, l);             // Skip remaining space.
  return i;
}

unsigned wordLength( const string& s, unsigned i ){
  // Given a word starting at index i,
  // find the number of characters in the word.
  unsigned l = s.size();
  assert (!isspace(s[i]) && i < l );
  unsigned j = 0;
  while ( i < l && !isspace( s[i] ) )
  {  ++i;  ++j; }
  return j;
}

void printSlice( const string& s, unsigned mwl ){
  // mwl = maximum word length
  unsigned iSlice;
  do{
      cout << "Which letter?  Enter the slice index (1-" << mwl << "): ";
      cin  >> iSlice;
  } while ( iSlice <= 0 || iSlice > mwl );
  
  cout << "Requested slice: ";
  unsigned l = s.size();
  unsigned i = skipSpace( s, 0, l);     // Start at first nonspace.
  while ( i < l ){     // Invariant: i indexes the beginning of the next word.
    unsigned wl = wordLength(s, i);
    cout << s[ i+(iSlice-1)%wl ];
    i = nextWord(s, i);
  }
}

unsigned maxWordLength( const string& s ){
  // Find the length of the longest word in the string.
  unsigned l = s.size(), cwl = 0,  // cwl == "current word length."
           i = 0, answer = 0;
  i = skipSpace( s, i, l );
  while (i < l){
     cwl = wordLength( s, i );
     if ( cwl > answer )
        answer = cwl;
     i = nextWord( s, i );
  }
  return answer;
}

void printTable( const string& s, unsigned mwl ){

  // Print the words of s in a rectangular table,
  // padding out words shorter than mwl==maxWordLength(s)
  // by periodic repetition to form a rectangle.

  unsigned i = 0, j;
  const char space = ' ';
  unsigned l = s.size();
  i = skipSpace( s, i, l);           // Go to start of the first word. 
  while ( i < l){
     unsigned cwl = wordLength( s, i );   // cwl == current word length
     unsigned i0 = i;
     while ( i < l && !isspace(s[i]) ){  // Print each word at least once,
        cout << space << s[i++];         // but watch out for the end of s!
     }
     j = i-i0;
     while ( j < mwl ){              // Repeat until the row is filled.
        cout << space << s[i0 + j++%cwl] ;
     }
     cout << endl;
     i = skipSpace( s, i, l);        // Go to start of the next word. 
  }
}


int main(){
   string input;
   char selection;
   cout << "Enter a one-line phrase: " << endl;
   getline(cin, input);
   if (input.empty()) 
     { cout << "Error: empty input phrase\n"; std::exit(-1); }
   unsigned mwl = maxWordLength( input ), iSlice=0;
   showMenu();

   do{
      showPrompt();
      cin >> selection;
      switch (selection){
         case 'P': case 'p':
            cout << input << endl;
            break;
         case 'S': case 's':
            printSlice(input, mwl);
            cout << endl;
            break;
         case 't': case 'T':
            printTable(input, mwl);
            break;
         case 'q': case 'Q':
            break;
         default:
            showMenu();
      }
   }
   while ( selection != 'Q' && selection != 'q' );
   return EXIT_SUCCESS;
}