// This program computes the Flesch Index for documents. The flesch
// index is a value that maps to a scale of reading levels. The higher 
// the value the easier the document should read, and the lower the
// grade level of the document.

#include <iostream.h>
#include <string>
#include <fstream.h>
#include <ctype.h>



// IsVowel
// Description: This function returns true if c is a vowel, or it
// returns false if c is not a vowel.
bool IsVowel(char c)
{
  return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
}


// IsSyllable
// Description: This function determines if the string starting at
// position 'pos' is a syllable. A syllable is a group of 1 or more
// consecutive vowels in a word. All words have at least one
// syllable. The 'newpos' is the position in the string at the end of the
// syllable if one is found. 'word' is the word that is being parsed
// for syllables.
bool IsSyllable(string& word, int pos, int& newpos)
{
  
  newpos = pos;

  // if the char at pos is not a vowel, then its not a syllable
  if ( !IsVowel(tolower(word[pos])) )
    return false;

  // the char is a vowel, and so we have to look for consecutive
  // vowel. 
  for (;pos < word.length(); pos++)
    {

      // if we find a consonant, then set the newpos to the char
      // before, and return true.
      if ( !IsVowel(tolower(word[pos])) )
	{
	  newpos = pos-1;
	  return true;
	}

    }
}


// ComputeNumOfSylls
// Description: Given a word 'theWord' compute the number of syllables 
// in that word.
float ComputeNumOfSylls(string& theWord)
{
   float syllCount=0;
   int newpos = 0;
   int curpos = 0;

   // curpos will move through the string to examine each character
   // for the start of a syllable.
   while (curpos < theWord.length())
   {
     // if a syllable is found here, then count it
     if (IsSyllable(theWord, curpos, newpos))
       {
	 syllCount++;
	 curpos = newpos;
       }
	
     curpos++;  // move to the next position after a syll or not
   }


   // if the word ends in an e then don't count that sequence as a
   // syllable 
   if ( (theWord[theWord.length()-1] == 'e') &&
	(syllCount > 1) )
     syllCount--;

   // if no sylls were found so far, then every word has at least one
   if (syllCount == 0) syllCount = 1;

	 
   return syllCount;
}


// IsSentence
// Description: Returns true is c is a punctuation character that
// represents the end of a sentence.
bool IsSentence(char c)
{
  return c == '.' ||  c == '?' || c == '!' || c == ';' || c == ':';
}
  
// ComputeNumOfSents
// Description: Scan the parameter 'theWord' and look for sentence
// ending punctuation.
float ComputeNumOfSents(string theWord)
{
   float sentenceCount=0;

   // if last char is punctuation char count a sentence
   if (IsSentence(theWord[theWord.length()-1]))
     {
       sentenceCount++;
     }
   
   return sentenceCount;
   
}

// ComputeIndex
// Description: This function computes the Flesch Index
float ComputeIndex(float NumOfWords,
		   float SyllablesCount,
		   float SentenceCount)
{
  if ( (NumOfWords > 0) && (SentenceCount > 0) )
    return  206.835 - 84.6 * (SyllablesCount/NumOfWords) -
      1.015*(NumOfWords/SentenceCount); 
  else
    return -1;
}

// ProcessFile
// Description: This function processes a file one word at a time. 
void ProcessFile(ifstream &input, string Name)
{
   string Aword;
   float NumOfWords=0;
   float  SyllablesCount=0;
   float  SentenceCount=0;
   
   // read one word at a time till end of file and count components
   while (input >> Aword)
   {
      NumOfWords++;
      SentenceCount += ComputeNumOfSents(Aword);
      SyllablesCount += ComputeNumOfSylls(Aword);
   }


   // outputs the information when done

   cout << "The # of words " << NumOfWords << endl;
   cout << "The # of syllables " << SyllablesCount  << endl;
   cout << "The # of sentences " << SentenceCount  << endl;
   
   cout << "The Flesch index for " << Name << " : " <<
      ComputeIndex(NumOfWords, SyllablesCount, SentenceCount) << endl;
}


// This is the driver program
void main()
{

   string FileName;
   ifstream InFile;

   // loop until user inputs the 'quit' command as a file name
   do
   {
      cout << "Please enter the name of a file (enter quit to exit): ";
      cin >> FileName;
   
      InFile.open(FileName.c_str());

      // if file opens then process it, otherwise prompt again
      if (InFile)
      {
	 ProcessFile(InFile, FileName);
	 InFile.close();
      }
      else
      {
	 if (FileName != "quit")
	    cerr << "The file, " << FileName << " could not be opened" << 
	       endl;
      }
   } while (FileName != "quit");

}