function word_indices = processEmail(email_contents)
  ##PROCESSEMAIL preprocesses a the body of an email and
  ##returns a list of word_indices 
  ##   word_indices = PROCESSEMAIL(email_contents) preprocesses 
  ##   the body of an email and returns a list of indices of the 
  ##   words contained in the email. 
  ##

  ## Load Vocabulary
  vocabList = getVocabList();

  ## Init return value
  word_indices = [];

  ## ========================== Preprocess Email ===========================

  ## Find the Headers ( \n\n and remove )
  ## Uncomment the following lines if you are working with raw emails with the
  ## full headers

  ## hdrstart = strfind(email_contents, ([char(10) char(10)]));
  ## email_contents = email_contents(hdrstart(1):end);

  ## Lower case
  email_contents = lower(email_contents);

  ## Strip all HTML
  ## Looks for any expression that starts with < and ends with > and replace
  ## and does not have any < or > in the tag it with a space
  email_contents = regexprep(email_contents, '<[^<>]+>', ' ');

  ## Handle Numbers
  ## Look for one or more characters between 0-9
  email_contents = regexprep(email_contents, '[0-9]+', 'number');

  ## Handle URLS
  ## Look for strings starting with http:// or https://
  email_contents = regexprep(email_contents, ...
                             '(http|https)://[^\s]*', 'httpaddr');

  ## Handle Email Addresses
  ## Look for strings with @ in the middle
  email_contents = regexprep(email_contents, '[^\s]+@[^\s]+', 'emailaddr');

  ## Handle $ sign
  email_contents = regexprep(email_contents, '[$]+', 'dollar');


  ## ========================== Tokenize Email ===========================

  ## Output the email to screen as well
  fprintf('\n==== Processed Email ====\n\n');

  ## Process file
  l = 0;

  str_words = {};

  while ~isempty(email_contents)

    ## Tokenize and also get rid of any punctuation
    [str, email_contents] = \
        strtok(email_contents, \
               [" @$/#.-:&*+=[]?!(){},'\">_<;%" char(10) char(13)]);
    
    ## Remove any non alphanumeric characters
    str = regexprep(str, '[^a-zA-Z0-9]', '');

    ## Stem the word 
    ## (the porterStemmer sometimes has issues, so we use a try catch block)
    try str = porterStemmer(strtrim(str)); 
    catch str = ''; continue;
    end_try_catch;

    ## Skip the word if it is too short
    if length(str) < 1
      continue;
    endif

    ## Store the words
    str_words{end+1} = str;

    ## Print to screen, ensuring that the output lines are not too long
    if (l + length(str) + 1) > 78
      fprintf('\n');
      l = 0;
    endif
    fprintf("%s ", str);
    l = l + length(str) + 1;
    
  endwhile

  word_indices = lookup (vocabList, str_words, "m");
  word_indices (word_indices == 0) = [];
  
  ## Print footer
  fprintf("\n\n=========================\n");
  
endfunction