/* The plan

   0. use official C++ libraries the official way

   1. read the file into an array

   2. be able to search the table

   3. read chemical formula from user

   4. work out total weight

*/

#include <string>
#include <iostream>
#include <fstream>

using namespace std;

struct element
{ string symbol, name;
  int atnumber;
  double atweight; };

// defined "element" as a new type of variable/constant

void print(element X)
{ cout << X.symbol << "(\"" << X.name << "\", ";
  cout << X.atnumber << ", " << X.atweight << ")\n"; }

void read(element & e, ifstream & f)
{ f >> e.symbol >> e.name >> e.atweight; }

element search(string sy, element tab[], int max)
   /* given symbol for an element, and
        whole periodic table, and
        number of elements in the table,
      search table for match, and return the element object */
{ for (int i = 1; i <= max; i += 1)
    if (tab[i].symbol == sy)
      return tab[i];
  // if user mistypes symbol got to return something easily detected
  tab[0].atnumber = 0;
  return tab[0]; }

int main()
{
  ifstream f;
  // f.open("http://rabbit.eng.miami.edu/class/een118/atwt.txt");
  //     Can't open a URL, files only
  string filename = "/home/www/class/een118/atwt.txt";
  f.open(filename.c_str());
  // .c_str() given old C equivalent of C++ string
  if (f.fail())
  { cout << "Can't open file '" << filename << "'\n";
    return 0; }

  element ptable[150];    // flexible for future growth
  int numels;

  // read the table
  for (int atno = 1; atno < 150; atno += 1)
  { element e;
    read(e, f);
    if (f.fail())
    { numels = atno - 1;
      break; }
    e.atnumber = atno;
    ptable[atno] = e; }
  f.close();

  // just while testing, verify it worked
  cout << "Finished reading " << numels << " elements\n";
  for (int i = 1; i <= numels; i += 1)
    print(ptable[i]); 

  // test the search function
  while (true)
  { cout << "type a symbol. ";
    string s;
    cin >> s;
    element x = search(s, ptable, numels);
    if (x.atnumber == 0)
      cout << "no such thing\n";  // special fake element to signal error
    else
      print(x); }
}