/**
 * triangle s1 s2 s2 - given three sides of the triangle, classifies
 *   the triangle.
 */

#include <stdio.h>
#include <stdlib.h>

// +-----------+-------------------------------------------------------
// | Utilities |
// +-----------+

/**
 * max(x,y) - compute the larger of x and y.
 */
int
max (int x, int y)
{
  return x > y ? x : y;
} // max

/**
 * min(x,y) - compute the smaller of x and y
 */
int
min (int x, int y)
{
  return x < y ? x : y;
} // min

/**
 * usage() - print a usage message.
 */
void
usage ()
{
  printf ("Usage: triangle side1 side2 side3\n");
  printf ("  where side1, side2, and side3 are integers.\n");
} // usage()


// +------+------------------------------------------------------------
// | Main |
// +------+

int
main (int argc, char *argv[])
{
  int sides[3];                 // The three sides of the triangle
  int perimeter;                // The perimiter of the triangle
  int shortest;                 // The shortest side
  int middle;                   // The middle side
  int longest;                  // The longest side
  int errors = 0;               // A count of errors
  int i;                        // Everyone's favorite counter variable

  // Check number of parameters
  if (argc != 4)
    {
      usage ();
      return EXIT_FAILURE;
    }

  // Read the three sides
  for (i = 0; i < 3; i++)
    {
      if (sscanf (argv[i+1], "%d", &(sides[i])) != 1)
        {
          printf ("For side%d received \"%s\", which is not an integer.\n", 
                  i+1, argv[i+1]);
          ++errors;
        } // if
    } // for
  if (errors)
    {
      usage ();
      return EXIT_FAILURE;
    }

  // Sanity checks
  for (i = 0; i < 3; i++)
    {
      if (sides[i] <= 0)
        {
          printf ("Invalid side length: %d.\n", sides[i]);
          ++errors;
        } // if
    } // for
  if (errors)
    {
      usage ();
      return EXIT_FAILURE;
    }
  
  // Classify the sides
  perimeter = sides[0] + sides[1] + sides[2];
  longest = max (max (sides[0], sides[1]), sides[2]);
  shortest = min (min (sides[0], sides[1]), sides[2]);
  middle = perimeter - longest - shortest;

  // Sanity check: Non-triangle and degenerate triangle
  if (shortest + middle < longest)
    {
      printf ("There is no triangle with side lengths %d, %d, and %d.\n",
              sides[0], sides[1], sides[2]);
      return EXIT_FAILURE;
    }
  if (shortest + middle == longest)
    {
      printf ("That's a degenerate triangle.  What does that say about you?\n");
      return EXIT_FAILURE;
    }

  // Start output
  printf ("The triangle with side lengths %d, %d, and %d is ",
          sides[0], sides[1], sides[2]);

  // Obtuse, acute, right
  if (shortest*shortest + middle*middle < longest*longest)
    printf ("an obtuse ");
  else if (shortest*shortest + middle*middle > longest*longest)
    printf ("an acute ");
  else
    printf ("a right ");

  // Equilateral, isosceles, scalene
  if (shortest == longest)
    printf ("equilateral ");
  else if ((shortest == middle) || (middle == longest))
    printf ("isosceles ");
  else
    printf ("scalene ");

  // Other characteristics?
  printf ("triangle\n");

  // And we're done.
  return EXIT_SUCCESS;
} // main