#include <stdio.h>

/**
 * Program to read jimitext (a very much simplified form of wikitext)
 * and output the links.  Links are in *single* brackets; templates are
 * in *single* braces.  There is no nesting, except for links inside
 * templates.  We want links inside templates to be output with
 * "Template: " in front of them.  So if the input is
 *
 * This is a [link] and I can put {[links] [inside] templates}.
 *
 * then the output should be
 *
 * link
 * Template: links
 * Template: inside
 *
 * Compile and link with
 *
 * gcc -Wall -std=c99 -pedantic -c jimilinks.c
 * gcc -o Jimilinks jimilinks.o
 */

// In addition to the compiler and linker, there is a third program involved
// in compiling C files: the preprocessor, which you normally won't
// run directly.  Everything that starts with a # like like #include or
// or #define or #ifndef...#endif is a preprocessor instruction.  Here we
// define four preprocessor variables (macros); when these are used later
// in the program, their values are used in place of their names.  So, given
// these definitions, when we write "int state = TEXT;" in our program,
// the compiler actually sees "int state = 0;". We could use constants
// as an alternative; preprocessor macros have additional capabilities that
// we aren't using here.  Run "cpp jimilinks.c" if you want to see the output
// of the preprocessor, which will include the files that were #include-d
// and the replacement of the symbols defined below.

#define TEXT 0
#define TEMPLATE 1
#define TEMPLATE_LINK 2
#define LINK 3

int main()
{
  // set the initial state
  int state = TEXT;

  // loop until end of input (start a new line with Control-D to signal
  // end of input in Unix)
  int ch = getchar();
  while (ch != EOF)
    {
      // now a big conditional to handle each state in our state machine
      switch (state)
	{
	case TEXT:
	  // the case for each state then has another conditional with
	  // cases for all the relevant characters; each one of these
	  // cases will correspond to one of the transitions in our diagram
	  if (ch == '{')
	    {
	      // saw an opening brace -- switch to "reading a template" state
	      state = TEMPLATE;
	    }
	  else if (ch == '[')
	    {
	      // saw an opening bracket -- switch to "reading a link" state
	      state = LINK;
	    }
	  break;

	case TEMPLATE:
	  if (ch == '}')
	    {
	      // closing brace in a template -- back to our initial state
	      state = TEXT;
	    }
	  else if (ch == '[')
	    {
	      // starting a link inside a template -- start the output and
	      // change state
	      state = TEMPLATE_LINK;
	      printf("Template: ");
	    }
	  break;

	case TEMPLATE_LINK:
	  if (ch == ']')
	    {
	      // closing bracket inside a template -- newline and still in
	      // template
	      printf("\n");
	      state = TEMPLATE;
	    }
	  else
	    {
	      // all other characters get output
	      putc(ch, stdout);
	    }
	  break;

	case LINK:
	  if (ch == ']')
	    {
	      // in a link (but not also a template) and link is closing --
	      // start new line and go back to initial state
	      printf("\n");
	      state = TEXT;
	    }
	  else
	    {
	      // all other characters get output
	      putc(ch, stdout);
	    }
	  break;
	}

      // read character for next time through loop
      ch = getchar();
    }
}