/* ----------------------------------------------------------------
**  Find the roots of a function f by either secant or bisection.
**      Figure 23.6: The main module for the root-finder.
**      Figure 23.7: The menu loop from main().
** ---------------------------------------------------------------- 
*/
#include "tools.h"
#include "ffam.h"
#include "root.h"

/* Global external variable to control verbose output everywhere. */
bool verbose = true;          

/* Menu of program options. ------------------------------- */
static string menu[] = { 
        "b  find root using Bisection method",
        "s  find root using Secant method",
        "n  choose New parameters for function",
        "v",   /* completed later according to state of verbose flag */
        "q  Quit"
    };
#define VMENU 3  /* position of "v" item in menu */

/* --------------------------------------------------------------- */
void main( void )
{   
    char c;                 /* menu choice */
    double root;            /* value of root */
    double x1, x2;          /* starting interval or end points */
    er_type return_code;    /* result error code */

    banner();
    puts( "Root finder program" );
    setup();                /* Get parameters for f(). */

    do {
        /* update menu */
        if (verbose) menu[VMENU] = "v  turn off Verbose feedback";
        else         menu[VMENU] = "v  turn on Verbose feedback";

        /* display menu and get user selection */
        c = menu_c( " Select next option:", 5, menu );
        switch (c) {
            case 'b': printf( " Enter endpoints of search interval: " );
                      scanf( "%lg%lg", &x1, &x2 ); 
                      return_code = bisect( x1, x2, &root );
                      break;

            case 's': printf( " Enter two initial estimates for the root: " );
                      scanf( "%lg%lg", &x1, &x2 ); 
                      return_code = secant( x1, x2, &root );
                      break;

            case 'n': setup();  /* Read new parameters for function f(). */
                      continue;

            case 'v': verbose = !verbose;
                      continue;
                    
            case 'q': continue;

            default:  cleanline( stdin );
                      continue;
        }

        if (return_code == ROOT_OK)  
            printf( "\n The root is %g \n\n", root );
        else 
            printf( "\n Failed to find root--%s\n\n", errmsg[return_code] );
    } while (c != 'q');

    bye();
}