#include "screen.h"

const char MANDEL_CHARS[] = "`.,:;!^=*?$%@HHHHHHHHHHBBBBBBBBBWWWWWWWWWWW#######";
const int NUM_MANDEL_CHARS = 50;
const int BAILOUT = 100;
const int INDENT = 10;

// Determine the number of iterations necessary to escape the Mandelbrot
// function, if it's possible at that point.
int computeMandel( double x, double y )
{
	double a = 0.0;
	double b = 0.0;

	for( int iter = 0; iter < BAILOUT; iter++ ) {
		double new_a = a * a - b * b + x;
		double new_b = 2 * a * b + y;

		a = new_a;
		b = new_b;

		if( a * a + b * b >= 4 ) {
			return iter;
		}
	}

	return -1;
}

// Fill in a region of the screen with a portion of the Mandelbrot set.
// (m_left, m_top) is the top left corner of the region to compute.
// The region has width m_width and height m_height.  The set should be
// drawn in a rectangle on the screen at (col,row) of width 'width' and
// height 'height'.
void drawMandel( 
	Screen& screen, 
	double m_left, double m_top, double m_width, double m_height,
	int col, int row, int width, int height )
{
	for( int idy = 0; idy < height; idy++ ) {
		double vfrac = (double)idy / (double)height;
		double y = m_top - vfrac * m_height;

		for( int idx = 0; idx < width; idx++ ) {
			double hfrac = (double)idx / (double)width;
			double x = m_left + hfrac * m_width;

			int iters = computeMandel( x, y );
			char ch = ' ';

			if( iters != -1 ) {
				ch = MANDEL_CHARS[ ( iters * NUM_MANDEL_CHARS ) / BAILOUT ];
			}

			screen.putChar( col + idx, row + idy, ch );
		}
	}
}

// Accept a region of the complex plane from the user, and draw a picture
// of the Mandelbrot set as it appears in that region.
// For a 'good' look at the whole set, try entering -1.4 1 2 2.
//
// As usual, when you run this program, it will sit there waiting for
// input.  It won't do anything until you type in four numbers.
int main( void )
{
	double m_left;
	double m_top;
	double m_width;
	double m_height;

	cin >> m_left >> m_top >> m_width >> m_height;
	while( cin && cin.get() != '\n' );

	Screen screen;

	// Fill the screen with a background character just to distinguish it
	// from the window we're going to draw.
	screen.fill( ':' );

	// Draw a rectangle to surround the set.

	screen.rectangle( INDENT - 1, 1, 
		SCREEN_WIDTH - 1 - 2 * ( INDENT - 1 ), SCREEN_HEIGHT - 4, ' ' );

	// Draw the Mandelbrot set inside that rectangle.
	drawMandel( screen, m_left, m_top, m_width, m_height, 
		INDENT, 2, SCREEN_WIDTH - 1 - 2 * INDENT, SCREEN_HEIGHT - 6 );

	// Put up a snazzy title.
	screen.putCenteredText( SCREEN_HEIGHT - 2, "    The Mandelbrot Set    " );

	screen.print( cout );

	cerr << "Press return to exit." << endl;
	while( cin && cin.get() != '\n' );

	return 0;
}