#include <sdl/SDL.h>
#include "video.h"
#include <math.h>

// 
#define sint64   signed long long
#define uint32 unsigned int
#define sint32   signed int
#define uint16 unsigned short
#define sint16   signed short
#define uint8  unsigned char
#define sint8    signed char

//
const int c_ScreenWidth  = 640;
const int c_ScreenHeight = 480;

//
SDL_Surface *screen = NULL;

//
static inline void plot( int x, int y, int c )
{
	if ( x <  0              ) return;
	if ( y <  0              ) return;
	if ( x >= c_ScreenWidth  ) return;
	if ( y >= c_ScreenHeight ) return;
	Uint32 *p  = (Uint32*)screen->pixels;
	        p += x + y * (screen->pitch >> 2);
		   *p  = c;
}

// 
bool start_sdl( void )
{
	// 
	if ( SDL_Init( SDL_INIT_VIDEO ) != 0 )
		return false;
	// 
	screen = SDL_SetVideoMode
	(
		c_ScreenWidth,
		c_ScreenHeight, 32, 0//SDL_FULLSCREEN
	);
	return ( screen != NULL );
}

//
const float pi = 3.14159265359f;

//
const int nodeCount = 27;

//
struct sTentacle
{
	float head;
	float girth;
	float friction;
	float muscleRange;
	float muscleFrequency;
	float tv;
	float theta;
	float count;
	float thetaMuscle;
	//
	float px;
	float py;
	// 
	float x[ nodeCount ];
	float y[ nodeCount ];
};

//
float random( float range = 1.0f )
{
	float i  = (float)( rand( ) & 0xFFFF );
	      i /= (float)   0xFFFF;
		  i *= range;
	return i;
}

//
const int snakeCount = 7;
sTentacle snake[snakeCount];

//
void generate( sTentacle *t )
{
	t->count           = 0;
	t->theta           = 0;
	t->tv              = 0;
	t->thetaMuscle     = 0;
	t->head            =  2.0f + random( 4   );
	t->girth           =  8.0f + random( 12  );
	t->friction        =  0.9f + random( 10  ) / 100.0f;
	t->muscleRange     = 20.0f + random( 50  );
	t->muscleFrequency =  0.1f + random( 100 ) / 250.0f;
	//
	for ( int i=0; i<nodeCount; i++ )
	{
		t->x[i] = 0;
		t->y[i] = 0;
	}
	//
	t->px = -64;
	t->py = c_ScreenHeight/2 + random( 100 );
}

//
void update( sTentacle *t )
{
	// 
	t->tv    += 0.5f * (random() - random( ));
	t->theta += t->tv;
	t->tv    *= t->friction;
	t->x[0]   = t->head * cos( pi / 180 * t->theta );
	t->y[0]   = t->head * sin( pi / 180 * t->theta );

	// 
	t->count       += t->muscleFrequency;
	t->thetaMuscle  = t->muscleRange * sin( t->count );
	
	// 
	t->x[1] = -t->head * cos( pi / 180 * ( t->theta + t->thetaMuscle ) );
	t->y[1] = -t->head * sin( pi / 180 * ( t->theta + t->thetaMuscle ) );

	//
	for ( int i=2; i<nodeCount; i++ )
	{
		float dx = t->x[i] - t->x[i-2];
		float dy = t->y[i] - t->y[i-2];

		//
		float  d = sqrtf( dx*dx + dy*dy );

		//
		t->x[i] = t->x[i-1] + (dx * t->girth) / d;
		t->y[i] = t->y[i-1] + (dy * t->girth) / d;

		// 
		setColour( 0xFFFFFF );
		drawLine
		(
			t->px + (int)t->x[i  ],
			t->py + (int)t->y[i  ],
			t->px + (int)t->x[i-1],
			t->py + (int)t->y[i-1]
		);
	}

	drawCircle( t->px + t->x[0], t->py + t->y[0], 6 );

	t->px -= t->x[1];
	t->py -= t->y[1];

	//
	if ( t->px > c_ScreenWidth + 200 ) generate( t );

}

// 
bool tick_sdl( void )
{
	SDL_Event event;
	while ( SDL_PollEvent( &event ) )
	{
		switch ( event.type )
		{
		case ( SDL_QUIT ):
			return false;
		case ( SDL_KEYDOWN ):
			if ( event.key.keysym.sym == SDLK_ESCAPE )
				return false;
			if ( event.key.keysym.sym == SDLK_r )
			{
				//
				for ( int i=0; i<snakeCount; i++ )
					generate( &(snake[i]) );
			}
			break;
		}
	}
	return true;
}

// 
int main( void )
{
	// 
	if (! start_sdl  ( ) )	return -1;

	//
	for ( int i=0; i<snakeCount; i++ )
		generate( &(snake[i]) );

	//
	int time = SDL_GetTicks( );

	// 
	while ( tick_sdl( ) )
	{
		//
		SDL_FillRect( screen, NULL, 0x000020 );

		
		//
		for ( int i=0; i<snakeCount; i++ )
			update( &(snake[i]) );

		//
		while ( true )
		{
			int dt = SDL_GetTicks( ) - time;
			if ( dt > 33 )
			{
				time += dt;
				break;
			}
			else
			{
				SDL_Delay( 1 );
			}
		}


		//
		SDL_Flip( screen );
	}
	//
	return 0;
}