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/* See LICENSE file for copyright and license details. */
#include "common.h"


/**
 * The psuedodevice pathname pattern used to access a framebuffer
 */
#ifndef FB_DEVICE_PATTERN
# define FB_DEVICE_PATTERN  "/dev/fb%lu"
#endif


/**
 * The number of elements to allocates to a buffer for a framebuffer device pathname
 */
#define FB_DEVICE_MAX_LEN (sizeof(FB_DEVICE_PATTERN) / sizeof(char) + 3 * sizeof(size_t))



/**
 * Figure out how many framebuffers there are on the system
 * 
 * @return  The number of framebuffers on the system
 */
size_t
fb_count(void)
{
	char buf[FB_DEVICE_MAX_LEN];
	size_t count = 0;
  
	for (;; count++) {
		sprintf(buf, FB_DEVICE_PATTERN, count);
		if (access(buf, F_OK) < 0)
			return count;
	}
}


/**
 * Open a framebuffer
 * 
 * @param   index  The index of the framebuffer to open
 * @param   fb     Framebuffer information to fill in
 * @return         Zero on success, -1 on error
 */
int
fb_open(size_t index, framebuffer_t *restrict fb)
{
	char buf[FB_DEVICE_MAX_LEN];
	struct fb_fix_screeninfo fix_info;
	struct fb_var_screeninfo var_info;
	int old_errno;

	fb->fd = -1;
	fb->mem = MAP_FAILED;

	sprintf(buf, FB_DEVICE_PATTERN, index);
	fb->fd = open(buf, O_RDWR);
	if (fb->fd < 0)
		goto fail;

	if (ioctl(fb->fd, (unsigned long int)FBIOGET_FSCREENINFO, &fix_info) ||
	    ioctl(fb->fd, (unsigned long int)FBIOGET_VSCREENINFO, &var_info))
		goto fail;

	fb->mem = mmap(NULL, (size_t)(fix_info.smem_len), PROT_WRITE, MAP_SHARED, fb->fd, (off_t)0);
	if (fb->mem == MAP_FAILED)
		goto fail;

	fb->mem += var_info.xoffset * (var_info.bits_per_pixel / 8);
	fb->mem += var_info.yoffset * fix_info.line_length;

	fb->width           = var_info.xres;
	fb->height          = var_info.yres;
	fb->bytes_per_pixel = var_info.bits_per_pixel / 8;
	fb->line_length     = fix_info.line_length;

	return 0;
fail:
	old_errno = errno;
	fb_close(fb);
	errno = old_errno;
	return -1;
}


/**
 * Close a framebuffer
 * 
 * @param  fb  The framebuffer information
 */
void
fb_close(framebuffer_t *restrict fb)
{
	if (fb->fd >= 0) {
		close(fb->fd);
		fb->fd = -1;
	}
}


/**
 * Construct an sRGB colour in 32-bit XRGB encoding to
 * use when specifying colours
 * 
 * @param   red    The red   component from [0, 255] sRGB
 * @param   green  The green component from [0, 255] sRGB
 * @param   blue   The blue  component from [0, 255] sRGB
 * @return         The colour as one 32-bit integer
 */
uint32_t
fb_colour(int red, int green, int blue)
{
	uint32_t rc = 0;
	rc |= (uint32_t)red,   rc <<= 8;
	rc |= (uint32_t)green, rc <<= 8;
	rc |= (uint32_t)blue;
	return rc;
}


/**
 * Print a filled in rectangle to a framebuffer
 * 
 * @param  fb      The framebuffer
 * @param  colour  The colour to use when drawing the rectangle
 * @param  x       The starting pixel on the X axis for the rectangle
 * @param  y       The starting pixel on the Y axis for the rectangle
 * @param  width   The width of the rectangle, in pixels
 * @param  height  The height of the rectangle, in pixels
 */
void
fb_fill_rectangle(framebuffer_t *restrict fb, uint32_t colour, uint32_t x, uint32_t y, uint32_t width, uint32_t height)
{
	int8_t *mem = fb->mem + y * fb->line_length;
	size_t x1 = x * fb->bytes_per_pixel;
	size_t x2 = (x + width) * fb->bytes_per_pixel;
	size_t y2 = y + height;
	size_t x_, y_;
	for (y_ = y; y_ != y2; y_++, mem += fb->line_length)
		for (x_ = x1; x_ != x2; x_ += fb->bytes_per_pixel)
			*(uint32_t *)&mem[x_] = colour;
}


/**
 * Draw a horizontal line segment on a framebuffer
 * 
 * @param  fb      The framebuffer
 * @param  colour  The colour to use when drawing the rectangle
 * @param  x       The starting pixel on the X axis for the line segment
 * @param  y       The starting pixel on the Y axis for the line segment
 * @param  length  The length of the line segment, in pixels
 */
void fb_draw_horizontal_line(framebuffer_t *restrict fb, uint32_t colour, uint32_t x, uint32_t y, uint32_t length)
{
	int8_t *mem = fb->mem + y * fb->line_length;
	size_t x1 = x * fb->bytes_per_pixel;
	size_t x2 = (x + length) * fb->bytes_per_pixel;
	size_t x_;
	for (x_ = x1; x_ != x2; x_ += fb->bytes_per_pixel)
		*(uint32_t *)&mem[x_] = colour;
}


/**
 * Draw a vertical line segment on a framebuffer
 * 
 * @param  fb      The framebuffer
 * @param  colour  The colour to use when drawing the rectangle
 * @param  x       The starting pixel on the X axis for the line segment
 * @param  y       The starting pixel on the Y axis for the line segment
 * @param  length  The length of the line segment, in pixels
 */
void fb_draw_vertical_line(framebuffer_t *restrict fb, uint32_t colour, uint32_t x, uint32_t y, uint32_t length)
{
	int8_t *mem = fb->mem + y * fb->line_length + x * fb->bytes_per_pixel;
	size_t y2 = y + length;
	size_t y_;

	for (y_ = y; y_ != y2; y_++, mem += fb->line_length)
		*(uint32_t *)mem = colour;
}