#include "./graphics.h"

#include "../boot/multiboot/data.h"
#include "./debug/output.h"
#include "./utils/string.h"

/// Replace size with `Graphics::SCREEN_BUF_SIZE`
/// We don't do this here, as this drastically increases the size of the kernel
/// image.
char frontbuffer[1] __attribute__((aligned(8)));
char backbuffer[1] __attribute__((aligned(8)));

/*! \brief Mode Information of the *Vesa BIOS Extension*
 *
 * \see Vesa BIOS Extension [ModeInfoBlock struc](vbe3.pdf#page=38)
 */
struct VbeModeInfo {
	enum ModeAttributes : uint16_t {
		SUPPORTED = 1 << 0,	 ///< Mode supported by hardware configuration
		TTY = 1 << 2,		 ///< TTY Output functions supported by BIOS
		COLOR = 1 << 3,		 ///< Color mode (otherwise monochrome)
		GRAPHICS = 1 << 4,	 ///< Graphic mode (otherwise text)
		VGA = 1 << 5,		 ///< VGA compatible
		VGA_PAGED =
			1 << 6,	   ///< VGA compatible windowed memory mode is available
		LFB = 1 << 7,  ///< Linear frame buffer mode is available
	};
	uint16_t mode_attributes;

	// Window functions (used by all VBE revisions, but ignored here)
	struct __attribute__((packed)) {
		uint8_t attrib_a;
		uint8_t attrib_b;
		uint16_t granularity;
		uint16_t size;
		uint16_t segment_a;
		uint16_t segment_b;
		uint32_t func_ptr;
	} win;

	uint16_t pitch;	 ///< Bytes per scan line
	uint16_t
		width;	///< Horizontal resolution in pixels (GRAPHICS) or characters
	uint16_t
		height;	 ///< Vertical resolution in pixels (GRAPHICS) or characters

	uint8_t char_width;	  ///< Character cell width in pixels (deprecated)
	uint8_t char_height;  ///< Character cell height in pixels (deprecated)
	uint8_t planes;		  ///< Number of memory planes

	uint8_t bpp;  ///< Bits per pixel

	uint8_t banks;	///< Number of banks
	enum MemoryModel : uint8_t {
		TEXT_MODE = 0,	   ///< Text mode
		CGA = 1,		   ///< CGA graphics
		HERCULES = 2,	   ///< Hercules graphics
		PLANAR = 3,		   ///< Planar
		PACKED = 4,		   ///< Packed pixel
		NON_CHAIN_4 = 5,   ///< Non-chain 4, 256 color
		DIRECT_COLOR = 6,  ///< Direct Color
		YUV = 7			   ///< YUV
	} memory_model;		   ///< Memory model type
	uint8_t bank_size;	   ///< Bank size in KB
	uint8_t image_pages;   ///< Number of images
	uint8_t reserved;	   ///< Reserved for page function

	// Direct Color fields (required for DIRECT_COLOR and YUV memory models)
	uint8_t bits_red;	   ///< Size of direct color red mask in bits
	uint8_t offset_red;	   ///< Bit position of lsb of red mask
	uint8_t bits_green;	   ///< Size of direct color green mask in bits
	uint8_t offset_green;  ///< Bit position of lsb of green mask
	uint8_t bits_blue;	   ///< Size of direct color blue mask in bits
	uint8_t offset_blue;   ///< Bit position of lsb of blue mask
	uint8_t bits_rsv;	   ///< Size of direct color reserved mask in bits
	uint8_t offset_rsv;	   ///< Bit position of lsb of reserved mask

	enum DirectColorAttributes : uint8_t {
		DYNAMIC_COLOR_RAMP =
			1 << 0,	 ///< Programmable (otherwise fixed) color ramp
		USABLE_BITS =
			1 << 1	///< Bits in reserved mask are usable (otherwise reserved)
	};
	uint8_t directcolor_attributes;	 ///< direct color mode attributes

	// Mandatory information for VBE 2.0 and above
	uint32_t address;  ///< physical address for flat memory frame buffer
	uint32_t offscreen_memory_offset;  ///< reserved
	uint16_t offscreen_memory_size;	   ///< reserved
} __attribute__((packed));

Graphics::Graphics()
	: buffer_size(SCREEN_BUF_SIZE),
	  buffer{frontbuffer, backbuffer},
	  scanout_buffer(0),
	  refresh(false) {}

bool Graphics::init(bool force) {
	assert(sizeof(frontbuffer) >= buffer_size &&
		   sizeof(backbuffer) >= buffer_size &&
		   "Buffers are too small, adjust them!!!");
	// Most boot loaders support the Vesa BIOS Extension (VBE) information quite
	// well
	Multiboot::VBE *vbe = Multiboot::getVesaBiosExtensionInfo();
	if (vbe != nullptr) {
		// However, you have to manually parse the required data out of all the
		// outdated crap
		struct VbeModeInfo *vbe_info = reinterpret_cast<struct VbeModeInfo *>(
			static_cast<uintptr_t>(vbe->mode_info));
		// Is there linear frame buffer (or just ignore the check with `force`
		// due to a misleading information)?
		if (force || (vbe_info->mode_attributes &
					  VbeModeInfo::ModeAttributes::LFB) != 0) {
			// Is there a suitable precompiled graphic mode
			printer = AbstractGraphicsPrinter::getMode(
				vbe_info->bpp, vbe_info->offset_red, vbe_info->offset_green,
				vbe_info->offset_blue, vbe_info->bits_red, vbe_info->bits_green,
				vbe_info->bits_blue);
			if (printer != nullptr) {
				address = reinterpret_cast<void *>(
					static_cast<uintptr_t>(vbe_info->address));
				size = vbe_info->height * vbe_info->pitch;
				if (size > buffer_size) {
					DBG_VERBOSE << "The current graphic buffer (" << buffer_size
								<< " bytes) is too small (at least " << size
								<< " bytes required)!" << endl;
					return false;
				} else {
					printer->init(vbe_info->width, vbe_info->height,
								  vbe_info->pitch);
					printer->buffer(buffer[1 - scanout_buffer]);
					return true;
				}
			}
		} else {
			DBG_VERBOSE << "Unsupported graphic mode" << endl;
		}
	}

	// Actually, \ref Multiboot::Framebuffer has everything we need in a real
	// smart structure, however boot loader like PXE don't support them (yet --
	// quite new, added in the last Multiboot revision).
	Multiboot::Framebuffer *fb = Multiboot::getFramebufferInfo();
	if (fb != nullptr) {
		if (force || fb->type == Multiboot::Framebuffer::RGB) {
			printer = AbstractGraphicsPrinter::getMode(
				fb->bpp, fb->offset_red, fb->offset_green, fb->offset_blue,
				fb->bits_red, fb->bits_green, fb->bits_blue);
			if (printer != nullptr) {
				address = reinterpret_cast<void *>(
					static_cast<uintptr_t>(fb->address));
				size = fb->height * fb->pitch;
				if (size > buffer_size) {
					DBG_VERBOSE << "The current graphic buffer (" << buffer_size
								<< " bytes) is too small (at least " << size
								<< " bytes required)!" << endl;
					return false;
				} else {
					printer->init(fb->width, fb->height, fb->pitch);
					printer->buffer(buffer[1 - scanout_buffer]);
					return true;
				}
			}
		} else {
			DBG_VERBOSE << "Unsupported graphic mode" << endl;
		}
	}

	// Unable to initialize mode
	return false;
}

bool Graphics::switchBuffers() {
	if (!refresh) {
		printer->buffer(buffer[scanout_buffer]);
		scanout_buffer = 1 - scanout_buffer;
		refresh = true;
		return true;
	} else {
		return false;
	}
}

void Graphics::scanoutFrontbuffer() {
	if (refresh) {
		memcpy(address, buffer[scanout_buffer], size);
		refresh = false;
	}
}