/*
img_ktx2.c - ktx2 format load
Copyright (C) 2023 Provod

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
*/

#include "imagelib.h"
#include "xash3d_mathlib.h"
#include "img_ktx2.h"

static void Image_KTX2Format( uint32_t ktx2_format )
{
	switch( ktx2_format )
	{
		case KTX2_FORMAT_BC4_UNORM_BLOCK:
			image.type = PF_BC4_UNSIGNED;
			// 1 component for ref_gl
			break;
		case KTX2_FORMAT_BC4_SNORM_BLOCK:
			image.type = PF_BC4_SIGNED;
			// 1 component for ref_gl
			break;
		case KTX2_FORMAT_BC5_UNORM_BLOCK:
			image.type = PF_BC5_UNSIGNED;
			// 2 components for ref_gl
			SetBits( image.flags, IMAGE_HAS_ALPHA );
			break;
		case KTX2_FORMAT_BC5_SNORM_BLOCK:
			image.type = PF_BC5_SIGNED;
			// 2 components for ref_gl
			SetBits( image.flags, IMAGE_HAS_ALPHA );
			break;
		case KTX2_FORMAT_BC6H_UFLOAT_BLOCK:
			image.type = PF_BC6H_UNSIGNED;
			// 3 components for ref_gl
			SetBits( image.flags, IMAGE_HAS_COLOR );
			break;
		case KTX2_FORMAT_BC6H_SFLOAT_BLOCK:
			image.type = PF_BC6H_SIGNED;
			// 3 components for ref_gl
			SetBits( image.flags, IMAGE_HAS_COLOR );
			break;
		case KTX2_FORMAT_BC7_UNORM_BLOCK:
			image.type = PF_BC7_UNORM;
			// 4 components for ref_gl
			SetBits( image.flags, IMAGE_HAS_COLOR | IMAGE_HAS_ALPHA );
			break;
		case KTX2_FORMAT_BC7_SRGB_BLOCK:
			image.type = PF_BC7_SRGB;
			// 4 components for ref_gl
			SetBits( image.flags, IMAGE_HAS_COLOR | IMAGE_HAS_ALPHA );
			break;
		default:
			image.type = PF_UNKNOWN;
			break;
	}
}

static qboolean Image_KTX2Parse( const ktx2_header_t *header, const byte *buffer, fs_offset_t filesize )
{
	ktx2_index_t index;
	size_t total_size = 0;
	size_t max_offset = 0;
	const byte *const levels_begin = buffer + KTX2_LEVELS_OFFSET;

	// Sets image.type and image.flags
	Image_KTX2Format( header->vkFormat );

	if( image.type == PF_UNKNOWN )
	{
		Con_DPrintf( S_ERROR "%s: unsupported KTX2 format %d\n", __FUNCTION__, header->vkFormat );
		return false;
	}

	if( !Image_CheckFlag( IL_DDS_HARDWARE ) && ImageCompressed( image.type ))
	{
		Con_DPrintf( S_WARN "%s: has compressed format, but support is not advertized\n", __FUNCTION__ );
		return false;
	}

	if( header->levelCount == 0 )
	{
		Con_DPrintf( S_ERROR "%s: file has no mip levels\n", __FUNCTION__ );
		return false;
	}

	if( header->pixelDepth > 1 )
	{
		Con_DPrintf( S_ERROR "%s: unsupported KTX2 pixelDepth %d\n", __FUNCTION__, header->pixelDepth );
		return false;
	}

	if( header->faceCount > 1 )
	{
		Con_DPrintf( S_ERROR "%s: unsupported KTX2 faceCount %d\n", __FUNCTION__, header->faceCount );
		return false;
	}

	if( header->layerCount > 1 )
	{
		Con_DPrintf( S_ERROR "%s: unsupported KTX2 layerCount %d\n", __FUNCTION__, header->layerCount );
		return false;
	}

	if( header->supercompressionScheme != 0 )
	{
		Con_DPrintf( S_ERROR "%s: unsupported KTX2 supercompressionScheme %d\n", __FUNCTION__, header->supercompressionScheme );
		return false;
	}

	if( header->levelCount * sizeof( ktx2_level_t ) + KTX2_LEVELS_OFFSET > filesize )
	{
		Con_DPrintf( S_ERROR "%s: file abruptly ends\n", __FUNCTION__ );
		return false;
	}

	memcpy( &index, buffer + KTX2_IDENTIFIER_SIZE + sizeof( ktx2_header_t ), sizeof( index ));

	for( int mip = 0; mip < header->levelCount; ++mip )
	{
		const uint32_t width = Q_max( 1, ( header->pixelWidth >> mip ));
		const uint32_t height = Q_max( 1, ( header->pixelHeight >> mip ));
		const uint32_t mip_size = Image_ComputeSize( image.type, width, height, image.depth );

		ktx2_level_t level;
		memcpy( &level, levels_begin + mip * sizeof( level ), sizeof( level ));

		if( mip_size != level.byteLength )
		{
			Con_DPrintf( S_ERROR "%s: mip=%d size mismatch read=%d, but computed=%d\n",
				__FUNCTION__, mip, (int)level.byteLength, mip_size );
			return false;
		}

		total_size += level.byteLength;
		max_offset = Q_max( max_offset, level.byteLength + level.byteOffset );
	}

	if( max_offset > filesize )
		return false;

	image.size = total_size;
	image.num_mips = header->levelCount;

	image.rgba = Mem_Malloc( host.imagepool, image.size );
	memcpy( image.rgba, buffer, image.size );

	for( int mip = 0, cursor = 0; mip < header->levelCount; ++mip )
	{
		ktx2_level_t level;
		memcpy( &level, levels_begin + mip * sizeof( level ), sizeof( level ));
		memcpy( image.rgba + cursor, buffer + level.byteOffset, level.byteLength );
		cursor += level.byteLength;
	}

	return true;
}

qboolean Image_LoadKTX2( const char *name, const byte *buffer, fs_offset_t filesize )
{
	ktx2_header_t header;

	if( filesize < KTX2_MINIMAL_HEADER_SIZE )
		return false;

	if( memcmp( buffer, KTX2_IDENTIFIER, KTX2_IDENTIFIER_SIZE ) != 0 )
	{
		Con_DPrintf( S_ERROR "%s: (%s) has invalid identifier\n", __FUNCTION__, name );
		return false;
	}

	memcpy( &header, buffer + KTX2_IDENTIFIER_SIZE, sizeof( header ));

	image.width = header.pixelWidth;
	image.height = header.pixelHeight;
	image.depth = Q_max( 1, header.pixelDepth );
	image.num_mips = 1;

	ClearBits( image.flags, IMAGE_HAS_COLOR | IMAGE_HAS_ALPHA | IMAGE_HAS_LUMA );

	if( !Image_KTX2Parse( &header, buffer, filesize ))
	{
		if( !Image_CheckFlag( IL_KTX2_RAW ))
			return false;

		// If KTX2 to imagelib conversion failed, try passing the file as raw data.
		// This is useful for ref_vk which can directly support hundreds of formats which we don't convert to pixformat_t here

		Con_DPrintf( S_WARN "%s: (%s) could not be converted to supported imagelib format, passing as raw KTX2 data\n", __FUNCTION__, name );
		// This is a catch-all for ref_vk, which can do this format directly and natively
		image.type = PF_KTX2_RAW;

		image.size = filesize;
		//image.encode = TODO custom encode type?

		image.rgba = Mem_Malloc( host.imagepool, image.size );
		memcpy( image.rgba, buffer, image.size );
	}

	return true;
}