/*************************************************************************/
/*  texture_loader_pvr.cpp                                               */
/*************************************************************************/
/*                         This file is part of:                         */
/*                          PANDEMONIUM ENGINE                           */
/*             https://github.com/Relintai/pandemonium_engine            */
/*************************************************************************/
/* Copyright (c) 2022-present Péter Magyar.                              */
/* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md).   */
/* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur.                 */
/*                                                                       */
/* Permission is hereby granted, free of charge, to any person obtaining */
/* a copy of this software and associated documentation files (the       */
/* "Software"), to deal in the Software without restriction, including   */
/* without limitation the rights to use, copy, modify, merge, publish,   */
/* distribute, sublicense, and/or sell copies of the Software, and to    */
/* permit persons to whom the Software is furnished to do so, subject to */
/* the following conditions:                                             */
/*                                                                       */
/* The above copyright notice and this permission notice shall be        */
/* included in all copies or substantial portions of the Software.       */
/*                                                                       */
/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
/*************************************************************************/

#include "texture_loader_pvr.h"

#include "core/os/file_access.h"

static void _pvrtc_decompress(Image *p_img);

enum PVRFLags {

	PVR_HAS_MIPMAPS = 0x00000100,
	PVR_TWIDDLED = 0x00000200,
	PVR_NORMAL_MAP = 0x00000400,
	PVR_BORDER = 0x00000800,
	PVR_CUBE_MAP = 0x00001000,
	PVR_FALSE_MIPMAPS = 0x00002000,
	PVR_VOLUME_TEXTURES = 0x00004000,
	PVR_HAS_ALPHA = 0x00008000,
	PVR_VFLIP = 0x00010000

};

RES ResourceFormatPVR::load(const String &p_path, const String &p_original_path, Error *r_error, bool p_no_subresource_cache) {
	if (r_error) {
		*r_error = ERR_CANT_OPEN;
	}

	Error err;
	FileAccess *f = FileAccess::open(p_path, FileAccess::READ, &err);
	if (!f) {
		return RES();
	}

	FileAccessRef faref(f);

	ERR_FAIL_COND_V(err, RES());

	if (r_error) {
		*r_error = ERR_FILE_CORRUPT;
	}

	uint32_t hsize = f->get_32();

	ERR_FAIL_COND_V(hsize != 52, RES());
	uint32_t height = f->get_32();
	uint32_t width = f->get_32();
	uint32_t mipmaps = f->get_32();
	uint32_t flags = f->get_32();
	uint32_t surfsize = f->get_32();
	f->seek(f->get_position() + 20); // bpp, rmask, gmask, bmask, amask
	uint8_t pvrid[5] = { 0, 0, 0, 0, 0 };
	f->get_buffer(pvrid, 4);
	ERR_FAIL_COND_V(String((char *)pvrid) != "PVR!", RES());
	f->get_32(); // surfcount

	/*
	print_line("height: "+itos(height));
	print_line("width: "+itos(width));
	print_line("mipmaps: "+itos(mipmaps));
	print_line("flags: "+itos(flags));
	print_line("surfsize: "+itos(surfsize));
	print_line("bpp: "+itos(bpp));
	print_line("rmask: "+itos(rmask));
	print_line("gmask: "+itos(gmask));
	print_line("bmask: "+itos(bmask));
	print_line("amask: "+itos(amask));
	print_line("surfcount: "+itos(surfcount));
	*/

	PoolVector<uint8_t> data;
	data.resize(surfsize);

	ERR_FAIL_COND_V(data.size() == 0, RES());

	PoolVector<uint8_t>::Write w = data.write();
	f->get_buffer(&w[0], surfsize);
	err = f->get_error();
	ERR_FAIL_COND_V(err != OK, RES());

	Image::Format format = Image::FORMAT_MAX;

	switch (flags & 0xFF) {
		case 0x18:
		case 0xC:
			format = (flags & PVR_HAS_ALPHA) ? Image::FORMAT_PVRTC2A : Image::FORMAT_PVRTC2;
			break;
		case 0x19:
		case 0xD:
			format = (flags & PVR_HAS_ALPHA) ? Image::FORMAT_PVRTC4A : Image::FORMAT_PVRTC4;
			break;
		case 0x16:
			format = Image::FORMAT_L8;
			break;
		case 0x17:
			format = Image::FORMAT_LA8;
			break;
		case 0x20:
		case 0x80:
		case 0x81:
			format = Image::FORMAT_DXT1;
			break;
		case 0x21:
		case 0x22:
		case 0x82:
		case 0x83:
			format = Image::FORMAT_DXT3;
			break;
		case 0x23:
		case 0x24:
		case 0x84:
		case 0x85:
			format = Image::FORMAT_DXT5;
			break;
		case 0x4:
		case 0x15:
			format = Image::FORMAT_RGB8;
			break;
		case 0x5:
		case 0x12:
			format = Image::FORMAT_RGBA8;
			break;
		case 0x36:
			format = Image::FORMAT_ETC;
			break;
		default:
			ERR_FAIL_V_MSG(RES(), "Unsupported format in PVR texture: " + itos(flags & 0xFF) + ".");
	}

	w.release();

	int tex_flags = Texture::FLAG_FILTER | Texture::FLAG_REPEAT;

	if (mipmaps) {
		tex_flags |= Texture::FLAG_MIPMAPS;
	}

	Ref<Image> image = memnew(Image(width, height, mipmaps, format, data));
	ERR_FAIL_COND_V(image->empty(), RES());

	Ref<ImageTexture> texture = memnew(ImageTexture);
	texture->create_from_image(image, tex_flags);

	if (r_error) {
		*r_error = OK;
	}

	return texture;
}

void ResourceFormatPVR::get_recognized_extensions(List<String> *p_extensions) const {
	p_extensions->push_back("pvr");
}
bool ResourceFormatPVR::handles_type(const String &p_type) const {
	return ClassDB::is_parent_class(p_type, "Texture");
}
String ResourceFormatPVR::get_resource_type(const String &p_path) const {
	if (p_path.get_extension().to_lower() == "pvr") {
		return "Texture";
	}
	return "";
}

ResourceFormatPVR::ResourceFormatPVR() {
	Image::_image_decompress_pvrtc = _pvrtc_decompress;
}

/////////////////////////////////////////////////////////

//PVRTC decompressor, Based on PVRTC decompressor by IMGTEC.

/////////////////////////////////////////////////////////

#define PT_INDEX 2
#define BLK_Y_SIZE 4
#define BLK_X_MAX 8
#define BLK_X_2BPP 8
#define BLK_X_4BPP 4

#define WRAP_COORD(Val, Size) ((Val) & ((Size)-1))

/*
	Define an expression to either wrap or clamp large or small vals to the
	legal coordinate range
*/
#define LIMIT_COORD(Val, Size, p_tiled) \
	((p_tiled) ? WRAP_COORD((Val), (Size)) : CLAMP((Val), 0, (Size)-1))

struct PVRTCBlock {
	//blocks are 64 bits
	uint32_t data[2];
};

_FORCE_INLINE_ bool is_po2(uint32_t p_input) {
	if (p_input == 0) {
		return false;
	}
	uint32_t minus1 = p_input - 1;
	return ((p_input | minus1) == (p_input ^ minus1)) ? true : false;
}

static void unpack_5554(const PVRTCBlock *p_block, int p_ab_colors[2][4]) {
	uint32_t raw_bits[2];
	raw_bits[0] = p_block->data[1] & (0xFFFE);
	raw_bits[1] = p_block->data[1] >> 16;

	for (int i = 0; i < 2; i++) {
		if (raw_bits[i] & (1 << 15)) {
			p_ab_colors[i][0] = (raw_bits[i] >> 10) & 0x1F;
			p_ab_colors[i][1] = (raw_bits[i] >> 5) & 0x1F;
			p_ab_colors[i][2] = raw_bits[i] & 0x1F;
			if (i == 0) {
				p_ab_colors[0][2] |= p_ab_colors[0][2] >> 4;
			}
			p_ab_colors[i][3] = 0xF;
		} else {
			p_ab_colors[i][0] = (raw_bits[i] >> (8 - 1)) & 0x1E;
			p_ab_colors[i][1] = (raw_bits[i] >> (4 - 1)) & 0x1E;

			p_ab_colors[i][0] |= p_ab_colors[i][0] >> 4;
			p_ab_colors[i][1] |= p_ab_colors[i][1] >> 4;

			p_ab_colors[i][2] = (raw_bits[i] & 0xF) << 1;

			if (i == 0) {
				p_ab_colors[0][2] |= p_ab_colors[0][2] >> 3;
			} else {
				p_ab_colors[0][2] |= p_ab_colors[0][2] >> 4;
			}

			p_ab_colors[i][3] = (raw_bits[i] >> 11) & 0xE;
		}
	}
}

static void unpack_modulations(const PVRTCBlock *p_block, const int p_2bit, int p_modulation[8][16], int p_modulation_modes[8][16], int p_x, int p_y) {
	int block_mod_mode = p_block->data[1] & 1;
	uint32_t modulation_bits = p_block->data[0];

	if (p_2bit && block_mod_mode) {
		for (int y = 0; y < BLK_Y_SIZE; y++) {
			for (int x = 0; x < BLK_X_2BPP; x++) {
				p_modulation_modes[y + p_y][x + p_x] = block_mod_mode;

				if (((x ^ y) & 1) == 0) {
					p_modulation[y + p_y][x + p_x] = modulation_bits & 3;
					modulation_bits >>= 2;
				}
			}
		}

	} else if (p_2bit) {
		for (int y = 0; y < BLK_Y_SIZE; y++) {
			for (int x = 0; x < BLK_X_2BPP; x++) {
				p_modulation_modes[y + p_y][x + p_x] = block_mod_mode;

				if (modulation_bits & 1) {
					p_modulation[y + p_y][x + p_x] = 0x3;
				} else {
					p_modulation[y + p_y][x + p_x] = 0x0;
				}

				modulation_bits >>= 1;
			}
		}
	} else {
		for (int y = 0; y < BLK_Y_SIZE; y++) {
			for (int x = 0; x < BLK_X_4BPP; x++) {
				p_modulation_modes[y + p_y][x + p_x] = block_mod_mode;
				p_modulation[y + p_y][x + p_x] = modulation_bits & 3;
				modulation_bits >>= 2;
			}
		}
	}

	ERR_FAIL_COND(modulation_bits != 0);
}

static void interpolate_colors(const int p_colorp[4], const int p_colorq[4], const int p_colorr[4], const int p_colors[4], bool p_2bit, const int x, const int y, int r_result[4]) {
	int u, v, uscale;
	int k;

	int tmp1, tmp2;

	int P[4], Q[4], R[4], S[4];

	for (k = 0; k < 4; k++) {
		P[k] = p_colorp[k];
		Q[k] = p_colorq[k];
		R[k] = p_colorr[k];
		S[k] = p_colors[k];
	}

	v = (y & 0x3) | ((~y & 0x2) << 1);

	if (p_2bit) {
		u = (x & 0x7) | ((~x & 0x4) << 1);
	} else {
		u = (x & 0x3) | ((~x & 0x2) << 1);
	}

	v = v - BLK_Y_SIZE / 2;

	if (p_2bit) {
		u = u - BLK_X_2BPP / 2;
		uscale = 8;
	} else {
		u = u - BLK_X_4BPP / 2;
		uscale = 4;
	}

	for (k = 0; k < 4; k++) {
		tmp1 = P[k] * uscale + u * (Q[k] - P[k]);
		tmp2 = R[k] * uscale + u * (S[k] - R[k]);

		tmp1 = tmp1 * 4 + v * (tmp2 - tmp1);

		r_result[k] = tmp1;
	}

	if (p_2bit) {
		for (k = 0; k < 3; k++) {
			r_result[k] >>= 2;
		}

		r_result[3] >>= 1;
	} else {
		for (k = 0; k < 3; k++) {
			r_result[k] >>= 1;
		}
	}

	for (k = 0; k < 4; k++) {
		ERR_FAIL_COND(r_result[k] >= 256);
	}

	for (k = 0; k < 3; k++) {
		r_result[k] += r_result[k] >> 5;
	}

	r_result[3] += r_result[3] >> 4;

	for (k = 0; k < 4; k++) {
		ERR_FAIL_COND(r_result[k] >= 256);
	}
}

static void get_modulation_value(int x, int y, const int p_2bit, const int p_modulation[8][16], const int p_modulation_modes[8][16], int *r_mod, int *p_dopt) {
	static const int rep_vals0[4] = { 0, 3, 5, 8 };
	static const int rep_vals1[4] = { 0, 4, 4, 8 };

	int mod_val;

	y = (y & 0x3) | ((~y & 0x2) << 1);

	if (p_2bit) {
		x = (x & 0x7) | ((~x & 0x4) << 1);
	} else {
		x = (x & 0x3) | ((~x & 0x2) << 1);
	}

	*p_dopt = 0;

	if (p_modulation_modes[y][x] == 0) {
		mod_val = rep_vals0[p_modulation[y][x]];
	} else if (p_2bit) {
		if (((x ^ y) & 1) == 0) {
			mod_val = rep_vals0[p_modulation[y][x]];
		} else if (p_modulation_modes[y][x] == 1) {
			mod_val = (rep_vals0[p_modulation[y - 1][x]] +
							  rep_vals0[p_modulation[y + 1][x]] +
							  rep_vals0[p_modulation[y][x - 1]] +
							  rep_vals0[p_modulation[y][x + 1]] + 2) /
					4;
		} else if (p_modulation_modes[y][x] == 2) {
			mod_val = (rep_vals0[p_modulation[y][x - 1]] +
							  rep_vals0[p_modulation[y][x + 1]] + 1) /
					2;
		} else {
			mod_val = (rep_vals0[p_modulation[y - 1][x]] +
							  rep_vals0[p_modulation[y + 1][x]] + 1) /
					2;
		}
	} else {
		mod_val = rep_vals1[p_modulation[y][x]];

		*p_dopt = p_modulation[y][x] == PT_INDEX;
	}

	*r_mod = mod_val;
}

static int disable_twiddling = 0;

static uint32_t twiddle_uv(uint32_t p_height, uint32_t p_width, uint32_t p_y, uint32_t p_x) {
	uint32_t twiddled;

	uint32_t min_dimension;
	uint32_t max_value;

	uint32_t scr_bit_pos;
	uint32_t dst_bit_pos;

	int shift_count;

	ERR_FAIL_COND_V(p_y >= p_height, 0);
	ERR_FAIL_COND_V(p_x >= p_width, 0);

	ERR_FAIL_COND_V(!is_po2(p_height), 0);
	ERR_FAIL_COND_V(!is_po2(p_width), 0);

	if (p_height < p_width) {
		min_dimension = p_height;
		max_value = p_x;
	} else {
		min_dimension = p_width;
		max_value = p_y;
	}

	if (disable_twiddling) {
		return (p_y * p_width + p_x);
	}

	scr_bit_pos = 1;
	dst_bit_pos = 1;
	twiddled = 0;
	shift_count = 0;

	while (scr_bit_pos < min_dimension) {
		if (p_y & scr_bit_pos) {
			twiddled |= dst_bit_pos;
		}

		if (p_x & scr_bit_pos) {
			twiddled |= (dst_bit_pos << 1);
		}

		scr_bit_pos <<= 1;
		dst_bit_pos <<= 2;
		shift_count += 1;
	}

	max_value >>= shift_count;

	twiddled |= (max_value << (2 * shift_count));

	return twiddled;
}

static void decompress_pvrtc(PVRTCBlock *p_comp_img, const int p_2bit, const int p_width, const int p_height, const int p_tiled, unsigned char *p_dst) {
	int x, y;
	int i, j;

	int block_x, blk_y;
	int block_xp1, blk_yp1;
	int x_block_size;
	int block_width, block_height;

	int p_x, p_y;

	int p_modulation[8][16] = { { 0 } };
	int p_modulation_modes[8][16] = { { 0 } };

	int Mod, DoPT;

	unsigned int u_pos;

	// local neighbourhood of blocks
	PVRTCBlock *p_blocks[2][2];

	PVRTCBlock *prev[2][2] = { { nullptr, nullptr }, { nullptr, nullptr } };

	struct
	{
		int Reps[2][4];
	} colors5554[2][2];

	int ASig[4], BSig[4];

	int r_result[4];

	if (p_2bit) {
		x_block_size = BLK_X_2BPP;
	} else {
		x_block_size = BLK_X_4BPP;
	}

	block_width = MAX(2, p_width / x_block_size);
	block_height = MAX(2, p_height / BLK_Y_SIZE);

	for (y = 0; y < p_height; y++) {
		for (x = 0; x < p_width; x++) {
			block_x = (x - x_block_size / 2);
			blk_y = (y - BLK_Y_SIZE / 2);

			block_x = LIMIT_COORD(block_x, p_width, p_tiled);
			blk_y = LIMIT_COORD(blk_y, p_height, p_tiled);

			block_x /= x_block_size;
			blk_y /= BLK_Y_SIZE;

			block_xp1 = LIMIT_COORD(block_x + 1, block_width, p_tiled);
			blk_yp1 = LIMIT_COORD(blk_y + 1, block_height, p_tiled);

			p_blocks[0][0] = p_comp_img + twiddle_uv(block_height, block_width, blk_y, block_x);
			p_blocks[0][1] = p_comp_img + twiddle_uv(block_height, block_width, blk_y, block_xp1);
			p_blocks[1][0] = p_comp_img + twiddle_uv(block_height, block_width, blk_yp1, block_x);
			p_blocks[1][1] = p_comp_img + twiddle_uv(block_height, block_width, blk_yp1, block_xp1);

			if (memcmp(prev, p_blocks, 4 * sizeof(void *)) != 0) {
				p_y = 0;
				for (i = 0; i < 2; i++) {
					p_x = 0;
					for (j = 0; j < 2; j++) {
						unpack_5554(p_blocks[i][j], colors5554[i][j].Reps);

						unpack_modulations(
								p_blocks[i][j],
								p_2bit,
								p_modulation,
								p_modulation_modes,
								p_x, p_y);

						p_x += x_block_size;
					}

					p_y += BLK_Y_SIZE;
				}

				memcpy(prev, p_blocks, 4 * sizeof(void *));
			}

			interpolate_colors(
					colors5554[0][0].Reps[0],
					colors5554[0][1].Reps[0],
					colors5554[1][0].Reps[0],
					colors5554[1][1].Reps[0],
					p_2bit, x, y,
					ASig);

			interpolate_colors(
					colors5554[0][0].Reps[1],
					colors5554[0][1].Reps[1],
					colors5554[1][0].Reps[1],
					colors5554[1][1].Reps[1],
					p_2bit, x, y,
					BSig);

			get_modulation_value(x, y, p_2bit, (const int(*)[16])p_modulation, (const int(*)[16])p_modulation_modes,
					&Mod, &DoPT);

			for (i = 0; i < 4; i++) {
				r_result[i] = ASig[i] * 8 + Mod * (BSig[i] - ASig[i]);
				r_result[i] >>= 3;
			}

			if (DoPT) {
				r_result[3] = 0;
			}

			u_pos = (x + y * p_width) << 2;
			p_dst[u_pos + 0] = (uint8_t)r_result[0];
			p_dst[u_pos + 1] = (uint8_t)r_result[1];
			p_dst[u_pos + 2] = (uint8_t)r_result[2];
			p_dst[u_pos + 3] = (uint8_t)r_result[3];
		}
	}
}

static void _pvrtc_decompress(Image *p_img) {
	ERR_FAIL_COND(p_img->get_format() != Image::FORMAT_PVRTC2 && p_img->get_format() != Image::FORMAT_PVRTC2A && p_img->get_format() != Image::FORMAT_PVRTC4 && p_img->get_format() != Image::FORMAT_PVRTC4A);

	bool _2bit = (p_img->get_format() == Image::FORMAT_PVRTC2 || p_img->get_format() == Image::FORMAT_PVRTC2A);

	PoolVector<uint8_t> data = p_img->get_data();
	PoolVector<uint8_t>::Read r = data.read();

	PoolVector<uint8_t> newdata;
	newdata.resize(p_img->get_width() * p_img->get_height() * 4);
	PoolVector<uint8_t>::Write w = newdata.write();

	decompress_pvrtc((PVRTCBlock *)r.ptr(), _2bit, p_img->get_width(), p_img->get_height(), 0, (unsigned char *)w.ptr());

	w.release();
	r.release();

	bool make_mipmaps = p_img->has_mipmaps();
	p_img->create(p_img->get_width(), p_img->get_height(), false, Image::FORMAT_RGBA8, newdata);
	if (make_mipmaps) {
		p_img->generate_mipmaps();
	}
}