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/* $Id$ */

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/** @file grf.cpp Reading graphics data from (New)GRF files. */

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#include "../stdafx.h"

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#include "../gfx_func.h"

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#include "../fileio.h"

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#include "../debug.h"

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#include "../core/alloc_func.hpp"

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#include "grf.hpp"

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bool SpriteLoaderGrf::LoadSprite(SpriteLoader::Sprite *sprite, uint8 file_slot, size_t file_pos)

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{

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	/* Open the right file and go to the correct position */

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	FioSeekToFile(file_slot, file_pos);

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	/* Read the size and type */

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	int num = FioReadWord();

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	byte type = FioReadByte();

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	/* Type 0xFF indicates either a colormap or some other non-sprite info; we do not handle them here */

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	if (type == 0xFF) return false;

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	sprite->height = FioReadByte();

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	sprite->width  = FioReadWord();

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	sprite->x_offs = FioReadWord();

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	sprite->y_offs = FioReadWord();

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	/* 0x02 indicates it is a compressed sprite, so we can't rely on 'num' to be valid.

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	 *  In case it is uncompressed, the size is 'num' - 8 (header-size). */

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	num = (type & 0x02) ? sprite->width * sprite->height : num - 8;

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	/* XXX -- We should use a pre-located memory segment for this, malloc/free is pretty expensive */

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	byte *dest_orig = MallocT<byte>(num);

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	byte *dest = dest_orig;

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	/* Read the file, which has some kind of compression */

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	while (num > 0) {

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		int8 code = FioReadByte();

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		if (code >= 0) {

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			/* Plain bytes to read */

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			int size = (code == 0) ? 0x80 : code;

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			num -= size;

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			for (; size > 0; size--) {

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				*dest = FioReadByte();

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				dest++;

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			}

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		} else {

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			/* Copy bytes from earlier in the sprite */

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			const uint data_offset = ((code & 7) << 8) | FioReadByte();

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			int size = -(code >> 3);

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			num -= size;

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			for (; size > 0; size--) {

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				*dest = *(dest - data_offset);

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				dest++;

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			}

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		}

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	}

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	assert(num == 0);

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	sprite->data = CallocT<SpriteLoader::CommonPixel>(sprite->width * sprite->height);

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	/* When there are transparency pixels, this format has an other trick.. decode it */

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	if (type & 0x08) {

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		for (int y = 0; y < sprite->height; y++) {

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			bool last_item = false;

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			/* Look up in the header-table where the real data is stored for this row */

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			int offset = (dest_orig[y * 2 + 1] << 8) | dest_orig[y * 2];

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			/* Go to that row */

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			dest = &dest_orig[offset];

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			do {

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				SpriteLoader::CommonPixel *data;

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				/* Read the header:

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				 *  0 .. 14  - length

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				 *  15       - last_item

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				 *  16 .. 31 - transparency bytes */

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				last_item  = ((*dest) & 0x80) != 0;

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				int length =  (*dest++) & 0x7F;

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				int skip   =   *dest++;

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				data = &sprite->data[y * sprite->width + skip];

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				for (int x = 0; x < length; x++) {

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					data->m = *dest;

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					dest++;

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					data++;

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				}

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			} while (!last_item);

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		}

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	} else {

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		dest = dest_orig;

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		for (int i = 0; i < sprite->width * sprite->height; i++)

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			sprite->data[i].m = dest[i];

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	}

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	/* Make sure to mark all transparent pixels transparent on the alpha channel too */

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	for (int i = 0; i < sprite->width * sprite->height; i++)

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		if (sprite->data[i].m != 0) sprite->data[i].a = 0xFF;

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	free(dest_orig);

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	return true;

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}