#include <dos.h>
#include "tiff.h"
#include "video.h"

/*** T I F F ***/
typedef struct {
  unsigned int endian;
  unsigned int version;
  unsigned long ifdOffset;
} TifHeader_t;

#define TIF_WIDTH 256
#define TIF_HEIGHT 257
#define TIF_BITSPERSAMPLE 258
#define TIF_COMPRESSION 259
#define TIF_STRIPOFFSETS 273
#define TIF_ROWSPERSTRIP 278

typedef struct {
  unsigned int id;
  unsigned int dataType;
  unsigned long dataCount;
  unsigned long dataOffset;
} TifTag_t;

TifImageMeta_t tifLoadMeta(FILE *f) {
  TifImageMeta_t meta = {0, 0, 0, 0, 0};
  TifHeader_t header;
  TifTag_t tag;
  unsigned int i, tagCount;

  fseek(f, 0, SEEK_SET);
  fread(&header, 8, 1, f);

  if (header.endian != 0x4949 || header.version != 0x2a) {
    goto fail;
  }
  fseek(f, header.ifdOffset, SEEK_SET);
  fread(&tagCount, 2, 1, f);
  for (i = 0; i < tagCount; i ++) {
    fread(&tag, 12, 1, f);
    if (tag.id == TIF_WIDTH) {
      meta.width = tag.dataOffset;
    } else if (tag.id == TIF_HEIGHT) {
      meta.height = tag.dataOffset;
    } else if (tag.id == TIF_BITSPERSAMPLE) {
      if (tag.dataOffset != 4) goto fail;
    } else if (tag.id == TIF_COMPRESSION) {
      if (tag.dataOffset != 1) goto fail;
    } else if (tag.id == TIF_STRIPOFFSETS) {
      meta.stripCount = tag.dataCount;
      meta.stripOffsets = tag.dataOffset;
    } else if (tag.id == TIF_ROWSPERSTRIP) {
      meta.rowsPerStrip = tag.dataOffset;
    }
  }
  return meta;
fail:
  meta.stripCount = 0;
  return meta;
}

int tifLoadEGA(FILE *f, TifImageMeta_t meta, unsigned int vidOffset, int maxY, unsigned int w) {
  int istrip;
  int irow;
  int ipixelpair;
  int y = 0;
  unsigned long offset;
  unsigned char rowData[MAX_WIDTH >> 1];
  volatile unsigned char far *out = &VID[vidOffset];
  unsigned char b, g, r, i;

  if (meta.width > MAX_WIDTH || (meta.width % 8) != 0) {
    return 0;
  }
  setWriteMode(0);

  for (istrip = 0; istrip < meta.stripCount; istrip ++) {
    fseek(f, meta.stripOffsets + (istrip << 2), SEEK_SET);
    fread(&offset, 4, 1, f);
    fseek(f, offset, SEEK_SET);

    for (irow = 0; irow < meta.rowsPerStrip; irow ++) {
      int ipixelpairLim = meta.width >> 1;
      fread(rowData, 1, ipixelpairLim, f);
      b = g = r = i = 0;
      for (ipixelpair = 0; ipixelpair < ipixelpairLim; ipixelpair ++) {
	unsigned char pixelpair = rowData[ipixelpair];
	int bpair = (pixelpair & 0x01) | (pixelpair & 0x10) >> 3;
	int gpair = (pixelpair & 0x02) >> 1 | (pixelpair & 0x20) >> 4;
	int rpair = (pixelpair & 0x04) >> 2 | (pixelpair & 0x40) >> 5;
	int ipair = (pixelpair & 0x08) >> 3 | (pixelpair & 0x80) >> 6;
	int shift = (3 - (ipixelpair % 4)) << 1;

	b |= bpair << shift;
	g |= gpair << shift;
	r |= rpair << shift;
	i |= ipair << shift;

	if (shift == 0 || ipixelpair == ipixelpairLim - 1) {
	  // todo: use write mode 2, this is slooww
	  setPlane(PLANE_B); *out = b;
	  setPlane(PLANE_R); *out = r;
	  setPlane(PLANE_G); *out = g;
	  setPlane(PLANE_I); *out = i;
	  out ++;
	  b = g = r = i = 0;
	}
      }
      y++;
      if (y == maxY) {
	return y;
      }
      out += (w - meta.width) >> 3;
    }
  }
  return y;
}

int tifLoad(FILE *f, TifImageMeta_t meta, unsigned int far *planeBuf, int maxY, int yRepeat, int planes) {
  int istrip;
  int irow;
  int ipixelpair;
  int y = 0;
  unsigned long offset;
  unsigned char rowData[MAX_WIDTH >> 1];
  unsigned int planeStride = (meta.width >> 4) * yRepeat;
  unsigned int far *bp = planeBuf;
  unsigned int far *gp = bp + planeStride;
  unsigned int far *rp = gp + planeStride;
  unsigned int far *ip = rp + planeStride;
  unsigned int far *mp = ip + planeStride;
  unsigned int bv, gv, rv, iv;

  if (meta.width > MAX_WIDTH || (meta.width % 16) != 0 || planes < 4 || planes > 5) {
    return 0;
  }

  for (istrip = 0; istrip < meta.stripCount; istrip ++) {
    fseek(f, meta.stripOffsets + (istrip << 2), SEEK_SET);
    fread(&offset, 4, 1, f);
    fseek(f, offset, SEEK_SET);

    for (irow = 0; irow < meta.rowsPerStrip; irow ++) {
      int ipixelpairLim = meta.width >> 1;
      fread(rowData, 1, ipixelpairLim, f);
      bv = gv = rv = iv = 0;
      for (ipixelpair = 0; ipixelpair < ipixelpairLim; ipixelpair ++) {
	unsigned char pixelpair = rowData[ipixelpair];
	int bpair = (pixelpair & 0x01) | (pixelpair & 0x10) >> 3;
	int gpair = (pixelpair & 0x02) >> 1 | (pixelpair & 0x20) >> 4;
	int rpair = (pixelpair & 0x04) >> 2 | (pixelpair & 0x40) >> 5;
	int ipair = (pixelpair & 0x08) >> 3 | (pixelpair & 0x80) >> 6;
	int shift = (7 - (ipixelpair % 8)) << 1;

	bv |= bpair << shift;
	gv |= gpair << shift;
	rv |= rpair << shift;
	iv |= ipair << shift;

	if (shift == 0 || ipixelpair == ipixelpairLim - 1) {
	  *bp++ = bv;
	  *gp++ = gv;
	  *rp++ = rv;
	  *ip++ = iv;
	  if (planes == 5) {
	    iv = ~(bv & gv & rv & iv);
	    *mp++ = iv;
	  }
	  bv = gv = rv = iv = 0;
	}
      }
      y++;
      if (y == maxY) {
	return y;
      }
      if (y % yRepeat == 0) {
	bp += planeStride * (planes - 1);
	gp += planeStride * (planes - 1);
	rp += planeStride * (planes - 1);
	ip += planeStride * (planes - 1);
	mp += planeStride * (planes - 1);
      }
    }
  }
  return y;
}