#include <dos.h>
#include <stdio.h>
#include <stdlib.h>
#include "video.h"
#include "tiles.h"
#include "egamap.h"

/*** T I L E S ***/

// Tiles are 16x16 bitmaps, stored as arrays of words.
// Each tile has 4 or 5 planes (depending on whether it is a tile or sprite)
// which are stored adjacant to each other; ie. a 16-word array of blue,
// followed by a 16-word array of green, etc.
// Tiles in RAM are stored byte-swapped to aid in fast bit-shifting, and must
// be byte-swapped before being written to video memory.

// Because bit-shifting operations happen on little-endian words:
// 01234567 89ABCDEF << 3 => 34567XXX BCDEF012
// which is wrong. So instead we do:
// 89ABCDEF 01234567 << 3 => BCDEFXXX 3456789A byteswap => 3456789A BCDEFXXX

void tile_init() {
  setLogicalWidth(PAGE_STRIDE >> 1);
}

void blitTile(unsigned int offsetFrom, unsigned int offsetTo) {
  int y;
  for (y = 0; y < 16; y ++) {
    VID[offsetTo] = VID[offsetFrom ++];
    VID[offsetTo + 1] = VID[offsetFrom ++];
    offsetTo += PAGE_STRIDE;
  }
}

void blitSolidBlock(unsigned int offsetTo, unsigned char color) {
  int y;
  setPlaneColor(color);
  for (y = 0; y < 16; y ++) {
    VID[offsetTo] = 0xff;
    VID[offsetTo + 1] = 0xff;
    offsetTo += PAGE_STRIDE;
  }
}

void blit32x32(unsigned int offsetFrom, unsigned int offsetTo) {
  int y;
  for (y = 0; y < 32; y ++) {
    VID[offsetTo] = VID[offsetFrom ++];
    VID[offsetTo + 1] = VID[offsetFrom ++];
    VID[offsetTo + 2] = VID[offsetFrom ++];
    VID[offsetTo + 3] = VID[offsetFrom ++];
    offsetTo += PAGE_STRIDE;
  }
}

void blitMemToVid(unsigned int offset, unsigned int far *mem, unsigned int planeStride, int count) {
  int i, j, plane;

  offset = offset >> 1; // word aligned
  setWriteMode(0);
  for (i = 0; i < count; i ++) {
    for (plane = 0; plane < 4; plane ++) {
      unsigned int drawOffset = offset;
      unsigned int bmp;

      setPlane(plane);
      for (j = 0; j < planeStride; j ++) {
	bmp = mem[j];
	WVID[drawOffset + j] = (bmp << 8) | (bmp >> 8);
      }
      mem += planeStride;
    }
    offset += planeStride;
  }
  setAllPlanes();
}

#define D_NOTHING 0x80
#define D_BGTILE 0x81
#define isBufIndex(d) (!((d) & 0x80))

#define nextBufferIndex(i) ((i + 1) % NUM_BUFFERS)

TiledScreen_t screen = { 0, 0, 0, 0, { OFF_PAGE1, OFF_PAGE2 }, 0, 0, NULL, NULL,
  0, 0, 0, 0, 0 };


void paintBufferPlane(unsigned int *buf, unsigned int vidOffset, int stride, int plane) {
  unsigned int drawOffset = vidOffset >> 1;
  unsigned int y, bmp;
  for (y = 0; y < 16; y ++) {
    bmp = buf[y + (BUF_WSTRIDE * plane)];
    WVID[drawOffset] = (bmp << 8) | (bmp >> 8);
    drawOffset += stride >> 1;
  }
}

void loadTiles(unsigned int tilesOffset, unsigned int far *memTiles) {
  int i, plane;
  screen.tilesOffset = tilesOffset;
  screen.memTiles = memTiles;
  setWriteMode(0);
  for (plane = 0; plane < 4; plane ++) {
    unsigned int drawOffset = tilesOffset >> 1;
    setPlane(plane);
    for (i = 0; i < NUM_TILES; i ++) {
      unsigned int y, bmp;
      unsigned int far *buf = &memTiles[(i * BUF_WSIZE) + (BUF_WSTRIDE * plane)];
      for (y = 0; y < 16; y ++) {
	bmp = buf[y];
	WVID[drawOffset ++] = (bmp << 8) | (bmp >> 8);
      }
    }
  }
  setAllPlanes();
}

void loadMap(unsigned char *map, unsigned int w, unsigned int h) {
  screen.map = map;
  screen.w = w;
  screen.h = h;
  memset(screen.dirty, D_BGTILE, PAGE_TILES_COUNT * 2);
}

void writeTile(unsigned int *buf, unsigned int far *tile) {
  int i;
  for (i = 0; i < BUF_WSIZE; i ++) {
    buf[i] = tile[i];
  }
}

void overlaySprite(unsigned int *buf, unsigned int far *sprite, int shift, int yStart, char *remap) {
  unsigned int far *mask;
  unsigned int maskval;
  int y, h, plane;

  if (yStart < 0) {
    sprite = &sprite[-yStart];
    h = yStart + 16;
  } else {
    buf = &buf[yStart];
    h = 16 - yStart;
  }
  mask = &sprite[BUF_WSTRIDE * 4];
  if (!remap) {
    if (shift < 0) {
      shift = -shift;
      for (plane = 0; plane < 4; plane ++) {
	for (y = 0; y < h; y ++) {
	  maskval = mask[y] << shift;
	  buf[y] = (buf[y] & ~maskval) | ((sprite[y] << shift) & maskval);
	}
	sprite += BUF_WSTRIDE;
	buf += BUF_WSTRIDE;
      }
    } else {
      for (plane = 0; plane < 4; plane ++) {
	for (y = 0; y < h; y ++) {
	  maskval = mask[y] >> shift;
	  buf[y] = (buf[y] & ~maskval) | ((sprite[y] >> shift) & maskval);
	}
	sprite += BUF_WSTRIDE;
	buf += BUF_WSTRIDE;
      }
    }
  } else {
    unsigned int b, bo, g, go, r, ro, i, io, bgri;
    int bit;
    if (shift < 0) {
      shift = -shift;
#define SPLANE(b, y, p) b[y + (BUF_WSTRIDE * (p))]
#define DO_REMAP(ss, bitstart, bitlim) \
      for (y = 0; y < h; y ++) { \
	bo = go = ro = io = 0; \
	b = SPLANE(sprite, y, 0); \
	g = SPLANE(sprite, y, 1); \
	r = SPLANE(sprite, y, 2); \
	i = SPLANE(sprite, y, 3); \
	for (bit = (bitstart); bit < (bitlim); bit ++) { \
	  int bshift = 1 << bit; \
	  bgri = ((b & bshift) ? 0x01 : 0x00) | \
		 ((g & bshift) ? 0x02 : 0x00) | \
		 ((r & bshift) ? 0x04 : 0x00) | \
		 ((i & bshift) ? 0x08 : 0x00); \
	  bgri = remap[bgri]; \
	  if (bgri & 0x01) bo |= bshift; \
	  if (bgri & 0x02) go |= bshift; \
	  if (bgri & 0x04) ro |= bshift; \
	  if (bgri & 0x08) io |= bshift; \
	} \
	maskval = mask[y] ss shift; \
	SPLANE(buf, y, 0) = (SPLANE(buf, y, 0) & ~maskval) | ((bo ss shift) & maskval); \
	SPLANE(buf, y, 1) = (SPLANE(buf, y, 1) & ~maskval) | ((go ss shift) & maskval); \
	SPLANE(buf, y, 2) = (SPLANE(buf, y, 2) & ~maskval) | ((ro ss shift) & maskval); \
	SPLANE(buf, y, 3) = (SPLANE(buf, y, 3) & ~maskval) | ((io ss shift) & maskval); \
      }

      DO_REMAP(<<, shift, 16)
    } else {
      DO_REMAP(>>, 0, 16 - shift)

#undef DO_REMAP
#undef SPLANE
    }
  }
}

int prepareBuffer(int pageX, int pageY) {
  unsigned char *dirty = &screen.dirty[screen.currentPage][pageX + (pageY * PAGE_TILES_W)];
  int i;
  if (!isBufIndex(*dirty)) {
    unsigned int startX = screen.scrollX >> 4;
    unsigned int startY = screen.scrollY >> 4;
    unsigned char tile = screen.map[startX + pageX + ((startY + pageY) * screen.w)];
    unsigned char ibuffer = screen.nextBuffer;
    screen.nextBuffer = nextBufferIndex(ibuffer);
    *dirty = ibuffer;
    writeTile(screen.buffer[ibuffer], &screen.memTiles[tile * BUF_WSIZE]);
    screen.bufferOffset[ibuffer] = screen.pageOffset[screen.currentPage]
      + (pageX << 1) + (pageY * PAGE_STRIDE * 16);
  }
  return *dirty;
}

void drawSpriteToBuf(unsigned int far *sprite, int pageX, int pageY, int shift, int yStart, char *remap) {
  unsigned int *buf;

  if (pageX < 0 || pageY < 0 ||
      pageX >= PAGE_TILES_W || pageY >= PAGE_TILES_H ||
      shift >= 16 || shift <= -16 ||
      yStart <= -16 || yStart >= 16) {
    return;
  }

  buf = screen.buffer[prepareBuffer(pageX, pageY)];
  overlaySprite(buf, sprite, shift, yStart, remap);
}

void drawSprite(unsigned int far *sprite, int x, int y, char *remap) {
  int pageX = (int)(x - (screen.scrollX & 0xfff0)) >> 4;
  int pageY = (int)(y - (screen.scrollY & 0xfff0)) >> 4;
  int pageOffsetX = x & 0x0f;
  int pageOffsetY = y & 0x0f;

  drawSpriteToBuf(sprite, pageX, pageY, pageOffsetX, pageOffsetY, remap);
  drawSpriteToBuf(sprite, pageX + 1, pageY, pageOffsetX - 16, pageOffsetY, remap);
  drawSpriteToBuf(sprite, pageX, pageY + 1, pageOffsetX, pageOffsetY - 16, remap);
  drawSpriteToBuf(sprite, pageX + 1, pageY + 1, pageOffsetX - 16, pageOffsetY - 16, remap);
}

void scroll(int newX, int newY) {
  newX = min(max(newX, 0), (screen.w << 4) - 320);
  newY = min(max(newY, 0), (screen.h << 4) - 200);
  if ((screen.scrollX & 0xfff0) != (newX & 0xfff0) ||
      (screen.scrollY & 0xfff0) != (newY & 0xfff0)) {
    int mapX, mapY;
    unsigned char page;
    for (page = 0; page < 2; page ++) {
      int mapOffsetOld = (screen.scrollX >> 4) + ((screen.scrollY >> 4) * screen.w);
      int mapOffsetNew = (newX >> 4) + ((newY >> 4) * screen.w);
      unsigned char *dirty = screen.dirty[page];
      for (mapY = 0; mapY < PAGE_TILES_H; mapY ++) {
	for (mapX = 0; mapX < PAGE_TILES_W; mapX ++) {
	  if (*dirty != D_NOTHING ||
	    screen.map[mapOffsetOld + mapX] != screen.map[mapOffsetNew + mapX]) {
	    *dirty = D_BGTILE;
	  }
	  dirty ++;
	}
	mapOffsetNew += screen.w;
	mapOffsetOld += screen.w;
      }
    }
  }
  screen.scrollX = newX;
  screen.scrollY = newY;
}

void paintBuffer(unsigned int *buf, unsigned int vidOffset) {
  int plane;
  setWriteMode(0);
  for (plane = 0; plane < 4; plane ++) {
    setPlane(plane);
    paintBufferPlane(buf, vidOffset, 40, plane);
  }
}

void drawScreen() {
  unsigned int startX = screen.scrollX >> 4;
  unsigned int startY = screen.scrollY >> 4;
  unsigned int offsetX = screen.scrollX - (startX << 4);
  unsigned int offsetY = screen.scrollY - (startY << 4);
  unsigned int drawOffset = screen.pageOffset[screen.currentPage];
  unsigned int scrollOffset = drawOffset + (offsetX >> 3) + (offsetY * PAGE_STRIDE);
  unsigned char *dirty = screen.dirty[screen.currentPage];
  unsigned int x, y, di, plane, bmp;

  setAllPlanes();
  setWriteMode(1);

  di = 0;
  for (y = startY; y < startY + PAGE_TILES_H; y ++) {
    for (x = startX; x < startX + PAGE_TILES_W; x ++) {
      if (dirty[di++] == D_BGTILE) {
	char tile = screen.map[x + (y * screen.w)];
	blitTile(screen.tilesOffset + (tile << 5), drawOffset);
      }
      drawOffset += 2;
    }
    drawOffset += PAGE_STRIDE * 15;
  }
  setWriteMode(0);
  for(plane = 0; plane < 4; plane ++) {
    setPlane(plane);
    for (di = screen.firstBuffer; di != screen.nextBuffer; di = nextBufferIndex(di)) {
      paintBufferPlane(screen.buffer[di], screen.bufferOffset[di], PAGE_STRIDE, plane);
    }
  }
  setAllPlanes();

  setDisplayOffset(scrollOffset);
  setHorizontalPan(screen.scrollX & 0x07);

  screen.currentPage ^= 1;
  screen.firstBuffer = screen.nextBuffer;
  for (di = 0; di < PAGE_TILES_COUNT; di ++) {
    dirty[di] = isBufIndex(dirty[di]) ? D_BGTILE : D_NOTHING;
  }
}