#include "PlasmaDisplay.h"

// Command bytes (see PlasmaProtocol.cs / FIRMWARE.md).
static const uint8_t ESC = 0x1B;
static const uint8_t BS = 0x08, HT = 0x09, LF = 0x0A, VT = 0x0B, CR = 0x0D;
static const uint8_t CMD_CLEAR = '@', CMD_CURSOR = 'G', CMD_ATTR = 'H';
static const uint8_t CMD_FONT = 'K', CMD_HOME = 'L', CMD_GRAPHICS = 'P';
static const uint8_t CMD_SETROW = 'Q', CMD_SETCOL = 'R';
static const uint8_t CMD_DRAWPAGE = 'I', CMD_DISPPAGE = 'i';

PlasmaDisplay::PlasmaDisplay() { reset(); }

void PlasmaDisplay::reset() {
  memset(pixels_, 0, sizeof(pixels_));
  cx_ = cy_ = 0;
  font_ = 0;
  face_ = &plasmaFonts[0];
  attrs_ = 0;
  cursorMode_ = CURSOR_STEADY;  // power-on default; the game hides it
  orient_ = HORIZONTAL;
  state_ = TEXT;
  headerFill_ = 0;
  dataIndex_ = dataLength_ = 0;
  dirty_ = true;
}

void PlasmaDisplay::setOrientation(Orientation o) {
  if (orient_ == o) return;
  orient_ = o;
  memset(pixels_, 0, sizeof(pixels_));
  cx_ = cy_ = 0;
  dirty_ = true;
}

// The real display's power-on test (JP1 jumper 5, firmware $B888) runs through
// several drawing sequences — solid, border+grid, and more — to expose dead
// dots and addressing faults. These stand in for that; the sketch cycles them.
static bool testDot(int index, int x, int y) {
  switch (index) {
    case 0: return true;                                                // all on
    case 1: return x == 0 || x == PlasmaDisplay::WIDTH - 1 ||           // frame
                   y == 0 || y == PlasmaDisplay::HEIGHT - 1 ||
                   (x % 16) == 0 || (y % 8) == 0;                        // + grid
    case 2: return ((y / 2) % 2) == 0;                                  // horizontal stripes
    case 3: return ((x / 4) % 2) == 0;                                  // vertical stripes
    default: return (((x / 8) + (y / 8)) % 2) == 0;                     // checkerboard
  }
}

void PlasmaDisplay::showTestPattern(int index) {
  for (int y = 0; y < HEIGHT; ++y)
    for (int x = 0; x < WIDTH; ++x)
      pixels_[y * WIDTH + x] = testDot(index, x, y) ? PIX_LIT : 0;
  dirty_ = true;
}

// One logical dot → the physical 128x32 buffer, rotated per orientation.
void PlasmaDisplay::plot(int lx, int ly, uint8_t flags) {
  if ((unsigned)lx >= (unsigned)logicalW() || (unsigned)ly >= (unsigned)logicalH()) return;
  int px, py;
  if (orient_ == HORIZONTAL) {
    px = lx;
    py = ly;
  } else {
    px = ly;
    py = HEIGHT - 1 - lx;  // 90° rotation onto landscape glass
  }
  pixels_[py * WIDTH + px] = flags;
}

void PlasmaDisplay::feed(const uint8_t *buf, size_t n) {
  for (size_t i = 0; i < n; ++i) feed(buf[i]);
}

void PlasmaDisplay::feed(uint8_t b) {
  switch (state_) {
    case TEXT: stepText(b); break;
    case ESCAPE: stepEscape(b); break;
    case OPERAND:
      state_ = TEXT;
      applyOperand(pendingCmd_, b);
      break;
    case GHEADER:
      header_[headerFill_++] = b;
      if (headerFill_ == 5) beginGraphics();
      break;
    case GDATA: stepGraphics(b); break;
  }
}

void PlasmaDisplay::stepText(uint8_t b) {
  switch (b) {
    case ESC: state_ = ESCAPE; return;
    case BS: cx_ = max(0, cx_ - face_->width); dirty_ = true; return;
    case HT: advanceCursor(); dirty_ = true; return;
    case LF: nextLine(); dirty_ = true; return;
    case VT:
      cy_ -= face_->height;
      if (cy_ < 0) cy_ = max(0, logicalH() - face_->height);
      dirty_ = true;
      return;
    case CR: cx_ = 0; dirty_ = true; return;
  }
  if (b < 0x20) return;  // any other control byte: swallow (matches firmware)
  drawChar(b);
}

void PlasmaDisplay::stepEscape(uint8_t b) {
  state_ = TEXT;
  switch (b) {
    case CMD_CLEAR:
      memset(pixels_, 0, sizeof(pixels_));
      cx_ = cy_ = 0;
      font_ = 0;
      face_ = &plasmaFonts[0];
      attrs_ = 0;
      dirty_ = true;
      break;
    case CMD_HOME:
      cx_ = cy_ = 0;
      dirty_ = true;
      break;
    case CMD_CURSOR:
    case CMD_FONT:
    case CMD_ATTR:
    case CMD_SETROW:
    case CMD_SETCOL:
    case CMD_DRAWPAGE:
    case CMD_DISPPAGE:
      pendingCmd_ = b;
      state_ = OPERAND;
      break;
    case CMD_GRAPHICS:
      headerFill_ = 0;
      state_ = GHEADER;
      break;
    default: break;  // unknown command: ignored (does not consume an operand)
  }
}

void PlasmaDisplay::applyOperand(uint8_t cmd, uint8_t op) {
  switch (cmd) {
    case CMD_CURSOR:
      cursorMode_ = (op == 0x00 || op == 0xFF) ? CURSOR_HIDDEN
                    : (op & 0x02)              ? CURSOR_FLASHING
                                               : CURSOR_STEADY;
      dirty_ = true;
      break;
    case CMD_FONT:
      if (op < 8) {  // 8 real fonts; firmware ignores larger operands
        font_ = op;
        face_ = &plasmaFonts[op];
        if (cx_ > logicalW() - 1) cx_ = logicalW() - 1;
        if (cy_ > logicalH() - 1) cy_ = logicalH() - 1;
        dirty_ = true;
      }
      break;
    case CMD_ATTR:
      attrs_ = op & 0x0F;  // low 4 bits: half/underline/reverse/flash
      break;
    case CMD_SETROW:
      if (op < logicalH()) { cy_ = op; dirty_ = true; }
      break;
    case CMD_SETCOL:
      if (op < logicalW()) { cx_ = op; dirty_ = true; }
      break;
    case CMD_DRAWPAGE:
    case CMD_DISPPAGE:
      break;  // page select: consumed but single-page (see FIRMWARE.md)
  }
}

void PlasmaDisplay::beginGraphics() {
  int w = header_[3], h = header_[4];
  dataLength_ = w * h;
  dataIndex_ = 0;
  state_ = dataLength_ > 0 ? GDATA : TEXT;
}

void PlasmaDisplay::stepGraphics(uint8_t b) {
  int w = header_[3];
  int rowOfBlock = dataIndex_ / w;
  int byteOfRow = dataIndex_ % w;
  int y = header_[1] + rowOfBlock;
  int baseX = (header_[2] + byteOfRow) * 8;
  // MSB = leftmost pixel (L4PLASMA.CPP packs 0x80 first).
  for (int bit = 0; bit < 8; ++bit)
    plot(baseX + bit, y, (b & (0x80 >> bit)) ? PIX_LIT : 0);
  dirty_ = true;
  if (++dataIndex_ >= dataLength_) state_ = TEXT;
}

void PlasmaDisplay::drawChar(uint8_t code) {
  if (!faceHas(code)) return;  // firmware ignores out-of-range chars

  int w = face_->width, h = face_->height;
  bool reverse = attrs_ & 0x04;
  bool underline = attrs_ & 0x02;
  uint8_t litFlags = PIX_LIT;
  if (attrs_ & 0x01) litFlags |= PIX_HALF;
  if (attrs_ & 0x08) litFlags |= PIX_FLASH;

  for (int row = 0; row < h; ++row) {
    uint16_t bits = faceRow(code, row);  // bit15 = leftmost pixel
    for (int col = 0; col < w; ++col) {
      bool on = bits & (0x8000 >> col);
      if (underline && row == h - 1) on = true;
      if (reverse) on = !on;
      plot(cx_ + col, cy_ + row, on ? litFlags : 0);
    }
  }
  dirty_ = true;
  advanceCursor();
}

void PlasmaDisplay::advanceCursor() {
  cx_ += face_->width;
  if (cx_ > logicalW() - face_->width) nextLine();
}

void PlasmaDisplay::nextLine() {
  cx_ = 0;
  cy_ += face_->height;
  if (cy_ > logicalH() - face_->height) cy_ = 0;  // wrap to top; no scroll
}