web-cad/frontend/src/services/dxfWriter.ts

/**
 * DXF Writer – converts CADElement[] to DXF string
 * Minimal DXF R12 format for compatibility
 */
import type { CADElement, CADLayer, ProjectData } from '../types/cad.types';

/**
 * Generate a DXF R12 string from project data.
 */
export function writeDXF(data: ProjectData): string {
  const lines: string[] = [];
  const w = (code: number, value: string | number) => {
    lines.push(String(code));
    lines.push(String(value));
  };

  // Header
  w(0, 'SECTION');
  w(2, 'HEADER');
  w(9, '$ACADVER'); w(1, 'AC1009'); // R12
  w(9, '$INSBASE'); w(10, 0); w(20, 0); w(30, 0);
  w(9, '$EXTMIN'); w(10, 0); w(20, 0);
  w(9, '$EXTMAX'); w(10, 1000); w(20, 1000);
  w(0, 'ENDSEC');

  // Tables section
  w(0, 'SECTION');
  w(2, 'TABLES');

  // Layer table
  w(0, 'TABLE');
  w(2, 'LAYER');
  w(70, data.layers.length);
  for (const layer of data.layers) {
    w(0, 'LAYER');
    w(2, layer.name);
    w(70, 0);
    w(62, hexToACI(layer.color));
    w(6, lineTypeToDXF(layer.lineType));
  }
  w(0, 'ENDTAB');
  w(0, 'ENDSEC');

  // Entities section
  w(0, 'SECTION');
  w(2, 'ENTITIES');

  for (const el of data.elements) {
    const layerName = getLayerName(data.layers, el.layerId);
    writeEntity(w, el, layerName);
  }

  w(0, 'ENDSEC');

  // EOF
  w(0, 'EOF');

  return lines.join('\n');
}

function writeEntity(
  w: (code: number, value: string | number) => void,
  el: CADElement,
  layerName: string,
): void {
  const p = el.properties;
  const stroke = (p.stroke as string) || '#ffffff';
  const aci = hexToACI(stroke);

  switch (el.type) {
    case 'line': {
      w(0, 'LINE');
      w(8, layerName);
      w(62, aci);
      w(10, p.x1 ?? el.x); w(20, p.y1 ?? el.y); w(30, 0);
      w(11, p.x2 ?? el.x + el.width); w(21, p.y2 ?? el.y + el.height); w(31, 0);
      break;
    }
    case 'circle': {
      const cx = el.x + el.width / 2;
      const cy = el.y + el.height / 2;
      const r = p.radius ?? el.width / 2;
      w(0, 'CIRCLE');
      w(8, layerName);
      w(62, aci);
      w(10, cx); w(20, cy); w(30, 0);
      w(40, r);
      break;
    }
    case 'arc': {
      const cx = el.x + el.width / 2;
      const cy = el.y + el.height / 2;
      const r = p.radius ?? el.width / 2;
      w(0, 'ARC');
      w(8, layerName);
      w(62, aci);
      w(10, cx); w(20, cy); w(30, 0);
      w(40, r);
      w(50, radToDeg(p.startAngle ?? 0));
      w(51, radToDeg(p.endAngle ?? 360));
      break;
    }
    case 'rect': {
      // Rectangle as LWPOLYLINE
      w(0, 'LWPOLYLINE');
      w(8, layerName);
      w(62, aci);
      w(90, 4);
      w(70, 1); // closed
      w(10, el.x); w(20, el.y);
      w(10, el.x + el.width); w(20, el.y);
      w(10, el.x + el.width); w(20, el.y + el.height);
      w(10, el.x); w(20, el.y + el.height);
      break;
    }
    case 'polygon':
    case 'polyline': {
      const pts = p.points ?? [];
      w(0, 'LWPOLYLINE');
      w(8, layerName);
      w(62, aci);
      w(90, pts.length);
      w(70, el.type === 'polygon' ? 1 : 0);
      for (const pt of pts) {
        w(10, pt.x); w(20, pt.y);
      }
      break;
    }
    case 'text': {
      w(0, 'TEXT');
      w(8, layerName);
      w(62, aci);
      w(10, el.x); w(20, el.y); w(30, 0);
      w(40, p.fontSize ?? 12);
      w(1, p.text ?? '');
      break;
    }
    case 'dimension': {
      const pts = p.points ?? [];
      if (pts.length >= 2) {
        // Draw dimension as LINE + TEXT
        w(0, 'LINE');
        w(8, layerName);
        w(62, aci);
        w(10, pts[0].x); w(20, pts[0].y); w(30, 0);
        w(11, pts[1].x); w(21, pts[1].y); w(31, 0);
        const midX = (pts[0].x + pts[1].x) / 2;
        const midY = (pts[0].y + pts[1].y) / 2;
        const dist = Math.hypot(pts[1].x - pts[0].x, pts[1].y - pts[0].y);
        w(0, 'TEXT');
        w(8, layerName);
        w(62, aci);
        w(10, midX); w(20, midY); w(30, 0);
        w(40, 12);
        w(1, dist.toFixed(2));
      }
      break;
    }
    case 'block_instance': {
      w(0, 'INSERT');
      w(8, layerName);
      w(62, aci);
      w(2, p.blockId ?? 'BLOCK');
      w(10, el.x); w(20, el.y); w(30, 0);
      w(41, p.scale ?? 1);
      w(42, p.scale ?? 1);
      w(50, radToDeg(p.rotation ?? 0));
      break;
    }
    default:
      // For chair, seating-row, etc. — export as LWPOLYLINE bounding box
      w(0, 'LWPOLYLINE');
      w(8, layerName);
      w(62, aci);
      w(90, 4);
      w(70, 1);
      w(10, el.x); w(20, el.y);
      w(10, el.x + el.width); w(20, el.y);
      w(10, el.x + el.width); w(20, el.y + el.height);
      w(10, el.x); w(20, el.y + el.height);
      break;
  }
}

function getLayerName(layers: CADLayer[], layerId: string): string {
  return layers.find(l => l.id === layerId)?.name ?? '0';
}

function hexToACI(hex: string): number {
  const h = hex.replace('#', '');
  const r = parseInt(h.substring(0, 2), 16);
  const g = parseInt(h.substring(2, 4), 16);
  const b = parseInt(h.substring(4, 6), 16);
  // Map common colors to ACI
  if (r > 200 && g < 100 && b < 100) return 1; // red
  if (r > 200 && g > 200 && b < 100) return 2; // yellow
  if (r < 100 && g > 200 && b < 100) return 3; // green
  if (r < 100 && g > 200 && b > 200) return 4; // cyan
  if (r < 100 && g < 100 && b > 200) return 5; // blue
  if (r > 200 && g < 100 && b > 200) return 6; // magenta
  if (r > 200 && g > 200 && b > 200) return 7; // white
  if (r < 100 && g < 100 && b < 100) return 8; // gray
  return 7; // default white
}

function lineTypeToDXF(lt: string): string {
  if (lt === 'dashed') return 'DASHED';
  if (lt === 'dotted') return 'DOT';
  return 'CONTINUOUS';
}

function radToDeg(rad: number): number {
  return (rad * 180) / Math.PI;
}