paint-ui/tools/eraser-tool.ts

import { BaseTool } from './base-tool';
import type { PointerState, ToolSettings } from '@/types';
import { distance } from '@/lib/utils';

/**
 * Eraser tool - Remove pixels
 */
export class EraserTool extends BaseTool {
  private lastX = 0;
  private lastY = 0;

  constructor() {
    super('Eraser');
  }

  onPointerDown(
    pointer: PointerState,
    ctx: CanvasRenderingContext2D,
    settings: ToolSettings
  ): void {
    this.isDrawing = true;
    this.lastX = pointer.x;
    this.lastY = pointer.y;

    // Erase initial stamp
    this.eraseStamp(pointer.x, pointer.y, ctx, settings);
  }

  onPointerMove(
    pointer: PointerState,
    ctx: CanvasRenderingContext2D,
    settings: ToolSettings
  ): void {
    if (!this.isDrawing) return;

    // Calculate distance from last point
    const dist = distance(this.lastX, this.lastY, pointer.x, pointer.y);
    const spacing = settings.size * settings.spacing;

    if (dist >= spacing) {
      // Interpolate between points for smooth erasing
      const steps = Math.ceil(dist / spacing);

      for (let i = 1; i <= steps; i++) {
        const t = i / steps;
        const x = this.lastX + (pointer.x - this.lastX) * t;
        const y = this.lastY + (pointer.y - this.lastY) * t;

        this.eraseStamp(x, y, ctx, settings);
      }

      this.lastX = pointer.x;
      this.lastY = pointer.y;
    }
  }

  onPointerUp(
    pointer: PointerState,
    ctx: CanvasRenderingContext2D,
    settings: ToolSettings
  ): void {
    this.isDrawing = false;
  }

  /**
   * Erase a circular area
   */
  private eraseStamp(
    x: number,
    y: number,
    ctx: CanvasRenderingContext2D,
    settings: ToolSettings
  ): void {
    ctx.save();
    ctx.globalCompositeOperation = 'destination-out';
    ctx.globalAlpha = settings.opacity;
    ctx.beginPath();
    ctx.arc(x, y, settings.size / 2, 0, Math.PI * 2);
    ctx.fill();
    ctx.restore();
  }
}