import { Injectable } from '@angular/core';

@Injectable({ providedIn: 'root' })
export class VizExportService {
  exportSvg(element: SVGSVGElement): string {
    const serializer = new XMLSerializer();
    const svgString = serializer.serializeToString(element);
    return `<?xml version="1.0" encoding="UTF-8"?>\n${svgString}`;
  }

  async exportPng(element: SVGSVGElement, width: number, height: number): Promise<Blob> {
    const svgString = this.exportSvg(element);
    const svgBlob = new Blob([svgString], { type: 'image/svg+xml;charset=utf-8' });
    const url = URL.createObjectURL(svgBlob);

    try {
      const img = new Image();
      img.width = width;
      img.height = height;

      await new Promise<void>((resolve, reject) => {
        img.onload = () => resolve();
        img.onerror = reject;
        img.src = url;
      });

      const canvas = document.createElement('canvas');
      canvas.width = width;
      canvas.height = height;
      const ctx = canvas.getContext('2d')!;
      ctx.drawImage(img, 0, 0, width, height);

      return new Promise<Blob>((resolve, reject) => {
        canvas.toBlob((blob) => {
          if (blob) {
            resolve(blob);
          } else {
            reject(new Error('Failed to create PNG blob'));
          }
        }, 'image/png');
      });
    } finally {
      URL.revokeObjectURL(url);
    }
  }

  downloadSvg(element: SVGSVGElement, filename = 'chart.svg'): void {
    const svgString = this.exportSvg(element);
    const blob = new Blob([svgString], { type: 'image/svg+xml;charset=utf-8' });
    this.downloadBlob(blob, filename);
  }

  async downloadPng(element: SVGSVGElement, width: number, height: number, filename = 'chart.png'): Promise<void> {
    const blob = await this.exportPng(element, width, height);
    this.downloadBlob(blob, filename);
  }

  private downloadBlob(blob: Blob, filename: string): void {
    const url = URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.href = url;
    a.download = filename;
    a.click();
    URL.revokeObjectURL(url);
  }
}