import { Injectable, Logger } from '@nestjs/common';
import * as QRCode from 'qrcode';
import { Resvg } from '@resvg/resvg-js';
import type { LabelElement } from '../database/entities/barcode-template.entity';

const MM_TO_PX = 300 / 25.4; // 300 DPI

function mm(v: number): number {
  return Math.round(v * MM_TO_PX);
}

function escape(s: string): string {
  return s.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;').replace(/"/g, '&quot;');
}

function applyVars(template: string, vars: Record<string, string>): string {
  return template.replace(/\{([^}]+)\}/g, (_, key: string) => {
    const colonIdx = key.indexOf(':');
    if (colonIdx !== -1) {
      const varName = key.slice(0, colonIdx);
      const width = parseInt(key.slice(colonIdx + 1), 10);
      if (!isNaN(width)) {
        return (vars[varName] ?? '').padStart(width, '0');
      }
    }
    return vars[key] ?? `{${key}}`;
  });
}

@Injectable()
export class LabelRendererService {
  private readonly logger = new Logger(LabelRendererService.name);

  async render(
    layout: LabelElement[],
    widthMm: number,
    heightMm: number,
    variables: Record<string, string>,
  ): Promise<Buffer> {
    const W = mm(widthMm);
    const H = mm(heightMm);

    const parts: string[] = [];

    for (const el of layout) {
      if (el.type === 'text') {
        const x = mm(el.x);
        const y = mm(el.y);
        const fontSize = mm(el.fontSize);
        const content = escape(applyVars(el.content, variables));
        const fontWeight = el.bold ? 'bold' : 'normal';
        const textAnchor = el.align === 'center' ? 'middle' : el.align === 'right' ? 'end' : 'start';
        const maxWidthAttr = el.maxWidth ? ` textLength="${mm(el.maxWidth)}" lengthAdjust="spacingAndGlyphs"` : '';
        // librsvg (used by sharp) ignores dominant-baseline; add fontSize to y so that
        // the stored coordinate is the top of the text, not the baseline.
        const yBaseline = y + fontSize;
        parts.push(
          `<text x="${x}" y="${yBaseline}" font-family="Arial,Helvetica,sans-serif" font-size="${fontSize}" font-weight="${fontWeight}" text-anchor="${textAnchor}"${maxWidthAttr}>${content}</text>`,
        );
      } else if (el.type === 'qr') {
        const x = mm(el.x);
        const y = mm(el.y);
        const size = mm(el.sizeMm);
        const content = applyVars(el.content, variables);
        try {
          const qrBuffer = await QRCode.toBuffer(content, {
            type: 'png',
            margin: 0,
            width: size,
            errorCorrectionLevel: 'M',
          });
          const b64 = qrBuffer.toString('base64');
          parts.push(`<image href="data:image/png;base64,${b64}" x="${x}" y="${y}" width="${size}" height="${size}"/>`);
        } catch (err: any) {
          this.logger.warn(`QR-Code-Rendering fehlgeschlagen für "${content}": ${err.message}`);
        }
      } else if (el.type === 'line') {
        const x1 = mm(el.x1);
        const y1 = mm(el.y1);
        const x2 = mm(el.x2);
        const y2 = mm(el.y2);
        const strokeWidth = el.lineWidth ? mm(el.lineWidth) : 1;
        parts.push(`<line x1="${x1}" y1="${y1}" x2="${x2}" y2="${y2}" stroke="black" stroke-width="${strokeWidth}"/>`);
      }
    }

    const svg = `<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="${W}" height="${H}" viewBox="0 0 ${W} ${H}">
  <rect width="${W}" height="${H}" fill="white"/>
  ${parts.join('\n  ')}
</svg>`;

    const resvg = new Resvg(svg, {
      font: {
        loadSystemFonts: true,
        fontDirs: ['/usr/share/fonts', '/usr/local/share/fonts'],
        defaultFontFamily: 'Liberation Sans',
        sansSerifFamily: 'Liberation Sans',
      },
    });
    return Buffer.from(resvg.render().asPng());
  }
}