import * as fs from 'fs';
import * as path from 'path';

type SharpLike = (input?: unknown, options?: unknown) => { png: () => { toBuffer: () => Promise<Buffer> } };

let sharpFn: SharpLike | null = null;
async function getSharp(): Promise<SharpLike> {
  if (sharpFn) return sharpFn;
  // eslint-disable-next-line @typescript-eslint/no-explicit-any
  const mod: any = await import('sharp');
  sharpFn = (mod?.default || mod) as SharpLike;
  return sharpFn;
}

const PUBLIC_DIR = path.join(process.cwd(), 'public');

async function fetchBytes(url: string): Promise<Uint8Array> {
  const res = await fetch(url);
  if (!res.ok) throw new Error(`Failed to fetch ${url}: ${res.status} ${res.statusText}`);
  return new Uint8Array(await res.arrayBuffer());
}

async function readBytesFromPublic(localPath: string): Promise<Uint8Array> {
  const abs = path.join(PUBLIC_DIR, localPath.replace(/^\//, ''));
  return new Uint8Array(fs.readFileSync(abs));
}

function transformLogoSvgToPrintBlack(svg: string): string {
  return svg
    .replace(/fill\s*:\s*white/gi, 'fill:#000000')
    .replace(/fill\s*=\s*"white"/gi, 'fill="#000000"')
    .replace(/fill\s*=\s*'white'/gi, "fill='#000000'")
    .replace(/fill\s*:\s*#[0-9a-fA-F]{6}/gi, 'fill:#000000')
    .replace(/fill\s*=\s*"#[0-9a-fA-F]{6}"/gi, 'fill="#000000"')
    .replace(/fill\s*=\s*'#[0-9a-fA-F]{6}'/gi, "fill='#000000'");
}

async function toPngBytes(inputBytes: Uint8Array, inputHint: string): Promise<Uint8Array> {
  const ext = (path.extname(inputHint).toLowerCase() || '').replace('.', '');
  if (ext === 'png') return inputBytes;

  if (ext === 'svg' && (/\/media\/logo\.svg$/i.test(inputHint) || /\/logo-blue\.svg$/i.test(inputHint))) {
    const svg = Buffer.from(inputBytes).toString('utf8');
    inputBytes = new Uint8Array(Buffer.from(transformLogoSvgToPrintBlack(svg), 'utf8'));
  }

  const sharp = await getSharp();
  return new Uint8Array(await sharp(Buffer.from(inputBytes)).png().toBuffer());
}

function toDataUrlPng(bytes: Uint8Array): string {
  return `data:image/png;base64,${Buffer.from(bytes).toString('base64')}`;
}

export async function loadImageAsPngDataUrl(src: string | null): Promise<string | null> {
  if (!src) return null;
  try {
    if (src.startsWith('/')) {
      const bytes = await readBytesFromPublic(src);
      const png = await toPngBytes(bytes, src);
      return toDataUrlPng(png);
    }
    const bytes = await fetchBytes(src);
    const png = await toPngBytes(bytes, src);
    return toDataUrlPng(png);
  } catch {
    return null;
  }
}

export async function loadQrAsPngDataUrl(data: string): Promise<string | null> {
  try {
    const safe = encodeURIComponent(data);
    const url = `https://api.qrserver.com/v1/create-qr-code/?size=180x180&data=${safe}`;
    const bytes = await fetchBytes(url);
    const png = await toPngBytes(bytes, url);
    return toDataUrlPng(png);
  } catch {
    return null;
  }
}