// @ts-check

import util from "node:util";
import potrace from "potrace";
import getSrcset from "./getSrcset.js";
import { sharp } from "../../utils/runtimeChecks.js";

export default async function getFallbackImage(
  src,
  placeholder,
  image,
  format,
  formatOptions,
  rest
) {
  const base = null;

  switch (placeholder) {
    case "blurred": {
      const dataUri = await getSrcset(src, base, [20], format, {
        inline: true,
        ...rest,
        ...formatOptions[format],
      });

      return dataUri;
    }
    case "tracedSVG": {
      const { function: fn, options } = formatOptions.tracedSVG;

      const traceSVG = util.promisify(potrace[fn]);

      const imageBuffer = sharp
        ? await image.toBuffer()
        : Buffer.from(
            (await image.encode(`image/${format === "jpg" ? "jpeg" : format}`))
              .data
          );

      const tracedSVG = await traceSVG(imageBuffer, options);

      return `data:image/svg+xml;utf8,${tracedSVG}`;
    }
    case "dominantColor": {
      if (sharp) {
        var { r, g, b } = (await image.stats()).dominant;
      } else {
        [r, g, b] = image.color;
      }

      const svg = `<svg xmlns="http://www.w3.org/2000/svg" style="background: rgb(${r},${g},${b})"></svg>`;

      return `data:image/svg+xml;utf8,${svg}`;
    }
    default:
      return null;
  }
}