ipx.ts

import { Accepts } from "https://deno.land/x/accepts@2.1.1/mod.ts";
import type { Context } from "netlify:edge";
// Available at build time
import imageconfig from "../functions-internal/_ipx/imageconfig.json" assert {
  type: "json",
};

const defaultFormat = "webp"

interface ImageConfig extends Record<string, unknown> {
  formats?: string[];
}

/**
 * Implement content negotiation for images
 */

// deno-lint-ignore require-await
const handler = async (req: Request, context: Context) => {
  const { searchParams } = new URL(req.url);
  const accept = new Accepts(req.headers);
  const { formats = [defaultFormat] } = imageconfig as ImageConfig;
  if (formats.length === 0) {
    formats.push(defaultFormat);
  }
  let type = accept.types(formats) || defaultFormat;
  if(Array.isArray(type)) {
    type = type[0];
  }


  const source = searchParams.get("url");
  const width = searchParams.get("w");
  const quality = searchParams.get("q") ?? 75;

  if (!source || !width) {
    return new Response("Invalid request", {
      status: 400,
    });
  }

  const modifiers = [`w_${width}`, `q_${quality}`];

  if (type) {
    if(type.includes('/')) {
      // If this is a mimetype, strip "image/"
      type = type.split('/')[1];
    }
    modifiers.push(`f_${type}`);
  }
  const target = `/_ipx/${modifiers.join(",")}/${encodeURIComponent(source)}`;
  return context.rewrite(
    target,
  );
};

export default handler;