svelte-kit-import-hook.mjs

/* !! This project can't be ESM yet, so hack it to get sveltekit to work. !! */
import babelCore from "@babel/core"
import * as t from "@babel/types"

/** transform code */
function transform(code, filename) {
  if (
    filename.includes("/@sveltejs/kit/") &&
    code.includes("svelte.config.js")
  ) {
    let transformed = false
    const newCode = babelCore.transformSync(code, {
      babelrc: false,
      plugins: [
        {
          visitor: {
            StringLiteral(path) {
              if (path.node.value === "svelte.config.js") {
                // The configuration file loads `svelte.config.mjs`.
                path.replaceWith(t.stringLiteral("svelte.config.mjs"))
                transformed = true
              }
            },
          },
        },
      ],
    })
    if (!transformed) {
      return code
    }
    return `${newCode.code}`
  }

  return code
}

/**
 * @param {string} url
 * @param {{
 *   format: string,
 * }} context If resolve settled with a `format`, that value is included here.
 * @param {Function} defaultLoad
 * @returns {Promise<{
 * format: !string,
 * source: !(string | ArrayBuffer | SharedArrayBuffer | Uint8Array),
 * }>}
 */
export async function load(url, context, defaultLoad) {
  const result = await defaultLoad(url, context, defaultLoad)
  return {
    format: result.format,
    source: transform(`${result.source}`, url),
  }
}

/**
 * @param {!(string | SharedArrayBuffer | Uint8Array)} source
 * @param {{
 *   format: string,
 *   url: string,
 * }} context
 * @param {Function} defaultTransformSource
 * @returns {Promise<{ source: !(string | SharedArrayBuffer | Uint8Array) }>}
 */
export async function transformSource(source, context, defaultTransformSource) {
  const result = await defaultTransformSource(
    source,
    context,
    defaultTransformSource,
  )
  return {
    source: transform(`${result.source}`, context.url),
  }
}