/**
 * Bundles the frontend's raw-app session recorder into a browser script the dev
 * server can serve, and writes it as a string constant the CLI bundle carries.
 *
 * The recorder is not re-implemented here: `wmill app dev --recording` must
 * produce the exact recording format the players read, and the event
 * classification it encodes is the hard part. The one adaptation is the `$state`
 * rune: outside Svelte the store's fields are read through its getters, so the
 * rune is stripped and the values become plain `let`s.
 *
 * Run `bun run gen:dev-recorder` after touching anything under
 * frontend/src/lib/components/recording/; test/dev_recorder_bundle_unit.test.ts
 * fails when the committed bundle no longer matches those sources.
 */
import * as esbuild from "esbuild";
import { createHash } from "node:crypto";
import { readFileSync, writeFileSync } from "node:fs";
import { join, relative } from "node:path";

const REPO_ROOT = join(import.meta.dir, "..");
const RECORDING_DIR = join(
  REPO_ROOT,
  "frontend",
  "src",
  "lib",
  "components",
  "recording",
);
const ENTRY = "./rawAppRecording.svelte";
const OUT_FILE = join(
  import.meta.dir,
  "src",
  "commands",
  "app",
  "devRecorderBundle.gen.ts",
);

/** Hash of everything that went into the bundle. Over the modules esbuild
 * actually pulled in rather than a hand-kept list, so a module added to the
 * recorder's import graph can't slip past the staleness check. Line endings are
 * normalized: a CRLF checkout is the same source, and must not read as drift. */
export function hashRecorderSources(
  sources: string[],
  root: string = REPO_ROOT,
): string {
  const hash = createHash("sha256");
  for (const file of sources) {
    hash.update(file);
    hash.update(
      readFileSync(join(root, file), "utf-8").replace(/\r\n/g, "\n"),
    );
  }
  return hash.digest("hex");
}

/** Reactivity has no meaning in a plain browser script, and the store exposes
 * every rune-backed field through a getter, so `$state(x)` collapses to `x`.
 * Every other rune is compiled away by Svelte and would survive here as an
 * undefined identifier, so refuse rather than emit a bundle that throws. */
function stripRunes(source: string, file: string): string {
  const unsupported = [
    ...(source.match(/\$state[\w.]*\s*\(?/g) ?? []).filter(
      (r) => r.replace(/\s/g, "") !== "$state(",
    ),
    ...(source.match(
      /\$(derived|effect|props|bindable|inspect|host)[\w.]*/g,
    ) ?? []),
  ];
  if (unsupported.length > 0) {
    throw new Error(
      `${file} uses ${
        [...new Set(unsupported)].join(", ")
      }, which this generator cannot strip. ` +
        `Keep the recorder store free of runes beyond \`$state(...)\`.`,
    );
  }
  return source.replace(/\$state\s*\(/g, "(");
}

const runeStripper: esbuild.Plugin = {
  name: "strip-svelte-runes",
  setup(build) {
    build.onLoad({ filter: /\.svelte\.ts$/ }, (args) => ({
      contents: stripRunes(readFileSync(args.path, "utf-8"), args.path),
      loader: "ts",
    }));
  },
};

if (import.meta.main) {
  const result = await esbuild.build({
    stdin: {
      contents: `export { createRawAppRecording } from '${ENTRY}'`,
      resolveDir: RECORDING_DIR,
      loader: "ts",
    },
    plugins: [runeStripper],
    bundle: true,
    format: "iife",
    globalName: "__wmillRecorder",
    target: "es2020",
    minify: true,
    metafile: true,
    write: false,
    legalComments: "none",
  });

  const js = result.outputFiles[0].text;
  // Repo-relative and sorted, so the hash does not move with the checkout path
  // or with esbuild's traversal order. `<stdin>` is the entry above, not a file.
  const sources = Object.keys(result.metafile.inputs)
    .filter((f) => f !== "<stdin>")
    .map((f) => relative(REPO_ROOT, join(import.meta.dir, f)))
    .sort();
  writeFileSync(
    OUT_FILE,
    `// Generated by cli/generate-dev-recorder.ts. Do not edit.\n` +
      `// Run \`bun run gen:dev-recorder\` from cli/ to rebuild it from\n` +
      `// frontend/src/lib/components/recording/.\n\n` +
      `/** Repo-relative sources bundled below. */\n` +
      `export const DEV_RECORDER_SOURCES = ${
        JSON.stringify(sources, null, 2)
      };\n\n` +
      `/** SHA-256 of those sources, as of this build. */\n` +
      `export const DEV_RECORDER_SOURCE_HASH = ${
        JSON.stringify(hashRecorderSources(sources))
      };\n\n` +
      `/** IIFE exposing \`createRawAppRecording\` on \`window.__wmillRecorder\`. */\n` +
      `export const DEV_RECORDER_BUNDLE = ${JSON.stringify(js)};\n`,
    "utf-8",
  );
  console.log(
    `Wrote ${OUT_FILE} (${
      Math.round(js.length / 1024)
    } KB of bundled JS from ${sources.length} sources)`,
  );
}