/**
 * build.cjs — esbuild script for the PDF viewer TypeScript bundle.
 *
 * Produces two output files in ../assets/viewer/:
 *   viewer.bundle.js        — main viewer (IIFE, no PDF.js included)
 *   render-worker.bundle.js — render worker (pdf.min.js prepended + IIFE)
 *
 * Usage:
 *   node build.cjs           — one-shot production build (minified)
 *   node build.cjs --watch   — watch mode for development (unminified)
 */

const esbuild = require("esbuild");
const fs      = require("fs");
const path    = require("path");

const isWatch = process.argv.includes("--watch");
const minify  = !isWatch;

const ROOT      = __dirname;
const PDFJS_WORKER_MIN = path.join(ROOT, "../viewer/pdfjs/pdf.worker.min.js");
const PDFJS_MIN        = path.join(ROOT, "../viewer/pdfjs/pdf.min.js");
const OUT_DIR          = path.join(ROOT, "../viewer");

// Preamble prepended to the render-worker bundle.
//
// Sets `globalThis.window = globalThis` before pdf.worker.min.js runs so that:
//  1. pdf.worker.min.js does NOT auto-call WorkerMessageHandler.initializeFromPort(self)
//     (which would hijack our render-worker's own onmessage handler).
//  2. pdf.worker.min.js DOES set globalThis.pdfjsWorker.WorkerMessageHandler as usual.
//  3. pdf.min.js's _mainThreadWorkerMessageHandler getter then finds the handler via
//     globalThis.pdfjsWorker and uses it inline — no document.createElement needed.
const RENDER_WORKER_PREAMBLE = Buffer.from("globalThis.window=globalThis;\n");

// ── Render-worker plugin: prepend preamble + pdf.worker.min.js + pdf.min.js ───
//
// Bundle order matters:
//   1. Preamble       — sets globalThis.window = globalThis
//   2. pdf.worker.min.js — sets globalThis.pdfjsWorker.WorkerMessageHandler
//                          (skips auto-setup because window is now defined)
//   3. pdf.min.js     — sets globalThis.pdfjsLib; fake-worker path reads pdfjsWorker
//   4. Compiled TS    — our render-worker code
function prependPdfjsPlugin() {
  const pdfjsWorkerMin = fs.readFileSync(PDFJS_WORKER_MIN);
  const pdfjsMin       = fs.readFileSync(PDFJS_MIN);
  const NL             = Buffer.from("\n");
  return {
    name: "prepend-pdfjs",
    setup(build) {
      build.onEnd(result => {
        if (result.errors.length > 0 || !result.outputFiles) return;
        const compiled = Buffer.from(result.outputFiles[0].contents);
        const combined = Buffer.concat([
          RENDER_WORKER_PREAMBLE,
          pdfjsWorkerMin, NL,
          pdfjsMin,       NL,
          compiled,
        ]);
        fs.writeFileSync(path.join(OUT_DIR, "render-worker.bundle.js"), combined);
        if (!isWatch) console.log("[viewer-src] render-worker.bundle.js written");
      });
    },
  };
}

async function main() {
  const sharedOptions = { bundle: true, format: "iife", target: "es2020", minify };

  if (isWatch) {
    const viewerCtx = await esbuild.context({
      ...sharedOptions,
      entryPoints: ["src/viewer.ts"],
      outfile:     path.join(OUT_DIR, "viewer.bundle.js"),
    });

    const workerCtx = await esbuild.context({
      ...sharedOptions,
      entryPoints: ["src/render-worker.ts"],
      write:       false,
      plugins:     [prependPdfjsPlugin()],
    });

    await viewerCtx.watch();
    await workerCtx.watch();
    console.log("[viewer-src] watching for changes…");
    // Keep the process alive
    return;
  }

  // One-shot build
  await esbuild.build({
    ...sharedOptions,
    entryPoints: ["src/viewer.ts"],
    outfile:     path.join(OUT_DIR, "viewer.bundle.js"),
  });
  console.log("[viewer-src] viewer.bundle.js written");

  // Render worker: build to memory then prepend preamble + worker + pdf.min.js
  const workerResult = await esbuild.build({
    ...sharedOptions,
    entryPoints: ["src/render-worker.ts"],
    write:       false,
  });
  const pdfjsWorkerMin = fs.readFileSync(PDFJS_WORKER_MIN);
  const pdfjsMin       = fs.readFileSync(PDFJS_MIN);
  const NL             = Buffer.from("\n");
  const compiled       = Buffer.from(workerResult.outputFiles[0].contents);
  fs.writeFileSync(
    path.join(OUT_DIR, "render-worker.bundle.js"),
    Buffer.concat([RENDER_WORKER_PREAMBLE, pdfjsWorkerMin, NL, pdfjsMin, NL, compiled]),
  );
  console.log("[viewer-src] render-worker.bundle.js written");
}

main().catch(e => { console.error(e); process.exit(1); });