/*
 * JSX/TSX compiler adapter.
 *
 * JSX and TypeScript are parsed by Sucrase rather than by preview-specific
 * lexer code. The dependency is dynamically imported so ordinary chat and
 * HTML/SVG previews do not download the compiler chunk. Only this small adapter
 * stays in the main bundle.
 *
 * Sucrase's CommonJS transform is intentional: a preview frame has no module
 * loader or network access, but languages.js can provide local React/Preact
 * modules through a tiny `require` shim. Unsupported imports then fail loudly
 * at evaluation time with the package name that cannot be loaded.
 */

export class TransformError extends Error {
  constructor(message, options) {
    super(message, options);
    this.name = "TransformError";
  }
}

/**
 * Find fallback component declarations for model output that omits an export.
 *
 * This is deliberately not syntax transformation. Sucrase owns all parsing;
 * these names only form guarded `typeof Name !== "undefined"` mount choices.
 * A false match is therefore ignored at runtime. Default exports and App take
 * precedence, so this compatibility fallback is used only for a bare component
 * such as `function Counter() { ... }`.
 */
function componentCandidates(source) {
  const names = [];
  const declarations = /\b(?:function|class|const|let|var)\s+([A-Z][$\w]*)/g;
  for (const match of source.matchAll(declarations)) {
    if (!names.includes(match[1])) names.push(match[1]);
  }
  return names;
}

/** Compile a self-contained JSX/TSX component into browser-ready CommonJS. */
export async function transform(source) {
  const input = String(source ?? "");

  try {
    const { transform: compile } = await import("sucrase");
    const { code } = compile(input, {
      transforms: ["typescript", "jsx", "imports"],
      jsxPragma: "h",
      jsxFragmentPragma: "Fragment",
      production: true,
      filePath: "preview.tsx",
    });
    return { code, components: componentCandidates(input) };
  } catch (error) {
    const detail = error && error.message ? error.message : String(error);
    throw new TransformError(`Could not compile JSX/TSX: ${detail}`, { cause: error });
  }
}