/**
 * Extract bare import specifiers from JS code.
 * Matches `from 'pkg'`, `from "pkg"`, `import 'pkg'`, `import "pkg"`
 * where the specifier doesn't start with `.`, `/`, `http:`, or `https:`.
 */
export function extractBareImports(jsCode) {
  const imports = new Set();
  const re = /(?:import\s+(?:[\s\S]*?\s+from\s+)?['"])([^'"\s][^'"]*?)(?=['"])/g;
  let match;
  while ((match = re.exec(jsCode)) !== null) {
    const spec = match[1];
    // Skip relative, absolute, and URL imports
    if (spec.startsWith('.') || spec.startsWith('/') || spec.startsWith('http:') || spec.startsWith('https:')) {
      continue;
    }
    // Skip svelte internal imports (already rewritten by the compiler)
    if (spec.startsWith('svelte')) continue;
    imports.add(spec);
  }
  return Array.from(imports);
}

/**
 * Build an HTML <script type="importmap"> tag from bare import specifiers.
 * Maps each bare import to its esm.sh URL.
 */
export function buildImportMapTag(bareImports) {
  if (!bareImports.length) return '';
  const imports = {};
  for (const spec of bareImports) {
    // Get the package name (handle scoped packages like @scope/pkg)
    const parts = spec.split('/');
    const pkgName = spec.startsWith('@') ? `${parts[0]}/${parts[1]}` : parts[0];
    // Map the full specifier (e.g. 'lodash/fp' -> 'https://esm.sh/lodash/fp')
    imports[spec] = `https://esm.sh/${spec}`;
    // Also map the base package if it's different
    if (spec !== pkgName) {
      imports[pkgName] = `https://esm.sh/${pkgName}`;
    }
  }
  const map = JSON.stringify({ imports }, null, 2);
  return `<script type="importmap">\n${map}\n<\/script>`;
}