import path from 'path';
import { ResolverIO } from '@beehexa/hexasync-template-compose';

/**
 * Build a hermetic, in-memory ResolverIO from a virtual filesystem map
 * (absolute POSIX path -> file text). No real disk, no reads of external
 * template repos (NFR6). Keys should be absolute paths under a synthetic root.
 */
export function makeVirtualIO(files: Record<string, string>): ResolverIO {
  const norm = (p: string) => path.posix.normalize(p);
  const fs = new Map<string, string>();
  for (const [k, v] of Object.entries(files)) fs.set(norm(k), v);

  // Async to match the port (AD-11), even though a Map lookup could answer synchronously.
  // A sync test double against an async port is exactly how a half-async chain hides: the
  // fixture would resolve immediately and mask a missing `await` in production code.
  return {
    canonical: async (p: string) => norm(p),
    readFileIfExists: async (p: string) =>
      fs.has(norm(p)) ? fs.get(norm(p))! : null,
    globYaml: async (componentPath: string) => {
      const base = norm(componentPath).replace(/\/$/, '') + '/';
      return [...fs.keys()]
        .filter((k) => k.startsWith(base) && k.endsWith('.yaml'))
        .sort();
    },
    searchMain: async (folder: string) => {
      const base = norm(folder).replace(/\/$/, '') + '/';
      const mains = [...fs.keys()].filter(
        (k) =>
          (k.startsWith(base) || k === norm(folder)) &&
          k.endsWith('/main.yaml'),
      );
      if (mains.length === 0)
        throw new Error(`There is no main.yaml file in the project.`);
      if (mains.length > 1)
        throw new Error(
          `Looks like there are more than one main.yaml file in the project.`,
        );
      return {
        mainYml: fs.get(mains[0])!,
        componentPath: path.posix.dirname(mains[0]),
      };
    },
  };
}