function registryError(message, code) {
  return Object.assign(new Error(message), { code });
}

function requireMethod(target, methodName, code) {
  if (!target || typeof target[methodName] !== 'function') {
    throw registryError(`MindSpace conversation package registry requires ${methodName}`, code);
  }
}

export function createConversationPackageRegistry({ store, service } = {}) {
  requireMethod(store, 'upsertPackage', 'missing_conversation_package_store');
  requireMethod(store, 'upsertArtifact', 'missing_conversation_package_store');
  requireMethod(store, 'getPackageBySession', 'missing_conversation_package_store');
  requireMethod(store, 'listArtifacts', 'missing_conversation_package_store');
  requireMethod(service, 'putConversationManifest', 'missing_mindspace_service');
  requireMethod(service, 'buildConversationManifest', 'missing_mindspace_service');
  requireMethod(service, 'putPackageObject', 'missing_mindspace_service');
  requireMethod(service, 'getPackageObject', 'missing_mindspace_service');

  return {
    async ensurePackage(input) {
      return store.upsertPackage(input);
    },

    async recordArtifact(input) {
      return store.upsertArtifact(input);
    },

    async writeManifestForSession({ userId, sessionId }) {
      const packageRecord = await store.getPackageBySession(userId, sessionId);
      if (!packageRecord) return null;
      const artifacts = await store.listArtifacts(packageRecord.id);
      return service.putConversationManifest({ packageRecord, artifacts });
    },

    async putObjectForSession({ userId, sessionId, title = null, relativePath, body }) {
      const packageRecord = await store.upsertPackage({ userId, sessionId, title });
      const writeResult = await service.putPackageObject({ packageRecord, relativePath, body });
      return { packageRecord, writeResult };
    },

    async readManifestForSession({ userId, sessionId }) {
      const packageRecord = await store.getPackageBySession(userId, sessionId);
      if (!packageRecord) return null;
      const artifacts = await store.listArtifacts(packageRecord.id);
      return service.buildConversationManifest({ packageRecord, artifacts });
    },

    async readArtifactObject({ userId, sessionId, artifactId }) {
      const packageRecord = await store.getPackageBySession(userId, sessionId);
      if (!packageRecord) return null;
      const artifacts = await store.listArtifacts(packageRecord.id);
      const artifact = artifacts.find((item) => item.id === artifactId);
      if (!artifact?.storageKey) return null;
      const prefix = `${packageRecord.storagePrefix}/`;
      if (!artifact.storageKey.startsWith(prefix)) {
        throw registryError('conversation artifact storage key is outside package', 'invalid_artifact_storage_key');
      }
      const body = await service.getPackageObject({
        packageRecord,
        relativePath: artifact.storageKey.slice(prefix.length),
      });
      return { packageRecord, artifact, body };
    },
  };
}

export const conversationPackageRegistryInternals = {
  registryError,
  requireMethod,
};