/*
 * Copyright 2025 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import {SchemaMatcher, ValidationResult} from './schema_matcher';

/**
 * A concrete matcher that verifies the top-level message type.
 */
export class MessageTypeMatcher extends SchemaMatcher {
  constructor(private messageType: string) {
    super();
  }

  validate(response: object): ValidationResult {
    if (!response || typeof response !== 'object') {
      return {
        success: false,
        error: 'Response is not a valid object.',
      };
    }
    const keys = Object.keys(response);
    if (keys.length === 1 && keys[0] === this.messageType) {
      return {success: true};
    } else {
      return {
        success: false,
        error: `Expected top-level message type to be '${
          this.messageType
        }', but found '${keys.join(', ')}'`,
      };
    }
  }

  get description(): string {
    return `Expected top-level message type to be '${this.messageType}'`;
  }
}
