# Api Designer — Code Examples

## Example 1

```typescript
// api-designer.ts
import * as yaml from 'js-yaml';
import { OpenAPIV3 } from 'openapi-types';
import { GraphQLSchema, buildSchema } from 'graphql';
import { JSONSchema7 } from 'json-schema';

interface APIDesign {
  id: string;
  name: string;
  version: string;
  type: APIType;
  specification: APISpecification;
  endpoints: Endpoint[];
  dataModels: DataModel[];
  authentication: AuthenticationScheme;
  authorization: AuthorizationModel;
  rateLimiting: RateLimitPolicy;
  versioning: VersioningStrategy;
  documentation: APIDocumentation;
  testing: TestStrategy;
  monitoring: MonitoringConfig;
}

interface Endpoint {
  id: string;
  path: string;
  method: HTTPMethod;
  operation: OperationObject;
  parameters: Parameter[];
  requestBody?: RequestBody;
  responses: ResponseObject[];
  security?: SecurityRequirement[];
  deprecated?: boolean;
  version?: string;
}

class APIDesigner {
  private specifications: Map<string, APISpecification> = new Map();
  private patterns: Map<string, DesignPattern> = new Map();
  private validator: SpecificationValidator;
  private generator: CodeGenerator;

  constructor() {
    this.validator = new SpecificationValidator();
    this.generator = new CodeGenerator();
    this.loadDesignPatterns();
  }

  async designRESTAPI(requirements: APIRequirements): Promise<OpenAPISpecification> {
    // Analyze requirements
    const analysis = await this.analyzeRequirements(requirements);
    
    // Design resource model
    const resources = this.designResources(analysis);
    
    // Design endpoints
    const endpoints = this.designEndpoints(resources, requirements);
    
    // Design data models
    const schemas = this.designSchemas(resources, requirements);
    
    // Design authentication
    const security = this.designSecurity(requirements);
    
    // Generate OpenAPI specification
    const spec = this.generateOpenAPISpec({
      info: this.generateAPIInfo(requirements),
      servers: this.generateServers(requirements),
      paths: this.generatePaths(endpoints),
      components: {
        schemas: schemas,
        securitySchemes: security,
        parameters: this.generateCommonParameters(),
        responses: this.generateCommonResponses(),
        requestBodies: this.generateCommonRequestBodies(),
        headers: this.generateCommonHeaders(),
        examples: this.generateExamples(endpoints),
        links: this.generateLinks(endpoints),
        callbacks: this.generateCallbacks(endpoints),
      },
      security: this.generateSecurityRequirements(security),
      tags: this.generateTags(resources),
      externalDocs: requirements.documentation,
    });
    
    // Validate specification
    await this.validator.validateOpenAPI(spec);
    
    // Apply best practices
    const optimized = this.applyBestPractices(spec);
    
    return optimized;
  }

  private designResources(analysis: RequirementAnalysis): Resource[] {
    const resources: Resource[] = [];
    
    for (const entity of analysis.entities) {
      const resource: Resource = {
        id: this.generateId('RES'),
        name: entity.name,
        plural: this.pluralize(entity.name),
        description: entity.description,
        attributes: this.mapAttributes(entity.properties),
        relationships: this.mapRelationships(entity.relationships),
        operations: this.determineOperations(entity),
        uri: this.generateURI(entity),
        subresources: [],
      };
      
      // Identify subresources
      resource.subresources = this.identifySubresources(entity, analysis.entities);
      
      resources.push(resource);
    }
    
    return resources;
  }

  private designEndpoints(resources: Resource[], requirements: APIRequirements): Endpoint[] {
    const endpoints: Endpoint[] = [];
    
    for (const resource of resources) {
      // Collection endpoints
      if (resource.operations.includes('list')) {
        endpoints.push(this.createListEndpoint(resource));
      }
      
      if (resource.operations.includes('create')) {
        endpoints.push(this.createCreateEndpoint(resource));
      }
      
      // Item endpoints
      if (resource.operations.includes('read')) {
        endpoints.push(this.createReadEndpoint(resource));
      }
      
      if (resource.operations.includes('update')) {
        endpoints.push(this.createUpdateEndpoint(resource));
        
        if (requirements.supportPatch) {
          endpoints.push(this.createPatchEndpoint(resource));
        }
      }
      
      if (resource.operations.includes('delete')) {
        endpoints.push(this.createDeleteEndpoint(resource));
      }
      
      // Custom actions
      for (const action of resource.customActions || []) {
        endpoints.push(this.createCustomActionEndpoint(resource, action));
      }
      
      // Subresource endpoints
      for (const subresource of resource.subresources) {
        endpoints.push(...this.createSubresourceEndpoints(resource, subresource));
      }
    }
    
    // Add utility endpoints
    endpoints.push(...this.createUtilityEndpoints(requirements));
    
    return endpoints;
  }

  private createListEndpoint(resource: Resource): Endpoint {
    return {
      id: `list-${resource.plural}`,
      path: `/${resource.plural}`,
      method: HTTPMethod.GET,
      operation: {
        operationId: `list${this.capitalize(resource.plural)}`,
        summary: `List ${resource.plural}`,
        description: `Retrieve a paginated list of ${resource.plural}`,
        tags: [resource.name],
        parameters: [
          this.createPaginationParameters(),
          this.createFilterParameters(resource),
          this.createSortParameters(resource),
          this.createFieldsParameter(),
        ].flat(),
        responses: [
          {
            status: '200',
            description: `Successful response with ${resource.plural} list`,
            content: {
              'application/json': {
                schema: {
                  type: 'object',
                  properties: {
                    data: {
                      type: 'array',
                      items: { $ref: `#/components/schemas/${resource.name}` },
                    },
                    meta: { $ref: '#/components/schemas/PaginationMeta' },
                    links: { $ref: '#/components/schemas/PaginationLinks' },
                  },
                },
                examples: {
                  success: this.generateListExample(resource),
                },
              },
            },
          },
          { $ref: '#/components/responses/400BadRequest' },
          { $ref: '#/components/responses/401Unauthorized' },
          { $ref: '#/components/responses/403Forbidden' },
          { $ref: '#/components/responses/500InternalServerError' },
        ],
      },
    };
  }

  private createCreateEndpoint(resource: Resource): Endpoint {
    return {
      id: `create-${resource.name}`,
      path: `/${resource.plural}`,
      method: HTTPMethod.POST,
      operation: {
        operationId: `create${this.capitalize(resource.name)}`,
        summary: `Create ${resource.name}`,
        description: `Create a new ${resource.name}`,
        tags: [resource.name],
        requestBody: {
          required: true,
          content: {
            'application/json': {
              schema: { $ref: `#/components/schemas/${resource.name}Input` },
              examples: {
                complete: this.generateCreateExample(resource, 'complete'),
                minimal: this.generateCreateExample(resource, 'minimal'),
              },
            },
          },
        },
        responses: [
          {
            status: '201',
            description: `${resource.name} created successfully`,
            headers: {
              Location: {
                description: 'URL of the created resource',
                schema: { type: 'string' },
              },
            },
            content: {
              'application/json': {
                schema: { $ref: `#/components/schemas/${resource.name}` },
              },
            },
          },
          { $ref: '#/components/responses/400BadRequest' },
          { $ref: '#/components/responses/401Unauthorized' },
          { $ref: '#/components/responses/403Forbidden' },
          { $ref: '#/components/responses/409Conflict' },
          { $ref: '#/components/responses/422UnprocessableEntity' },
        ],
      },
    };
  }

  private createReadEndpoint(resource: Resource): Endpoint {
    return {
      id: `get-${resource.name}`,
      path: `/${resource.plural}/{id}`,
      method: HTTPMethod.GET,
      operation: {
        operationId: `get${this.capitalize(resource.name)}`,
        summary: `Get ${resource.name}`,
        description: `Retrieve a specific ${resource.name} by ID`,
        tags: [resource.name],
        parameters: [
          {
            name: 'id',
            in: 'path',
            required: true,
            description: `${resource.name} identifier`,
            schema: { type: 'string', format: 'uuid' },
          },
          this.createFieldsParameter(),
          this.createExpandParameter(resource),
        ],
        responses: [
          {
            status: '200',
            description: `${resource.name} retrieved successfully`,
            content: {
              'application/json': {
                schema: { $ref: `#/components/schemas/${resource.name}` },
              },
            },
          },
          { $ref: '#/components/responses/401Unauthorized' },
          { $ref: '#/components/responses/403Forbidden' },
          { $ref: '#/components/responses/404NotFound' },
        ],
      },
    };
  }

  private createUpdateEndpoint(resource: Resource): Endpoint {
    return {
      id: `update-${resource.name}`,
      path: `/${resource.plural}/{id}`,
      method: HTTPMethod.PUT,
      operation: {
        operationId: `update${this.capitalize(resource.name)}`,
        summary: `Update ${resource.name}`,
        description: `Replace an entire ${resource.name}`,
        tags: [resource.name],
        parameters: [
          {
            name: 'id',
            in: 'path',
            required: true,
            description: `${resource.name} identifier`,
            schema: { type: 'string', format: 'uuid' },
          },
        ],
        requestBody: {
          required: true,
          content: {
            'application/json': {
              schema: { $ref: `#/components/schemas/${resource.name}Input` },
            },
          },
        },
        responses: [
          {
            status: '200',
            description: `${resource.name} updated successfully`,
            content: {
              'application/json': {
                schema: { $ref: `#/components/schemas/${resource.name}` },
              },
            },
          },
          { $ref: '#/components/responses/400BadRequest' },
          { $ref: '#/components/responses/401Unauthorized' },
          { $ref: '#/components/responses/403Forbidden' },
          { $ref: '#/components/responses/404NotFound' },
          { $ref: '#/components/responses/409Conflict' },
          { $ref: '#/components/responses/422UnprocessableEntity' },
        ],
      },
    };
  }

  private createPatchEndpoint(resource: Resource): Endpoint {
    return {
      id: `patch-${resource.name}`,
      path: `/${resource.plural}/{id}`,
      method: HTTPMethod.PATCH,
      operation: {
        operationId: `patch${this.capitalize(resource.name)}`,
        summary: `Partially update ${resource.name}`,
        description: `Update specific fields of a ${resource.name}`,
        tags: [resource.name],
        parameters: [
          {
            name: 'id',
            in: 'path',
            required: true,
            description: `${resource.name} identifier`,
            schema: { type: 'string', format: 'uuid' },
          },
        ],
        requestBody: {
          required: true,
          content: {
            'application/json-patch+json': {
              schema: { $ref: '#/components/schemas/JSONPatch' },
              examples: {
                updateField: {
                  value: [
                    { op: 'replace', path: '/status', value: 'active' },
                  ],
                },
              },
            },
            'application/merge-patch+json': {
              schema: { $ref: `#/components/schemas/${resource.name}Patch` },
            },
          },
        },
        responses: [
          {
            status: '200',
            description: `${resource.name} patched successfully`,
            content: {
              'application/json': {
                schema: { $ref: `#/components/schemas/${resource.name}` },
              },
            },
          },
          { $ref: '#/components/responses/400BadRequest' },
          { $ref: '#/components/responses/401Unauthorized' },
          { $ref: '#/components/responses/403Forbidden' },
          { $ref: '#/components/responses/404NotFound' },
          { $ref: '#/components/responses/409Conflict' },
          { $ref: '#/components/responses/422UnprocessableEntity' },
        ],
      },
    };
  }

  async designGraphQLAPI(requirements: APIRequirements): Promise<GraphQLDesign> {
    // Design type system
    const types = this.designGraphQLTypes(requirements);
    
    // Design queries
    const queries = this.designQueries(types, requirements);
    
    // Design mutations
    const mutations = this.designMutations(types, requirements);
    
    // Design subscriptions
    const subscriptions = this.designSubscriptions(types, requirements);
    
    // Generate SDL
    const sdl = this.generateGraphQLSDL({
      types,
      queries,
      mutations,
      subscriptions,
      directives: this.designDirectives(requirements),
      scalars: this.designScalars(requirements),
    });
    
    // Build schema
    const schema = buildSchema(sdl);
    
    // Generate resolvers template
    const resolvers = this.generateResolvers(schema);
    
    // Validate schema
    await this.validator.validateGraphQLSchema(schema);
    
    return {
      schema,
      sdl,
      resolvers,
      documentation: this.generateGraphQLDocumentation(schema),
      examples: this.generateGraphQLExamples(schema),
    };
  }

  private designGraphQLTypes(requirements: APIRequirements): GraphQLType[] {
    const types: GraphQLType[] = [];
    
    for (const entity of requirements.entities) {
      // Object type
      types.push({
        kind: 'ObjectType',
        name: entity.name,
        description: entity.description,
        fields: this.mapGraphQLFields(entity.properties),
        interfaces: this.identifyInterfaces(entity),
      });
      
      // Input type
      types.push({
        kind: 'InputType',
        name: `${entity.name}Input`,
        description: `Input for creating/updating ${entity.name}`,
        fields: this.mapGraphQLInputFields(entity.properties),
      });
      
      // Filter type
      types.push({
        kind: 'InputType',
        name: `${entity.name}Filter`,
        description: `Filter for querying ${entity.name}`,
        fields: this.generateFilterFields(entity.properties),
      });
      
      // Connection type for pagination
      if (requirements.usePagination) {
        types.push(this.generateConnectionType(entity));
        types.push(this.generateEdgeType(entity));
      }
    }
    
    // Add common types
    types.push(...this.generateCommonGraphQLTypes());
    
    return types;
  }

  private designQueries(types: GraphQLType[], requirements: APIRequirements): Query[] {
    const queries: Query[] = [];
    
    for (const type of types.filter(t => t.kind === 'ObjectType' && !t.name.includes('Connection'))) {
      // Single item query
      queries.push({
        name: this.uncapitalize(type.name),
        description: `Get a single ${type.name}`,
        args: [
          { name: 'id', type: 'ID!', description: `${type.name} ID` },
        ],
        returnType: type.name,
      });
      
      // List query
      const listQuery: Query = {
        name: this.pluralize(this.uncapitalize(type.name)),
        description: `List ${type.name} items`,
        args: [
          { name: 'filter', type: `${type.name}Filter`, description: 'Filter criteria' },
          { name: 'sort', type: 'SortInput', description: 'Sort options' },
        ],
        returnType: `[${type.name}!]!`,
      };
      
      // Add pagination args if needed
      if (requirements.usePagination) {
        listQuery.args.push(
          { name: 'first', type: 'Int', description: 'Number of items to return' },
          { name: 'after', type: 'String', description: 'Cursor for pagination' },
        );
        listQuery.returnType = `${type.name}Connection!`;
      } else {
        listQuery.args.push(
          { name: 'limit', type: 'Int', description: 'Maximum number of items' },
          { name: 'offset', type: 'Int', description: 'Number of items to skip' },
        );
      }
      
      queries.push(listQuery);
      
      // Search query
      if (requirements.includeSearch) {
        queries.push({
          name: `search${type.name}`,
          description: `Search ${type.name} items`,
          args: [
            { name: 'query', type: 'String!', description: 'Search query' },
            { name: 'limit', type: 'Int', description: 'Maximum results' },
          ],
          returnType: `[${type.name}!]!`,
        });
      }
    }
    
    return queries;
  }

  private designMutations(types: GraphQLType[], requirements: APIRequirements): Mutation[] {
    const mutations: Mutation[] = [];
    
    for (const type of types.filter(t => t.kind === 'ObjectType' && !t.name.includes('Connection'))) {
      // Create mutation
      mutations.push({
        name: `create${type.name}`,
        description: `Create a new ${type.name}`,
        args: [
          { name: 'input', type: `${type.name}Input!`, description: 'Input data' },
        ],
        returnType: `${type.name}!`,
      });
      
      // Update mutation
      mutations.push({
        name: `update${type.name}`,
        description: `Update an existing ${type.name}`,
        args: [
          { name: 'id', type: 'ID!', description: `${type.name} ID` },
          { name: 'input', type: `${type.name}Input!`, description: 'Updated data' },
        ],
        returnType: `${type.name}!`,
      });
      
      // Delete mutation
      mutations.push({
        name: `delete${type.name}`,
        description: `Delete a ${type.name}`,
        args: [
          { name: 'id', type: 'ID!', description: `${type.name} ID` },
        ],
        returnType: 'Boolean!',
      });
      
      // Batch operations
      if (requirements.includeBatchOperations) {
        mutations.push({
          name: `batchCreate${type.name}`,
          description: `Create multiple ${type.name} items`,
          args: [
            { name: 'inputs', type: `[${type.name}Input!]!`, description: 'Input data array' },
          ],
          returnType: `[${type.name}!]!`,
        });
        
        mutations.push({
          name: `batchDelete${type.name}`,
          description: `Delete multiple ${type.name} items`,
          args: [
            { name: 'ids', type: '[ID!]!', description: 'IDs to delete' },
          ],
          returnType: 'Int!', // Number of deleted items
        });
      }
    }
    
    return mutations;
  }

  async generateAPIClient(specification: APISpecification): Promise<ClientSDK> {
    const sdk: ClientSDK = {
      language: specification.targetLanguage || 'typescript',
      name: `${specification.name}Client`,
      version: specification.version,
      files: [],
    };
    
    switch (sdk.language) {
      case 'typescript':
        sdk.files = await this.generateTypeScriptClient(specification);
        break;
      case 'python':
        sdk.files = await this.generatePythonClient(specification);
        break;
      case 'go':
        sdk.files = await this.generateGoClient(specification);
        break;
      case 'java':
        sdk.files = await this.generateJavaClient(specification);
        break;
    }
    
    return sdk;
  }

  private async generateTypeScriptClient(spec: APISpecification): Promise<ClientFile[]> {
    const files: ClientFile[] = [];
    
    // Types file
    files.push({
      name: 'types.ts',
      content: this.generateTypeScriptTypes(spec),
    });
    
    // API client class
    files.push({
      name: 'client.ts',
      content: this.generateTypeScriptClientClass(spec),
    });
    
    // Individual service classes
    for (const tag of spec.tags || []) {
      files.push({
        name: `${tag.name.toLowerCase()}.service.ts`,
        content: this.generateTypeScriptService(spec, tag),
      });
    }
    
    // Utils
    files.push({
      name: 'utils.ts',
      content: this.generateTypeScriptUtils(),
    });
    
    // Index file
    files.push({
      name: 'index.ts',
      content: this.generateTypeScriptIndex(spec),
    });
    
    return files;
  }

  private generateTypeScriptTypes(spec: APISpecification): string {
    let types = `// Auto-generated types from ${spec.name} v${spec.version}\n\n`;
    
    // Generate interfaces from schemas
    for (const [name, schema] of Object.entries(spec.components?.schemas || {})) {
      types += this.schemaToTypeScript(name, schema);
      types += '\n\n';
    }
    
    // Generate enums
    for (const [name, schema] of Object.entries(spec.components?.schemas || {})) {
      if (schema.enum) {
        types += `export enum ${name} {\n`;
        for (const value of schema.enum) {
          types += `  ${this.toEnumKey(value)} = '${value}',\n`;
        }
        types += '}\n\n';
      }
    }
    
    return types;
  }

  private schemaToTypeScript(name: string, schema: any): string {
    let ts = `export interface ${name} {\n`;
    
    if (schema.properties) {
      for (const [propName, propSchema] of Object.entries(schema.properties)) {
        const required = schema.required?.includes(propName) || false;
        const optional = required ? '' : '?';
        const type = this.jsonSchemaToTypeScript(propSchema);
        
        ts += `  ${propName}${optional}: ${type};\n`;
      }
    }
    
    ts += '}';
    return ts;
  }

  private generateTypeScriptClientClass(spec: APISpecification): string {
    return `
import axios, { AxiosInstance, AxiosRequestConfig } from 'axios';
import { ${this.getTypeImports(spec).join(', ')} } from './types';

export interface ClientConfig {
  baseURL: string;
  apiKey?: string;
  accessToken?: string;
  timeout?: number;
  headers?: Record<string, string>;
}

export class ${spec.name}Client {
  private client: AxiosInstance;
  ${this.generateServiceProperties(spec)}

  constructor(config: ClientConfig) {
    this.client = axios.create({
      baseURL: config.baseURL,
      timeout: config.timeout || 30000,
      headers: {
        'Content-Type': 'application/json',
        ...config.headers,
      },
    });

    // Add authentication
    if (config.apiKey) {
      this.client.defaults.headers.common['X-API-Key'] = config.apiKey;
    }
    if (config.accessToken) {
      this.client.defaults.headers.common['Authorization'] = \`Bearer \${config.accessToken}\`;
    }

    // Add interceptors
    this.setupInterceptors();

    // Initialize services
    ${this.generateServiceInitialization(spec)}
  }

  private setupInterceptors(): void {
    // Request interceptor
    this.client.interceptors.request.use(
      (config) => {
        // Add request ID
        config.headers['X-Request-Id'] = this.generateRequestId();
        return config;
      },
      (error) => Promise.reject(error)
    );

    // Response interceptor
    this.client.interceptors.response.use(
      (response) => response,
      async (error) => {
        if (error.response?.status === 401) {
          // Handle token refresh
          await this.refreshToken();
          return this.client.request(error.config);
        }
        return Promise.reject(error);
      }
    );
  }

  private generateRequestId(): string {
    return \`\${Date.now()}-\${Math.random().toString(36).substr(2, 9)}\`;
  }

  private async refreshToken(): Promise<void> {
    // Implement token refresh logic
  }

  async setAccessToken(token: string): Promise<void> {
    this.client.defaults.headers.common['Authorization'] = \`Bearer \${token}\`;
  }
}
`;
  }

  async validateAPIDesign(design: APIDesign): Promise<ValidationResult> {
    const issues: ValidationIssue[] = [];
    
    // Validate naming conventions
    issues.push(...this.validateNaming(design));
    
    // Validate HTTP methods usage
    issues.push(...this.validateHTTPMethods(design));
    
    // Validate status codes
    issues.push(...this.validateStatusCodes(design));
    
    // Validate pagination
    issues.push(...this.validatePagination(design));
    
    // Validate error handling
    issues.push(...this.validateErrorHandling(design));
    
    // Validate security
    issues.push(...this.validateSecurity(design));
    
    // Validate versioning
    issues.push(...this.validateVersioning(design));
    
    // Check for breaking changes
    if (design.previousVersion) {
      issues.push(...await this.checkBreakingChanges(design));
    }
    
    return {
      valid: issues.filter(i => i.severity === 'error').length === 0,
      issues,
      score: this.calculateDesignScore(issues),
      recommendations: this.generateRecommendations(issues),
    };
  }

  private validateNaming(design: APIDesign): ValidationIssue[] {
    const issues: ValidationIssue[] = [];
    
    for (const endpoint of design.endpoints) {
      // Check path naming
      if (!this.isValidPath(endpoint.path)) {
        issues.push({
          type: 'naming',
          severity: 'warning',
          message: `Path '${endpoint.path}' does not follow REST naming conventions`,
          location: endpoint.path,
        });
      }
      
      // Check for verbs in URIs
      if (this.containsVerb(endpoint.path)) {
        issues.push({
          type: 'naming',
          severity: 'error',
          message: `Path '${endpoint.path}' contains a verb, use HTTP methods instead`,
          location: endpoint.path,
        });
      }
    }
    
    return issues;
  }

  private validateHTTPMethods(design: APIDesign): ValidationIssue[] {
    const issues: ValidationIssue[] = [];
    
    for (const endpoint of design.endpoints) {
      // Check idempotency
      if (['PUT', 'DELETE'].includes(endpoint.method) && !endpoint.idempotent) {
        issues.push({
          type: 'http-method',
          severity: 'warning',
          message: `${endpoint.method} ${endpoint.path} should be idempotent`,
          location: endpoint.path,
        });
      }
      
      // Check safe methods
      if (endpoint.method === 'GET' && endpoint.hasSideEffects) {
        issues.push({
          type: 'http-method',
          severity: 'error',
          message: `GET ${endpoint.path} should not have side effects`,
          location: endpoint.path,
        });
      }
    }
    
    return issues;
  }

  private applyBestPractices(spec: OpenAPISpecification): OpenAPISpecification {
    // Add common responses
    spec.components.responses = {
      ...spec.components.responses,
      ...this.getCommonResponses(),
    };
    
    // Add common parameters
    spec.components.parameters = {
      ...spec.components.parameters,
      ...this.getCommonParameters(),
    };
    
    // Add security schemes
    if (!spec.components.securitySchemes) {
      spec.components.securitySchemes = this.getDefaultSecuritySchemes();
    }
    
    // Add rate limiting headers
    for (const path of Object.values(spec.paths)) {
      for (const operation of Object.values(path)) {
        if (operation.responses) {
          this.addRateLimitHeaders(operation.responses);
        }
      }
    }
    
    return spec;
  }

  private getCommonResponses(): Record<string, any> {
    return {
      '400BadRequest': {
        description: 'Bad request',
        content: {
          'application/json': {
            schema: { $ref: '#/components/schemas/Error' },
            example: {
              error: {
                code: 'BAD_REQUEST',
                message: 'Invalid request parameters',
              },
            },
          },
        },
      },
      '401Unauthorized': {
        description: 'Authentication required',
        content: {
          'application/json': {
            schema: { $ref: '#/components/schemas/Error' },
            example: {
              error: {
                code: 'UNAUTHORIZED',
                message: 'Authentication required',
              },
            },
          },
        },
      },
      '403Forbidden': {
        description: 'Insufficient permissions',
        content: {
          'application/json': {
            schema: { $ref: '#/components/schemas/Error' },
          },
        },
      },
      '404NotFound': {
        description: 'Resource not found',
        content: {
          'application/json': {
            schema: { $ref: '#/components/schemas/Error' },
          },
        },
      },
      '409Conflict': {
        description: 'Resource conflict',
        content: {
          'application/json': {
            schema: { $ref: '#/components/schemas/Error' },
          },
        },
      },
      '422UnprocessableEntity': {
        description: 'Validation error',
        content: {
          'application/json': {
            schema: { $ref: '#/components/schemas/ValidationError' },
          },
        },
      },
      '429TooManyRequests': {
        description: 'Rate limit exceeded',
        headers: {
          'X-RateLimit-Limit': {
            schema: { type: 'integer' },
            description: 'Request limit per hour',
          },
          'X-RateLimit-Remaining': {
            schema: { type: 'integer' },
            description: 'Remaining requests',
          },
          'X-RateLimit-Reset': {
            schema: { type: 'integer' },
            description: 'Unix timestamp when limit resets',
          },
        },
        content: {
          'application/json': {
            schema: { $ref: '#/components/schemas/Error' },
          },
        },
      },
      '500InternalServerError': {
        description: 'Internal server error',
        content: {
          'application/json': {
            schema: { $ref: '#/components/schemas/Error' },
          },
        },
      },
    };
  }

  private generateId(prefix: string): string {
    return `${prefix}-${Date.now()}-${Math.random().toString(36).substr(2, 9)}`;
  }

  private pluralize(word: string): string {
    // Simple pluralization
    if (word.endsWith('y')) {
      return word.slice(0, -1) + 'ies';
    }
    if (word.endsWith('s')) {
      return word + 'es';
    }
    return word + 's';
  }

  private capitalize(word: string): string {
    return word.charAt(0).toUpperCase() + word.slice(1);
  }

  private uncapitalize(word: string): string {
    return word.charAt(0).toLowerCase() + word.slice(1);
  }

  private toEnumKey(value: string): string {
    return value.toUpperCase().replace(/[^A-Z0-9]/g, '_');
  }
}

// Supporting classes
class SpecificationValidator {
  async validateOpenAPI(spec: OpenAPISpecification): Promise<void> {
    // Validate against OpenAPI schema
    // Check for required fields
    // Validate references
    // Check for circular references
  }

  async validateGraphQLSchema(schema: GraphQLSchema): Promise<void> {
    // Validate schema
    // Check for orphaned types
    // Validate directives
    // Check query complexity
  }
}

class CodeGenerator {
  generateTypeScript(spec: APISpecification): string {
    // Generate TypeScript code
    return '';
  }

  generatePython(spec: APISpecification): string {
    // Generate Python code
    return '';
  }

  generateGo(spec: APISpecification): string {
    // Generate Go code
    return '';
  }
}

// Type definitions
enum APIType {
  REST = 'rest',
  GRAPHQL = 'graphql',
  GRPC = 'grpc',
  WEBSOCKET = 'websocket',
}

enum HTTPMethod {
  GET = 'GET',
  POST = 'POST',
  PUT = 'PUT',
  PATCH = 'PATCH',
  DELETE = 'DELETE',
  HEAD = 'HEAD',
  OPTIONS = 'OPTIONS',
}

interface APISpecification {
  name: string;
  version: string;
  type: APIType;
  baseUrl?: string;
  paths?: any;
  components?: any;
  tags?: Tag[];
  servers?: Server[];
  security?: SecurityRequirement[];
  targetLanguage?: string;
  previousVersion?: APISpecification;
}

interface OpenAPISpecification extends APISpecification {
  openapi: string;
  info: Info;
  paths: Paths;
  components: Components;
  security?: SecurityRequirement[];
  tags?: Tag[];
  servers?: Server[];
  externalDocs?: ExternalDocumentation;
}

interface GraphQLDesign {
  schema: GraphQLSchema;
  sdl: string;
  resolvers: any;
  documentation: any;
  examples: any[];
}

interface APIRequirements {
  name: string;
  description: string;
  version: string;
  entities: Entity[];
  useCases: UseCase[];
  authentication?: AuthRequirement;
  authorization?: AuthzRequirement;
  rateLimiting?: RateLimitRequirement;
  pagination?: PaginationRequirement;
  supportPatch?: boolean;
  usePagination?: boolean;
  includeSearch?: boolean;
  includeBatchOperations?: boolean;
  documentation?: any;
}

interface Entity {
  name: string;
  description: string;
  properties: Property[];
  relationships: Relationship[];
}

interface Property {
  name: string;
  type: string;
  required: boolean;
  description: string;
  constraints?: Constraint[];
}

interface Relationship {
  type: string;
  target: string;
  cardinality: string;
}

interface Constraint {
  type: string;
  value: any;
}

interface UseCase {
  name: string;
  description: string;
  actors: string[];
  preconditions: string[];
  steps: string[];
  postconditions: string[];
}

interface AuthRequirement {
  type: string;
  flows: string[];
}

interface AuthzRequirement {
  model: string;
  roles: string[];
  permissions: string[];
}

interface RateLimitRequirement {
  default: number;
  endpoints: Record<string, number>;
}

interface PaginationRequirement {
  defaultLimit: number;
  maxLimit: number;
  style: 'offset' | 'cursor' | 'page';
}

interface RequirementAnalysis {
  entities: Entity[];
  operations: Operation[];
  constraints: Constraint[];
  nonFunctional: NonFunctionalRequirement[];
}

interface Resource {
  id: string;
  name: string;
  plural: string;
  description: string;
  attributes: Attribute[];
  relationships: ResourceRelationship[];
  operations: string[];
  uri: string;
  subresources: Resource[];
  customActions?: CustomAction[];
}

interface Attribute {
  name: string;
  type: string;
  required: boolean;
  description: string;
  validation?: any;
}

interface ResourceRelationship {
  name: string;
  type: string;
  target: string;
  cardinality: string;
}

interface CustomAction {
  name: string;
  method: HTTPMethod;
  path: string;
  description: string;
}

interface Operation {
  type: string;
  resource: string;
  description: string;
}

interface NonFunctionalRequirement {
  type: string;
  requirement: string;
  metric: string;
}

interface OperationObject {
  operationId: string;
  summary: string;
  description: string;
  tags: string[];
  parameters?: Parameter[];
  requestBody?: RequestBody;
  responses: ResponseObject[];
  security?: SecurityRequirement[];
  deprecated?: boolean;
}

interface Parameter {
  name: string;
  in: string;
  required: boolean;
  description: string;
  schema: any;
  style?: string;
  explode?: boolean;
  example?: any;
}

interface RequestBody {
  required: boolean;
  description?: string;
  content: Record<string, MediaType>;
}

interface MediaType {
  schema: any;
  examples?: Record<string, any>;
  example?: any;
}

interface ResponseObject {
  status: string;
  description: string;
  headers?: Record<string, any>;
  content?: Record<string, MediaType>;
  links?: Record<string, any>;
  $ref?: string;
}

interface SecurityRequirement {
  [key: string]: string[];
}

interface AuthenticationScheme {
  type: string;
  scheme?: string;
  bearerFormat?: string;
  flows?: any;
  openIdConnectUrl?: string;
  description?: string;
}

interface AuthorizationModel {
  type: string;
  roles: Role[];
  permissions: Permission[];
  policies: Policy[];
}

interface Role {
  name: string;
  description: string;
  permissions: string[];
}

interface Permission {
  name: string;
  resource: string;
  action: string;
}

interface Policy {
  name: string;
  effect: string;
  conditions: any[];
}

interface RateLimitPolicy {
  default: RateLimit;
  endpoints: Map<string, RateLimit>;
  tiers: RateLimitTier[];
}

interface RateLimit {
  requests: number;
  window: string;
  strategy: string;
}

interface RateLimitTier {
  name: string;
  limits: RateLimit;
  price?: number;
}

interface VersioningStrategy {
  type: 'uri' | 'header' | 'query' | 'media-type';
  format: string;
  default: string;
  supported: string[];
  deprecation: DeprecationPolicy;
}

interface DeprecationPolicy {
  notice: string;
  sunset: string;
  migration: string;
}

interface APIDocumentation {
  format: string;
  sections: DocumentationSection[];
  examples: Example[];
  tutorials: Tutorial[];
}

interface DocumentationSection {
  title: string;
  content: string;
  subsections?: DocumentationSection[];
}

interface Example {
  title: string;
  description: string;
  request: any;
  response: any;
}

interface Tutorial {
  title: string;
  steps: TutorialStep[];
}

interface TutorialStep {
  title: string;
  description: string;
  code: string;
}

interface TestStrategy {
  unit: boolean;
  integration: boolean;
  contract: boolean;
  performance: boolean;
  security: boolean;
}

interface MonitoringConfig {
  metrics: string[];
  logging: LoggingConfig;
  tracing: TracingConfig;
  alerts: Alert[];
}

interface LoggingConfig {
  level: string;
  format: string;
  destination: string;
}

interface TracingConfig {
  enabled: boolean;
  sampling: number;
  backend: string;
}

interface Alert {
  name: string;
  condition: string;
  threshold: number;
  action: string;
}

interface DesignPattern {
  name: string;
  description: string;
  context: string;
  solution: any;
  examples: any[];
}

interface GraphQLType {
  kind: string;
  name: string;
  description: string;
  fields: Field[];
  interfaces?: string[];
}

interface Field {
  name: string;
  type: string;
  description: string;
  args?: Argument[];
  deprecated?: boolean;
  deprecationReason?: string;
}

interface Argument {
  name: string;
  type: string;
  description: string;
  defaultValue?: any;
}

interface Query {
  name: string;
  description: string;
  args: Argument[];
  returnType: string;
}

interface Mutation {
  name: string;
  description: string;
  args: Argument[];
  returnType: string;
}

interface Subscription {
  name: string;
  description: string;
  args: Argument[];
  returnType: string;
}

interface ClientSDK {
  language: string;
  name: string;
  version: string;
  files: ClientFile[];
}

interface ClientFile {
  name: string;
  content: string;
}

interface ValidationResult {
  valid: boolean;
  issues: ValidationIssue[];
  score: number;
  recommendations: string[];
}

interface ValidationIssue {
  type: string;
  severity: string;
  message: string;
  location?: string;
  suggestion?: string;
}

interface Info {
  title: string;
  version: string;
  description?: string;
  termsOfService?: string;
  contact?: Contact;
  license?: License;
}

interface Contact {
  name?: string;
  url?: string;
  email?: string;
}

interface License {
  name: string;
  url?: string;
}

interface Server {
  url: string;
  description?: string;
  variables?: Record<string, ServerVariable>;
}

interface ServerVariable {
  enum?: string[];
  default: string;
  description?: string;
}

interface Tag {
  name: string;
  description?: string;
  externalDocs?: ExternalDocumentation;
}

interface ExternalDocumentation {
  description?: string;
  url: string;
}

interface Paths {
  [path: string]: PathItem;
}

interface PathItem {
  [method: string]: Operation;
  $ref?: string;
  summary?: string;
  description?: string;
  servers?: Server[];
  parameters?: Parameter[];
}

interface Components {
  schemas?: Record<string, any>;
  responses?: Record<string, any>;
  parameters?: Record<string, any>;
  examples?: Record<string, any>;
  requestBodies?: Record<string, any>;
  headers?: Record<string, any>;
  securitySchemes?: Record<string, any>;
  links?: Record<string, any>;
  callbacks?: Record<string, any>;
}

// Export the designer
export { APIDesigner, APIDesign, OpenAPISpecification };
```