@decaf-ts/db-decorators
Version:
Agnostic database decorators and repository
92 lines • 13.4 kB
JavaScript
import { Operations } from "./Operations.js";
/**
* @description Registry for database operation handlers
* @summary Manages and stores operation handlers for different model properties and operations
* @class OperationsRegistry
* @template M - Model type
* @template R - Repository type
* @template V - Metadata type
* @template F - Repository flags
* @template C - Context type
* @example
* // Create a registry and register a handler
* const registry = new OperationsRegistry();
* registry.register(myHandler, OperationKeys.CREATE, targetModel, 'propertyName');
*
* // Get handlers for a specific operation
* const handlers = registry.get(targetModel.constructor.name, 'propertyName', 'onCreate');
*
* @mermaid
* classDiagram
* class OperationsRegistry {
* -cache: Record~string, Record~string|symbol, Record~string, Record~string, OperationHandler~~~~
* +get(target, propKey, operation, accum)
* +register(handler, operation, target, propKey)
* }
*/
export class OperationsRegistry {
constructor() {
this.cache = {};
}
/**
* @description Retrieves operation handlers for a specific target and operation
* @summary Finds all registered handlers for a given target, property, and operation, including from parent classes
* @template M - Model type extending Model
* @template R - Repository type extending IRepository
* @template V - Metadata type
* @template F - Repository flags extending RepositoryFlags
* @template C - Context type extending Context<F>
* @param {string | Record<string, any>} target - The target class name or object
* @param {string} propKey - The property key to get handlers for
* @param {string} operation - The operation key to get handlers for
* @param {OperationHandler[]} [accum] - Accumulator for recursive calls
* @return {OperationHandler[] | undefined} Array of handlers or undefined if none found
*/
get(target, propKey, operation, accum) {
accum = accum || [];
let name;
try {
name = typeof target === "string" ? target : target.constructor.name;
accum.unshift(...Object.values(this.cache[name][propKey][operation] || []));
// eslint-disable-next-line @typescript-eslint/no-unused-vars
}
catch (e) {
if (typeof target === "string" ||
target === Object.prototype ||
Object.getPrototypeOf(target) === Object.prototype)
return accum;
}
let proto = Object.getPrototypeOf(target);
if (proto.constructor.name === name)
proto = Object.getPrototypeOf(proto);
return this.get(proto, propKey, operation, accum);
}
/**
* @description Registers an operation handler for a specific target and operation
* @summary Stores a handler in the registry for a given target, property, and operation
* @template M - Model type extending Model
* @template R - Repository type extending IRepository
* @template V - Metadata type
* @template F - Repository flags extending RepositoryFlags
* @template C - Context type extending Context<F>
* @param {OperationHandler} handler - The handler function to register
* @param {OperationKeys} operation - The operation key to register the handler for
* @param {M} target - The target model instance
* @param {string | symbol} propKey - The property key to register the handler for
* @return {void}
*/
register(handler, operation, target, propKey) {
const name = target.constructor.name;
const handlerName = Operations.getHandlerName(handler);
if (!this.cache[name])
this.cache[name] = {};
if (!this.cache[name][propKey])
this.cache[name][propKey] = {};
if (!this.cache[name][propKey][operation])
this.cache[name][propKey][operation] = {};
if (this.cache[name][propKey][operation][handlerName])
return;
this.cache[name][propKey][operation][handlerName] = handler;
}
}
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target : target.constructor.name;\n      accum.unshift(\n        ...Object.values(this.cache[name][propKey][operation] || [])\n      );\n      // eslint-disable-next-line @typescript-eslint/no-unused-vars\n    } catch (e: unknown) {\n      if (\n        typeof target === \"string\" ||\n        target === Object.prototype ||\n        Object.getPrototypeOf(target) === Object.prototype\n      )\n        return accum;\n    }\n\n    let proto = Object.getPrototypeOf(target);\n    if (proto.constructor.name === name) proto = Object.getPrototypeOf(proto);\n\n    return this.get<M, R, V, F, C>(proto, propKey, operation, accum);\n  }\n\n  /**\n   * @description Registers an operation handler for a specific target and operation\n   * @summary Stores a handler in the registry for a given target, property, and operation\n   * @template M - Model type extending Model\n   * @template R - Repository type extending IRepository\n   * @template V - Metadata type\n   * @template F - Repository flags extending RepositoryFlags\n   * @template C - Context type extending Context<F>\n   * @param {OperationHandler} handler - The handler function to register\n   * @param {OperationKeys} operation - The operation key to register the handler for\n   * @param {M} target - The target model instance\n   * @param {string | symbol} propKey - The property key to register the handler for\n   * @return {void}\n   */\n  register<\n    M extends Model,\n    R extends IRepository<M, F, C>,\n    V,\n    F extends RepositoryFlags,\n    C extends Context<F>,\n  >(\n    handler: OperationHandler<M, R, V, F, C>,\n    operation: OperationKeys,\n    target: M,\n    propKey: string | symbol\n  ): void {\n    const name = target.constructor.name;\n    const handlerName = Operations.getHandlerName(handler);\n\n    if (!this.cache[name]) this.cache[name] = {};\n    if (!this.cache[name][propKey]) this.cache[name][propKey] = {};\n    if (!this.cache[name][propKey][operation])\n      this.cache[name][propKey][operation] = {};\n    if (this.cache[name][propKey][operation][handlerName]) return;\n    this.cache[name][propKey][operation][handlerName] = handler;\n  }\n}\n"]}