import type { DatasetId } from '../domain/value-objects/dataset-id.js';
import type { FieldName } from '../domain/value-objects/field-name.js';
import type { QueryResult } from '../domain/entities/query-result.js';
import type { DatasetStoragePort } from '../ports/secondary/dataset-storage-port.js';
import { DatasetCatalogService } from '../domain/services/dataset-catalog-service.js';
import { FieldValidator } from '../domain/services/field-validator.js';
import { ProjectionService } from '../domain/services/projection-service.js';
/**
* Use case for retrieving a single row by its key field value.
*
* Fetches one specific row from a dataset and optionally projects
* selected fields.
*/
export class GetByIdUseCase {
private readonly projectionService = new ProjectionService();
constructor(
private readonly storage: DatasetStoragePort,
private readonly catalog: DatasetCatalogService,
private readonly fieldValidator: FieldValidator
) {}
/**
* Execute the get by ID operation.
*
* @param datasetId - The ID of the dataset
* @param keyValue - The value of the key field to search for
* @param selectFields - Optional fields to return (defaults to visible fields)
* @returns Query result with the matching row, or empty result if not found
* @throws DatasetNotFoundError if the dataset doesn't exist
* @throws InvalidFieldError if select fields are invalid
*/
async execute(
datasetId: DatasetId,
keyValue: string | number,
selectFields?: FieldName[]
): Promise<QueryResult> {
// Get dataset schema
const schema = this.catalog.getSchema(datasetId);
// Determine fields to return (select fields or visible fields)
const fieldsToReturn = selectFields && selectFields.length > 0
? selectFields
: schema.visibleFields;
// Validate select fields
this.fieldValidator.validateSelectFields(fieldsToReturn, schema);
// Load the specific row by key
const row = await this.storage.loadById(datasetId, keyValue);
// If not found, return empty result
if (!row) {
return {
rows: [],
count: 0,
limitApplied: false,
truncated: false,
totalMatched: 0,
fields: fieldsToReturn,
};
}
// Project fields
const projectedRows = this.projectionService.projectRows([row], fieldsToReturn);
// Return result
return {
rows: projectedRows,
count: 1,
limitApplied: false, // GetById always returns exactly one row
truncated: false,
totalMatched: 1,
fields: fieldsToReturn,
};
}
}
