import {
  TransformCallback,
  TransformWithPath,
  rxTransformTextFile
} from '@ibm-wch-sdk/schematics-utils';
import { Tree } from '@angular-devkit/schematics';
import { Observable } from 'rxjs';
import { safeLoad, safeDump } from 'js-yaml';
import { map } from 'rxjs/operators';

/**
 * Reads a YAML file from the tree and then transforms it using the given function. If the result
 * is null or undefined, the file will be deleted, else replaced or created.
 *
 * @param aName   name of the file
 * @param aOp     the operator
 * @param aTree   the tree to work in
 */
export function rxTransformYamlFile(
  aName: string,
  aOp: TransformCallback<any>,
  aTree: Tree
): Observable<string> {
  // cast
  const op: TransformWithPath<any> = aOp as any;
  // dispatch
  return rxTransformTextFile(
    aName,
    (textContent, path) =>
      op(textContent ? safeLoad(textContent) : undefined, path).pipe(
        map(data => safeDump(data))
      ),
    aTree
  );
}