/**
 * @license
 * Copyright 2018 Google Inc. All Rights Reserved.
 * 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
 *
 * http://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 {ENGINE} from '../engine';

/**
 * Used for wrapping functions that perform math operations on
 * Tensors. The function will be wrapped in a named scope that cleans all
 * memory usage after the function is done.
 */
export function op<T extends Function>(f: {[name: string]: T}): T {
  const keys = Object.keys(f);
  if (keys.length !== 1) {
    throw new Error(
        `Please provide an object with a single key ` +
        `(operation name) mapping to a function. Got an object with ` +
        `${keys.length} keys.`);
  }

  let opName = keys[0];
  const fn = f[opName];

  // Strip the underscore from the end of the function name.
  if (opName.endsWith('_')) {
    opName = opName.substring(0, opName.length - 1);
  }

  // tslint:disable-next-line:no-any
  const f2 = (...args: any[]) => {
    ENGINE.startScope(opName);
    try {
      const result = fn(...args);
      if (result instanceof Promise) {
        console.error('Cannot return a Promise inside of tidy.');
      }
      ENGINE.endScope(result);
      return result;
    } catch (ex) {
      ENGINE.endScope(null);
      throw ex;
    }
  };
  Object.defineProperty(f2, 'name', {value: opName, configurable: true});

  // tslint:disable-next-line:no-any
  return f2 as any as T;
}