/**

 * Copyright (c) Meta Platforms, Inc. and affiliates.

 * Copyright (c) 2017, Amjad Masad

 *

 * This source code is licensed under the MIT license found in the

 * LICENSE file in the root directory of this source tree.

 */

'use strict';

// Based on https://repl.it/site/blog/infinite-loops.

// This should be reasonable for all loops in the source.

// Note that if the numbers are too large, the tests will take too long to fail

// for this to be useful (each individual test case might hit an infinite loop).

const MAX_SOURCE_ITERATIONS = 1500;

// Code in tests themselves is permitted to run longer.

// For example, in the fuzz tester.

const MAX_TEST_ITERATIONS = 5000;

module.exports = ({types: t, template}) => {

  // We set a global so that we can later fail the test

  // even if the error ends up being caught by the code.

  const buildGuard = template(`

    if (%%iterator%%++ > %%maxIterations%%) {

      global.infiniteLoopError = new RangeError(

        'Potential infinite loop: exceeded ' +

        %%maxIterations%% +

        ' iterations.'

      );

      throw global.infiniteLoopError;

    }

  `);

  return {

    visitor: {

      'WhileStatement|ForStatement|DoWhileStatement': (path, file) => {

        const filename = file.file.opts.filename;

        const maxIterations = t.logicalExpression(

          '||',

          t.memberExpression(

            t.identifier('global'),

            t.identifier('__MAX_ITERATIONS__')

          ),

          t.numericLiteral(

            filename.indexOf('__tests__') === -1

              ? MAX_SOURCE_ITERATIONS

              : MAX_TEST_ITERATIONS

          )

        );

        // An iterator that is incremented with each iteration

        const iterator = path.scope.parent.generateUidIdentifier('loopIt');

        const iteratorInit = t.numericLiteral(0);

        path.scope.parent.push({

          id: iterator,

          init: iteratorInit,

        });

        // If statement and throw error if it matches our criteria

        const guard = buildGuard({

          iterator,

          maxIterations,

        });

        // No block statement e.g. `while (1) 1;`

        if (!path.get('body').isBlockStatement()) {

          const statement = path.get('body').node;

          path.get('body').replaceWith(t.blockStatement([guard, statement]));

        } else {

          path.get('body').unshiftContainer('body', guard);

        }

      },

    },

  };

};