BlockStatementControlFlowTransformer.ts

import { injectable, inject } from 'inversify';
import { ServiceIdentifiers } from '../../container/ServiceIdentifiers';

import * as estraverse from 'estraverse';
import * as ESTree from 'estree';

import { TControlFlowCustomNodeFactory } from '../../types/container/custom-nodes/TControlFlowCustomNodeFactory';

import { IArrayUtils } from '../../interfaces/utils/IArrayUtils';
import { ICustomNode } from '../../interfaces/custom-nodes/ICustomNode';
import { IOptions } from '../../interfaces/options/IOptions';
import { IRandomGenerator } from '../../interfaces/utils/IRandomGenerator';
import { IVisitor } from '../../interfaces/IVisitor';

import { ControlFlowCustomNode } from '../../enums/container/custom-nodes/ControlFlowCustomNode';

import { AbstractNodeTransformer } from '../AbstractNodeTransformer';
import { Node } from '../../node/Node';

@injectable()
export class BlockStatementControlFlowTransformer extends AbstractNodeTransformer {
    /**
     * @type {IArrayUtils}
     */
    private readonly arrayUtils: IArrayUtils;

    /**
     * @type {TControlFlowCustomNodeFactory}
     */
    private readonly controlFlowCustomNodeFactory: TControlFlowCustomNodeFactory;

    /**
     * @param {TControlFlowCustomNodeFactory} controlFlowCustomNodeFactory
     * @param {IArrayUtils} arrayUtils
     * @param {IRandomGenerator} randomGenerator
     * @param {IOptions} options
     */
    constructor (
        @inject(ServiceIdentifiers.Factory__IControlFlowCustomNode)
            controlFlowCustomNodeFactory: TControlFlowCustomNodeFactory,
        @inject(ServiceIdentifiers.IArrayUtils) arrayUtils: IArrayUtils,
        @inject(ServiceIdentifiers.IRandomGenerator) randomGenerator: IRandomGenerator,
        @inject(ServiceIdentifiers.IOptions) options: IOptions
    ) {
        super(randomGenerator, options);

        this.controlFlowCustomNodeFactory = controlFlowCustomNodeFactory;
        this.arrayUtils = arrayUtils;
    }

    /**
     * @param {BlockStatement} blockStatementNode
     * @returns {boolean}
     */
    private static blockStatementHasProhibitedStatements (blockStatementNode: ESTree.BlockStatement): boolean {
        return blockStatementNode.body.some((statement: ESTree.Statement) => {
            const isBreakOrContinueStatement: boolean = Node.isBreakStatementNode(statement) || Node.isContinueStatementNode(statement);
            const isVariableDeclarationWithLetOrConstKind: boolean = Node.isVariableDeclarationNode(statement)
                && (statement.kind === 'const' || statement.kind === 'let');

            return Node.isFunctionDeclarationNode(statement) || isBreakOrContinueStatement || isVariableDeclarationWithLetOrConstKind;
        });
    }

    /**
     * @param {BlockStatement} blockStatementNode
     * @returns {boolean}
     */
    private static canTransformBlockStatementNode (blockStatementNode: ESTree.BlockStatement): boolean {
        let canTransform: boolean = true;

        estraverse.traverse(blockStatementNode, {
            enter: (node: ESTree.Node): any => {
                if (Node.isWhileStatementNode(node)) {
                    return estraverse.VisitorOption.Skip;
                }

                if (
                    Node.isBlockStatementNode(node)
                    && BlockStatementControlFlowTransformer.blockStatementHasProhibitedStatements(node)
                ) {
                    canTransform = false;
                }
            }
        });

        if (blockStatementNode.body.length <= 4) {
            canTransform = false;
        }

        return canTransform;
    }

    /**
     * @return {IVisitor}
     */
    public getVisitor (): IVisitor {
        return {
            leave: (node: ESTree.Node, parentNode: ESTree.Node) => {
                if (Node.isBlockStatementNode(node)) {
                    return this.transformNode(node, parentNode);
                }
            }
        };
    }

    /**
     * @param {BlockStatement} blockStatementNode
     * @param {Node} parentNode
     * @returns {Node}
     */
    public transformNode (blockStatementNode: ESTree.BlockStatement, parentNode: ESTree.Node): ESTree.Node {
        if (
            this.randomGenerator.getMathRandom() > this.options.controlFlowFlatteningThreshold ||
            !BlockStatementControlFlowTransformer.canTransformBlockStatementNode(blockStatementNode)
        ) {
            return blockStatementNode;
        }

        const blockStatementBody: ESTree.Statement[] = blockStatementNode.body;
        const originalKeys: number[] = this.arrayUtils.arrayRange(blockStatementBody.length);
        const shuffledKeys: number[] = this.arrayUtils.arrayShuffle(originalKeys);
        const originalKeysIndexesInShuffledArray: number[] = originalKeys.map((key: number) => shuffledKeys.indexOf(key));
        const blockStatementControlFlowFlatteningCustomNode: ICustomNode = this.controlFlowCustomNodeFactory(
            ControlFlowCustomNode.BlockStatementControlFlowFlatteningNode
        );

        blockStatementControlFlowFlatteningCustomNode.initialize(
            blockStatementBody,
            shuffledKeys,
            originalKeysIndexesInShuffledArray
        );

        return blockStatementControlFlowFlatteningCustomNode.getNode()[0];
    }
}