react-diff-view/src/tokenize/backToTree.ts

A git diff component to consume the git unified diff output.

import {last, isEqual, isEqualWith} from 'lodash';
import {ProcessingNode, TokenNode, TokenPath} from './interface';

function areNodesMeregable(x: TokenNode, y: TokenNode): boolean {

    if (x.type !== y.type) {
        return false;
    }

    if (x.type === 'text') {
        return true;
    }

    if (!x.children || !y.children) {
        return false;
    }

    return isEqualWith(x, y, (x, y, name) => (name === 'chlidren' || isEqual(x, y)));
}

function mergeNode(x: ProcessingNode, y: ProcessingNode) {
    if ('value' in x && 'value' in y) {
        return {
            ...x,
            value: `${x.value}${y.value}`,
        };
    }

    return x;
}

function attachNode(parent: TokenNode, node: TokenNode): TokenNode {
    if (!parent.children) {
        throw new Error('parent node missing children property');
    }

    const previousSibling = last(parent.children);

    if (previousSibling && areNodesMeregable(previousSibling, node)) {
        /* eslint-disable no-param-reassign */
        parent.children[parent.children.length - 1] = mergeNode(previousSibling, node);
        /* eslint-enable no-param-reassign */
    }
    else {
        parent.children.push(node);
    }

    const leaf = parent.children[parent.children.length - 1];
    return leaf;
}

export default function backToTree(pathList: TokenPath[]): TokenNode {
    const root: TokenNode = {type: 'root', children: []};

    for (const path of pathList) {
        path.reduce<TokenNode>(
            (parent: TokenNode, node: ProcessingNode, i: number) => {
                const nodeToUse: TokenNode = i === path.length - 1 ? {...node} : {...node, children: []};
                return attachNode(parent, nodeToUse);
            },
            root
        );
    }

    return root;
}