MatchOperation.ts

import * as jsonpath from "jsonpath";
import * as jsonPtr from "json-ptr";
import Operation from "./Operation";

export default class MatchOperation extends Operation {

    name() {
        return "match";
    }

    processInArray(keyword: string, source: any, sourceArray: any[], sourceArrayIndex: number, resultArray: any[], resultArrayIndex: number, target: any[]) {
        const keywordValue: MatchKeywordValue = source[keyword];

        let matchedResultArrayIndex: number;

        // Handle $match.index
        if (keywordValue.index !== undefined) {
            matchedResultArrayIndex = keywordValue.index === "-" ? resultArray.length - 1 : keywordValue.index;
        }

        // Handle $match.query
        else if (keywordValue.query !== undefined) {
            // Try to find a matching item in the result
            const path = jsonpath.paths(resultArray, keywordValue.query)[0];
            matchedResultArrayIndex = path !== undefined ? path[1] as number : undefined;
        }

        // Handle $match.path
        else if (keywordValue.path !== undefined) {
            // Try to find a matching item in the result
            if (jsonPtr.get(resultArray, keywordValue.path) !== undefined) {
                [matchedResultArrayIndex] = jsonPtr.decodePointer(keywordValue.path)[0];
            }
        }

        // Ignore the item if no match found
        if (matchedResultArrayIndex === undefined || resultArray[matchedResultArrayIndex] === undefined) {
            return {resultArray, resultArrayIndex};
        }

        // Process result array item
        const result = this._processor.processArrayItem(keywordValue.value, sourceArray, sourceArrayIndex, resultArray, matchedResultArrayIndex, target);

        // Check if an array item has been inserted or removed below or at the current array item
        if (matchedResultArrayIndex <= resultArrayIndex) {
            resultArrayIndex += result.resultArrayIndex - matchedResultArrayIndex;
        }

        return {resultArray: result.resultArray, resultArrayIndex};
    }
}

/*
 * TYPES
 */

export interface MatchKeywordValue {
    "index"?: number | "-"; // the index to match against, use '-' to match on the last item
    "path"?: string; // the json pointer to match against
    "query"?: string; // the json path to match against
    "value": any; // the operation or value to use if a match is found
}