@lunaticmuch/front-matter-manipulator/lib/util/getFieldPermutations.js

A utility for parsing and manipulating documents with Front Matter

import isMissing from './isMissing.js';
import parseField from './parseField.js';


export default function getFieldPermutations(field, data) {
    var permutations = getFieldFromKey(field, data);

    if (!Array.isArray(permutations))
        permutations = [permutations];

    return permutations.filter(function (p) {
        return !isMissing(p);
    });
}

function getFieldFromKey(field, data, target) {
    if (isMissing(field)) throw new Error('Missing value for "field"');
    if (!data) throw new Error('Missing value for "data"');

    var {
        currentField,
        subFields,
        fieldValue } = parseField(field, data);

    if (isMissing(target)) {
        target = currentField;
    } else {
        target += `.${currentField}`;
    }

    if (subFields.length >= 1 && Array.isArray(fieldValue)) {
        return getFieldFromArray(subFields, fieldValue, target);
    } else if (subFields.length >= 1 && !isMissing(fieldValue)) {
        return getFieldFromKey(subFields, fieldValue, target);
    } else if (Array.isArray(fieldValue)) {
        return getFieldFromArray(subFields, fieldValue, target);
    } else {
        return target;
    }
}

function getFieldFromArray(field, data, target) {
    if (isMissing(field)) throw new Error('Missing value for "field"');
    if (!data) throw new Error('Missing value for "data"');

    if (data.length > 0) {
        return data.map(function (item, i) {
            var newTarget = target;
            var {
                totalSubFields,
                currentField,
                subFields,
                fieldValue } = parseField(field, item);

            if (currentField) {
                newTarget += `.${i}.${currentField}`;
            } else {
                newTarget += `.${i}`;
            }

            if (Array.isArray(fieldValue)) {
                return getFieldFromArray(subFields, fieldValue, newTarget);
            } else if (totalSubFields.length >= 1) {
                return getFieldFromKey(subFields, fieldValue, newTarget);
            } else {
                return newTarget;
            }
        });
    }
}