trc-client-core/src/course/Prerequisite.js

The core of the TRC Client

import Expression, {OperationOrderMap} from 'trc-client-core/src/utils/Expression';

import {COURSE_COMPLETED, COURSE_ENROLLED} from 'trc-client-core/src/constants/Prerequisite';
import {COMPLETED} from 'trc-client-core/src/constants/CourseStatus';

const INVALID_CHARACTERS = /[-]/;

function getValue(obj) {
    switch(obj.type) {
        case 'Literal':
            return obj.value;
        default:
            return obj.name;
    }
}

function recurseToPrerequisite(branch) {
    // recurse if there are more prequisites to determine
    if (branch.left && branch.right) {
        return {
            type: branch.operator.toUpperCase(),
            prerequisite1: recurseToPrerequisite(branch.left),
            prerequisite2: recurseToPrerequisite(branch.right)
        }
    } else {
        if (branch.type === 'MemberExpression') {
            return {
                type: COURSE_ENROLLED,
                courseCode: getValue(branch.object)
            }
        } else {
            return {
                type: COURSE_COMPLETED,
                courseCode: getValue(branch)
            }
        }
    }
}

function recurseToString(branch, upperBanchValue) {
    var {type, prerequisite1, prerequisite2, courseCode, currentStatus} = branch;
    const branchValue = OperationOrderMap[type];

    // recurse if there are more prequisites to determine
    if (prerequisite1 && prerequisite2) {
        const binaryOperation = `${recurseToString(prerequisite1, branchValue)} ${type} ${recurseToString(prerequisite2, branchValue)}`;

        // Because expression objects are nested in reverse order
        // if the upper banch has a higher OperationOrder number it means that
        // the original string used brackets to change the order of operations;
        return (upperBanchValue > branchValue) ? `(${binaryOperation})` : binaryOperation;
    } else {
        courseCode = (courseCode.match(INVALID_CHARACTERS)) ? `'${courseCode}'` : courseCode;
        return `${courseCode}${(type !== COURSE_COMPLETED) ? '.' + type.replace('COURSE_', '') : ''}`;
    }
}

export function parsePrerequisite(str) {
    return recurseToPrerequisite(Expression(str));
}

export function stringifyPrerequisite(obj) {
    if(obj.type === "NONE"){
        return null
    }
    return recurseToString(obj);
}