plant discovery - final exam - fundamentals

function solve(input) {
    // parse first part of input, creating initial plant catalog
    // - determine how many element of the input represent the catalog
    // - for each element of the input, create new catalog entry or update existing entry

    let actions = {
        'Rate': rate,
        'Update': update,
        'Reset': reset
    };
    let catalog = {};

    let n = Number(input.shift());

    for (let i = 0; i < n; i++) {
        let [name, rarity] = input.shift().split('<->');

        catalog[name] = {
            rarity: Number(rarity),
            ratings: [],
            avgRating: 0
        };
    }

    // parse second part of input, updating the catalog, according to commands
    // - for each remaining input element, until 'Exhibition' is reached:
    // -- parse input, to determine command
    // -- perform given command with given parameters

    while (input[0] != 'Exhibition') {
        let [command, params] = input.shift().split(': ');
        let action = actions[command];
        action(params);
    }

    // sort catalog
    // - convert catalog to array
    // - pass compare function into sorting operation
    // -- return difference between plats' rarity
    // -- if rarity is the same, return difference between plants' average rating
    let sorted = Object.entries(catalog).sort(comparePlants);

    // print result
    // - print static line
    // - for each plant of the sorted array, print stats
    console.log('Plants for the exhibition:');
    for (let [name, plant] of sorted) {
        console.log(`- ${name}; Rarity: ${plant.rarity}; Rating: ${plant.avgRating.toFixed(2)}`);
    }

    function comparePlants(a, b) {
        let rarityA = a[1].rarity;
        let rarityB = b[1].rarity;

        let ratingA = a[1].avgRating;
        let ratingB = b[1].avgRating;

        return (rarityB - rarityA) || (ratingB - ratingA);
    }

    // Rate
    // - parse parameters to determine plant name and given rating
    // - if the plant exists in the catalog, add given rating (as number)

    function rate(line) {
        let [name, rating] = line.split(' - ');
        if (catalog[name] != undefined) {
            let plant = catalog[name];
            plant.ratings.push(Number(rating));

            let total = 0;
            for (let rating of plant.ratings) {
                total += rating;
            }
            plant.avgRating = total / plant.ratings.length;

        } else {
            console.log('error');
        }
    }

    // Update
    // - parse parameters to determine plant name and given rarity
    // - if the plant exists in the catalog, update its rarity (as number)

    function update(line) {
        let [name, rarity] = line.split(' - ');
        if (catalog[name] != undefined) {
            let plant = catalog[name];
            plant.rarity = Number(rarity);
        } else {
            console.log('error');
        }
    }

    // Reset
    // - if the plant exists in the catalog, remove all ratings
    function reset(name) {
        if (catalog[name] != undefined) {
            let plant = catalog[name];
            plant.ratings.length = 0;
            plant.avgRating = 0;
        } else {
            console.log('error');
        }
    }
}

solve(['3',
    'Arnoldii<->4',
    'Woodii<->7',
    'Welwitschia<->2',
    'Rate: Woodii - 10',
    'Rate: Welwitschia - 7',
    'Rate: Arnoldii - 3',
    'Rate: Woodii - 5',
    'Update: Woodii - 5',
    'Reset: Arnoldii',
    'Exhibition']);