munch-ease-frontend/src/components/shopping/shopping.js

export function groupsToItems(groups) {
    return groups.map(group => group.shoppingListItems).flat();
}

export function itemsToGroups(shoppingListItems) {
    const ingredients_by_product_id = {};
    const ingredients_by_name = {};
    for (const item of shoppingListItems) {
        if (item.ingredient.product) {
            let group = ingredients_by_product_id[item.ingredient.product.id];
            if (!group) {
                group = ingredients_by_product_id[item.ingredient.product.id] = {
                    product: item.ingredient.product,
                    shoppingListItems: []
                };
            }
            group.shoppingListItems.push(item);
        }
        else {
            let group = ingredients_by_name[item.ingredient.name];
            if (!group) {
                group = ingredients_by_name[item.ingredient.name] = {
                    name: item.ingredient.name,
                    shoppingListItems: []
                };
            }
            group.shoppingListItems.push(item);
        }
    }

    return [
        ...Object.values(ingredients_by_product_id),
        ...Object.values(ingredients_by_name)
    ]
}