Homework

import java.util.function.Supplier

// ---------------------------
//
// HOMEWORK
//
// You can use either Groovy or Java.
//
// Design a routine that will calculate the average Product price per Group.
//
// The Price of each Product is calculated as:
// Cost * (1 + Margin)
//
// Assume there can be a large number of products.
//
// Plus points:
// - use Groovy and its closures
// - make the category look-up performance effective
// - use method Collection.inject

// contains information about [Product, Group, Cost]
def products = [
    ["A", "G1", 20.1],
    ["B", "G2", 98.4],
    ["C", "G1", 49.7],
    ["D", "G3", 35.8],
    ["E", "G3", 105.5],
    ["F", "G1", 55.2],
    ["G", "G1", 12.7],
    ["H", "G3", 88.6],
    ["I", "G1", 5.2],
    ["J", "G2", 72.4]
]

// contains information about Category classification based on product Cost
// [Category, Cost range from (inclusive), Cost range to (exclusive)]
// i.e. if a Product has Cost between 0 and 25, it belongs to category C1
// ranges are mutually exclusive and the last range has a null as uppoer limit.
def category = [
    ["C3", 50, 75],
    ["C4", 75, 100],
    ["C2", 25, 50],
    ["C5", 100, null],
    ["C1", 0, 25]]

// contains information about margins for each product Category
// [Category, Margin (either percentage or absolute value)]
def margins = [
    "C1" : "20%",
    "C2" : "30%",
    "C3" : "0.4",
    "C4" : "50%",
    "C5" : "0.6"]

// ---------------------------
//
// YOUR CODE GOES BELOW THIS LINE
//
for(margin in margins) {
    if(margin.value.contains("%")) {
        def e = margin.value.replaceAll("%", "")
        margins[margin.key] = Float.parseFloat(e) / 100
    } else {
        margins[margin.key] = Float.parseFloat(margin.value)
    }
}

def result = [:]

products.stream()
        .map{product ->
            def cat = getCategory(product[2], category)
            product.plus(product[2] * (1 + margins[getCategoryCost(cat)]))
        }
        .collect{product -> product}
        .groupBy {product -> product[1]}
        .each { product ->
            def groupSum = product.value.inject(0){current, value -> current + value[3] }
            def avg = groupSum / product.value.size()
            result[product.key] = roundToNDigits(avg, 1)
        }

static def getCategory(cost, category) {
    return category.findResult {cost >= it[1] && cost < Optional.ofNullable(it[2]).orElse(Integer.MAX_VALUE) ? it : null}
}

static def getCategoryCost(cat) {
    if(cat == null) {
        throw new Exception("No category found")
    }
    return cat.get(0)
}

static def roundToNDigits(double value, int nDigits) {
    return Math.round(value * Math.pow(10, nDigits)) / Math.pow(10, nDigits);
}

// ---------------------------
//
// IF YOUR CODE WORKS, YOU SHOULD GET "It works!" WRITTEN IN THE CONSOLE
//
// ---------------------------
assert result == [
    "G1" : 37.5,
    "G2" : 124.5,
    "G3" : 116.1
    ] : "It doesn't work"

//a.each {p -> println p[3] }
//println b['G1'][0][3].orElse([])[0]
//println margins[a​[0]​[3]​.orElse([])[0]​]​
//println a
//println result