merge.go

package main

import (
	"encoding/csv"
	"fmt"
	"log"
	"os"
	"regexp"
	"sort"
	"strconv"
	"strings"
)

var (
	prefixes = lines(`
Baby Sushi
Drinks/Chill j
Drinks/Flavoured Milk
Drinks/Milky Max Fresh
Drinks/Fruit Juice Pop
Hot Food/Hamburger
Hot Food/Grilled Chicken Burger
Hot Food/Pizza Slab
Hot Food/Spaghetti
NEW!!! Icy Treats
Rice Paper Rolls
Snacks/Humus
Snacks/Muffin
Sushi/Inari Sushi (3 Pieces)
Sushi/Edamame
Sushi
Birthday Box/Birthday Box
Sandwiches & Rolls
Wraps
Salad Bowls
`)
)

type money int

func (m money) String() string {
	d, c := m/100, m%100
	if d > 1000 {
		return fmt.Sprintf("$%d,%.3d.%.2d", d/1000, d%1000, c)
	}
	return fmt.Sprintf("$%d.%.2d", d, c)
}

func main() {

	filenames := strings.Fields("bdaybox.csv lunch.csv recess.csv sushi.csv")
	revenue := make(map[string]money)
	counts := make(map[string]int)
	var items []string

	priceRanges := make(map[string]map[money]int)

	for _, filename := range filenames {
		records := readCSV(filename)
		for _, r := range records {
			category, fullItem, quantity, price := r[0], r[1], toInt(r[2]), toMoney(r[3])
			item := generic(category+"/"+fullItem, prefixes)
			itemPrices, ok := priceRanges[item]
			if !ok {
				itemPrices = make(map[money]int)
				priceRanges[item] = itemPrices
				items = append(items, item)
			}
			itemPrices[price]++
			revenue[item] += money(quantity * int(price))
			counts[item] += quantity
		}
	}
	var totalRevenue money
	for _, v := range revenue {
		totalRevenue += v
	}
	fmt.Println("total revenue", totalRevenue)

	sort.Slice(items, func(i, j int) bool {
		return revenue[items[i]] > revenue[items[j]]
	})
	for k, v := range priceRanges {
		if len(v) == 1 {
			continue
		}
		fmt.Println(k, v)
	}
	fmt.Println("----------------")
	var revSubtotal money
	found90, found50 := false, false
	for _, i := range items {
		fmt.Println(revenue[i], i, counts[i])
		revSubtotal += revenue[i]
		if !found90 && float64(revSubtotal) > (0.9*float64(totalRevenue)) {
			fmt.Println("************************")
			found90 = true
		}
		if !found50 && float64(revSubtotal) > (0.5*float64(totalRevenue)) {
			fmt.Println("#########################")
			found50 = true
		}
	}
}

func readCSV(filename string) [][]string {
	f, err := os.Open(filename)
	if err != nil {
		log.Fatal(err)
	}
	defer f.Close()
	r := csv.NewReader(f)
	records, err := r.ReadAll()
	if err != nil {
		log.Fatal(err)
	}
	return records
}

func toInt(s string) int {
	n, err := strconv.Atoi(s)
	if err != nil {
		log.Fatal(err)
	}
	return n
}

var dollarPattern = regexp.MustCompile(`\$([0-9]+)\.([0-9]+)`)

func toMoney(s string) money {
	m := dollarPattern.FindStringSubmatch(s)
	if m == nil {
		log.Fatal("%s no match for %v", s, dollarPattern)
	}
	return money(100*toInt(m[1]) + toInt(m[2]))
}

func generic(s string, prefixes []string) string {
	for _, p := range prefixes {
		if strings.HasPrefix(s, p) {
			return p
		}
	}
	return s
}

func lines(p string) []string {
	lines := strings.Split(p, "\n")
	reply := make([]string, 0, len(lines))
	for _, l := range lines {
		if len(l) > 0 {
			reply = append(reply, l)
		}
	}
	return reply
}