table_driven_doughnuts_box.go

package doughnuts_box

import (
    "fmt"
)

type doughnutsBox struct {
    capacity  int
    doughnuts []string
}

var knownDoughnutTypes = map[string]bool{
    "Matcha Tea":                true,
    "Lime & Coconut (ve)":       true,
    "Home Made Raspberry Jam":   true,
    "Cinnamon Scroll (ve)":      true,
    "Sri Lankan Cinnamon Sugar": true,
}

func newDoughnutsBox(capacity int) *doughnutsBox {
    return &doughnutsBox{
        capacity:  capacity,
        doughnuts: make([]string, 0),
    }
}

func (b *doughnutsBox) pack(doughnuts []string) (int, error) {
    unrecognizedItems := make([]string, 0)
    var err error

    if len(doughnuts) > b.capacity {
        return 0, fmt.Errorf("failed to put %d doughnuts in the box, it's only has %d doughnuts capacity", len(doughnuts), b.capacity)
    }

    for _, doughnut := range doughnuts {
        if _, found := knownDoughnutTypes[doughnut]; found {
            b.doughnuts = append(b.doughnuts, doughnut)
            continue
        }
        unrecognizedItems = append(unrecognizedItems, doughnut)
    }

    if len(unrecognizedItems) > 0 {
        err = fmt.Errorf("the following items cannot be placed into the box: %v", unrecognizedItems)
    }
    return len(b.doughnuts), err
}