ianadiwibowo/central-park

// PupuruHashmap is reinventing the wheel of a hashmap
package pupuruhashmap

type PupuruHashmapInterface interface {
    Set(key string, value string) error
    Get(key string) (value string)
}

const (
    hashmapSize = 10
)

type PupuruHashmap struct {
    Data [hashmapSize]*PupuruHashmapNode
}

type PupuruHashmapNode struct {
    Key   string
    Value string
    Next  *PupuruHashmapNode
}

func NewPupuruHashmap() *PupuruHashmap {
    return &PupuruHashmap{}
}

func (h *PupuruHashmap) Set(key string, value string) {
    index := mapKeyToIndex(key)
    newNode := &PupuruHashmapNode{key, value, nil}

    if h.Data[index] == nil {
        h.Data[index] = newNode
        return
    }

    currentNode := h.Data[index]
    for {
        if currentNode.Key == key {
            currentNode.Value = value
            return
        } else if currentNode.Next == nil {
            currentNode.Next = newNode
            return
        }
        currentNode = currentNode.Next
    }
}

func (h *PupuruHashmap) Get(key string) (value string) {
    index := mapKeyToIndex(key)

    if h.Data[index] == nil {
        return ""
    }

    currentNode := h.Data[index]
    for {
        if currentNode.Key == key {
            return currentNode.Value
        }
        currentNode = currentNode.Next
    }
}

// In this fake hash function, we just take the first chart of the key
// and convert it into int. In real life, this will use a real hash function
// like SipHash (or MD5, SHA1).
func mapKeyToIndex(key string) int {
    hashCode := int(key[0])
    return hashCode % hashmapSize
}