ruby LRU cache with constant get/set, Ruby

ruby LRU cache with constant get/set

#Title of this code
#ruby 2.1.2p95

Node = Struct.new(:value,:next,:prev)

#double link list implementation to work as a queue 
class DListQueue
    def initialize(size)
        @size = size
        @head = nil 
        @tail = nil
        @counter = 0
        
    end 
    
    def enqueue(node)
        @counter = @counter+1
        if @head == nil and @tail == nil 
                @head = @tail = node
        else 
                node.next = @head
                @head.prev = node 
                @head = node
        end 
    end 
    
    def dequeue()
        temp = @tail 
        @tail.prev.next = nil 
        @tail = @tail.prev
        @counter = @counter -1
        return temp
    end 
    
    def move_back(node)
        cur = node
        
        cur.prev.next = cur.next 
        cur.next.prev = cur.prev 
        
        node.next = @head
        @head.prev = node 
        @head = node
    end 
    
    def traversal
        cur  = @head
        while cur != nil
            puts cur.value
            cur = cur.next 
        end 
    end 
end

#lru cache implementatio to work 
class LRUCache
    
    def initialize(size)
        @size = size
        @hash = {} 
        @queue = DListQueue.new(size)
    end 
    
    def get(cache_id)
        if @hash[cache_id]
            update_access_table(@hash[cache_id][1])
            return @hash[cache_id][0]
        else
            "invalid cache_id"
        end 
    end 
    
    
    
    def set(cache_id,value)
        remove_least_accesed if @hash.length > @size-1
        if @hash[cache_id]
            @hash[cache_id][0] = value 
        else
            node = Node.new(cache_id)
            @hash[cache_id] = [value,node]
            @queue.enqueue(node)
        end      
    end 
    
    
    def remove_least_accesed
        
        item = @queue.dequeue()
        @hash.delete(item.value)
        
    end 
    
    
    def update_access_table(node)
        
        @queue.move_back(node)
             
    end 
    
    
    
    def hash
        @hash
    end 
    
    def queue
        @queue
    end 
    
end


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