Data Structure: Singly Linked List

class Node:
    # Class properties
    var data
    var next

    constructor(data):
        this.data = data
        this.next = null
    end constructor
    
end class

class SinglyLinkedList:
    # Class properties
    head
    tail
    length

    // Initialize class property values
    constructor():
        this.head = null
        this.tail = null
        this.length = 0
    end constructor

    # Push item to list
    function push(data):
        node = new Node(data)
        if this.head is null:
            this.head = node
        else:
            this.tail.next = node
        end if
        
        this.tail = node
        this.length++
        
        return this
    end function

    # Pop item from list
    function pop():
        if this.head is null:
            return null
        end if
        
        current = this.head
        newTail = current
        
        while current.next is not null:
            newTail = current
            current = current.next
        end while
        
        this.tail = newTail
        this.tail.next = null
        this.length--
        
        if this.length is 0:
            this.head = null
            this.tail = null
        end if
        
        return current
    end function

    # Traverse full list
    function traverse():
        current = this.head
        while current is not null:
            output current.data
            current = current.next
        end while
        
    end function

    # Shift the head node
    function shift():
        if this.head is null:
            return null
        end if
        
        currHead = this.head
        this.head = currHead.next
        this.length--
        
        if this.length is 0:
            this.head = null
            this.tail = null
        end if
        return currHead
    end function

    # Unshift the head node and add new node as head
    function unshift(value):
        newHead = new Node(value)
        
        if this.head is null:
            this.tail = newHead
        else:
            newHead.next = this.head
        end if
            
        this.head = newHead
        this.length++
        
        return this
    end function

    # Get a node by index
    function get(index):
        if index < 0 or index >= this.length:
            return null
        selectedNode = this.head
        for i from 1 to index:
            selectedNode = selectedNode.next
        return selectedNode
    end function

    # Set node data at specific index
    function set(index, data):
        nodeAtIndex = this.get(index)
        if nodeAtIndex is not null:
            nodeAtIndex.data = data
            return true
        return false
    end function

    # Insert a new node at a specific index
    function insert(index, data):
        if index < 0 or index > this.length:
            return false
        end if
        
        if index is this.length:
            this.push(data)
            return true
        end if
        
        if index is 0:
            this.unshift(data)
            return true
        end if
        
        newNode = new Node(data)
        prevNode = this.get(index - 1)
        newNode.next = prevNode.next
        prevNode.next = newNode
        
        this.length++
        
        return true
    end function

    # Rmove a node at specific index
    function remove(index):
        if index < 0 or index >= this.length:
            return undefined
        end if
        
        if index is 0:
            return this.shift()
        end if
        
        if index is this.length - 1:
            return this.pop()
        end if
        
        prevNode = this.get(index - 1)
        removedNode = prevNode.next
        prevNode.next = prevNode.next.next
        
        this.length--
        
        return removedNode
    end function

    # Reverse the linked list
    function reverse():
        currentNode = this.head
        prevNode = null
        nextNode = null
        
        while currentNode is not null:
            nextNode = currentNode.next
            currentNode.next = prevNode
            prevNode = currentNode
            currentNode = nextNode
        end while
        
        this.tail = this.head
        this.head = prevNode
        
        return this
    end function
    
end class