Method LINSERT

lists.go:259–312

LINSERT inserts the given element on the given side of the pivot element.

(key string, side LSide, pivot, element Value)

// LINSERT inserts the given element on the given side of the pivot element.
func (c Client) LINSERT(key string, side LSide, pivot, element Value) (newLength int64, done bool, err error) {
	var actions []dynamodb.TransactWriteItem

	pivotNode, found, err := c.listNodeAtPivot(key, pivot, Left)
	if err != nil || !found {
		return newLength, false, err
	}

	switch {
	case pivotNode.isHead() && side == Left:
		_, err = c.LPUSHX(key, element)
		done = true
	case pivotNode.isTail() && side == Right:
		_, err = c.RPUSHX(key, element)
		done = true
	default:
		otherNode, ok, err := c.listGetByAddress(key, pivotNode.prev(side))
		if err != nil || !ok {
			return newLength, false, fmt.Errorf("could not find or load required node %v: %w", pivotNode, err)
		}

		newNode := listNode{
			key:     key,
			address: ulid.MustNew(ulid.Now(), rand.Reader).String(),
			value:   ReturnValue{element.ToAV()},
		}
		newNode.setPrev(side, otherNode.address)
		newNode.setNext(side, pivotNode.address)

		actions = append(actions, otherNode.updateSideAction(side.otherSide(), newNode.address, c))
		actions = append(actions, pivotNode.updateSideAction(side, newNode.address, c))
		actions = append(actions, newNode.putAction(c))
		actions = append(actions, c.listCountDeltaAction(key, 1))
	}

	if err != nil {
		return newLength, done, err
	}

	if len(actions) > 0 {
		_, err = c.ddbClient.TransactWriteItemsRequest(&dynamodb.TransactWriteItemsInput{
			TransactItems: actions,
		}).Send(context.TODO())
		if err != nil {
			return newLength, done, err
		}

		done = true
	}

	newLength, err = c.LLEN(key)

	return newLength, done, err
}

func (c Client) listNodeAtPivot(key string, pivot Value, side LSide) (node listNode, found bool, err error) {
	node, found, err = c.listFindEnd(key, side)