<think>
Okay, I need to implement the mid_pair function. Let's see the requirements. The function takes a list of values and returns two values that are closest to the middle when the list is ordered. For odd-length lists, the middle value is repeated twice. If the list is empty, return an empty list.

First, I need to sort the input list. Then find the middle positions. Let's think about the steps.

So, the first step is to sort the list. Then determine the middle index. For a list of length n, the middle is at n//2 when using integer division. But wait, for even lengths, there's a middle between two elements. But the problem says to return the two values closest to the middle. So for even n, maybe the two middle elements?

Wait, the problem says that for a list of odd length, the middle value is given twice. For even length, perhaps the two middle elements are selected. For example, if the list has 4 elements, the middle is between index 1 and 2. So the two closest would be elements at 1 and 2.

So the process is: sort the list, then find the middle positions. For a list of length n:

If n is odd, the middle is at n//2. So return [values[n//2], values[n//2]].

If n is even, the middle is between n//2 -1 and n//2. So return [values[n//2 -1], values[n//2]].

Wait, but the problem says "the two values standing closest to the middle". So for even n, the two middle elements are the ones at positions (n//2 -1) and (n//2). For example, if the list is [1,2,3,4], sorted, the middle is between 2 and 3. So the two closest are 2 and 3.

So the function should return those two elements.

But what if the list is empty? Then return an empty list.

So the steps are:

1. Sort the input list.

2. Determine the middle indices based on the length.

3. Return the two elements at those indices.

But how to handle the case when the list is empty? The function should return an empty list.

So, let's code this.

First, sort the list. Then check the length.

If the list is empty, return empty list.

Else, calculate the middle indices.

For n = len(values):

if n is odd:

   mid = n // 2

   return [values[mid], values[mid]]

if n is even:

   mid = n // 2

   return [values[mid-1], values[mid]]

Wait, but for even n, the two middle elements are at mid-1 and mid. For example, n=4, mid is 2. So indices 1 and 2.

Yes.

So, code:

def mid_pair(values: list) -> list:

    sorted_values = sorted(values)

    n = len(sorted_values)

    if n == 0:

        return []

    if n % 2 == 1:

        mid = n // 2

        return [sorted_values[mid], sorted_values[mid]]

    else:

        mid = n // 2

        return [sorted_values[mid - 1], sorted_values[mid]]

Wait, but what if the list is of length 1? Then n is 1, which is odd. mid is 0. So return [values[0], values[0]], which is correct.

Testing for even length, say 2 elements: [a, b]. sorted. mid is 1. return [0, 1], which are