<think>
Okay, I need to implement the hop_chain function. The task is to check if a list of hops forms one unbroken chain. Each hop must start where the previous one ended. So, for example, if the first hop ends at position 5, the next hop must start at 5, and so on.

First, I need to think about the parameters. The function takes a list of hops, where each hop is a pair (probably a tuple of two elements). So each hop is like (start, end). The function should return True if all hops form a continuous chain, False otherwise.

Let me think about the steps. For a single hop, it's automatically valid. For an empty list, it's also valid. So the base cases are handled.

Now, for the general case. I need to iterate through the hops and check that each hop's start is equal to the previous hop's end. So, for the first hop, there's nothing before it, so it's okay. Then, for each subsequent hop, check if its start matches the end of the previous hop.

Wait, but what if the list is empty? The function should return True. Similarly, if there's one hop, it's True.

So the algorithm would be:

- If the list is empty, return True.
- If the list has one element, return True.
- Otherwise, iterate through each hop starting from the second one.
- For each hop, check if its start is equal to the end of the previous hop.
- If any of these checks fail, return False.
- If all pass, return True.

Now, how to implement this in Python.

The function is called hop_chain, takes a list of hops. Each hop is a pair, probably a tuple of two elements. So, for each hop in hops, we can access the start and end.

So, code steps:

def hop_chain(hops: list) -> bool:
    if not hops:
        return True
    if len(hops) == 1:
        return True
    for i in range(1, len(hops)):
        if hops[i][0] != hops[i-1][1]:
            return False
    return True

Wait, but what if the hops are not pairs? Like, if each hop is a list or a tuple with two elements. The function assumes that each hop is a pair. The problem says that each hop is a pair, so the input is correct.

But the function should not validate the input. The problem says that the function should check the chain, not the validity of the hops. So, the function can assume that each hop is a pair.

So the code above should work.

Testing some cases:

Case 1: empty list → returns True.

Case 2: one hop → returns True.

Case 3: two hops. First ends at 5, second starts at 5 → True. If second starts at 6 → False.

Case 4: three hops. Each consecutive starts where the previous ended → True.

What about if the first hop is (a, b), second (b, c), third (c, d) → True.

Yes.

What if the hops are not in order? Like, first hop is (a, b), then (c, d), then (d, e). Then the second hop starts at c, which is not equal to the first's end (b). So returns False.

Yes.

So the code seems correct.

Now, check for edge cases. For example, if the hops list is empty, returns True. If there's one hop, returns True. If the hops list has two hops that are invalid, returns False.

I think this covers all cases