Question

Implement a fixed-capacity ring buffer that overwrites the oldest element when full. Replay operations: ["write", x] appends x (overwriting the oldest if at capacity), ["read"] removes and returns the oldest element or -1 if empty, ["snapshot"] returns -2 as a marker and the snapshot itself is appended to results as the current buffer contents oldest-to-newest. Actually, to keep results flat: on ["read"] append the returned value; on ["oldest"] append the oldest value without removing (or -1 if empty); ignore other introspection. Capacity is between 1 and 10^4. Return the list of values produced by read and oldest operations in order.