"""Assign pyannote speaker labels to whisper segments via max-overlap."""


def _overlap(a_start, a_end, b_start, b_end):
    return max(0.0, min(a_end, b_end) - max(a_start, b_start))


def assign_speakers(whisper_segs, diar_turns):
    """For each whisper segment, pick the speaker whose pyannote turn overlaps most.

    Falls back to the nearest-midpoint speaker if no overlap exists.
    If diar_turns is empty, every segment is labeled SPEAKER_00.
    """
    if not diar_turns:
        return [{**s, "speaker": "SPEAKER_00"} for s in whisper_segs]

    result = []
    for seg in whisper_segs:
        best_speaker = None
        best_overlap = 0.0
        nearest_speaker = None
        best_distance = float("inf")
        seg_mid = (seg["start"] + seg["end"]) / 2

        for turn in diar_turns:
            ov = _overlap(seg["start"], seg["end"], turn["start"], turn["end"])
            if ov > best_overlap:
                best_overlap = ov
                best_speaker = turn["speaker"]
            turn_mid = (turn["start"] + turn["end"]) / 2
            d = abs(seg_mid - turn_mid)
            if d < best_distance:
                best_distance = d
                nearest_speaker = turn["speaker"]

        speaker = best_speaker or nearest_speaker or "SPEAKER_00"
        result.append({**seg, "speaker": speaker})
    return result