"""Native conditioning for duplex inference."""
import torch

def native_prefix(record, config):
    """Reproduce the pinned official CustomVoice non-streaming prompt using IDs.

    A position can have projected text, codec conditioning, or their sum.
    -1 means no embedding contribution; it is not a vocabulary token.
    """
    c = config.talker_config
    text_ids, codec_ids = [], []
    def add(t=-1, a=-1):
        text_ids.append(int(t))
        codec_ids.append([int(a)] + [-1] * (c.num_code_groups - 1))
    for token in record["instruct_ids"]:
        add(t=token)
    ids = record["text_ids"]
    for token in ids[:3]:
        add(t=token)
    lang = record["language"].lower()
    if lang == "auto":
        control = [c.codec_nothink_id, c.codec_think_bos_id, c.codec_think_eos_id]
    else:
        control = [c.codec_think_id, c.codec_think_bos_id, c.codec_language_id[lang], c.codec_think_eos_id]
    control += [c.spk_id[record["speaker"].lower()]]
    for token in control:
        add(config.tts_pad_token_id, token)
    add(config.tts_bos_token_id, c.codec_pad_id)
    for token in ids[3:-5]:
        add(token, c.codec_pad_id)
    add(config.tts_eos_token_id, c.codec_pad_id)
    add(config.tts_pad_token_id, c.codec_bos_id)
    return torch.tensor(text_ids), torch.tensor(codec_ids)