"""WS pipeline 分段持久化（语音分段、按需 TTS 等独立 commit 场景）。

Each helper here opens its own ``transactional()`` on the long-lived WS
``AsyncSession`` (see ``app.core.db``): multiple commits per connection are
intentional for incremental durability.

``ConversationHistoryStore`` handles whole human/AI turn writes and refreshes
Redis after those commits. Pipeline code may interleave ``persist.py`` segment
commits with turn-level ``history_store`` writes; readers should treat DB as
authoritative when cache and DB diverge briefly.
"""

from __future__ import annotations

from datetime import datetime, timezone
from typing import Optional

from sqlalchemy.ext.asyncio import AsyncSession

from app.core.db import transactional
from app.features.conversation.models import Conversation, ConversationMessage, Segment


def mark_conversation_active(
    conversation: Conversation, at: Optional[datetime] = None
) -> datetime:
    activity_time = at or datetime.now(timezone.utc)
    conversation.last_message_at = activity_time
    return activity_time


async def persist_message_tts_url_segment(
    db: AsyncSession,
    msg: ConversationMessage,
    segment_index: int,
    url_stored: str,
) -> None:
    """按需 TTS：写入 message.tts_audio_urls[segment_index] 并提交。"""
    urls = list(msg.tts_audio_urls or [])
    while len(urls) <= segment_index:
        urls.append("")
    urls[segment_index] = url_stored
    async with transactional(db):
        msg.tts_audio_urls = urls


async def persist_voice_segment_row(
    db: AsyncSession,
    segment: Segment,
    conversation: Conversation,
) -> None:
    """语音分段入库并刷新会话活跃时间。"""
    async with transactional(db):
        db.add(segment)
        mark_conversation_active(conversation)