audio2text/app/services/pipeline.py

"""转写管线各阶段：提取音频 → ASR → 断句 → 翻译 → 写 SRT。

阶段拆分供 scheduler 调度：ffmpeg 阶段独立线程（CPU），GPU 阶段（ASR+翻译）
由 scheduler 串行化并在切换模型前查队列复用已加载模型。

每个阶段函数接收 db Session + Task，更新状态/进度，写入中间产物：
    extract_phase:  queued → extracting → (写 wav_path, status 置 transcribing)
    asr_phase:      transcribing → segmenting → (写 segments_json, status 置 translating)
    translate_phase: translating → done (写 SRT)

阶段间传递的中间数据存在 Task.wav_path / Task.segments_json，避免跨线程传对象。
"""

from __future__ import annotations

import json
import logging
import traceback
from dataclasses import asdict
from datetime import datetime, timezone
from pathlib import Path

from ..config import get_settings
from ..models.task import (
    STATUS_EXTRACTING, STATUS_TRANSCRIBING, STATUS_SEGMENTING,
    STATUS_TRANSLATING, STATUS_DONE, STATUS_FAILED,
)
from . import asr_service, ffmpeg_service, segmenter, srt_writer, translate_service
from .types import Subtitle

logger = logging.getLogger("audio2text.pipeline")

# 进度锚点（各阶段在 0-100 中的占比）
P_EXTRACT = 5.0
P_TRANSCRIBE_START = 5.0
P_TRANSCRIBE_END = 55.0
P_SEGMENT_START = 55.0
P_SEGMENT_END = 60.0
P_TRANSLATE_START = 60.0
P_TRANSLATE_END = 98.0
P_DONE = 100.0


# ---------------- 阶段 1：提取音频（CPU，可并行）----------------

def extract_phase(db, task) -> None:
    """ffmpeg 提取 16k mono wav，写 task.wav_path，状态置 transcribing。

    由 scheduler 在独立线程调用（与 GPU 阶段并行）。提取完即可让 GPU 调度线程接管。
    """
    s = get_settings()
    src = s.upload_dir() / task.source_path
    logger.info("任务 %d [音频提取开始] %s", task.id, src.name)
    _set_status(db, task, STATUS_EXTRACTING, P_EXTRACT)
    wav = s.work_dir() / f"task_{task.id}.wav"
    ffmpeg_service.extract_audio(src, wav)

    # 按配置决定是否删原始视频（提取成功后）
    if s.processing.delete_original_after_extract and src.is_file():
        try:
            src.unlink()
            logger.info("已删除原始视频 %s（delete_original_after_extract=true）。", src.name)
        except OSError as exc:
            logger.warning("删除原始视频失败 %s: %s", src, exc)

    # 记录 wav 路径，状态置 transcribing（待 GPU 调度线程接管 ASR）
    task.wav_path = str(wav)
    task.status = STATUS_TRANSCRIBING
    task.progress = P_TRANSCRIBE_START
    task.updated_at = datetime.now(timezone.utc)
    db.commit()
    logger.info("任务 %d [音频提取完成] → 待 ASR：%s", task.id, wav.name)


# ---------------- 阶段 2：ASR + 断句（GPU）----------------

def asr_phase(db, task) -> None:
    """加载 Whisper 转写 + 断句，写 task.segments_json，状态置 translating。

    由 GPU 调度线程调用。model_manager 保证 ASR 与翻译器不共驻。
    """
    wav_path = Path(task.wav_path) if task.wav_path else None
    if wav_path is None or not wav_path.is_file():
        raise FileNotFoundError(f"音频不存在：{wav_path}（task {task.id}）")

    logger.info("任务 %d [ASR 开始] %s", task.id, wav_path.name)
    _set_status(db, task, STATUS_TRANSCRIBING, P_TRANSCRIBE_START)
    segments = asr_service.transcribe(wav_path)
    _set_status(db, task, STATUS_TRANSCRIBING, P_TRANSCRIBE_END,
                note=f"识别出 {len(segments)} 段")

    _set_status(db, task, STATUS_SEGMENTING, P_SEGMENT_START)
    subs = segmenter.resegment(segments)
    _set_status(db, task, STATUS_SEGMENTING, P_SEGMENT_END,
                note=f"重组为 {len(subs)} 条字幕")

    # 序列化断句结果供翻译阶段用（dataclass → JSON）
    task.segments_json = json.dumps([asdict(s) for s in subs], ensure_ascii=False)
    task.status = STATUS_TRANSLATING
    task.progress = P_TRANSLATE_START
    task.updated_at = datetime.now(timezone.utc)
    db.commit()
    logger.info("任务 %d [ASR 完成] → 待翻译：%d 条字幕", task.id, len(subs))


# ---------------- 阶段 3：翻译 + 写 SRT（GPU）----------------

def translate_phase(db, task) -> None:
    """加载 NLLB 翻译 + 写 SRT，状态置 done。由 GPU 调度线程调用。"""
    if not task.segments_json:
        raise ValueError(f"任务 {task.id} 无 segments_json，无法翻译")

    logger.info("任务 %d [翻译开始] %d 条字幕", task.id, len(json.loads(task.segments_json)))
    _set_status(db, task, STATUS_TRANSLATING, P_TRANSLATE_START)
    subs = [_dict_to_subtitle(d) for d in json.loads(task.segments_json)]

    zh_texts = translate_service.translate(subs)
    _set_status(db, task, STATUS_TRANSLATING, P_TRANSLATE_END,
                note=f"翻译 {len(zh_texts)} 条")

    # 写 SRT
    out_dir = s_output_dir()
    stem = Path(task.filename).stem
    en_path = out_dir / f"task_{task.id}/{stem}.en.srt"
    zh_path = out_dir / f"task_{task.id}/{stem}.zh.srt"
    bi_path = out_dir / f"task_{task.id}/{stem}.srt"

    srt_writer.write_srt(subs, en_path)
    zh_subs = [Subtitle(text=zh, start=sub.start, end=sub.end)
               for zh, sub in zip(zh_texts, subs)]
    srt_writer.write_srt(zh_subs, zh_path)
    srt_writer.write_bilingual_srt(subs, zh_texts, bi_path)

    task.en_srt_path = str(en_path.relative_to(out_dir))
    task.zh_srt_path = str(zh_path.relative_to(out_dir))
    task.bilingual_srt_path = str(bi_path.relative_to(out_dir))
    task.status = STATUS_DONE
    task.progress = P_DONE
    task.updated_at = datetime.now(timezone.utc)
    db.commit()

    # 清理中间音频
    s = get_settings()
    if not s.processing.keep_audio and task.wav_path:
        try:
            Path(task.wav_path).unlink()
        except OSError:
            pass

    logger.info("任务 %d [完成] %s", task.id, bi_path.name)


# ---------------- 工具函数 ----------------

def s_output_dir() -> Path:
    return get_settings().output_dir()


def _dict_to_subtitle(d: dict) -> Subtitle:
    return Subtitle(text=d["text"], start=d["start"], end=d["end"])


def _set_status(db, task, status: str, progress: float, note: str = "") -> None:
    """更新任务状态/进度并落库。

    日志级别策略：
    - 带 note 的（如“识别出 N 段”）是阶段内里程碑 → INFO
    - 仅进度百分比更新（同状态同阶段）→ DEBUG，避免 INFO 被进度刷屏
    """
    task.status = status
    task.progress = progress
    task.updated_at = datetime.now(timezone.utc)
    db.commit()
    if note:
        logger.info("任务 %d [%s %.0f%%] %s", task.id, status, progress, note)
    else:
        logger.debug("任务 %d [%s %.0f%%]", task.id, status, progress)


def mark_failed(db, task_id: int, error: str) -> None:
    """标记任务失败（对外公开，供 scheduler 调用）。"""
    from ..models.task import Task
    try:
        task = db.get(Task, task_id)
        if task is None:
            return
        task.status = STATUS_FAILED
        task.error = error[:2000]
        task.updated_at = datetime.now(timezone.utc)
        db.commit()
    except Exception:  # pragma: no cover
        logger.error("写入失败状态时又失败：\n%s", traceback.format_exc())