"""转写管线编排：提取音频 → ASR → 断句 → 翻译 → 写 SRT。

任务状态机：
    queued → extracting → transcribing → segmenting → translating → done
    任一步失败 → failed

模型不共驻：ASR 与翻译分阶段加载，翻译时先卸载 Whisper 释放显存跑大 batch。
管线在后台线程跑（每个任务一个线程），通过 DB 更新状态与进度。
"""

from __future__ import annotations

import logging
import threading
import traceback
from datetime import datetime, timezone
from pathlib import Path

from ..config import get_settings
from ..database import get_session_local
from ..models.task import Task
from . import ffmpeg_service, asr_service, segmenter, translate_service, srt_writer
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


def enqueue_task(task_id: int) -> None:
    """把任务交给后台线程处理（非阻塞，供 upload_service.complete 调用）。"""
    t = threading.Thread(target=_run_task, args=(task_id,), daemon=True)
    t.start()
    logger.info("任务 %d 已入队（后台线程 %s）。", task_id, t.name)


def _run_task(task_id: int) -> None:
    """后台执行完整管线。所有异常都被捕获并写入 task.error。"""
    db = get_session_local()()
    try:
        task = db.get(Task, task_id)
        if task is None:
            logger.error("任务 %d 不存在。", task_id)
            return
        _pipeline(db, task)
    except Exception as exc:
        logger.exception("任务 %d 失败：%s", task_id, exc)
        _mark_failed(db, task_id, str(exc))
    finally:
        db.close()


def _pipeline(db, task: Task) -> None:
    s = get_settings()
    src = s.upload_dir() / task.source_path

    # ---------- 1. 提取音频 ----------
    _set_status(db, task, "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)

    # ---------- 2. 语音识别 ----------
    _set_status(db, task, "transcribing", P_TRANSCRIBE_START)
    segments = asr_service.transcribe(wav)
    _set_status(db, task, "transcribing", P_TRANSCRIBE_END,
                note=f"识别出 {len(segments)} 段")

    # ---------- 3. 断句 + 时间戳重算 ----------
    _set_status(db, task, "segmenting", P_SEGMENT_START)
    subs = segmenter.resegment(segments)
    _set_status(db, task, "segmenting", P_SEGMENT_END,
                note=f"重组为 {len(subs)} 条字幕")

    # ---------- 4. 翻译 ----------
    _set_status(db, task, "translating", P_TRANSLATE_START)
    # 翻译阶段：model_manager 会自动卸载 ASR、加载翻译器（独占显存）
    zh_texts = translate_service.translate(subs)
    _set_status(db, task, "translating", P_TRANSLATE_END,
                note=f"翻译 {len(zh_texts)} 条")

    # ---------- 5. 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)
    # 中文 SRT（用译文 + 同时间戳）
    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)

    # 记录相对路径
    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 = "done"
    task.progress = P_DONE
    task.updated_at = datetime.now(timezone.utc)
    db.commit()

    # 清理中间音频
    if not s.processing.keep_audio and wav.is_file():
        try:
            wav.unlink()
        except OSError:
            pass

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


# ---------------- DB 状态更新 ----------------

def _set_status(db, task: Task, status: str, progress: float, note: str = "") -> None:
    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.info("任务 %d [%s %.0f%%]", task.id, status, progress)


def _mark_failed(db, task_id: int, error: str) -> None:
    try:
        task = db.get(Task, task_id)
        if task is None:
            return
        task.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())