"""运行时配置：所有参数从 config.yaml 读取。

CPU dev / GPU prod 仅靠 device / model / compute_type 三项切换，代码完全不变。
默认值与 config.example.yaml 对齐，确保无 yaml 时也能用最小配置启动。
"""

from __future__ import annotations

import os
from functools import lru_cache
from pathlib import Path

import yaml
from pydantic import BaseModel, Field, field_validator

PROJECT_ROOT = Path(__file__).resolve().parent.parent
DEFAULT_CONFIG_PATH = PROJECT_ROOT / "config.yaml"


class ServerConfig(BaseModel):
    host: str = "0.0.0.0"
    port: int = 8000
    workers: int = 1


class StorageConfig(BaseModel):
    upload_dir: str = "/data/uploads"
    work_dir: str = "/data/.work"
    output_dir: str = "/data/outputs"
    chunk_bytes: int = 1024 * 1024
    chunk_session_ttl_seconds: int = 300
    # 缓存保留：超期任务产物（输出字幕 / 中间音频 / 保留的原始视频）连同 DB 记录一并清理
    cache_retention_days: int = 7
    # 定时清理间隔（小时）：启动时跑一次，之后按此间隔循环
    cache_cleanup_interval_hours: int = 24


class ProcessingConfig(BaseModel):
    delete_original_after_extract: bool = True
    keep_audio: bool = False


class AsrConfig(BaseModel):
    model: str = "tiny.en"       # CPU: tiny.en；GPU: large-v3-turbo
    device: str = "cpu"          # cpu | cuda
    compute_type: str = "int8"   # cpu: int8；gpu: float16
    language: str = "en"
    word_timestamps: bool = True
    vad_filter: bool = True
    batch_size: int = 8          # BatchedInferencePipeline 的音频块批大小；GPU 建议 16
    beam_size: int = 5           # beam search 宽度；GPU turbo 可降到 2 加速（候选数↓ 解码步数↓），质量损失小


class TranslationConfig(BaseModel):
    model: str = "Helsinki-NLP/opus-mt-en-zh"  # CPU: opus-mt（轻量）；GPU: facebook/nllb-200-distilled-1.3B
    device: str = "cpu"          # cpu | cuda
    src_lang: str = "eng_Latn"   # NLLB 语言码：英语
    tgt_lang: str = "zho_Hans"   # NLLB 语言码：简体中文
    batch_size: int = 8          # 排序后单批最大条数；CPU: 8，GPU: 32（显存独占可用大 batch）
    max_length: int = 256        # 单条最大生成 token 数
    sort_by_length: bool = True  # 按句子长度排序后分批，减少批内 padding 浪费（GPU 收益大）


class SegmentationConfig(BaseModel):
    max_words_per_line: int = 14
    max_duration_seconds: float = 7.0
    min_duration_seconds: float = 1.0
    max_chars_per_line: int = 42


class LoggingConfig(BaseModel):
    """日志配置：控制台 + 内存缓冲的最低级别，以及缓冲条数。

    分层语义：
    - debug：进度详情（任务 [status pct%]、转写/翻译逐批统计、ffmpeg 命令）
    - info：任务流转里程碑（音频提取/ASR/翻译 的开始与完成、模型加载与卸载）
    - error：详细错误（完整 traceback，由 logger.exception 自带）
    """

    level: str = "info"            # debug | info | warning | error
    buffer_size: int = 2000        # /logs 页面内存缓冲条数

    @field_validator("level", mode="before")
    @classmethod
    def _normalize_level(cls, v):
        return str(v).lower() if v else "info"


class DocsConfig(BaseModel):
    """/docs Basic Auth 凭据（明文，对齐 server）。"""

    enabled: bool = True
    username: str = "admin"
    password: str = ""
    realm: str = "audio2text docs"

    @field_validator("password", mode="before")
    @classmethod
    def _coerce(cls, v):
        return "" if v is None else str(v)


class Settings(BaseModel):
    server: ServerConfig = ServerConfig()
    storage: StorageConfig = StorageConfig()
    processing: ProcessingConfig = ProcessingConfig()
    asr: AsrConfig = AsrConfig()
    translation: TranslationConfig = TranslationConfig()
    segmentation: SegmentationConfig = SegmentationConfig()
    logging: LoggingConfig = LoggingConfig()
    docs: DocsConfig = DocsConfig()

    def upload_dir(self) -> Path:
        return Path(self.storage.upload_dir)

    def work_dir(self) -> Path:
        return Path(self.storage.work_dir)

    def output_dir(self) -> Path:
        return Path(self.storage.output_dir)


def _load_yaml(path: Path) -> dict:
    if not path.exists():
        raise FileNotFoundError(
            f"未找到配置文件 {path}；请先 cp config.example.yaml config.yaml 并填值。"
        )
    return yaml.safe_load(path.read_text(encoding="utf-8")) or {}


# ---------------- 运行时覆盖 ----------------
# 允许通过设置页修改的配置项（点分路径 -> 类型）。config.yaml 是只读挂载，
# 改它需重启容器；运行时覆盖存 DB，进程重启后自动加载，无需重建镜像。
# 设置页保存时调 save_setting() 写 DB + 清 lru_cache，下次 get_settings() 生效。
_applying_overrides = False  # 防递归标志：_apply_overrides 内部 DB 初始化会回调 get_settings()
_OVERIDEABLE_FIELDS: dict[str, type] = {
    "asr.batch_size": int,
    "asr.beam_size": int,
    "translation.batch_size": int,
    "translation.sort_by_length": bool,
}


def _apply_overrides(settings: Settings) -> Settings:
    """从 DB 读取覆盖值并应用到 Settings 对象。

    在 lru_cache 的 get_settings() 内部调用，保证缓存的对象已含覆盖。
    DB 还没初始化时（首次 import）静默跳过，用 YAML 原值。

    注意：get_session_local() -> get_engine() -> _db_path() -> get_settings()
    会形成递归。用 _applying_overrides 标志阻断：递归调用直接返回当前 settings
    （此时 DB 路径只需 work_dir，无覆盖也无妨）。
    """
    global _applying_overrides
    if _applying_overrides:
        return settings  # 递归调用（_db_path 触发），直接返回 YAML 原值
    _applying_overrides = True
    try:
        from .database import get_session_local
        from .models.setting import Setting
        import json
        db = get_session_local()()
        try:
            rows = db.query(Setting).all()
            overrides = {r.key: r.value for r in rows}
        finally:
            db.close()
        for key, type_ in _OVERIDEABLE_FIELDS.items():
            if key not in overrides:
                continue
            try:
                val = json.loads(overrides[key])
                val = type_(val)
            except (json.JSONDecodeError, ValueError, TypeError):
                continue
            _set_nested(settings, key, val)
    except Exception:
        # DB 未就绪（首次 import 时 database.py 可能还在初始化）-> 跳过，用 YAML 原值
        pass
    finally:
        _applying_overrides = False
    return settings


def _set_nested(settings: Settings, key: str, val) -> None:
    """按点分路径设置嵌套属性，如 'asr.batch_size' -> settings.asr.batch_size"""
    parts = key.split(".")
    obj = settings
    for p in parts[:-1]:
        obj = getattr(obj, p)
    setattr(obj, parts[-1], val)


@lru_cache(maxsize=1)
def get_settings() -> Settings:
    """读取 config.yaml + 应用 DB 覆盖，返回完整 Settings。

    结果被 lru_cache 缓存。修改设置后调 reload_settings() 清缓存，
    下次调用返回含新值的 Settings。
    """
    path = Path(os.getenv("CONFIG_PATH", str(DEFAULT_CONFIG_PATH)))
    settings = Settings.model_validate(_load_yaml(path))
    return _apply_overrides(settings)


def reload_settings() -> Settings:
    """清缓存并重新读取（含 DB 覆盖），供设置页保存后调用。"""
    get_settings.cache_clear()
    return get_settings()


def save_setting(key: str, value) -> None:
    """保存单个配置项覆盖到 DB + 清 lru_cache。

    Args:
        key: 点分路径，必须在 _OVERIDEABLE_FIELDS 中
        value: 要保存的值（自动 JSON 编码）
    """
    import json
    if key not in _OVERIDEABLE_FIELDS:
        raise ValueError(f"不允许修改的配置项：{key}")
    from .database import get_session_local
    from .models.setting import Setting
    type_ = _OVERIDEABLE_FIELDS[key]
    encoded = json.dumps(type_(value))
    db = get_session_local()()
    try:
        row = db.get(Setting, key)
        if row is None:
            row = Setting(key=key, value=encoded)
            db.add(row)
        else:
            row.value = encoded
        db.commit()
    finally:
        db.close()
    # 清缓存，让后续 get_settings() 读到新值
    get_settings.cache_clear()