from datetime import datetime
import uuid

from sqlalchemy import JSON, Column, DateTime, Float, Integer, String, Text
from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
from sqlalchemy.orm import declarative_base

from app.config import get_settings

settings = get_settings()

Base = declarative_base()

# 延迟创建 engine/session，在首次使用时再实例化
_engine = None
_async_session = None


def _get_engine():
    global _engine
    if _engine is None:
        _engine = create_async_engine(
            settings.database_url,
            echo=settings.backend_env == "development",
            pool_pre_ping=True,
        )
    return _engine


def _get_session():
    global _async_session
    if _async_session is None:
        _async_session = async_sessionmaker(_get_engine(), class_=AsyncSession, expire_on_commit=False)
    return _async_session


# async_session 是 async_sessionmaker 实例，调用它返回 AsyncSession
async_session = _get_session()


async def init_db():
    """创建所有表（首次启动时调用）。"""
    async with _get_engine().begin() as conn:
        await conn.run_sync(Base.metadata.create_all)


class TrainingJobModel(Base):
    __tablename__ = "training_jobs"

    id = Column(String(36), primary_key=True)
    model_id = Column(String(256), nullable=False)
    model_type = Column(String(32), nullable=False)
    dataset_id = Column(String(36), nullable=False)
    peft_method = Column(String(32), nullable=False)
    task_type = Column(String(32), default="sft")
    dataset_template = Column(String(32), default="alpaca")

    status = Column(String(32), default="pending")
    progress = Column(Float, default=0.0)
    current_epoch = Column(Integer, default=0)
    current_step = Column(Integer, default=0)
    total_steps = Column(Integer, default=0)
    loss = Column(Float, nullable=True)
    learning_rate = Column(Float, nullable=True)

    epochs = Column(Integer, default=3)
    batch_size = Column(Integer, default=4)
    gradient_accumulation = Column(Integer, default=4)
    max_seq_length = Column(Integer, default=2048)
    warmup_ratio = Column(Float, default=0.05)
    save_strategy = Column(String(32), default="epoch")
    eval_strategy = Column(String(32), default="epoch")
    eval_steps = Column(Integer, default=100)

    lora_r = Column(Integer, default=16)
    lora_alpha = Column(Integer, default=32)
    lora_dropout = Column(Float, default=0.05)
    lora_target_modules = Column(String(256), default="all-linear")
    qlora_bits = Column(Integer, default=4)

    created_at = Column(DateTime, default=datetime.utcnow)
    started_at = Column(DateTime, nullable=True)
    finished_at = Column(DateTime, nullable=True)
    error_message = Column(Text, nullable=True)
    adapter_path = Column(String(512), nullable=True)


class DatasetRecord(Base):
    __tablename__ = "datasets"

    id = Column(String(36), primary_key=True)
    name = Column(String(256), nullable=False)
    format = Column(String(16), nullable=False)
    record_count = Column(Integer, default=0)
    file_path = Column(String(512), nullable=False)
    created_at = Column(DateTime, default=datetime.utcnow)


class ModelCache(Base):
    __tablename__ = "model_cache"

    id = Column(String(256), primary_key=True)
    name = Column(String(256), nullable=False)
    model_type = Column(String(32), nullable=False)
    path = Column(String(512), nullable=True)
    is_downloaded = Column(Integer, default=0)
    context_length = Column(Integer, nullable=True)
    supported_peft_methods = Column(String(256), default="")
    created_at = Column(DateTime, default=datetime.utcnow)


class EvalResultModel(Base):
    __tablename__ = "eval_results"

    id = Column(String(36), primary_key=True)
    job_id = Column(String(36), nullable=False)
    metrics = Column(Text, default="{}")
    created_at = Column(DateTime, default=datetime.utcnow)


class DeployTaskModel(Base):
    __tablename__ = "deploy_tasks"

    id = Column(String(36), primary_key=True)
    job_id = Column(String(36), nullable=False)
    status = Column(String(32), default="pending")
    output_path = Column(String(512), nullable=True)
    error = Column(Text, nullable=True)
    created_at = Column(DateTime, default=datetime.utcnow)


class UserModel(Base):
    __tablename__ = "users"

    id = Column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
    username = Column(String(128), unique=True, nullable=False, index=True)
    email = Column(String(256), nullable=True)
    real_name = Column(String(128), nullable=True)
    avatar_url = Column(String(512), nullable=True)
    company = Column(String(128), nullable=True)
    department = Column(String(128), nullable=True)
    position = Column(String(128), nullable=True)
    roles = Column(JSON, default=list)
    is_active = Column(Integer, default=1, nullable=False)
    is_superuser = Column(Integer, default=0, nullable=False)
    created_at = Column(DateTime, default=datetime.utcnow)
    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)


class RefreshTokenModel(Base):
    __tablename__ = "refresh_tokens"

    id = Column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
    user_id = Column(String(36), nullable=False, index=True)
    token = Column(String(512), unique=True, nullable=False, index=True)
    expires_at = Column(DateTime, nullable=False)
    revoked = Column(Integer, default=0, nullable=False)
    created_at = Column(DateTime, default=datetime.utcnow)


async def get_db() -> AsyncSession:
    async with async_session() as session:
        yield session