import uuid
from datetime import datetime
from typing import AsyncGenerator

from sqlalchemy import Column, String, Boolean, DateTime, ForeignKey, Text, select
from sqlalchemy.dialects.postgresql import UUID
from sqlalchemy.ext.asyncio import create_async_engine, async_sessionmaker, AsyncSession
from sqlalchemy.orm import DeclarativeBase

from app.config import settings

# Create async engine
engine = create_async_engine(settings.DATABASE_URL, echo=False)

# Create session factory
SessionLocal = async_sessionmaker(
    bind=engine,
    class_=AsyncSession,
    expire_on_commit=False,
    autocommit=False,
    autoflush=False
)

class Base(DeclarativeBase):
    pass

class User(Base):
    __tablename__ = "users"

    id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
    email = Column(String, unique=True, index=True, nullable=False)
    name = Column(String, nullable=True)
    oauth_token_encrypted = Column(Text, nullable=True)
    hashed_password = Column(String, nullable=True)
    created_at = Column(DateTime, default=datetime.utcnow, nullable=False)

class Email(Base):
    __tablename__ = "emails"

    id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
    user_id = Column(UUID(as_uuid=True), ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
    gmail_message_id = Column(String, unique=True, index=True, nullable=True)
    subject = Column(String, nullable=True)
    sender = Column(String, nullable=False)
    received_at = Column(DateTime, default=datetime.utcnow, nullable=False)
    category = Column(String, default="personal", nullable=False)  # urgent, personal, invoice, newsletter
    is_read = Column(Boolean, default=False, nullable=False)
    is_starred = Column(Boolean, default=False, nullable=False)
    thread_id = Column(String, nullable=True)
    has_attachment = Column(Boolean, default=False, nullable=False)

class AgentRun(Base):
    __tablename__ = "agent_runs"

    id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
    user_id = Column(UUID(as_uuid=True), ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
    email_id = Column(UUID(as_uuid=True), ForeignKey("emails.id", ondelete="CASCADE"), nullable=True, index=True)
    action_type = Column(String, nullable=False)  # TRIAGE | SUMMARIZE | DRAFT | TASK_EXTRACTION
    status = Column(String, default="PENDING", nullable=False)  # PENDING | RUNNING | COMPLETED | FAILED
    started_at = Column(DateTime, default=datetime.utcnow, nullable=False)
    completed_at = Column(DateTime, nullable=True)
    celery_task_id = Column(String, nullable=True)

class Followup(Base):
    __tablename__ = "followups"

    id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
    user_id = Column(UUID(as_uuid=True), ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
    email_id = Column(UUID(as_uuid=True), ForeignKey("emails.id", ondelete="CASCADE"), nullable=False, index=True)
    due_at = Column(DateTime, nullable=False)
    message = Column(Text, nullable=False)
    status = Column(String, default="PENDING", nullable=False)  # PENDING | COMPLETED

async def init_db() -> None:
    """Initialize tables in the database."""
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)

async def get_db() -> AsyncGenerator[AsyncSession, None]:
    """Dependency for getting async db sessions in routes."""
    async with SessionLocal() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()