import uuid
from datetime import datetime, timezone
from typing import Optional, Any, TYPE_CHECKING
from sqlalchemy import String, DateTime, ForeignKey, Boolean, Text
import sqlalchemy as sa
from sqlalchemy.orm import Mapped, mapped_column, relationship
from sqlalchemy.dialects.postgresql import UUID, JSONB
from app.core.database import Base

if TYPE_CHECKING:
    from app.models.session_share import SessionShare


class Session(Base):
    __tablename__ = "sessions"

    id: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True),
        primary_key=True,
        default=uuid.uuid4
    )
    tree_id: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("trees.id"),
        nullable=False,
        index=True
    )
    user_id: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("users.id"),
        nullable=False,
        index=True
    )
    tree_snapshot: Mapped[dict[str, Any]] = mapped_column(JSONB, nullable=False)
    path_taken: Mapped[list[str]] = mapped_column(JSONB, nullable=False, default=list)
    decisions: Mapped[list[dict[str, Any]]] = mapped_column(JSONB, nullable=False, default=list)
    custom_steps: Mapped[list[dict[str, Any]]] = mapped_column(JSONB, nullable=False, default=list)
    started_at: Mapped[Optional[datetime]] = mapped_column(
        DateTime(timezone=True),
        nullable=True,
        default=lambda: datetime.now(timezone.utc),
        index=True
    )
    completed_at: Mapped[Optional[datetime]] = mapped_column(
        DateTime(timezone=True),
        nullable=True,
        index=True
    )
    outcome: Mapped[Optional[str]] = mapped_column(String(20), nullable=True, index=True)
    outcome_notes: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
    ticket_number: Mapped[Optional[str]] = mapped_column(String(100), nullable=True)
    client_name: Mapped[Optional[str]] = mapped_column(String(255), nullable=True)
    exported: Mapped[bool] = mapped_column(Boolean, default=False)
    session_variables: Mapped[dict[str, Any]] = mapped_column(
        JSONB, nullable=False, server_default=sa.text("'{}'::jsonb")
    )
    scratchpad: Mapped[Optional[str]] = mapped_column(
        Text, nullable=True, server_default=sa.text("''")
    )
    next_steps: Mapped[Optional[str]] = mapped_column(
        Text, nullable=True, server_default=sa.text("''")
    )

    # Prepared sessions (flexible intake)
    prepared_by_id: Mapped[Optional[uuid.UUID]] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("users.id"),
        nullable=True,
        index=True
    )
    assigned_to_id: Mapped[Optional[uuid.UUID]] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("users.id"),
        nullable=True,
        index=True
    )

    # Relationships
    tree: Mapped["Tree"] = relationship("Tree", back_populates="sessions")
    user: Mapped["User"] = relationship("User", foreign_keys=[user_id], back_populates="sessions")
    prepared_by: Mapped[Optional["User"]] = relationship("User", foreign_keys=[prepared_by_id])
    assigned_to: Mapped[Optional["User"]] = relationship("User", foreign_keys=[assigned_to_id])
    attachments: Mapped[list["Attachment"]] = relationship("Attachment", back_populates="session")
    shares: Mapped[list["SessionShare"]] = relationship("SessionShare", back_populates="session", cascade="all, delete-orphan")

    # Batch tracking (maintenance flows)
    batch_id: Mapped[Optional[uuid.UUID]] = mapped_column(
        UUID(as_uuid=True), nullable=True, index=True
    )
    target_label: Mapped[Optional[str]] = mapped_column(
        String(255), nullable=True
    )