from __future__ import annotations

from decimal import Decimal
import uuid
from enum import Enum

from sqlalchemy import (
    JSON,
    Enum as SqlEnum,
    ForeignKey,
    Integer,
    Numeric,
    String,
    Text,
    UniqueConstraint,
)
from sqlalchemy.dialects.postgresql import JSONB, UUID
from sqlalchemy.orm import Mapped, mapped_column

from core.db.base import Base, SoftDeleteMixin, TimestampMixin


class AgentChatMessageRole(str, Enum):
    USER = "user"
    ASSISTANT = "assistant"
    SYSTEM = "system"
    TOOL = "tool"


class AgentChatMessage(TimestampMixin, SoftDeleteMixin, Base):
    __tablename__: str = "messages"
    __table_args__: tuple[UniqueConstraint] = (
        UniqueConstraint("session_id", "seq", name="uq_messages_session_seq"),
    )

    id: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True), primary_key=True, default=uuid.uuid4
    )
    session_id: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("sessions.id", ondelete="CASCADE"),
        nullable=False,
        index=True,
    )
    seq: Mapped[int] = mapped_column(Integer, nullable=False)
    role: Mapped[AgentChatMessageRole] = mapped_column(
        SqlEnum(
            AgentChatMessageRole, name="agent_chat_message_role", native_enum=False
        ),
        nullable=False,
    )
    content: Mapped[str] = mapped_column(Text, nullable=False)
    model_code: Mapped[str | None] = mapped_column(String(50), nullable=True)
    tool_name: Mapped[str | None] = mapped_column(String(100), nullable=True)
    input_tokens: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
    output_tokens: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
    cost: Mapped[Decimal] = mapped_column(Numeric(12, 6), nullable=False, default=0)
    currency: Mapped[str] = mapped_column(String(3), nullable=False, default="USD")
    latency_ms: Mapped[int | None] = mapped_column(Integer, nullable=True)
    metadata_json: Mapped[dict[str, object] | None] = mapped_column(
        "metadata", JSON().with_variant(JSONB, "postgresql"), nullable=True
    )