"""Agent model — tracks OpenClaw agents linked to HarborForge users.

An Agent represents an AI agent (identified by its OpenClaw ``agent_id``)
that is bound to exactly one HarborForge User.  The Calendar system uses
Agent status to decide whether to wake an agent for scheduled slots.

See: NEXT_WAVE_DEV_DIRECTION.md §1.4 (Agent table) and §6 (Agent wakeup)
Implements: BE-CAL-003
"""

from sqlalchemy import (
    Column,
    Integer,
    String,
    DateTime,
    Enum,
    ForeignKey,
)
from sqlalchemy.orm import relationship
from sqlalchemy.sql import func
from app.core.config import Base
import enum


# ---------------------------------------------------------------------------
# Enums
# ---------------------------------------------------------------------------

class AgentStatus(str, enum.Enum):
    """Runtime status of an Agent."""
    IDLE = "idle"
    ON_CALL = "on_call"
    BUSY = "busy"
    EXHAUSTED = "exhausted"
    OFFLINE = "offline"


class ExhaustReason(str, enum.Enum):
    """Why an agent entered the Exhausted state."""
    RATE_LIMIT = "rate_limit"
    BILLING = "billing"


# ---------------------------------------------------------------------------
# Agent model
# ---------------------------------------------------------------------------

class Agent(Base):
    """An OpenClaw agent bound to a HarborForge user.

    Fields
    ------
    user_id : int
        One-to-one FK to ``users.id``.  Each user has at most one agent.
    agent_id : str
        The ``$AGENT_ID`` value from OpenClaw (globally unique).
    claw_identifier : str
        The OpenClaw instance identifier (matches ``MonitoredServer.identifier``
        by convention, but has no FK — they are independent concepts).
    status : AgentStatus
        Current runtime status, managed by heartbeat / calendar wakeup logic.
    last_heartbeat : datetime | None
        Timestamp of the most recent heartbeat received from this agent.
    exhausted_at : datetime | None
        When the agent entered the ``EXHAUSTED`` state.
    recovery_at : datetime | None
        Estimated time the agent will recover from ``EXHAUSTED`` → ``IDLE``.
    exhaust_reason : ExhaustReason | None
        Why the agent became exhausted (rate-limit vs billing).
    """

    __tablename__ = "agents"

    id = Column(Integer, primary_key=True, index=True)

    user_id = Column(
        Integer,
        ForeignKey("users.id"),
        nullable=False,
        unique=True,
        index=True,
        comment="1-to-1 link to the owning HarborForge user",
    )

    agent_id = Column(
        String(128),
        nullable=False,
        unique=True,
        index=True,
        comment="OpenClaw $AGENT_ID",
    )

    claw_identifier = Column(
        String(128),
        nullable=False,
        comment="OpenClaw instance identifier (same value as MonitoredServer.identifier by convention)",
    )

    # -- runtime status fields ----------------------------------------------

    status = Column(
        Enum(AgentStatus, values_callable=lambda x: [e.value for e in x]),
        nullable=False,
        default=AgentStatus.IDLE,
        comment="Current agent status: idle | on_call | busy | exhausted | offline",
    )

    last_heartbeat = Column(
        DateTime(timezone=True),
        nullable=True,
        comment="Timestamp of the most recent heartbeat",
    )

    # -- exhausted state detail ---------------------------------------------

    exhausted_at = Column(
        DateTime(timezone=True),
        nullable=True,
        comment="When the agent entered EXHAUSTED state",
    )

    recovery_at = Column(
        DateTime(timezone=True),
        nullable=True,
        comment="Estimated recovery time from EXHAUSTED → IDLE",
    )

    exhaust_reason = Column(
        Enum(ExhaustReason, values_callable=lambda x: [e.value for e in x]),
        nullable=True,
        comment="rate_limit | billing — why the agent is exhausted",
    )

    # -- timestamps ---------------------------------------------------------

    created_at = Column(DateTime(timezone=True), server_default=func.now())

    # -- relationships ------------------------------------------------------

    user = relationship("User", back_populates="agent", uselist=False)