"""
Session Models for Breakpilot Agents

Data classes for agent sessions, checkpoints, and state tracking.
"""

from dataclasses import dataclass, field
from datetime import datetime, timezone, timedelta
from typing import Dict, Any, Optional, List
from enum import Enum
import uuid
import logging

logger = logging.getLogger(__name__)


class SessionState(Enum):
    """Agent session states"""
    ACTIVE = "active"
    PAUSED = "paused"
    COMPLETED = "completed"
    FAILED = "failed"


@dataclass
class SessionCheckpoint:
    """Represents a checkpoint in an agent session"""
    name: str
    timestamp: datetime
    data: Dict[str, Any]

    def to_dict(self) -> Dict[str, Any]:
        return {
            "name": self.name,
            "timestamp": self.timestamp.isoformat(),
            "data": self.data
        }

    @classmethod
    def from_dict(cls, data: Dict[str, Any]) -> "SessionCheckpoint":
        return cls(
            name=data["name"],
            timestamp=datetime.fromisoformat(data["timestamp"]),
            data=data["data"]
        )


@dataclass
class AgentSession:
    """
    Represents an active agent session.

    Attributes:
        session_id: Unique session identifier
        agent_type: Type of agent (tutor, grader, quality-judge, alert, orchestrator)
        user_id: Associated user ID
        state: Current session state
        created_at: Session creation timestamp
        last_heartbeat: Last heartbeat timestamp
        context: Session context data
        checkpoints: List of session checkpoints for recovery
    """
    session_id: str = field(default_factory=lambda: str(uuid.uuid4()))
    agent_type: str = ""
    user_id: str = ""
    state: SessionState = SessionState.ACTIVE
    created_at: datetime = field(default_factory=lambda: datetime.now(timezone.utc))
    last_heartbeat: datetime = field(default_factory=lambda: datetime.now(timezone.utc))
    context: Dict[str, Any] = field(default_factory=dict)
    checkpoints: List[SessionCheckpoint] = field(default_factory=list)
    metadata: Dict[str, Any] = field(default_factory=dict)

    def checkpoint(self, name: str, data: Dict[str, Any]) -> SessionCheckpoint:
        """
        Creates a checkpoint for recovery.

        Args:
            name: Checkpoint name (e.g., "task_received", "processing_complete")
            data: Checkpoint data to store

        Returns:
            The created checkpoint
        """
        checkpoint = SessionCheckpoint(
            name=name,
            timestamp=datetime.now(timezone.utc),
            data=data
        )
        self.checkpoints.append(checkpoint)
        logger.debug(f"Session {self.session_id}: Checkpoint '{name}' created")
        return checkpoint

    def heartbeat(self) -> None:
        """Updates the heartbeat timestamp"""
        self.last_heartbeat = datetime.now(timezone.utc)

    def pause(self) -> None:
        """Pauses the session"""
        self.state = SessionState.PAUSED
        self.checkpoint("session_paused", {"previous_state": "active"})

    def resume(self) -> None:
        """Resumes a paused session"""
        if self.state == SessionState.PAUSED:
            self.state = SessionState.ACTIVE
            self.heartbeat()
            self.checkpoint("session_resumed", {})

    def complete(self, result: Optional[Dict[str, Any]] = None) -> None:
        """Marks the session as completed"""
        self.state = SessionState.COMPLETED
        self.checkpoint("session_completed", {"result": result or {}})

    def fail(self, error: str, error_details: Optional[Dict[str, Any]] = None) -> None:
        """Marks the session as failed"""
        self.state = SessionState.FAILED
        self.checkpoint("session_failed", {
            "error": error,
            "details": error_details or {}
        })

    def get_last_checkpoint(self, name: Optional[str] = None) -> Optional[SessionCheckpoint]:
        """
        Gets the last checkpoint, optionally filtered by name.

        Args:
            name: Optional checkpoint name to filter by

        Returns:
            The last matching checkpoint or None
        """
        if not self.checkpoints:
            return None

        if name:
            matching = [cp for cp in self.checkpoints if cp.name == name]
            return matching[-1] if matching else None

        return self.checkpoints[-1]

    def get_duration(self) -> timedelta:
        """Returns the session duration"""
        end_time = datetime.now(timezone.utc)
        if self.state in (SessionState.COMPLETED, SessionState.FAILED):
            last_cp = self.get_last_checkpoint()
            if last_cp:
                end_time = last_cp.timestamp
        return end_time - self.created_at

    def to_dict(self) -> Dict[str, Any]:
        """Serializes the session to a dictionary"""
        return {
            "session_id": self.session_id,
            "agent_type": self.agent_type,
            "user_id": self.user_id,
            "state": self.state.value,
            "created_at": self.created_at.isoformat(),
            "last_heartbeat": self.last_heartbeat.isoformat(),
            "context": self.context,
            "checkpoints": [cp.to_dict() for cp in self.checkpoints],
            "metadata": self.metadata
        }

    @classmethod
    def from_dict(cls, data: Dict[str, Any]) -> "AgentSession":
        """Deserializes a session from a dictionary"""
        return cls(
            session_id=data["session_id"],
            agent_type=data["agent_type"],
            user_id=data["user_id"],
            state=SessionState(data["state"]),
            created_at=datetime.fromisoformat(data["created_at"]),
            last_heartbeat=datetime.fromisoformat(data["last_heartbeat"]),
            context=data.get("context", {}),
            checkpoints=[
                SessionCheckpoint.from_dict(cp)
                for cp in data.get("checkpoints", [])
            ],
            metadata=data.get("metadata", {})
        )