"""Session state and conversation history manager."""

from datetime import UTC, datetime

from app.models.config import AppConfig
from app.models.message import Message
from app.utils.token_counter import TokenCounter


class SessionContext:
    """In-memory conversation state manager.

    Tracks conversation history, token usage estimates, and session metadata.
    """

    def __init__(self, config: AppConfig) -> None:
        """Initialize session context.

        Args:
            config: Application configuration.
        """
        self._config = config
        self._history: list[Message] = []
        self._token_counter = TokenCounter(config.agent.max_conversation_tokens)
        self._start_time = datetime.now(UTC)
        self._message_count: int = 0

    def add_message(self, role: str, content: str | None = None, **kwargs: object) -> Message:
        """Create and append a message to conversation history.

        Args:
            role: Message role (system, user, assistant, tool).
            content: Text content of the message.
            **kwargs: Additional Message fields (tool_calls, tool_call_id, name).

        Returns:
            The created Message instance.
        """
        message = Message(role=role, content=content, **kwargs)  # type: ignore[arg-type]
        self._history.append(message)
        self._message_count += 1
        return message

    def get_history(self) -> list[Message]:
        """Return a shallow copy of the conversation history."""
        return list(self._history)

    def clear_history(self) -> None:
        """Clear conversation history and reset counters."""
        self._history.clear()
        self._message_count = 0
        self._token_counter = TokenCounter(self._config.agent.max_conversation_tokens)

    @property
    def estimated_tokens(self) -> int:
        """Estimated token count for the current conversation history."""
        return self._token_counter.estimate_messages_tokens(self._history)

    @property
    def token_counter(self) -> TokenCounter:
        """The token counter instance."""
        return self._token_counter

    @property
    def message_count(self) -> int:
        """Number of messages added to this session."""
        return self._message_count

    @property
    def start_time(self) -> datetime:
        """Session start timestamp (UTC)."""
        return self._start_time