physix/models.py

"""Pydantic schemas + constants. Behaviour lives elsewhere."""

from __future__ import annotations

from typing import Any

from pydantic import BaseModel, ConfigDict, Field

from openenv.core.env_server import Action, Observation, State


#: Per-episode turn budget. Episodes terminate earlier if r_match crosses
#: :data:`CONVERGENCE_THRESHOLD`.
DEFAULT_MAX_TURNS: int = 8
CONVERGENCE_THRESHOLD: float = 0.93

#: Reward component weights. Ablations only edit this dict.
REWARD_WEIGHTS: dict[str, float] = {
    "match": 0.5,
    "progress": 0.2,
    "simplicity": 0.2,
    "format": 0.1,
}


class PhysiXAction(Action):
    """One agent step.

    Fields have defaults so tests can construct partial actions, and so
    the env can fabricate a ``format=0`` no-op action for completions
    that fail to parse JSON. The LLM is expected to fill all three;
    an empty string / dict is fine when irrelevant.
    """

    equation: str = Field(default="", description="ODE in the verifier DSL")
    params: dict[str, float] = Field(
        default_factory=dict,
        description="Numerical substitutions for free symbols on the RHS",
    )
    rationale: str = Field(default="")


class PhysiXObservation(Observation):
    """What the agent sees per step. Inherits ``done`` / ``reward`` from
    :class:`openenv.core.env_server.Observation`."""

    trajectory: list[dict[str, float]] = Field(
        default_factory=list,
        description="Observed (noisy) trajectory as list of timestep dicts",
    )
    state_variables: list[str] = Field(
        default_factory=list,
        description="Names of state-variable keys present in trajectory[i] (excluding t)",
    )
    hint: str = Field(default="", description="One-sentence physical-context string")
    history: list[dict[str, Any]] = Field(
        default_factory=list,
        description="Prior turns surfaced back so the agent can refine",
    )
    mismatch_summary: str = Field(
        default="",
        description="English description of where last prediction diverged",
    )
    turn: int = Field(default=0, ge=0, description="0-indexed turn counter")
    turn_remaining: int = Field(
        default=DEFAULT_MAX_TURNS,
        ge=0,
        description="Turns left in the episode budget",
    )
    system_id: str = Field(default="", description="Stable id of underlying system")
    stats: dict[str, float] = Field(
        default_factory=dict, description="Aggregate trajectory statistics"
    )
    reward_breakdown: dict[str, float] = Field(
        default_factory=dict,
        description="Four reward components from the previous step",
    )


class PhysiXState(State):
    """Episode-level state. The ground-truth equation lives here for logging;
    it is *never* surfaced to the agent. ``last_reward_total`` feeds the
    per-turn ``progress`` reward delta."""

    system_id: str = Field(default="")
    ground_truth_equation: str = Field(default="")
    ground_truth_params: dict[str, float] = Field(default_factory=dict)
    last_reward_total: float = Field(default=0.0)
    last_r_match: float = Field(default=0.0)
    converged: bool = Field(default=False)
    max_turns: int = Field(default=DEFAULT_MAX_TURNS, ge=1)


class HistoryEntry(BaseModel):
    """One previous turn, surfaced back to the agent on the next step."""

    model_config = ConfigDict(extra="forbid")

    turn: int
    equation: str
    params: dict[str, float]
    reward_total: float
    reward_components: dict[str, float]
    mismatch_summary: str

    def as_dict(self) -> dict[str, Any]:
        return {
            "turn": self.turn,
            "equation": self.equation,
            "params": self.params,
            "reward_total": round(self.reward_total, 4),
            "reward_components": {
                k: round(v, 4) for k, v in self.reward_components.items()
            },
            "mismatch_summary": self.mismatch_summary,
        }


class RewardBreakdown(BaseModel):
    """4-component reward, each in ``[0, 1]``. ``total`` is the weighted sum
    using :data:`REWARD_WEIGHTS`."""

    model_config = ConfigDict(extra="forbid")

    match: float = 0.0
    progress: float = 0.0
    simplicity: float = 0.0
    format: float = 0.0
    total: float = 0.0

    def as_dict(self) -> dict[str, float]:
        return {
            "match": self.match,
            "progress": self.progress,
            "simplicity": self.simplicity,
            "format": self.format,
            "total": self.total,
        }