"""``CERNCollisionEnvironment``: orchestrates simulator + rules + rewards.

This is the OpenEnv-compatible ``Environment`` that the FastAPI app exposes.
It owns one episode at a time:

  reset(seed)  → builds a fresh latent state from a sampled scenario.
  step(action) → validates → generates noisy output → updates state →
                 computes reward → builds the agent observation.
"""

from __future__ import annotations

import logging
import uuid
from typing import Any, List, Optional

from openenv.core.env_server import Environment, State

from models import (
    AGENT_ENVIRONMENT_RULES,
    ActionType,
    CollisionObservation,
    DiscoveryClaim,
    ExperimentAction,
    IntermediateOutput,
    OutputType,
    PipelineStepRecord,
    ResourceUsage,
    TaskSpec,
    build_agent_system_prompt,
)

from server.rewards import (
    RewardWeights,
    compute_step_reward,
    compute_terminal_reward,
)
from server.rules import RulesEngine, ViolationCode
from server.simulator import (
    NoiseModel,
    OutputGenerator,
    TransitionEngine,
    compute_action_cost,
)
from server.simulator.latent_state import FullLatentState
from server.tasks import sample_scenario, Scenario


logger = logging.getLogger(__name__)


# ── State container ──────────────────────────────────────────────────────


class CernState(State):
    """OpenEnv State subclass: includes hidden truth & runtime stats."""

    scenario_name: Optional[str] = None
    difficulty: Optional[str] = None
    episode_done: bool = False
    cumulative_reward: float = 0.0
    terminal_reward: Optional[float] = None
    discovered: Optional[bool] = None
    correct_mass: Optional[bool] = None
    correct_channel: Optional[bool] = None
    correct_spin: Optional[bool] = None
    truth_mass_gev: Optional[float] = None
    truth_channel: Optional[str] = None


# ── Environment ──────────────────────────────────────────────────────────


class CERNCollisionEnvironment(Environment[ExperimentAction, CollisionObservation, CernState]):
    """LHC particle-discovery POMDP environment."""

    SUPPORTS_CONCURRENT_SESSIONS = True

    def __init__(
        self,
        *,
        max_steps: int = 40,
        default_difficulty: Optional[str] = None,
        default_scenario_name: Optional[str] = None,
        reward_weights: Optional[RewardWeights] = None,
    ) -> None:
        super().__init__()
        self.max_steps = max_steps
        self.default_difficulty = default_difficulty
        self.default_scenario_name = default_scenario_name
        self.reward_weights = reward_weights or RewardWeights()

        self._state = CernState()
        self._scenario: Optional[Scenario] = None
        self._latent: Optional[FullLatentState] = None
        self._task: Optional[TaskSpec] = None
        self._noise: Optional[NoiseModel] = None
        self._output_gen: Optional[OutputGenerator] = None
        self._transition: Optional[TransitionEngine] = None
        self._rules: Optional[RulesEngine] = None
        self._history: List[PipelineStepRecord] = []
        self._all_outputs: List[IntermediateOutput] = []

    # ── Environment API ────────────────────────────────────────────────

    @property
    def state(self) -> CernState:
        return self._state

    def reset(
        self,
        seed: Optional[int] = None,
        episode_id: Optional[str] = None,
        **kwargs: Any,
    ) -> CollisionObservation:
        difficulty = kwargs.get("difficulty") or self.default_difficulty
        scenario_name = kwargs.get("scenario") or self.default_scenario_name

        scenario = sample_scenario(
            difficulty=difficulty,
            name=scenario_name,
            seed=seed,
        )
        self._scenario = scenario
        self._latent = scenario.fresh_latent()
        self._task = scenario.task
        if seed is not None:
            self._latent.rng_seed = int(seed)
        self._noise = NoiseModel(seed=self._latent.rng_seed)
        self._output_gen = OutputGenerator(self._noise)
        self._transition = TransitionEngine()
        self._rules = RulesEngine(
            mass_search_window_gev=tuple(self._task.mass_search_window_gev),
        )
        self._history = []
        self._all_outputs = []

        self._state = CernState(
            episode_id=episode_id or f"ep-{uuid.uuid4().hex[:8]}",
            step_count=0,
            scenario_name=scenario.name,
            difficulty=scenario.difficulty,
            episode_done=False,
            cumulative_reward=0.0,
            truth_mass_gev=self._latent.particle.mass_gev,
            truth_channel=self._latent.particle.primary_channel,
        )

        obs = self._build_observation(
            latest_output=None,
            done=False,
            reward=0.0,
            step_breakdown={},
            rule_violations=[],
        )
        return obs

    def step(
        self,
        action: ExperimentAction,
        timeout_s: Optional[float] = None,
        **kwargs: Any,
    ) -> CollisionObservation:
        if self._latent is None:
            self.reset()
        if self._state.episode_done:
            return self._build_terminal_observation(reason="episode already complete")

        assert self._rules is not None
        assert self._output_gen is not None
        assert self._transition is not None

        prev_state = self._latent.model_copy(deep=True)
        rule_result = self._rules.validate(action, self._latent)

        if not rule_result.allowed:
            output = IntermediateOutput(
                output_type=OutputType.FAILURE_REPORT,
                step_index=self._state.step_count,
                success=False,
                quality_score=0.0,
                summary="Action rejected: " + "; ".join(rule_result.messages),
                warnings=rule_result.messages,
            )
        else:
            output = self._output_gen.generate(
                action=action,
                state=self._latent,
                step_index=self._state.step_count,
            )

        # Apply transition (state mutation + cost accounting)
        if rule_result.allowed:
            self._transition.step(self._latent, action, output)
        else:
            cost = compute_action_cost(action, output)
            self._latent.resources.budget_used_musd += cost["musd"]
            self._latent.resources.time_used_days += cost["days"]
            self._latent.step_count += 1

        self._all_outputs.append(output)
        cost = compute_action_cost(action, output)
        record = PipelineStepRecord(
            step_index=self._state.step_count,
            action_type=action.action_type,
            method=action.method,
            parameters=action.parameters,
            output_summary=output.summary,
            output_type=output.output_type,
            success=output.success,
            quality_score=float(output.quality_score),
            cost_musd=float(cost["musd"]),
            luminosity_cost_fb=float(cost["luminosity_fb"]),
            time_cost_days=float(cost["days"]),
        )
        self._history.append(record)

        step_reward = compute_step_reward(
            action=action,
            output=output,
            state_before=prev_state,
            state_after=self._latent,
            rule_result=rule_result,
            weights=self.reward_weights,
        )

        self._state.cumulative_reward += step_reward.reward
        self._state.step_count += 1

        terminal_now = (
            action.action_type == ActionType.SUBMIT_DISCOVERY_CLAIM
            and rule_result.allowed
        )
        time_up = (
            self._state.step_count >= self.max_steps
            or self._latent.resources.budget_exhausted
            or self._latent.resources.time_exhausted
        )

        terminal_reward_value = 0.0
        if terminal_now:
            claim = self._claim_from_action(action)
            term = compute_terminal_reward(
                state=self._latent,
                claim=claim,
                weights=self.reward_weights,
            )
            terminal_reward_value = term.reward
            self._state.cumulative_reward += terminal_reward_value
            self._state.terminal_reward = terminal_reward_value
            self._state.discovered = term.discovered
            self._state.correct_mass = term.correct_mass
            self._state.correct_channel = term.correct_channel
            self._state.correct_spin = term.correct_spin

        done = terminal_now or time_up
        if done:
            self._state.episode_done = True

        observation = self._build_observation(
            latest_output=output,
            done=done,
            reward=step_reward.reward + terminal_reward_value,
            step_breakdown=step_reward.breakdown.components,
            rule_violations=[
                *(v.value for v in rule_result.violations),
                *(v.value for v in rule_result.soft_violations),
            ],
        )
        return observation

    # ── Helpers ────────────────────────────────────────────────────────

    def _claim_from_action(self, action: ExperimentAction) -> DiscoveryClaim:
        raw = action.parameters.get("claim") or {}
        try:
            return DiscoveryClaim(**raw)
        except Exception as exc:  # pragma: no cover - defensive
            logger.warning("Malformed claim, defaulting: %s", exc)
            return DiscoveryClaim()

    def _build_terminal_observation(self, reason: str) -> CollisionObservation:
        obs = self._build_observation(
            latest_output=IntermediateOutput(
                output_type=OutputType.FAILURE_REPORT,
                step_index=self._state.step_count,
                success=False,
                summary=reason,
            ),
            done=True,
            reward=0.0,
            step_breakdown={},
            rule_violations=["episode_terminated"],
        )
        return obs

    def _build_observation(
        self,
        *,
        latest_output: Optional[IntermediateOutput],
        done: bool,
        reward: float,
        step_breakdown: dict,
        rule_violations: list,
    ) -> CollisionObservation:
        assert self._latent is not None
        assert self._task is not None

        res = self._latent.resources
        usage = ResourceUsage(
            budget_used_musd=res.budget_used_musd,
            budget_remaining_musd=res.budget_remaining,
            luminosity_used_fb=res.luminosity_used_fb,
            luminosity_remaining_fb=res.luminosity_remaining,
            time_used_days=res.time_used_days,
            time_remaining_days=res.time_remaining,
            compute_hours_used=res.compute_hours_used,
        )

        obs = CollisionObservation(
            done=done,
            reward=float(reward),
            task=self._task,
            step_index=self._state.step_count,
            pipeline_history=list(self._history),
            available_channels=self._task.available_channels,
            available_triggers=self._task.available_triggers,
            available_tools=self._task.available_tools,
            resource_usage=usage,
            latest_output=latest_output,
            all_outputs=list(self._all_outputs),
            candidate_masses_gev=list(self._latent.candidate_masses_gev),
            candidate_significances=list(self._latent.candidate_significances),
            selected_channel=self._latent.selected_channel,
            selected_beam_energy=self._latent.selected_beam_energy,
            cumulative_significance=float(
                self._latent.progress.best_significance_sigma or 0.0
            ),
            uncertainty_summary={
                "energy_scale_unc_gev": self._latent.detector.energy_scale_uncertainty,
                "luminosity_unc": self._latent.detector.luminosity_uncertainty,
                "resolution_gev": self._latent.detector.detector_resolution_gev,
            },
            rule_violations=rule_violations,
            step_reward_breakdown=dict(step_breakdown),
        )
        return obs

    # ── Convenience for diagnostics ────────────────────────────────────

    def hidden_truth(self) -> Optional[dict]:
        """Reveal the hidden particle (debug / evaluation only)."""
        if self._latent is None:
            return None
        return self._latent.particle.model_dump()


__all__ = [
    "CernState",
    "CERNCollisionEnvironment",
    "AGENT_ENVIRONMENT_RULES",
    "build_agent_system_prompt",
]