"""Pure-function transition engine.

Given a (latent_state, action, generated_output) triple, produces the next
latent state plus the deltas needed for the agent-visible observation. The
``TransitionEngine`` does **not** generate randomness directly; it consumes
artifacts from the ``OutputGenerator``.
"""

from __future__ import annotations

from dataclasses import dataclass
from typing import Dict

from models import (
    ActionType,
    ExperimentAction,
    IntermediateOutput,
    OutputType,
)

from .latent_state import FullLatentState


# Per-action default cost in (millions of USD, days, compute hours)
ACTION_COSTS: Dict[ActionType, Dict[str, float]] = {
    ActionType.CONFIGURE_BEAM:        {"musd": 0.10, "days": 0.5, "compute": 0.1},
    ActionType.ALLOCATE_LUMINOSITY:   {"musd": 0.05, "days": 0.2, "compute": 0.0},
    ActionType.SET_TRIGGER:           {"musd": 0.05, "days": 0.1, "compute": 0.0},
    ActionType.COLLECT_COLLISIONS:    {"musd": 0.00, "days": 0.0, "compute": 1.0},  # main cost is in luminosity
    ActionType.CALIBRATE_DETECTOR:    {"musd": 0.20, "days": 1.0, "compute": 1.5},
    ActionType.RECONSTRUCT_TRACKS:    {"musd": 0.15, "days": 0.8, "compute": 5.0},
    ActionType.SELECT_CHANNEL:        {"musd": 0.00, "days": 0.05, "compute": 0.0},
    ActionType.BUILD_INVARIANT_MASS:  {"musd": 0.05, "days": 0.3, "compute": 1.0},
    ActionType.SUBTRACT_BACKGROUND:   {"musd": 0.05, "days": 0.3, "compute": 0.5},
    ActionType.FIT_RESONANCE:         {"musd": 0.10, "days": 0.4, "compute": 0.5},
    ActionType.SCAN_BUMP:             {"musd": 0.05, "days": 0.2, "compute": 0.5},
    ActionType.MEASURE_ANGULAR:       {"musd": 0.10, "days": 0.4, "compute": 0.5},
    ActionType.ESTIMATE_SIGNIFICANCE: {"musd": 0.05, "days": 0.1, "compute": 0.2},
    ActionType.REQUEST_SYSTEMATICS:   {"musd": 0.30, "days": 1.5, "compute": 1.0},
    ActionType.REQUEST_THEORY_REVIEW: {"musd": 0.05, "days": 0.5, "compute": 0.0},
    ActionType.SUBMIT_DISCOVERY_CLAIM:{"musd": 0.0,  "days": 0.1, "compute": 0.0},
}


def compute_action_cost(action: ExperimentAction, output: IntermediateOutput) -> Dict[str, float]:
    """Return realised (musd, days, compute_hours, luminosity_fb) for this action."""
    base = ACTION_COSTS.get(action.action_type, {"musd": 0.0, "days": 0.0, "compute": 0.0})
    musd = float(base.get("musd", 0.0))
    days = float(base.get("days", 0.0))
    compute = float(base.get("compute", 0.0))
    lumi_fb = 0.0

    data = output.data or {}
    if action.action_type == ActionType.COLLECT_COLLISIONS:
        lumi_fb = float(data.get("luminosity_fb", 0.0))
        musd += float(data.get("cost_musd", 0.0))
        days += float(data.get("time_days", 0.0))

    return {
        "musd": musd,
        "days": days,
        "compute_hours": compute,
        "luminosity_fb": lumi_fb,
    }


@dataclass
class TransitionResult:
    next_state: FullLatentState
    realised_cost: Dict[str, float]


class TransitionEngine:
    """Applies an action's output to evolve the latent state."""

    def step(
        self,
        state: FullLatentState,
        action: ExperimentAction,
        output: IntermediateOutput,
    ) -> TransitionResult:
        # We mutate the live state in place, then return it. This is fine
        # because the environment owns the only reference.
        cost = compute_action_cost(action, output)
        state.resources.budget_used_musd += cost["musd"]
        state.resources.time_used_days += cost["days"]
        state.resources.compute_hours_used += cost["compute_hours"]
        state.resources.luminosity_used_fb += cost["luminosity_fb"]

        if not output.success:
            state.step_count += 1
            return TransitionResult(next_state=state, realised_cost=cost)

        a = action.action_type
        data = output.data or {}

        if a == ActionType.CONFIGURE_BEAM:
            beam = data.get("beam_energy")
            # latent_state.selected_beam_energy is typed Optional[str] and
            # CollisionObservation re-validates it as a str; LLM completions
            # sometimes emit numeric beam_energy (e.g. 13.0), which would
            # later fail Pydantic string validation in _build_observation.
            # Coerce to str at the source so all downstream consumers
            # (latent state, observation, output_generator) see a string.
            state.selected_beam_energy = str(beam) if beam is not None else None
            state.progress.beam_configured = True

        elif a == ActionType.ALLOCATE_LUMINOSITY:
            state.progress.luminosity_allocated = True

        elif a == ActionType.SET_TRIGGER:
            trig = data.get("trigger")
            state.selected_trigger = trig
            state.progress.trigger_set = True

        elif a == ActionType.COLLECT_COLLISIONS:
            state.progress.collisions_collected = True
            state.progress.n_events_collected += int(
                data.get("n_signal_candidates", 0)
            ) + int(data.get("n_background_estimate", 0))
            state.progress.n_signal_candidates += int(data.get("n_signal_candidates", 0))
            state.progress.n_background_estimate += int(data.get("n_background_estimate", 0))
            state.progress.best_channel = data.get("channel") or state.progress.best_channel
            _be = data.get("beam_energy")
            state.progress.best_beam_energy = (
                (str(_be) if _be is not None else None)
                or state.progress.best_beam_energy
            )

        elif a == ActionType.CALIBRATE_DETECTOR:
            state.progress.detector_calibrated = True
            state.detector.detector_calibrated = True
            improvement = float(data.get("resolution_improvement", 0.0))
            state.detector.detector_resolution_gev = max(
                0.05,
                state.detector.detector_resolution_gev * (1.0 - improvement),
            )

        elif a == ActionType.RECONSTRUCT_TRACKS:
            state.progress.tracks_reconstructed = True
            state.detector.tracker_aligned = True

        elif a == ActionType.SELECT_CHANNEL:
            channel = data.get("channel")
            if channel:
                state.selected_channel = channel
                state.progress.channel_selected = True

        elif a == ActionType.BUILD_INVARIANT_MASS:
            state.progress.invariant_mass_built = True

        elif a == ActionType.SUBTRACT_BACKGROUND:
            state.progress.background_subtracted = True

        elif a == ActionType.FIT_RESONANCE:
            state.progress.resonance_fitted = True
            m = float(data.get("fit_mass_gev", 0.0))
            unc = float(data.get("fit_mass_unc_gev", 0.0))
            w = float(data.get("fit_width_gev", 0.0))
            if m > 0:
                state.candidate_masses_gev.append(m)
                state.candidate_significances.append(0.0)
                state.progress.best_fit_mass_gev = m
                state.progress.best_fit_width_gev = w

        elif a == ActionType.SCAN_BUMP:
            state.progress.bump_scanned = True
            cm = float(data.get("candidate_mass_gev", 0.0))
            if cm > 0:
                state.candidate_masses_gev.append(cm)
                state.candidate_significances.append(0.0)

        elif a == ActionType.MEASURE_ANGULAR:
            state.progress.angular_measured = True

        elif a == ActionType.ESTIMATE_SIGNIFICANCE:
            state.progress.significance_estimated = True
            sig = float(data.get("significance_sigma", 0.0))
            state.progress.best_significance_sigma = max(
                state.progress.best_significance_sigma or 0.0, sig
            )
            if state.candidate_significances:
                state.candidate_significances[-1] = sig

        elif a == ActionType.REQUEST_SYSTEMATICS:
            state.progress.systematics_requested = True
            state.detector.energy_scale_uncertainty *= 0.6
            state.detector.luminosity_uncertainty *= 0.7

        elif a == ActionType.REQUEST_THEORY_REVIEW:
            state.progress.theory_review_requested = True

        elif a == ActionType.SUBMIT_DISCOVERY_CLAIM:
            state.progress.claim_submitted = True

        state.step_count += 1
        return TransitionResult(next_state=state, realised_cost=cost)


__all__ = [
    "ACTION_COSTS",
    "TransitionEngine",
    "TransitionResult",
    "compute_action_cost",
]