"""Auxiliary diesel generator model with spool dynamics."""

from __future__ import annotations

from dataclasses import dataclass
import logging

from . import constants

LOGGER = logging.getLogger(__name__)


@dataclass
class GeneratorState:
    running: bool
    starting: bool
    spool_remaining: float
    power_output_mw: float
    battery_charge: float


@dataclass
class DieselGenerator:
    rated_output_mw: float = 50.0
    spool_time: float = constants.GENERATOR_SPOOL_TIME

    def start(self, state: GeneratorState) -> None:
        if state.running or state.starting:
            return
        if state.battery_charge <= 0.05:
            LOGGER.warning("Generator start failed: insufficient battery")
            return
        state.starting = True
        state.spool_remaining = self.spool_time
        LOGGER.info("Generator starting (spool %.0fs)", self.spool_time)

    def stop(self, state: GeneratorState) -> None:
        if not (state.running or state.starting):
            return
        state.running = False
        state.starting = False
        state.spool_remaining = 0.0
        state.power_output_mw = 0.0
        LOGGER.info("Generator stopped")

    def step(self, state: GeneratorState, load_demand_mw: float, dt: float) -> float:
        """Advance generator dynamics and return delivered power."""
        if state.starting:
            state.spool_remaining = max(0.0, state.spool_remaining - dt)
            state.power_output_mw = self.rated_output_mw * (1.0 - state.spool_remaining / max(self.spool_time, 1e-6))
            if state.spool_remaining <= 0.0:
                state.starting = False
                state.running = True
                LOGGER.info("Generator online at %.1f MW", self.rated_output_mw)
        elif state.running:
            available = self.rated_output_mw
            state.power_output_mw = min(available, load_demand_mw)
        else:
            state.power_output_mw = 0.0

        if state.running:
            state.battery_charge = min(1.0, state.battery_charge + 0.02 * dt)
        elif state.starting:
            state.battery_charge = max(0.0, state.battery_charge - 0.01 * dt)
        else:
            state.battery_charge = max(0.0, state.battery_charge - 0.001 * dt)

        return state.power_output_mw