from __future__ import annotations

from typing import Any

from .registry import EVOLUTION_DIAL_STEPS, EVOLUTION_GAIN_LIMITS
from .schemas import ClassEvolution, GeneratedSkillSpec


EVOLUTION_BUDGETS = {1: 3, 2: 4}


def dial_change_cost(dial: str, delta: float) -> int:
    options = EVOLUTION_DIAL_STEPS.get(dial)
    if not options:
        raise ValueError(f"{dial} is not an approved evolution dial")
    for approved_delta, cost in options.items():
        if abs(float(delta) - approved_delta) < 1e-6:
            return cost
    approved = ", ".join(f"{value:g}" for value in options)
    raise ValueError(f"{dial} delta must be one of: {approved}")


def validate_evolution_rules(
    evolution: ClassEvolution,
    state: dict[str, Any],
    stage: int,
) -> None:
    if stage not in EVOLUTION_BUDGETS:
        raise ValueError("evolution stage must be 1 or 2")
    budget = sum(
        dial_change_cost(change.dial, change.delta)
        for change in evolution.dial_changes
    )
    if budget > EVOLUTION_BUDGETS[stage]:
        raise ValueError(
            f"evolution {stage} uses {budget} dial points; "
            f"the budget is {EVOLUTION_BUDGETS[stage]}"
        )

    changes = {change.dial: float(change.delta) for change in evolution.dial_changes}
    if "global_dmg_mult" in changes and "crit_multiplier_dial" in changes:
        raise ValueError("global damage and critical multiplier cannot grow together")
    if "max_ap_bonus" in changes and "ap_regen_bonus" in changes:
        raise ValueError("maximum AP and AP regeneration cannot grow together")
    if "ap_regen_bonus" in changes and stage != 2:
        raise ValueError("AP regeneration is only available at Evolution 2")

    previous_specials = set(state.get("evolution_special_dials", []))
    if "max_ap_bonus" in changes and "max_ap_bonus" in previous_specials:
        raise ValueError("maximum AP may increase only once per run")
    if "ap_regen_bonus" in changes and "ap_regen_bonus" in previous_specials:
        raise ValueError("AP regeneration may increase only once per run")
    if (
        ("max_ap_bonus" in changes and "ap_regen_bonus" in previous_specials)
        or ("ap_regen_bonus" in changes and "max_ap_bonus" in previous_specials)
    ):
        raise ValueError("maximum AP and AP regeneration cannot both grow in one run")

    current_gains = state.get("evolution_dial_gains", {})
    for dial, delta in changes.items():
        ceiling = EVOLUTION_GAIN_LIMITS[dial]
        if float(current_gains.get(dial, 0.0)) + delta > ceiling + 1e-6:
            raise ValueError(f"{dial} exceeds its cumulative evolution ceiling")

    signature: GeneratedSkillSpec | None = evolution.signature_skill
    if (
        signature is not None
        and signature.effect_id == "heavy_damage"
        and signature.base_power > 17
        and ({"global_dmg_mult", "crit_multiplier_dial"} & changes.keys())
    ):
        raise ValueError(
            "a heavy signature above 17 cannot also grow global damage "
            "or critical multiplier"
        )