"""Defines and samples the render-spec search space."""

from __future__ import annotations

import random
from dataclasses import replace

from veil_pgd.config import OptimizerConfig
from veil_pgd.types import Position, RenderSpec

_POSITIONS: list[Position] = [
    "bottom_middle", "top_middle", "top_right", "bottom_right",
    "top_left", "bottom_left", "center",
]
_COLOR_STRATEGIES = ["bg_mean_offset", "near_bg_dark", "near_bg_light"]


def grid_specs(
    decoys: list[str], positions: list[Position], cfg: OptimizerConfig
) -> list[RenderSpec]:
    """Coarse grid over structural knobs at a fixed mid alpha.

    Caps positions/colors to `cfg.grid_positions`/`cfg.grid_colors` so grid size
    stays bounded; the evolutionary phase explores the rest of the space.
    """
    positions = positions[: cfg.grid_positions]
    colors = _COLOR_STRATEGIES[: cfg.grid_colors]
    specs: list[RenderSpec] = []
    for text in decoys:
        for pos in positions:
            for color in colors:
                for px in cfg.grid_font_px:
                    specs.append(
                        RenderSpec(
                            text=text,
                            font_px=px,
                            alpha=cfg.grid_alpha,
                            color_strategy=color,  # type: ignore[arg-type]
                            position=pos,
                        )
                    )
    return specs


def mutate(spec: RenderSpec, cfg: OptimizerConfig, rng: random.Random) -> RenderSpec:
    """Perturb the continuous/fine knobs for the evolutionary phase."""
    lo, hi = cfg.alpha_range
    flo, fhi = cfg.font_px_range
    choice = rng.choice(["alpha", "font", "offset", "rep", "color"])
    if choice == "alpha":
        return replace(spec, alpha=min(hi, max(lo, spec.alpha + rng.uniform(-0.05, 0.05))))
    if choice == "font":
        return replace(spec, font_px=min(fhi, max(flo, spec.font_px + rng.choice([-2, -1, 1, 2]))))
    if choice == "offset":
        return replace(spec, brightness_offset=min(30, max(5, spec.brightness_offset + rng.choice([-5, 5]))))
    if choice == "rep":
        return replace(spec, repetition=min(4, max(1, spec.repetition + rng.choice([-1, 1]))))
    return replace(spec, color_strategy=rng.choice(_COLOR_STRATEGIES))  # type: ignore[arg-type]


def default_positions() -> list[Position]:
    return list(_POSITIONS)