"""The alteration engine: a knob vector -> a layered RenderPlan (design §4, §5).

Reconciled slice (2026-06-07): the Right axis is a DISCRETE selection of a
pre-baked, flow-stabilized restyle variant (not a continuous blend), the Left
axis carries its knob LEVEL so a runtime annotation track can pick which labels
show, and a frozen `Calibration` parameterizes the knob->strength curves so they
can be tuned by eye in the simulator and baked into DEFAULT_CALIBRATION.

Layers compose per §4.2:
  - Substrate: ColorGrade (Dark/Light mood, center = identity §5) + a pre-baked
    Right restyle variant.
  - Overlay: AnalyticalOverlay (Left), composited on top at runtime.
Left and Right stack (different layers); Dark/Light are the two poles of one
mood grade. See docs/superpowers/specs/2026-06-07-reconciled-simulator-
alteration-slice-design.md.
"""

from __future__ import annotations

from dataclasses import dataclass

from hef.selection import Coordinate

KNOB_MAX = 4  # knob full-scale (0..4)


def _clamp(x: float, lo: float, hi: float) -> float:
    return max(lo, min(hi, x))


@dataclass(frozen=True)
class Calibration:
    """Tunable knob->strength curves (settled by eye in the sim, then baked).

    - mood_gain: scales the signed Dark/Light tone (result clamped to [-1, 1]).
    - overlay_gain: scales the Left overlay intensity (clamped to [0, 1]).
    - right_variant_map: knob value (0..4) -> pre-baked Right variant index.
    """

    mood_gain: float = 1.0
    overlay_gain: float = 1.0
    right_variant_map: tuple = (0, 1, 2, 3, 4)


# The LOCKED calibration (session 0010, 2026-06-07) — settled by eye in the
# simulator, closing the open session-0006 knob->strength decision. Convention:
# every experience knob runs 0 = off .. 4 = max, and equal Dark/Light = identity
# (raw footage); there is no "centered at 2 = no push" coordinate.
#   - mood_gain = 1.0: full Dark/Light knob reaches the full mood grade. By-eye
#     evidence (POC renders + sim, after the dark-grade fix this session) shows
#     full tilt is peaceful on every axis, so no softening is warranted.
#   - overlay_gain = 1.0: full Left = opacity 1.0; the HUD is legible, not
#     overwhelming, sitting above the grade.
#   - right_variant_map linear: the 5 knob notches map 1:1 onto the 5 discrete
#     pre-baked Right strengths (0 = raw base).
# These are unity/linear by deliberate choice, not as placeholders. The curve
# stays parameterized so a future re-bake or a different feel is one edit away;
# test_default_calibration_is_locked guards the values from drifting silently.
DEFAULT_CALIBRATION = Calibration(
    mood_gain=1.0,
    overlay_gain=1.0,
    right_variant_map=(0, 1, 2, 3, 4),
)


@dataclass(frozen=True)
class ColorGrade:
    """Mood-axis grade (§5). `tone` is signed: >0 warm yellow->white (light),
    <0 cool blue->black (dark), 0 = identity (raw, ungraded)."""

    tone: float

    @property
    def is_identity(self) -> bool:
        return self.tone == 0.0


@dataclass(frozen=True)
class AnalyticalOverlay:
    """Left axis (§4.1): analytical HUD/annotation, composited on top at runtime.
    `level` is the Left knob (0..4); a runtime annotation track uses it to pick
    which labels appear. `intensity` 0..1 is the overlay opacity/strength."""

    level: int
    intensity: float


@dataclass(frozen=True)
class Restyle:
    """Right axis (§4.1): selects a pre-baked, flow-stabilized restyle variant.
    `variant` is a discrete index (0 = raw base, no restyle)."""

    variant: int


@dataclass(frozen=True)
class RenderPlan:
    """The full layered alteration for one knob vector (§4.2)."""

    grade: ColorGrade
    overlay: AnalyticalOverlay
    restyle: Restyle

    @property
    def is_identity(self) -> bool:
        """True when the plan leaves the neutral base un-altered."""
        return (
            self.grade.is_identity
            and self.overlay.level == 0
            and self.restyle.variant == 0
        )


def _overlay_intensity(left: int, cal: Calibration) -> float:
    return _clamp(cal.overlay_gain * left / KNOB_MAX, 0.0, 1.0)


def _right_variant(right: int, cal: Calibration) -> int:
    return cal.right_variant_map[right]


def _mood_tone(dark: int, light: int, cal: Calibration) -> float:
    return _clamp(cal.mood_gain * (light - dark) / KNOB_MAX, -1.0, 1.0)


def plan_alteration(
    coord: Coordinate, calibration: Calibration = DEFAULT_CALIBRATION
) -> RenderPlan:
    """Map a knob vector to its layered RenderPlan (design §4)."""
    return RenderPlan(
        grade=ColorGrade(tone=_mood_tone(coord.dark, coord.light, calibration)),
        overlay=AnalyticalOverlay(
            level=coord.left,
            intensity=_overlay_intensity(coord.left, calibration),
        ),
        restyle=Restyle(variant=_right_variant(coord.right, calibration)),
    )


def render_plan_to_dict(plan: RenderPlan) -> dict:
    """JSON-serializable form for the simulator API."""
    return {
        "grade": {"tone": plan.grade.tone},
        "overlay": {"level": plan.overlay.level, "intensity": plan.overlay.intensity},
        "restyle": {"variant": plan.restyle.variant},
        "is_identity": plan.is_identity,
    }