"""The strike and the listener."""

from __future__ import annotations

import math
from dataclasses import dataclass


@dataclass(frozen=True)
class Strike:
    """A drumstick strike: a free mass arriving at a point of the plate with a Hertz contact.

    The default contact stiffness is softer than the Hertz value for a hard
    wooden tip on metal (of order 1e8 to 1e9); it stands for the compliance of
    a real tip and gives a rounder attack.
    """

    x: float = 0.9
    """Strike point as a fraction of the bounding-box width from the left edge."""
    y: float = 0.5
    """Strike point as a fraction of the bounding-box height from the bottom edge."""
    velocity: float = 3.0
    """Stick tip speed at impact [m/s]."""
    mass: float = 0.03
    """Effective mass of the stick [kg]."""
    stiffness: float = 1e7
    """Hertz contact stiffness K [N/m^alpha]."""
    exponent: float = 1.5
    """Hertz exponent alpha (1.5 for a rounded tip)."""
    radius: float = 5e-3
    """Radius of the contact patch [m]."""

    def __post_init__(self) -> None:
        if not (0 <= self.x <= 1 and 0 <= self.y <= 1):
            raise ValueError("the strike point (x, y) is given as fractions of the bounding box in [0, 1]")
        if not (self.velocity > 0 and self.mass > 0 and self.stiffness > 0 and self.exponent >= 1 and self.radius >= 0):
            raise ValueError("velocity, mass and stiffness must be positive, exponent at least 1, radius non-negative")


@dataclass(frozen=True)
class Listener:
    """The listener (a microphone) in spherical coordinates about the center of the plate."""

    distance: float = 0.5
    """Distance from the center of the plate [m]."""
    angle: float = 30.0
    """Angle from the plate's normal [deg]; 0 is straight above the plate."""
    azimuth: float = 0.0
    """Rotation about the normal [deg]; 0 is toward +x."""

    def __post_init__(self) -> None:
        if not self.distance > 0:
            raise ValueError("distance must be positive")

    @property
    def position(self) -> tuple[float, float, float]:
        """Cartesian position relative to the center of the plate, z along the normal [m]."""
        th = math.radians(self.angle)
        ph = math.radians(self.azimuth)
        return (
            self.distance * math.sin(th) * math.cos(ph),
            self.distance * math.sin(th) * math.sin(ph),
            self.distance * math.cos(th),
        )