"""AS7341 spektri -> ligikaudne värvus (CIE 1931 XYZ -> sRGB).

Kasutab Wyman, Sloan & Shirley (2013) analüütilist CIE 1931 2° CMF
lähendust 8 kanali kesk lainepikkustel.

NB! See EI ole kalibreeritud kolorimeetria — absoluutse värvuse jaoks on
vaja valge referentsi ja fikseeritud valgustust (vt LOEMIND.md).
"""
from __future__ import annotations

import math

# ESPHome as7341 kanalite F1..F8 kesk lainepikkused (nm)
CHANNEL_WAVELENGTHS: dict[str, int] = {
    "f1": 415,
    "f2": 445,
    "f3": 480,
    "f4": 515,
    "f5": 555,
    "f6": 590,
    "f7": 630,
    "f8": 680,
}


def _piecewise_gaussian(x: float, mu: float, sigma1: float, sigma2: float) -> float:
    sigma = sigma1 if x < mu else sigma2
    return math.exp(-0.5 * ((x - mu) / sigma) ** 2)


def cie_xyz_cmf(wavelength_nm: float) -> tuple[float, float, float]:
    """Wyman et al. (2013) lähendus CIE 1931 2° värvusfunktsioonidele."""
    x_bar = (
        1.056 * _piecewise_gaussian(wavelength_nm, 599.8, 37.9, 31.0)
        + 0.362 * _piecewise_gaussian(wavelength_nm, 442.0, 16.0, 26.7)
        - 0.065 * _piecewise_gaussian(wavelength_nm, 501.1, 20.4, 26.2)
    )
    y_bar = (
        0.821 * _piecewise_gaussian(wavelength_nm, 568.8, 46.9, 40.5)
        + 0.286 * _piecewise_gaussian(wavelength_nm, 530.9, 16.3, 31.1)
    )
    z_bar = (
        1.217 * _piecewise_gaussian(wavelength_nm, 437.0, 11.8, 36.0)
        + 0.681 * _piecewise_gaussian(wavelength_nm, 459.0, 26.0, 13.8)
    )
    return x_bar, y_bar, z_bar


def channels_to_xyz(channels: dict[str, float]) -> tuple[float, float, float]:
    """Ligikaudne XYZ: iga kanali väärtus kaalutakse CMF-iga kesk lainepikkusel."""
    x = y = z = 0.0
    for name, wavelength in CHANNEL_WAVELENGTHS.items():
        value = channels.get(name)
        if value is None:
            continue
        cx, cy, cz = cie_xyz_cmf(wavelength)
        x += value * cx
        y += value * cy
        z += value * cz
    return x, y, z


def xyz_to_srgb(x: float, y: float, z: float) -> tuple[int, int, int]:
    """XYZ -> lineaarne sRGB (D65) -> gamma -> 8-bit. Heledus normaliseeritakse."""
    r_lin = 3.2406 * x - 1.5372 * y - 0.4986 * z
    g_lin = -0.9689 * x + 1.8758 * y + 0.0415 * z
    b_lin = 0.0557 * x - 0.2040 * y + 1.0570 * z

    def gamma(c: float) -> float:
        c = max(0.0, c)
        return 12.92 * c if c <= 0.0031308 else 1.055 * c ** (1 / 2.4) - 0.055

    r, g, b = gamma(r_lin), gamma(g_lin), gamma(b_lin)
    scale = max(r, g, b, 1e-9)
    return (
        int(round(255 * r / scale)),
        int(round(255 * g / scale)),
        int(round(255 * b / scale)),
    )


def chromaticity_xy(x: float, y: float, z: float) -> tuple[float, float]:
    total = x + y + z
    if total <= 0:
        return 0.0, 0.0
    return x / total, y / total


def analyze(channels: dict[str, float]) -> dict:
    """Tagastab tuletatud värviväljad ClickHouse'i rea jaoks."""
    x, y, z = channels_to_xyz(channels)
    cx, cy = chromaticity_xy(x, y, z)
    r, g, b = xyz_to_srgb(x, y, z)
    return {
        "x_chrom": round(cx, 5),
        "y_chrom": round(cy, 5),
        "r": r,
        "g": g,
        "b": b,
        "rgb_hex": f"#{r:02X}{g:02X}{b:02X}",
    }