// Reference: https://cie.co.at/datatable/cie-1931-colour-matching-functions-2-degree-observer

import type { Vector3 } from 'three'

// prettier-ignore
const DATA: ReadonlyArray<
  readonly [number, number, number, number]
> = [
  [360, 0.000129900000, 0.000003917000, 0.000606100000],
  [365, 0.000232100000, 0.000006965000, 0.001086000000],
  [370, 0.000414900000, 0.000012390000, 0.001946000000],
  [375, 0.000741600000, 0.000022020000, 0.003486000000],
  [380, 0.001368000000, 0.000039000000, 0.006450001000],
  [385, 0.002236000000, 0.000064000000, 0.010549990000],
  [390, 0.004243000000, 0.000120000000, 0.020050010000],
  [395, 0.007650000000, 0.000217000000, 0.036210000000],
  [400, 0.014310000000, 0.000396000000, 0.067850010000],
  [405, 0.023190000000, 0.000640000000, 0.110200000000],
  [410, 0.043510000000, 0.001210000000, 0.207400000000],
  [415, 0.077630000000, 0.002180000000, 0.371300000000],
  [420, 0.134380000000, 0.004000000000, 0.645600000000],
  [425, 0.214770000000, 0.007300000000, 1.039050100000],
  [430, 0.283900000000, 0.011600000000, 1.385600000000],
  [435, 0.328500000000, 0.016840000000, 1.622960000000],
  [440, 0.348280000000, 0.023000000000, 1.747060000000],
  [445, 0.348060000000, 0.029800000000, 1.782600000000],
  [450, 0.336200000000, 0.038000000000, 1.772110000000],
  [455, 0.318700000000, 0.048000000000, 1.744100000000],
  [460, 0.290800000000, 0.060000000000, 1.669200000000],
  [465, 0.251100000000, 0.073900000000, 1.528100000000],
  [470, 0.195360000000, 0.090980000000, 1.287640000000],
  [475, 0.142100000000, 0.112600000000, 1.041900000000],
  [480, 0.095640000000, 0.139020000000, 0.812950100000],
  [485, 0.057950010000, 0.169300000000, 0.616200000000],
  [490, 0.032010000000, 0.208020000000, 0.465180000000],
  [495, 0.014700000000, 0.258600000000, 0.353300000000],
  [500, 0.004900000000, 0.323000000000, 0.272000000000],
  [505, 0.002400000000, 0.407300000000, 0.212300000000],
  [510, 0.009300000000, 0.503000000000, 0.158200000000],
  [515, 0.029100000000, 0.608200000000, 0.111700000000],
  [520, 0.063270000000, 0.710000000000, 0.078249990000],
  [525, 0.109600000000, 0.793200000000, 0.057250010000],
  [530, 0.165500000000, 0.862000000000, 0.042160000000],
  [535, 0.225749900000, 0.914850100000, 0.029840000000],
  [540, 0.290400000000, 0.954000000000, 0.020300000000],
  [545, 0.359700000000, 0.980300000000, 0.013400000000],
  [550, 0.433449900000, 0.994950100000, 0.008749999000],
  [555, 0.512050100000, 1.000000000000, 0.005749999000],
  [560, 0.594500000000, 0.995000000000, 0.003900000000],
  [565, 0.678400000000, 0.978600000000, 0.002749999000],
  [570, 0.762100000000, 0.952000000000, 0.002100000000],
  [575, 0.842500000000, 0.915400000000, 0.001800000000],
  [580, 0.916300000000, 0.870000000000, 0.001650001000],
  [585, 0.978600000000, 0.816300000000, 0.001400000000],
  [590, 1.026300000000, 0.757000000000, 0.001100000000],
  [595, 1.056700000000, 0.694900000000, 0.001000000000],
  [600, 1.062200000000, 0.631000000000, 0.000800000000],
  [605, 1.045600000000, 0.566800000000, 0.000600000000],
  [610, 1.002600000000, 0.503000000000, 0.000340000000],
  [615, 0.938400000000, 0.441200000000, 0.000240000000],
  [620, 0.854449900000, 0.381000000000, 0.000190000000],
  [625, 0.751400000000, 0.321000000000, 0.000100000000],
  [630, 0.642400000000, 0.265000000000, 0.000049999990],
  [635, 0.541900000000, 0.217000000000, 0.000030000000],
  [640, 0.447900000000, 0.175000000000, 0.000020000000],
  [645, 0.360800000000, 0.138200000000, 0.000010000000],
  [650, 0.283500000000, 0.107000000000, 0.000000000000],
  [655, 0.218700000000, 0.081600000000, 0.000000000000],
  [660, 0.164900000000, 0.061000000000, 0.000000000000],
  [665, 0.121200000000, 0.044580000000, 0.000000000000],
  [670, 0.087400000000, 0.032000000000, 0.000000000000],
  [675, 0.063600000000, 0.023200000000, 0.000000000000],
  [680, 0.046770000000, 0.017000000000, 0.000000000000],
  [685, 0.032900000000, 0.011920000000, 0.000000000000],
  [690, 0.022700000000, 0.008210000000, 0.000000000000],
  [695, 0.015840000000, 0.005723000000, 0.000000000000],
  [700, 0.011359160000, 0.004102000000, 0.000000000000],
  [705, 0.008110916000, 0.002929000000, 0.000000000000],
  [710, 0.005790346000, 0.002091000000, 0.000000000000],
  [715, 0.004109457000, 0.001484000000, 0.000000000000],
  [720, 0.002899327000, 0.001047000000, 0.000000000000],
  [725, 0.002049190000, 0.000740000000, 0.000000000000],
  [730, 0.001439971000, 0.000520000000, 0.000000000000],
  [735, 0.000999949300, 0.000361100000, 0.000000000000],
  [740, 0.000690078600, 0.000249200000, 0.000000000000],
  [745, 0.000476021300, 0.000171900000, 0.000000000000],
  [750, 0.000332301100, 0.000120000000, 0.000000000000],
  [755, 0.000234826100, 0.000084800000, 0.000000000000],
  [760, 0.000166150500, 0.000060000000, 0.000000000000],
  [765, 0.000117413000, 0.000042400000, 0.000000000000],
  [770, 0.000083075270, 0.000030000000, 0.000000000000],
  [775, 0.000058706520, 0.000021200000, 0.000000000000],
  [780, 0.000041509940, 0.000014990000, 0.000000000000],
  [785, 0.000029353260, 0.000010600000, 0.000000000000],
  [790, 0.000020673830, 0.000007465700, 0.000000000000],
  [795, 0.000014559770, 0.000005257800, 0.000000000000],
  [800, 0.000010253980, 0.000003702900, 0.000000000000],
  [805, 0.000007221456, 0.000002607800, 0.000000000000],
  [810, 0.000005085868, 0.000001836600, 0.000000000000],
  [815, 0.000003581652, 0.000001293400, 0.000000000000],
  [820, 0.000002522525, 0.000000910930, 0.000000000000],
  [825, 0.000001776509, 0.000000641530, 0.000000000000],
  [830, 0.000001251141, 0.000000451810, 0.000000000000]
]

export const MIN_LAMBDA = 360
export const MAX_LAMBDA = 830

export function getCIEColorMatchingFunctionValue(
  wavelength: number,
  result: Vector3
): Vector3 {
  if (wavelength <= MIN_LAMBDA || wavelength >= MAX_LAMBDA) {
    return result.setScalar(0)
  }
  const u = (wavelength - MIN_LAMBDA) / 5
  const row = Math.floor(u)
  const prev = DATA[row]
  const next = DATA[row + 1]
  const t = u - row
  return result.set(
    prev[1] * (1 - t) + next[1] * t,
    prev[2] * (1 - t) + next[2] * t,
    prev[3] * (1 - t) + next[3] * t
  )
}