import { internalRoundColorFloat } from "../internal.ts"
import type { XyChromaticityValue, XyzColorValue } from "../types.ts"

import { createXyzColorValue } from "./construct.ts"

const internalGetNormalizedXyzColorData = (
  color: XyzColorValue,
): { color: XyzColorValue; tristimulusSum: number } => {
  const normalizedColor = createXyzColorValue(color)
  const tristimulusSum = internalRoundColorFloat(
    normalizedColor.x + normalizedColor.y + normalizedColor.z,
  )

  return {
    color: normalizedColor,
    tristimulusSum,
  }
}

/**
 * @description 读取 XYZ 颜色值的相对亮度。
 *
 * 在当前模块约定下，`Y` 通道直接表示相对亮度。
 *
 * @example
 *   ```
 *   // Expect: 0.3
 *   const example1 = xyzColorValueToRelativeLuminance({ x: 0.25, y: 0.3, z: 0.4, alpha: 1 })
 *
 *   // Expect: 0
 *   const example2 = xyzColorValueToRelativeLuminance({ x: 0, y: 0, z: 0, alpha: 1 })
 *   ```
 */
export const xyzColorValueToRelativeLuminance = (color: XyzColorValue): number => {
  return createXyzColorValue(color).y
}

/**
 * @description 读取 XYZ 颜色值的三刺激总量。
 *
 * 在当前模块约定下，结果等于 `x + y + z`。
 *
 * @example
 *   ```
 *   // Expect: 0.95
 *   const example1 = xyzColorValueToTristimulusSum({ x: 0.25, y: 0.3, z: 0.4, alpha: 1 })
 *
 *   // Expect: 0
 *   const example2 = xyzColorValueToTristimulusSum({ x: 0, y: 0, z: 0, alpha: 1 })
 *   ```
 */
export const xyzColorValueToTristimulusSum = (color: XyzColorValue): number => {
  return internalGetNormalizedXyzColorData(color).tristimulusSum
}

/**
 * @description 读取 XYZ 颜色值对应的 `xy` 色度坐标。
 *
 * 当三刺激总量为 `0` 时，该结果没有定义，因此会抛出异常。
 *
 * @example
 *   ```
 *   // Expect: { x: 0.263158, y: 0.315789 }
 *   const example1 = xyzColorValueToXyChromaticityValue({ x: 0.25, y: 0.3, z: 0.4, alpha: 1 })
 *
 *   // Expect: { x: 0.64, y: 0.33 }
 *   const example2 = xyzColorValueToXyChromaticityValue({ x: 0.412456, y: 0.212673, z: 0.019334, alpha: 1 })
 *   ```
 */
export const xyzColorValueToXyChromaticityValue = (color: XyzColorValue): XyChromaticityValue => {
  const normalizedData = internalGetNormalizedXyzColorData(color)

  if (normalizedData.tristimulusSum === 0) {
    throw new RangeError("XYZ tristimulus sum must be greater than 0 to compute xy chromaticity")
  }

  return {
    x: internalRoundColorFloat(normalizedData.color.x / normalizedData.tristimulusSum),
    y: internalRoundColorFloat(normalizedData.color.y / normalizedData.tristimulusSum),
  }
}