<?php

namespace TablePress\PhpOffice\PhpSpreadsheet\Style;

/**
 * Class to handle tint applied to color.
 * Code borrows heavily from some Python projects.
 *
 * @see https://docs.python.org/3/library/colorsys.html
 * @see https://gist.github.com/Mike-Honey/b36e651e9a7f1d2e1d60ce1c63b9b633
 */
class RgbTint
{
	private const ONE_THIRD = 1.0 / 3.0;
	private const ONE_SIXTH = 1.0 / 6.0;
	private const TWO_THIRD = 2.0 / 3.0;
	private const RGBMAX = 255.0;
	/**
	 * MS excel's tint function expects that HLS is base 240.
	 *
	 * @see https://social.msdn.microsoft.com/Forums/en-US/e9d8c136-6d62-4098-9b1b-dac786149f43/excel-color-tint-algorithm-incorrect?forum=os_binaryfile#d3c2ac95-52e0-476b-86f1-e2a697f24969
	 */
	private const HLSMAX = 240.0;

	/**
	 * Convert red/green/blue to hue/luminance/saturation.
	 *
	 * @param float $red 0.0 through 1.0
	 * @param float $green 0.0 through 1.0
	 * @param float $blue 0.0 through 1.0
	 *
	 * @return float[]
	 */
	private static function rgbToHls(float $red, float $green, float $blue): array
	{
		$maxc = max($red, $green, $blue);
		$minc = min($red, $green, $blue);
		$luminance = ($minc + $maxc) / 2.0;
		if ($minc === $maxc) {
			return [0.0, $luminance, 0.0];
		}
		$maxMinusMin = $maxc - $minc;
		if ($luminance <= 0.5) {
			$s = $maxMinusMin / ($maxc + $minc);
		} else {
			$s = $maxMinusMin / (2.0 - $maxc - $minc);
		}
		$rc = ($maxc - $red) / $maxMinusMin;
		$gc = ($maxc - $green) / $maxMinusMin;
		$bc = ($maxc - $blue) / $maxMinusMin;
		if ($red === $maxc) {
			$h = $bc - $gc;
		} elseif ($green === $maxc) {
			$h = 2.0 + $rc - $bc;
		} else {
			$h = 4.0 + $gc - $rc;
		}
		$h = self::positiveDecimalPart($h / 6.0);

		return [$h, $luminance, $s];
	}

	/**
	 * Convert hue/luminance/saturation to red/green/blue.
	 *
	 * @param float $hue 0.0 through 1.0
	 * @param float $luminance 0.0 through 1.0
	 * @param float $saturation 0.0 through 1.0
	 *
	 * @return float[]
	 */
	private static function hlsToRgb(float $hue, float $luminance, float $saturation): array
	{
		if ($saturation === 0.0) {
			return [$luminance, $luminance, $luminance];
		}
		if ($luminance <= 0.5) {
			$m2 = $luminance * (1.0 + $saturation);
		} else {
			$m2 = $luminance + $saturation - ($luminance * $saturation);
		}
		$m1 = 2.0 * $luminance - $m2;

		return [
			self::vFunction($m1, $m2, $hue + self::ONE_THIRD),
			self::vFunction($m1, $m2, $hue),
			self::vFunction($m1, $m2, $hue - self::ONE_THIRD),
		];
	}

	private static function vFunction(float $m1, float $m2, float $hue): float
	{
		$hue = self::positiveDecimalPart($hue);
		if ($hue < self::ONE_SIXTH) {
			return $m1 + ($m2 - $m1) * $hue * 6.0;
		}
		if ($hue < 0.5) {
			return $m2;
		}
		if ($hue < self::TWO_THIRD) {
			return $m1 + ($m2 - $m1) * (self::TWO_THIRD - $hue) * 6.0;
		}

		return $m1;
	}

	private static function positiveDecimalPart(float $hue): float
	{
		$hue = fmod($hue, 1.0);

		return ($hue >= 0.0) ? $hue : (1.0 + $hue);
	}

	/**
	 * Convert red/green/blue to HLSMAX-based hue/luminance/saturation.
	 *
	 * @return int[]
	 */
	private static function rgbToMsHls(int $red, int $green, int $blue): array
	{
		$red01 = $red / self::RGBMAX;
		$green01 = $green / self::RGBMAX;
		$blue01 = $blue / self::RGBMAX;
		[$hue, $luminance, $saturation] = self::rgbToHls($red01, $green01, $blue01);

		return [
			(int) round($hue * self::HLSMAX),
			(int) round($luminance * self::HLSMAX),
			(int) round($saturation * self::HLSMAX),
		];
	}

	/**
	 * Converts HLSMAX based HLS values to rgb values in the range (0,1).
	 *
	 * @return float[]
	 */
	private static function msHlsToRgb(int $hue, int $lightness, int $saturation): array
	{
		return self::hlsToRgb($hue / self::HLSMAX, $lightness / self::HLSMAX, $saturation / self::HLSMAX);
	}

	/**
	 * Tints HLSMAX based luminance.
	 *
	 * @see http://ciintelligence.blogspot.co.uk/2012/02/converting-excel-theme-color-and-tint.html
	 */
	private static function tintLuminance(float $tint, float $luminance): int
	{
		if ($tint < 0) {
			return (int) round($luminance * (1.0 + $tint));
		}

		return (int) round($luminance * (1.0 - $tint) + (self::HLSMAX - self::HLSMAX * (1.0 - $tint)));
	}

	/**
	 * Return result of tinting supplied rgb as 6 hex digits.
	 */
	public static function rgbAndTintToRgb(int $red, int $green, int $blue, float $tint): string
	{
		[$hue, $luminance, $saturation] = self::rgbToMsHls($red, $green, $blue);
		[$red, $green, $blue] = self::msHlsToRgb($hue, self::tintLuminance($tint, $luminance), $saturation);

		return sprintf(
			'%02X%02X%02X',
			(int) round($red * self::RGBMAX),
			(int) round($green * self::RGBMAX),
			(int) round($blue * self::RGBMAX)
		);
	}
}
