<?php
/** Presentation-only mint branding; canonical business color values remain stored. */
namespace Abientot\Support;
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}
final class BrandPalette {
	public const MINT = '#46c8b2';
	public const INK  = '#131f29';
	public const LINK = '#117563';
	private static function rgb( string $color ): ?array {
		if ( ! preg_match( '/^#([a-f0-9]{3}|[a-f0-9]{6})$/iD', $color, $match ) ) {
			return null;
		}
		$hex = $match[1];
		if ( strlen( $hex ) === 3 ) {
			$hex = $hex[0] . $hex[0] . $hex[1] . $hex[1] . $hex[2] . $hex[2];
		}
		return array( hexdec( substr( $hex, 0, 2 ) ) / 255, hexdec( substr( $hex, 2, 2 ) ) / 255, hexdec( substr( $hex, 4, 2 ) ) / 255 );
	}
	public static function color( string $color, string $role = 'accent' ): string {
		$rgb = self::rgb( $color );
		if ( ! $rgb ) {
			return $color;
		}[$r, $g, $b] = $rgb;
		$max          = max( $rgb );
		$min          = min( $rgb );
		$delta        = $max - $min;
		$light        = ( $max + $min ) / 2;
		if ( $delta <= 0 ) {
			return $color;
		}
		$saturation = $delta / ( 1 - abs( 2 * $light - 1 ) );
		$hue        = $max === $r ? 60 * fmod( ( $g - $b ) / $delta, 6 ) : ( $max === $g ? 60 * ( ( $b - $r ) / $delta + 2 ) : 60 * ( ( $r - $g ) / $delta + 4 ) );
		if ( $hue < 0 ) {
			$hue += 360;
		}
		if ( $hue < 235 || $hue > 330 || $saturation < .035 ) {
			return $color;
		}
		if ( $role === 'text' ) {
			return $light > .68 ? '#e6f8f2' : ( $light < .25 ? self::INK : self::LINK );
		}
		if ( $saturation < .18 ) {
			return $light > .93 ? '#f5f9f8' : ( $light > .78 ? '#dce9e5' : ( $light > .55 ? '#91a6a2' : ( $light > .28 ? '#5e7274' : self::INK ) ) );
		}
		return $light > .84 ? '#e6f8f2' : ( $light > .68 ? '#bfebdf' : ( $light < .25 ? self::INK : self::MINT ) );
	}
	private static function luminance( string $color ): float {
		$rgb    = self::rgb( $color ) ?? array( 0, 0, 0 );
		$linear = array_map( static fn( float $v ): float=>$v <= .04045 ? $v / 12.92 : pow( ( $v + .055 ) / 1.055, 2.4 ), $rgb );
		return .2126 * $linear[0] + .7152 * $linear[1] + .0722 * $linear[2];
	}
	public static function contrast( string $a, string $b ): float {
		$x = self::luminance( $a );
		$y = self::luminance( $b );
		return( max( $x, $y ) + .05 ) / ( min( $x, $y ) + .05 );
	}
	public static function on_primary( string $primary ): string {
		return self::contrast( $primary, self::INK ) > self::contrast( $primary, '#ffffff' ) ? self::INK : '#ffffff';
	}
	public static function text( string $primary ): string {
		return self::contrast( $primary, '#ffffff' ) >= 4.5 ? $primary : self::LINK;
	}
	/** Hex for 0–1 RGB channels. */
	private static function hex( array $rgb ): string {
		return sprintf( '#%02x%02x%02x', ...array_map( static fn( float $v ): int=> (int) round( max( 0, min( 1, $v ) ) * 255 ), $rgb ) );
	}
	private static function hsl( array $rgb ): array {
		[$r, $g, $b] = $rgb;
		$max         = max( $rgb );
		$min         = min( $rgb );
		$l           = ( $max + $min ) / 2;
		$d           = $max - $min;
		if ( $d <= 0 ) {
			return array( 0.0, 0.0, $l );
		}
		$s  = $d / ( 1 - abs( 2 * $l - 1 ) );
		$h  = $max === $r ? fmod( ( $g - $b ) / $d, 6 ) : ( $max === $g ? ( $b - $r ) / $d + 2 : ( $r - $g ) / $d + 4 );
		$h *= 60;
		if ( $h < 0 ) {
			$h += 360;
		}
		return array( $h, $s, $l );
	}
	private static function from_hsl( float $h, float $s, float $l ): array {
		$c   = ( 1 - abs( 2 * $l - 1 ) ) * $s;
		$x   = $c * ( 1 - abs( fmod( $h / 60, 2 ) - 1 ) );
		$m   = $l - $c / 2;
		$i   = (int) floor( $h / 60 ) % 6;
		$set = array( array( $c, $x, 0 ), array( $x, $c, 0 ), array( 0, $c, $x ), array( 0, $x, $c ), array( $x, 0, $c ), array( $c, 0, $x ) )[ $i ];
		return array( $set[0] + $m, $set[1] + $m, $set[2] + $m );
	}
	/** Mixes two hex colors; $weight is the share of $a. */
	public static function mix( string $a, string $b, float $weight ): string {
		$x = self::rgb( $a );
		$y = self::rgb( $b );
		if ( ! $x || ! $y ) {
			return $a;
		}
		return self::hex( array_map( static fn( float $p, float $q ): float=>$p * $weight + $q * ( 1 - $weight ), $x, $y ) );
	}
	/**
	 * Automatic text color: keeps the hue and saturation of $color and moves only its lightness,
	 * as little as possible, until it reaches $target contrast (WCAG) against $background.
	 * Mirrored by assets/frontend/contrast.js for the preview and see-through forms.
	 */
	public static function readable( string $color, string $background, float $target = 4.5 ): string {
		$rgb = self::rgb( $color );
		if ( ! $rgb || ! self::rgb( $background ) ) {
			return $color;
		}
		if ( self::contrast( $color, $background ) >= $target ) {
			return $color;
		}
		[$h, $s, $l] = self::hsl( $rgb );
		$darken      = self::contrast( '#000000', $background ) >= self::contrast( '#ffffff', $background );
		$extreme     = self::hex( self::from_hsl( $h, $s, $darken ? 0.0 : 1.0 ) );
		if ( self::contrast( $extreme, $background ) < $target ) {
			return $darken ? '#000000' : '#ffffff';
		}
		$near = $l;
		$far  = $darken ? 0.0 : 1.0;for ( $i = 0;$i < 24;$i++ ) {
			$mid = ( $near + $far ) / 2;
			if ( self::contrast( self::hex( self::from_hsl( $h, $s, $mid ) ), $background ) >= $target ) {
				$far = $mid;
			} else {
				$near = $mid;
			}
		}
		return self::hex( self::from_hsl( $h, $s, $far ) );
	}
	/** Secondary text: closer to the background, still readable. */
	public static function readable_muted( string $text, string $background ): string {
		return self::readable( self::mix( $text, $background, .72 ), $background );
	}
	public static function foreground( string $color, string $background ): string {
		$paint   = self::color( $color, 'text' );
		$surface = self::color( $background );
		return( $paint !== $color || $surface !== $background ) && self::contrast( $paint, $surface ) < 4.5 ? self::on_primary( $surface ) : $paint;
	}
}