<?php

namespace AcademicCrew\Core;

/**
 * Minimal hex-color mixing, used to derive a role's background/text shades
 * from a single admin-picked accent color (Settings → Member Roles).
 */
class ColorMath {

    /** Mixes $hex with $with, keeping $weight (0–1) of $hex. */
    public static function mix( string $hex, string $with, float $weight ): string {
        [ $r1, $g1, $b1 ] = self::to_rgb( $hex );
        [ $r2, $g2, $b2 ] = self::to_rgb( $with );

        $mix = static fn( int $a, int $b ): int => (int) round( $a * $weight + $b * ( 1 - $weight ) );

        return self::to_hex( $mix( $r1, $r2 ), $mix( $g1, $g2 ), $mix( $b1, $b2 ) );
    }

    /** Light background tint for a role badge, derived from its accent color. */
    public static function tint( string $hex ): string {
        return self::mix( $hex, '#ffffff', 0.10 );
    }

    /** Darker, more legible text shade for a role badge. */
    public static function shade( string $hex ): string {
        return self::mix( $hex, '#000000', 0.65 );
    }

    private static function to_rgb( string $hex ): array {
        $hex = ltrim( $hex, '#' );
        if ( 3 === strlen( $hex ) ) {
            $hex = $hex[0] . $hex[0] . $hex[1] . $hex[1] . $hex[2] . $hex[2];
        }
        return [
            hexdec( substr( $hex, 0, 2 ) ),
            hexdec( substr( $hex, 2, 2 ) ),
            hexdec( substr( $hex, 4, 2 ) ),
        ];
    }

    private static function to_hex( int $r, int $g, int $b ): string {
        $clamp = static fn( int $v ): int => max( 0, min( 255, $v ) );
        return sprintf( '#%02x%02x%02x', $clamp( $r ), $clamp( $g ), $clamp( $b ) );
    }
}