<?php
/** Bounded local background CSS and the native content container. GPL-2.0-or-later. */
defined( 'ABSPATH' ) || exit;

function sflo_background_number( $value, $fallback, $min, $max ) {
    if ( is_string( $value ) ) {
        // Match JavaScript String.trim() before validating numeric strings.
        $spaces = '[\x09-\x0d \x{00a0}\x{1680}\x{2000}-\x{200a}\x{2028}\x{2029}\x{202f}\x{205f}\x{3000}\x{feff}]';
        $value = preg_replace( '/\A' . $spaces . '+|' . $spaces . '+\z/u', '', $value );
        if ( ! is_string( $value ) || ! preg_match( '/^[+-]?(?:\d+(?:\.\d*)?|\.\d+)(?:e[+-]?\d+)?$/iD', $value ) ) { return $fallback; }
    } elseif ( ! is_int( $value ) && ! is_float( $value ) ) {
        return $fallback;
    }
    if ( ! is_finite( (float) $value ) ) { return $fallback; }
    return (int) max( $min, min( $max, floor( (float) $value + 0.5 ) ) );
}

function sflo_background_color( $value, $fallback ) {
    if ( ! is_string( $value ) ) { return $fallback; }
    if ( preg_match( '/^#[0-9a-f]{3}$/iD', $value ) ) {
        $value = '#' . $value[1] . $value[1] . $value[2] . $value[2] . $value[3] . $value[3];
    }
    return preg_match( '/^#[0-9a-f]{6}$/iD', $value ) ? strtolower( $value ) : $fallback;
}

function sflo_background_normalize( $input ) {
    $c = is_array( $input ) ? $input : array();
    return array(
        'family' => isset( $c['family'] ) && in_array( $c['family'], array( 'gradient', 'dots', 'grid', 'stripes' ), true ) ? $c['family'] : 'gradient',
        'background' => sflo_background_color( $c['background'] ?? null, '#eee8ff' ),
        'accent' => sflo_background_color( $c['accent'] ?? null, '#7255de' ),
        'scale' => sflo_background_number( $c['scale'] ?? null, 32, 8, 120 ),
        'angle' => sflo_background_number( $c['angle'] ?? null, 135, 0, 359 ),
        'motion' => ( $c['motion'] ?? null ) === true,
        'speed' => sflo_background_number( $c['speed'] ?? null, 16, 4, 40 ),
    );
}

function sflo_background_declarations( $input ) {
    $c = sflo_background_normalize( $input );
    if ( $c['family'] === 'dots' ) {
        $dot = (int) max( 1, min( 6, floor( $c['scale'] / 10 + 0.5 ) ) );
        $image = 'radial-gradient(circle,' . $c['accent'] . ' ' . $dot . 'px,transparent ' . ( $dot + 0.5 ) . 'px)';
        $size = $c['scale'] . 'px ' . $c['scale'] . 'px';
    } elseif ( $c['family'] === 'grid' ) {
        $image = 'linear-gradient(' . $c['accent'] . ' 1px,transparent 1px),linear-gradient(90deg,' . $c['accent'] . ' 1px,transparent 1px)';
        $size = $c['scale'] . 'px ' . $c['scale'] . 'px';
    } elseif ( $c['family'] === 'stripes' ) {
        $half = $c['scale'] / 2;
        $image = 'repeating-linear-gradient(' . $c['angle'] . 'deg,' . $c['background'] . ' 0px,' . $c['background'] . ' ' . $half . 'px,' . $c['accent'] . ' ' . $half . 'px,' . $c['accent'] . ' ' . $c['scale'] . 'px)';
        $size = 'auto';
    } else {
        $image = 'linear-gradient(' . $c['angle'] . 'deg,' . $c['background'] . ',' . $c['accent'] . ')';
        $size = '200% 200%';
    }
    return 'background-color:' . $c['background'] . ';background-image:' . $image . ';background-size:' . $size . ';background-position:0 0;';
}

/** Same bounded ASCII hash as the JavaScript exporter; no user CSS is accepted. */
function sflo_background_hash( $value ) {
    $hash = 0;
    for ( $i = 0, $length = strlen( $value ); $i < $length; $i++ ) { $hash = ( $hash * 31 + ord( $value[$i] ) ) & 0xffffffff; }
    return base_convert( (string) $hash, 10, 36 );
}

function sflo_background_stylesheet( $input, $requested_selector = '.sflo-background' ) {
    $c = sflo_background_normalize( $input );
    $target = is_string( $requested_selector ) && strlen( $requested_selector ) <= 80 && preg_match( '/^\.[a-z][a-z0-9-]*$/iD', $requested_selector ) ? $requested_selector : '.sflo-background';
    $css = $target . '{' . sflo_background_declarations( $c ) . '}';
    if ( $c['motion'] ) {
        $name = 'sfloBackgroundMove-' . sflo_background_hash( json_encode( $c ) . $target );
        $css .= '@keyframes ' . $name . '{from{background-position:0 0}to{background-position:' . ( $c['family'] === 'gradient' ? '100% 50%' : '64px 64px' ) . '}}'
            . $target . '{animation:' . $name . ' ' . $c['speed'] . 's ease-in-out infinite alternate}'
            . '@media(prefers-reduced-motion:reduce){' . $target . '{animation:none}}';
    }
    return $css;
}

function sflo_background_ink( $hex ) {
    $channels = array();
    foreach ( array( 1, 3, 5 ) as $offset ) {
        $v = hexdec( substr( $hex, $offset, 2 ) ) / 255;
        $channels[] = $v <= 0.04045 ? $v / 12.92 : pow( ( $v + 0.055 ) / 1.055, 2.4 );
    }
    return $channels[0] * 0.2126 + $channels[1] * 0.7152 + $channels[2] * 0.0722 > 0.179 ? '#111820' : '#ffffff';
}