<?php
/**
 * Per-form look: style preset, accent colour, label position and button
 * style.
 *
 * @package TFlexForms
 */

declare( strict_types = 1 );

namespace TFlexForms;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Reads, sanitizes and renders a form's Style tab settings.
 *
 * The look itself lives in tflexforms.css: each choice is a class on the
 * form and the accent colour is a CSS custom property, so a theme (or
 * WordPress's Additional CSS) can override any part of it.
 */
final class Style {

	/** Post meta holding the style settings. */
	public const META = '_tflexforms_style';

	/** Choices for each setting; the first one is the default. */
	public const PRESETS = array( 'default', 'theme', 'minimal', 'bordered' );
	public const LABELS  = array( 'above', 'beside' );
	public const BUTTONS = array( 'theme', 'filled', 'outline' );

	/** Largest corner radius and row spacing a form can set, in px. */
	public const RADIUS_MAX = 40;
	public const GAP_MAX    = 96;

	/** Preset a new form starts with (forms saved before it existed keep 'default'). */
	public const NEW_FORM_PRESET = 'theme';

	/**
	 * Default settings: the theme's own look, as before styles existed.
	 *
	 * @return array<string,string>
	 */
	public static function defaults(): array {
		return array(
			'preset'     => 'default',
			'accent'     => '', // A #rrggbb colour, or '' for none.
			'labels'     => 'above',
			'button'     => 'theme',
			// Overrides of the theme-based values ('' = take it from the theme).
			'radius'     => '', // Corner radius in px, 0 to RADIUS_MAX.
			'gap'        => '', // Space between rows in px, 0 to GAP_MAX.
			'border'     => '', // Field border colour, #rrggbb.
			'background' => '', // Field background colour, #rrggbb.
		);
	}

	/**
	 * A form's style settings, with defaults for anything not stored.
	 *
	 * @param int $form_id Form post ID.
	 * @return array<string,string>
	 */
	public static function get( int $form_id ): array {
		$stored = $form_id > 0 ? get_post_meta( $form_id, self::META, true ) : array();
		return self::sanitize( is_array( $stored ) ? $stored : array() );
	}

	/**
	 * Sanitizes style settings (also the registered meta sanitize callback).
	 * Unknown choices fall back to the default; unknown keys (such as the
	 * custom CSS that versions before 1.0.0 stored) are dropped.
	 *
	 * @param mixed $value Raw settings.
	 * @return array<string,string>
	 */
	public static function sanitize( mixed $value ): array {
		$value  = is_array( $value ) ? $value : array();
		$choose = static function ( string $key, array $choices ) use ( $value ): string {
			$choice = is_string( $value[ $key ] ?? null ) ? $value[ $key ] : '';
			return in_array( $choice, $choices, true ) ? $choice : $choices[0];
		};
		$colour = static function ( string $key ) use ( $value ): string {
			$hex = is_string( $value[ $key ] ?? null ) ? strtolower( trim( $value[ $key ] ) ) : '';
			return 1 === preg_match( '/^#[0-9a-f]{6}$/', $hex ) ? $hex : '';
		};
		$pixels = static function ( string $key, int $max ) use ( $value ): string {
			$number = is_scalar( $value[ $key ] ?? null ) ? trim( (string) $value[ $key ] ) : '';
			return 1 === preg_match( '/^\d{1,3}$/', $number ) && (int) $number <= $max ? (string) (int) $number : '';
		};
		return array(
			'preset'     => $choose( 'preset', self::PRESETS ),
			'accent'     => $colour( 'accent' ),
			'labels'     => $choose( 'labels', self::LABELS ),
			'button'     => $choose( 'button', self::BUTTONS ),
			'radius'     => $pixels( 'radius', self::RADIUS_MAX ),
			'gap'        => $pixels( 'gap', self::GAP_MAX ),
			'border'     => $colour( 'border' ),
			'background' => $colour( 'background' ),
		);
	}

	/**
	 * Settings posted from the Style tab, sanitized.
	 *
	 * @param mixed $posted Raw posted settings.
	 * @return array<string,string>
	 */
	public static function from_request( mixed $posted ): array {
		$posted = is_array( $posted ) ? $posted : array();
		// A colour input always sends a value; its checkbox says whether to use it.
		foreach ( array( 'accent', 'border', 'background' ) as $key ) {
			if ( empty( $posted[ $key . '_on' ] ) ) {
				$posted[ $key ] = '';
			}
		}
		return self::sanitize( $posted );
	}

	/**
	 * CSS classes for the form element.
	 *
	 * @param int                 $form_id Form post ID.
	 * @param array<string,mixed> $style   Sanitized settings.
	 * @return string[]
	 */
	public static function classes( int $form_id, array $style ): array {
		$classes = array(
			'tflexforms-form-' . $form_id,
			'tflexforms-style-' . $style['preset'],
			'tflexforms-labels-' . $style['labels'],
			'tflexforms-button-' . $style['button'],
		);
		if ( '' !== $style['accent'] ) {
			$classes[] = 'tflexforms-has-accent';
		}
		return $classes;
	}

	/**
	 * Extra classes for the submit button. With the Theme preset and the
	 * theme button, the button also gets WordPress's element class, so it
	 * looks like the buttons set in the theme's Global Styles.
	 *
	 * @param array<string,mixed> $style Sanitized settings.
	 * @return string[]
	 */
	public static function button_classes( array $style ): array {
		return 'theme' === $style['preset'] && 'theme' === $style['button'] ? array( 'wp-element-button' ) : array();
	}

	/**
	 * Inline custom properties for the form element ('' when none): the
	 * accent with a text colour that stays readable on it, and each override
	 * of a theme-based value. They win over the theme's values because they
	 * sit on the form itself.
	 *
	 * @param array<string,mixed> $style Sanitized settings.
	 */
	public static function inline_style( array $style ): string {
		$properties = array();
		if ( '' !== $style['accent'] ) {
			$properties['accent']      = $style['accent'];
			$properties['accent-text'] = self::text_on( $style['accent'] );
		}
		if ( '' !== ( $style['radius'] ?? '' ) ) {
			$properties['radius'] = $style['radius'] . 'px';
		}
		if ( '' !== ( $style['gap'] ?? '' ) ) {
			$properties['gap'] = $style['gap'] . 'px';
		}
		if ( '' !== ( $style['border'] ?? '' ) ) {
			$properties['border-color'] = $style['border'];
		}
		if ( '' !== ( $style['background'] ?? '' ) ) {
			$properties['field-background'] = $style['background'];
		}
		$css = array();
		foreach ( $properties as $name => $property_value ) {
			$css[] = '--tflexforms-' . $name . ':' . $property_value;
		}
		return implode( ';', $css );
	}

	/**
	 * Black or white, whichever contrasts more with a #rrggbb colour
	 * (WCAG relative luminance).
	 *
	 * @param string $hex Colour.
	 */
	public static function text_on( string $hex ): string {
		$channel   = static function ( string $pair ): float {
			$c = hexdec( $pair ) / 255;
			return $c <= 0.03928 ? $c / 12.92 : ( ( $c + 0.055 ) / 1.055 ) ** 2.4;
		};
		$luminance = 0.2126 * $channel( substr( $hex, 1, 2 ) ) + 0.7152 * $channel( substr( $hex, 3, 2 ) ) + 0.0722 * $channel( substr( $hex, 5, 2 ) );
		// Contrast with white is 1.05 / (L + 0.05); with black (L + 0.05) / 0.05.
		return 1.05 / ( $luminance + 0.05 ) >= ( $luminance + 0.05 ) / 0.05 ? '#ffffff' : '#000000';
	}
}