<?php

namespace AcademicCrew\Core;

/**
 * Resolves the admin-configured colour palette and fonts (Settings →
 * Appearance) against the built-in defaults defined in assets/css/system.css.
 */
class Appearance {

    public const DEFAULT_PRIMARY   = '#0d2340';
    public const DEFAULT_SECONDARY = '#1cb0c9';
    public const DEFAULT_ACCENT    = '#c8102e';

    public static function primary_color(): string {
        return self::color_setting( 'appearance_primary_color', self::DEFAULT_PRIMARY );
    }

    public static function secondary_color(): string {
        return self::color_setting( 'appearance_secondary_color', self::DEFAULT_SECONDARY );
    }

    public static function accent_color(): string {
        return self::color_setting( 'appearance_accent_color', self::DEFAULT_ACCENT );
    }

    public static function display_font_slug(): string {
        $slug = (string) ( self::settings()['appearance_font_display'] ?? '' );
        return FontRegistry::is_valid_display( $slug ) ? $slug : FontRegistry::DEFAULT_DISPLAY;
    }

    public static function body_font_slug(): string {
        $slug = (string) ( self::settings()['appearance_font_body'] ?? '' );
        return FontRegistry::is_valid_body( $slug ) ? $slug : FontRegistry::DEFAULT_BODY;
    }

    public static function is_customized(): bool {
        return self::primary_color()   !== self::DEFAULT_PRIMARY
            || self::secondary_color() !== self::DEFAULT_SECONDARY
            || self::accent_color()    !== self::DEFAULT_ACCENT
            || self::display_font_slug() !== FontRegistry::DEFAULT_DISPLAY
            || self::body_font_slug()    !== FontRegistry::DEFAULT_BODY;
    }

    /**
     * :root override block re-pointing the design tokens at the admin's
     * chosen palette/fonts. Always emitted (even at defaults) so it is the
     * single place these five tokens are set to their effective value.
     */
    public static function css_overrides(): string {
        $vars = [
            '--acc-primary'      => self::primary_color(),
            '--acc-secondary'    => self::secondary_color(),
            '--acc-accent'       => self::accent_color(),
            '--acc-font-display' => FontRegistry::display_stack( self::display_font_slug() ),
            '--acc-font-body'    => FontRegistry::body_stack( self::body_font_slug() ),
        ];

        $decls = '';
        foreach ( $vars as $name => $value ) {
            $decls .= $name . ':' . $value . ';';
        }

        return ':root{' . $decls . '}';
    }

    /**
     * Google Fonts URL for any chosen font that isn't already loaded by the
     * default @import in system.css (Zilla Slab, DM Sans). Returns null when
     * both fonts are system fonts or already covered by the default import.
     */
    public static function google_fonts_url(): ?string {
        $params = [];

        if ( self::display_font_slug() !== FontRegistry::DEFAULT_DISPLAY ) {
            $param = FontRegistry::display_google_param( self::display_font_slug() );
            if ( $param ) {
                $params[] = 'family=' . $param;
            }
        }
        if ( self::body_font_slug() !== FontRegistry::DEFAULT_BODY ) {
            $param = FontRegistry::body_google_param( self::body_font_slug() );
            if ( $param ) {
                $params[] = 'family=' . $param;
            }
        }

        if ( ! $params ) {
            return null;
        }

        return 'https://fonts.googleapis.com/css2?' . implode( '&', $params ) . '&display=swap';
    }

    private static function color_setting( string $key, string $default ): string {
        $value = (string) ( self::settings()[ $key ] ?? '' );
        return $value !== '' && preg_match( '/^#[0-9a-fA-F]{6}$/', $value ) ? $value : $default;
    }

    private static function settings(): array {
        return get_option( 'academiccrew_settings', [] );
    }
}