<?php

declare(strict_types=1);

namespace Sarcio\WordPress\Assistant;

final class StyleAbilities
{
    /** @return array<int,Ability> */
    public static function abilities(): array
    {
        $allowed = static fn (array $args): bool => current_user_can('edit_theme_options');
        return [
            new Ability(
                'sarcio/css-get',
                __('Look at the extra styles', 'sarcio'),
                Ability::READ,
                'The site’s Additional CSS (the Customizer’s extra stylesheet for the active theme).',
                ['properties' => [], 'type' => 'object'],
                $allowed,
                static fn (array $args): array => ['css' => (string) wp_get_custom_css()],
            ),
            new Ability(
                'sarcio/styles-get',
                __('Look at the site styles', 'sarcio'),
                Ability::READ,
                'The site’s Global Styles as the owner set them in the Site Editor: the settings and styles objects (colors, typography, spacing) in theme.json form. Empty when nothing was customised.',
                ['properties' => [], 'type' => 'object'],
                $allowed,
                static fn (array $args): array => self::styles(),
            ),
            new Ability(
                'sarcio/styles-update',
                __('Change the site styles', 'sarcio'),
                Ability::WRITE,
                'Merge the given settings and styles objects (theme.json form, e.g. styles.color.background or styles.typography.fontSize) into the site’s Global Styles. Keys not given are kept. WordPress keeps a revision. No css keys: CSS text is refused.',
                [
                    'properties' => [
                        'settings' => ['additionalProperties' => true, 'type' => 'object'],
                        'styles' => ['additionalProperties' => true, 'type' => 'object'],
                    ],
                    'required' => [],
                    'type' => 'object',
                ],
                $allowed,
                static fn (array $args): array => self::updateStyles($args),
                null,
                static fn (array $before, array $after): array => self::writeStyles($before) + ['restored' => true],
                false,
                static fn (array $args, Overlay $overlay): array => self::stageStyles($args, $overlay),
            ),
        ];
    }

    /** Whether a styles or settings patch carries custom CSS text anywhere (styles.css, styles.blocks.*.css). */
    public static function carriesCss(mixed $value): bool
    {
        if (!is_array($value)) {
            return false;
        }
        foreach ($value as $key => $item) {
            if ($key === 'css' || self::carriesCss($item)) {
                return true;
            }
        }
        return false;
    }

    /** @param array<mixed> $value */
    private static function isList(array $value): bool
    {
        return $value === [] || array_keys($value) === range(0, count($value) - 1);
    }

    /**
     * @param array<string,mixed> $base
     * @param array<string,mixed> $patch
     */
    public static function merge(array $base, array $patch): array
    {
        foreach ($patch as $key => $value) {
            if (is_array($value) && isset($base[$key]) && is_array($base[$key]) && !self::isList($value)) {
                $base[$key] = self::merge($base[$key], $value);
            } else {
                $base[$key] = $value;
            }
        }
        return $base;
    }

    /** @return array{id:int,settings:array<string,mixed>,styles:array<string,mixed>,raw:array<string,mixed>} */
    private static function current(?Overlay $overlay = null): array
    {
        $id = class_exists('WP_Theme_JSON_Resolver') ? (int) \WP_Theme_JSON_Resolver::get_user_global_styles_post_id() : 0;
        $post = $id > 0 ? get_post($id) : null;
        $raw = $post !== null ? json_decode((string) $post->post_content, true) : null;
        $raw = is_array($raw) ? $raw : [];
        $staged = $overlay?->globalStyles;
        return [
            'id' => $id,
            'raw' => $raw,
            'settings' => $staged !== null ? $staged['settings'] : (is_array($raw['settings'] ?? null) ? $raw['settings'] : []),
            'styles' => $staged !== null ? $staged['styles'] : (is_array($raw['styles'] ?? null) ? $raw['styles'] : []),
        ];
    }

    private static function styles(): array
    {
        $current = self::current(Stage::active() ? Stage::overlay() : null);
        return ['settings' => $current['settings'], 'styles' => $current['styles']];
    }

    /** @param array<string,mixed> $args */
    private static function stageStyles(array $args, Overlay $overlay): array
    {
        if (self::carriesCss($args)) {
            return ['error' => __('Site styles take colours, fonts and spacing, not CSS text.', 'sarcio')];
        }
        $current = self::current($overlay);
        if ($current['id'] <= 0) {
            return ['error' => __('This theme does not support site styles.', 'sarcio')];
        }
        $before = ['settings' => $current['settings'], 'styles' => $current['styles']];
        $after = [
            'settings' => self::merge($current['settings'], (array) ($args['settings'] ?? [])),
            'styles' => self::merge($current['styles'], (array) ($args['styles'] ?? [])),
        ];
        if ($after === $before) {
            return ['error' => __('Nothing would change.', 'sarcio')];
        }
        $overlay->globalStyles = $after;
        $patch = array_filter(['settings' => $args['settings'] ?? [], 'styles' => $args['styles'] ?? []]);
        return [
            'after' => (string) wp_json_encode($patch, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES),
            'before' => (string) wp_json_encode(self::pick($before, $patch), JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES),
            'summary' => __('Change the site styles', 'sarcio'),
        ];
    }

    /** @param array<string,mixed> $args */
    private static function updateStyles(array $args): array
    {
        if (self::carriesCss($args)) {
            return ['error' => __('Site styles take colours, fonts and spacing, not CSS text.', 'sarcio')];
        }
        $current = self::current();
        if ($current['id'] <= 0) {
            return ['error' => __('This theme does not support site styles.', 'sarcio')];
        }
        $before = ['settings' => $current['settings'], 'styles' => $current['styles']];
        $after = [
            'settings' => self::merge($current['settings'], (array) ($args['settings'] ?? [])),
            'styles' => self::merge($current['styles'], (array) ($args['styles'] ?? [])),
        ];
        if ($after === $before) {
            return ['error' => __('Nothing would change.', 'sarcio')];
        }
        $written = self::writeStyles($after);
        if (isset($written['error'])) {
            return $written;
        }
        return [
            'journal' => [
                'after' => $after,
                'before' => $before,
                'summary' => __('Changed the site styles', 'sarcio'),
                'target' => 'global_styles',
            ],
            'saved' => true,
        ];
    }

    /** @param array<string,mixed> $fields */
    private static function writeStyles(array $fields): array
    {
        $current = self::current();
        if ($current['id'] <= 0) {
            return ['error' => __('This theme does not support site styles.', 'sarcio')];
        }
        $raw = $current['raw'];
        $raw['isGlobalStylesUserThemeJSON'] = true;
        $raw['version'] = $raw['version'] ?? (class_exists('WP_Theme_JSON') ? \WP_Theme_JSON::LATEST_SCHEMA : 3);
        $raw['settings'] = (array) ($fields['settings'] ?? []);
        $raw['styles'] = (array) ($fields['styles'] ?? []);
        $result = wp_update_post([
            'ID' => $current['id'],
            'post_content' => (string) wp_json_encode($raw, JSON_UNESCAPED_SLASHES),
        ], true);
        if (is_wp_error($result) || (int) $result <= 0) {
            return ['error' => __('WordPress could not save the site styles.', 'sarcio')];
        }
        return ['id' => $current['id']];
    }

    /**
     * The current values of exactly the keys a patch touches, so a before block
     * shows what changes and not the whole stylesheet.
     *
     * @param array<string,mixed> $current
     * @param array<string,mixed> $patch
     */
    private static function pick(array $current, array $patch): array
    {
        $out = [];
        foreach ($patch as $key => $value) {
            if (!array_key_exists($key, $current)) {
                continue;
            }
            $out[$key] = is_array($value) && is_array($current[$key]) && !self::isList($value)
                ? self::pick($current[$key], $value)
                : $current[$key];
        }
        return $out;
    }
}