<?php

declare(strict_types=1);

namespace Sarcio\WordPress\Assistant;

/**
 * The site as it would look with the staged changes applied: fields of posts,
 * options, the site styles, menu items and product
 * prices, layered over what WordPress holds. Nothing here is written; the
 * abilities read through it while a preview is active, and the front end
 * renders through it for the one browser that holds the preview cookie.
 */
final class Overlay
{
    /** @var array<int,array<string,mixed>> post id => WP_Post fields */
    public array $posts = [];

    /** @var array<string,mixed> option name => value */
    public array $options = [];

    /** @var array<string,mixed> extension ability name => what it staged */
    public array $extensions = [];

    /** @var array{settings:array<string,mixed>,styles:array<string,mixed>}|null */
    public ?array $globalStyles = null;

    /** @var array<int,array{added:array<int,array<string,mixed>>,removed:array<int,int>,updated:array<int,array<string,mixed>>}> menu id => edits */
    public array $menus = [];

    /** @var array<int,array<string,mixed>> product id => meta fields */
    public array $products = [];

    /** @var array<string,string> template part slug => block markup, for parts the site has not customised */
    public array $templateParts = [];

    /** @var array<int,array<string,mixed>> post id => meta key => staged value (a page builder's data) */
    public array $meta = [];

    private int $nextItemId = -1;

    public function empty(): bool
    {
        return $this->posts === [] && $this->options === [] && $this->extensions === [] && $this->globalStyles === null && $this->menus === [] && $this->products === [] && $this->templateParts === [] && $this->meta === [];
    }

    /** A post with the staged fields applied, or null when it does not exist. */
    public function post(int $id): ?object
    {
        $post = get_post($id);
        if ($post === null) {
            return null;
        }
        return $this->applyToPost($post);
    }

    public function applyToPost(object $post): object
    {
        $fields = $this->posts[(int) $post->ID] ?? null;
        if ($fields === null) {
            return $post;
        }
        $copy = clone $post;
        foreach ($fields as $key => $value) {
            $copy->$key = $value;
        }
        return $copy;
    }

    public function setMeta(int $id, string $key, mixed $value): void
    {
        $this->meta[$id] ??= [];
        $this->meta[$id][$key] = $value;
    }

    /** @param array<string,mixed> $fields WP_Post field names */
    public function setPost(int $id, array $fields): void
    {
        $this->posts[$id] ??= [];
        foreach ($fields as $key => $value) {
            $this->posts[$id][$key] = $value;
        }
    }

    public function option(string $name, mixed $default = false): mixed
    {
        return array_key_exists($name, $this->options) ? $this->options[$name] : get_option($name, $default);
    }

    /** @return array<int,object> */
    public function menuItems(int $menuId): array
    {
        $items = (array) wp_get_nav_menu_items($menuId);
        return $this->applyToMenu($menuId, array_values(array_filter($items, 'is_object')));
    }

    /**
     * @param array<int,object> $items
     * @return array<int,object>
     */
    public function applyToMenu(int $menuId, array $items): array
    {
        $edits = $this->menus[$menuId] ?? null;
        if ($edits === null) {
            return $items;
        }
        $out = [];
        foreach ($items as $item) {
            $id = (int) $item->ID;
            if (in_array($id, $edits['removed'], true)) {
                continue;
            }
            if (isset($edits['updated'][$id])) {
                $item = clone $item;
                foreach ($edits['updated'][$id] as $key => $value) {
                    $item->$key = $value;
                }
            }
            $out[] = $item;
        }
        foreach ($edits['added'] as $added) {
            $out[] = (object) $added;
        }
        usort($out, static fn (object $a, object $b): int => ((int) ($a->menu_order ?? 0)) <=> ((int) ($b->menu_order ?? 0)));
        return $out;
    }

    /** @return int the id the preview knows the new item by (negative, so it can never collide) */
    public function addMenuItem(int $menuId, array $fields): int
    {
        $this->menu($menuId);
        $id = $this->nextItemId--;
        $this->menus[$menuId]['added'][] = self::menuItemObject($id, $menuId, $fields);
        return $id;
    }

    /** @param array<string,mixed> $fields WP nav menu item object fields */
    public function updateMenuItem(int $menuId, int $itemId, array $fields): void
    {
        $this->menu($menuId);
        if ($itemId < 0) {
            foreach ($this->menus[$menuId]['added'] as $index => $added) {
                if ((int) $added['ID'] === $itemId) {
                    $this->menus[$menuId]['added'][$index] = array_merge($added, $fields);
                }
            }
            return;
        }
        $this->menus[$menuId]['updated'][$itemId] = array_merge($this->menus[$menuId]['updated'][$itemId] ?? [], $fields);
    }

    public function removeMenuItem(int $menuId, int $itemId): void
    {
        $this->menu($menuId);
        if ($itemId < 0) {
            $this->menus[$menuId]['added'] = array_values(array_filter($this->menus[$menuId]['added'], static fn (array $added): bool => (int) $added['ID'] !== $itemId));
            return;
        }
        $this->menus[$menuId]['removed'][] = $itemId;
        unset($this->menus[$menuId]['updated'][$itemId]);
    }

    /** The staged product fields over the ones given (the ability's snapshot shape). */
    public function applyToProduct(int $id, array $snapshot): array
    {
        return array_merge($snapshot, $this->products[$id] ?? []);
    }

    /** @param array<string,mixed> $fields the ability's snapshot shape */
    public function setProduct(int $id, array $fields): void
    {
        $this->products[$id] = array_merge($this->products[$id] ?? [], $fields);
    }

    /** What a staged product's meta reads as on the front end, or null for a key the preview does not touch. */
    public function productMeta(int $id, string $key): ?string
    {
        $fields = $this->products[$id] ?? null;
        if ($fields === null) {
            return null;
        }
        switch ($key) {
            case '_regular_price':
                return isset($fields['regularPrice']) ? (string) $fields['regularPrice'] : null;
            case '_sale_price':
                return isset($fields['salePrice']) ? (string) $fields['salePrice'] : null;
            case '_price':
                if (!isset($fields['regularPrice']) && !isset($fields['salePrice']) && !isset($fields['saleFrom']) && !isset($fields['saleTo'])) {
                    return null;
                }
                $regular = (string) ($fields['regularPrice'] ?? get_post_meta($id, '_regular_price', true));
                $sale = (string) ($fields['salePrice'] ?? get_post_meta($id, '_sale_price', true));
                $from = (string) ($fields['saleFrom'] ?? '');
                $to = (string) ($fields['saleTo'] ?? '');
                $today = gmdate('Y-m-d');
                $onSale = $sale !== '' && ($from === '' || $from <= $today) && ($to === '' || $to >= $today);
                return $onSale ? $sale : $regular;
            case '_stock_status':
                return isset($fields['stockStatus']) ? (string) $fields['stockStatus'] : null;
            case '_stock':
                return array_key_exists('stockQuantity', $fields) && $fields['stockQuantity'] !== null ? (string) $fields['stockQuantity'] : null;
            case '_manage_stock':
                return array_key_exists('stockQuantity', $fields) && $fields['stockQuantity'] !== null ? 'yes' : null;
            default:
                return null;
        }
    }

    private function menu(int $menuId): void
    {
        $this->menus[$menuId] ??= ['added' => [], 'removed' => [], 'updated' => []];
    }

    /** @param array<string,mixed> $fields */
    public static function menuItemObject(int $id, int $menuId, array $fields): array
    {
        $objectId = (int) ($fields['objectId'] ?? 0);
        $url = $objectId > 0 ? (string) get_permalink($objectId) : (string) ($fields['url'] ?? '');
        return [
            'ID' => $id,
            'attr_title' => '',
            'classes' => [],
            'db_id' => $id,
            'description' => '',
            'menu_item_parent' => (int) ($fields['parent'] ?? 0),
            'menu_order' => (int) ($fields['position'] ?? 0) > 0 ? (int) $fields['position'] : 9999,
            'object' => $objectId > 0 ? (string) ($fields['object'] ?? (get_post_type($objectId) ?: 'page')) : 'custom',
            'object_id' => $objectId,
            'post_parent' => 0,
            'post_title' => (string) ($fields['title'] ?? ''),
            'post_type' => 'nav_menu_item',
            'target' => '',
            'title' => (string) ($fields['title'] ?? ''),
            'type' => $objectId > 0 ? 'post_type' : 'custom',
            'type_label' => $objectId > 0 ? __('Page', 'sarcio') : __('Custom Link', 'sarcio'),
            'url' => $url,
            'xfn' => '',
            'menu_id' => $menuId,
        ];
    }
}