<?php
/**
 * AKSRT Download State
 *
 * Unified download state resolver for resource pages.
 * Replaces scattered per-template download status checks
 * with a single service that returns a normalized state object.
 *
 * @package AKSRT
 */

defined('ABSPATH') || exit;

class AKSRT_Download_State {

    private static $instance = null;

    /**
     * State constants
     */
    const STATE_NOT_LOGGED_IN = 'not_logged_in';
    const STATE_NO_PERMISSION = 'no_permission';
    const STATE_INSUFFICIENT_CREDITS = 'insufficient_credits';
    const STATE_OWNED           = 'owned';
    const STATE_AVAILABLE       = 'available';
    const STATE_PENDING_DELIVERY = 'pending_delivery';

    private function __construct() {}

    public static function get_instance(): self {
        if (null === self::$instance) {
            self::$instance = new self();
        }
        return self::$instance;
    }

    /**
     * Resolve the current user's download state for a given resource post.
     *
     * @param int $post_id Resource post ID.
     * @return array {
     *     @type string $state       One of the STATE_* constants.
     *     @type bool   $can_download Whether the user can initiate download.
     *     @type string $message      Human-readable status message.
     *     @type string $action_label Suggested button label.
     *     @type string $action_url   Suggested button URL (if applicable).
     *     @type int    $cost         Download cost in credits.
     *     @type int    $balance      Current user credit balance.
     *     @type string $login_url    Login URL (if not logged in).
     * }
     */
    public function resolve(int $post_id): array {
        $meta = function_exists('aksrt_get_resource_meta') ? aksrt_get_resource_meta($post_id) : [];
        $price = (float) ($meta['price'] ?? 0);
        $downloads = is_array($meta['downloads'] ?? null) ? $meta['downloads'] : [];

        $is_logged_in = is_user_logged_in();
        $user_id = $is_logged_in ? get_current_user_id() : 0;
        $login_url = wp_login_url(get_permalink($post_id));

        // No downloads available
        if (empty($downloads)) {
            return $this->build_result(
                self::STATE_NO_PERMISSION,
                false,
                __('该资源暂未提供下载链接。', 'aksrt'),
                __('暂无下载', 'aksrt'),
                '',
                0, 0, $login_url
            );
        }

        // Not logged in
        if (!$is_logged_in) {
            $requires_login = false;
            if (class_exists('AKSRT_Settings')) {
                $paid = AKSRT_Settings::get_paid_content_settings();
                $requires_login = !empty($paid['download_requires_login']);
            }
            if ($requires_login) {
                return $this->build_result(
                    self::STATE_NOT_LOGGED_IN,
                    false,
                    __('登录后可下载此资源。', 'aksrt'),
                    __('登录下载', 'aksrt'),
                    $login_url,
                    0, 0, $login_url
                );
            }
        }

        // Check gate (credits, permission, etc.)
        $gate = function_exists('aksrt_can_download') ? aksrt_can_download($post_id) : true;
        if (is_wp_error($gate)) {
            $code = $gate->get_error_code();
            $data = (array) $gate->get_error_data();
            $balance = (int) ($data['balance'] ?? 0);
            $cost = function_exists('aksrt_resource_download_cost')
                ? aksrt_resource_download_cost($post_id)
                : (int) ceil($price);

            if ($code === 'aksrt_need_login') {
                return $this->build_result(
                    self::STATE_NOT_LOGGED_IN,
                    false,
                    __('登录后可下载此资源。', 'aksrt'),
                    __('登录下载', 'aksrt'),
                    (string) ($data['login_url'] ?? $login_url),
                    $cost, $balance, (string) ($data['login_url'] ?? $login_url)
                );
            }

            if ($code === 'aksrt_credits_insufficient') {
                return $this->build_result(
                    self::STATE_INSUFFICIENT_CREDITS,
                    false,
                    sprintf(
                        /* translators: 1: current balance, 2: required cost */
                        __('当前余额 %1$d 积分，需要 %2$d 积分。', 'aksrt'),
                        $balance,
                        $cost
                    ),
                    sprintf(__('付费下载（%d 积分）', 'aksrt'), $cost),
                    '',
                    $cost, $balance, $login_url
                );
            }

            // Other gate error — treat as no permission
            return $this->build_result(
                self::STATE_NO_PERMISSION,
                false,
                $gate->get_error_message() ?: __('无下载权限。', 'aksrt'),
                __('无权限', 'aksrt'),
                '',
                0, 0, $login_url
            );
        }

        // Check if user already owns/downloads
        $has_downloaded = false;
        if ($is_logged_in) {
            $downloaded = get_user_meta($user_id, '_aksrt_downloaded_resources', true);
            $downloaded = is_array($downloaded) ? $downloaded : [];
            $has_downloaded = in_array($post_id, $downloaded, true);
        }

        $cost = function_exists('aksrt_resource_download_cost')
            ? aksrt_resource_download_cost($post_id)
            : (int) ceil($price);
        $balance = 0;
        if ($is_logged_in && class_exists('AKSRT_Credits')) {
            $balance = AKSRT_Credits::balance($user_id);
        }

        if ($has_downloaded) {
            return $this->build_result(
                self::STATE_OWNED,
                true,
                __('已下载，可再次下载。', 'aksrt'),
                __('再次下载', 'aksrt'),
                '',
                $cost, $balance, $login_url
            );
        }

        // Available
        $label = $cost > 0
            ? sprintf(__('下载（%d 积分）', 'aksrt'), $cost)
            : __('立即下载', 'aksrt');

        return $this->build_result(
            self::STATE_AVAILABLE,
            true,
            $cost > 0
                ? sprintf(__('下载此资源将消耗 %d 积分。', 'aksrt'), $cost)
                : __('此资源可免费下载。', 'aksrt'),
            $label,
            '',
            $cost, $balance, $login_url
        );
    }

    /**
     * Build a normalized result array.
     */
    private function build_result(
        string $state,
        bool $can_download,
        string $message,
        string $action_label,
        string $action_url,
        int $cost,
        int $balance,
        string $login_url
    ): array {
        return [
            'state'        => $state,
            'can_download' => $can_download,
            'message'      => $message,
            'action_label' => $action_label,
            'action_url'   => $action_url,
            'cost'         => $cost,
            'balance'      => $balance,
            'login_url'    => $login_url,
        ];
    }
}