<?php
/** Signed display control with atomic local revision checks and durable readback. */
if (!defined('ABSPATH')) { exit; }

final class Chat4U_Placement {
    public static function ensure(): void {
        if (get_option('chat4u_placement_version') !== CHAT4U_VERSION) {
            update_option('chat4u_placement_version', CHAT4U_VERSION, false);
            self::invalidate_home();
        }
    }
    public static function snapshot(?array $state = null): array {
        $state = $state ?? Chat4U_Protocol::connection();
        return ['revision' => (int) ($state['placement_revision'] ?? 0),
            'enabled' => !empty($state['widget_enabled']),
            'intent_revision' => (int) ($state['placement_intent_revision'] ?? 0),
            'operation_id' => $state['placement_operation'] ?? null,
            'origin' => $state['placement_origin'] ?? null,
            'observe_existing' => !empty($state['placement_observe_existing'])];
    }

    public static function capability(): array {
        $state = Chat4U_Protocol::connection();
        return ['version' => 1, 'grant_version' => (int) ($state['pending']['placement_grant'] ?? $state['placement_grant'] ?? 0),
                'state' => self::snapshot($state)];
    }

    private static function compare_and_set(array $before, array $after): bool {
        global $wpdb;
        $changed = $wpdb->query($wpdb->prepare('UPDATE %i SET option_value = %s WHERE option_name = %s AND option_value = %s',
            $wpdb->options, maybe_serialize($after), 'chat4u_connection', maybe_serialize($before)));
        wp_cache_delete('chat4u_connection', 'options');
        wp_cache_delete('alloptions', 'options');
        return $changed === 1;
    }

    public static function control(WP_REST_Request $request) {
        $state = Chat4U_Protocol::connection();
        if (($state['placement_grant'] ?? 0) !== 1 || ($state['state'] ?? '') !== 'connected') {
            return new WP_Error('chat4u_placement_permission_required', __('Confirm the new setup controls from WordPress.', 'chat4u'), ['status' => 409]);
        }
        if ($request->get_method() === 'GET') { return Chat4U_Protocol::response($request, self::snapshot($state)); }
        $operation = $request->get_param('operation_id');
        $enabled = $request->get_param('enabled');
        $expected = $request->get_param('expected_revision');
        $intent = $request->get_param('intent_revision');
        $observe = $request->get_param('observe_existing') ?? false;
        if (!is_string($operation) || !preg_match('/^[a-f0-9]{8}-(?:[a-f0-9]{4}-){3}[a-f0-9]{12}$/Di', $operation) ||
            !is_bool($enabled) || !is_int($expected) || $expected < 0 || !is_int($intent) || $intent < 1 || !is_bool($observe)) {
            return new WP_Error('chat4u_placement_invalid', __('Review the website display choice in Chat4U.', 'chat4u'), ['status' => 422]);
        }
        $receipts = $state['placement_receipts'] ?? [];
        $command_hash = hash('sha256', wp_json_encode([$enabled, $expected, $intent, $observe]));
        if (isset($receipts[$operation])) {
            if (($receipts[$operation]['command_hash'] ?? '') !== $command_hash) {
                return new WP_Error('chat4u_placement_changed', __('Review the saved display choice in Chat4U.', 'chat4u'), ['status' => 409]);
            }
            return Chat4U_Protocol::response($request, self::snapshot($state) + ['original_receipt' => $receipts[$operation]]);
        }
        if ($expected !== (int) ($state['placement_revision'] ?? 0)) {
            return Chat4U_Protocol::response($request, self::snapshot($state) + ['conflict' => true]);
        }
        $next = $state;
        $next['widget_enabled'] = $enabled;
        $next['placement_revision'] = $expected + 1;
        $next['placement_intent_revision'] = $intent;
        $next['placement_operation'] = $operation;
        $next['placement_origin'] = 'chat4u';
        $next['placement_observe_existing'] = $observe;
        $receipts[$operation] = self::snapshot($next) + ['command_hash' => $command_hash];
        $next['placement_receipts'] = array_slice($receipts, -100, null, true);
        if (!self::compare_and_set($state, $next)) {
            return Chat4U_Protocol::response($request, self::snapshot() + ['conflict' => true]);
        }
        self::invalidate_home();
        return Chat4U_Protocol::response($request, self::snapshot($next));
    }

    public static function local_save(bool $enabled): bool {
        for ($attempt = 0; $attempt < 3; $attempt++) {
            $state = Chat4U_Protocol::connection();
            if (($state['state'] ?? '') !== 'connected') { return false; }
            $next = $state;
            $next['widget_enabled'] = $enabled;
            $next['placement_revision'] = (int) ($state['placement_revision'] ?? 0) + 1;
            $next['placement_origin'] = 'wordpress';
            $next['placement_operation'] = wp_generate_uuid4();
            $next['placement_observe_existing'] = false;
            if (self::compare_and_set($state, $next)) {
                update_option('chat4u_placement_delivery', ['delivery_id' => wp_generate_uuid4(), 'placement' => self::snapshot($next)], false);
                wp_schedule_single_event(time() + 1, 'chat4u_deliver_placement');
                self::invalidate_home();
                return true;
            }
        }
        return false;
    }

    public static function deliver(): void {
        $delivery = get_option('chat4u_placement_delivery', []);
        $state = Chat4U_Protocol::connection();
        if (!$delivery || ($state['state'] ?? '') !== 'connected') { return; }
        $result = Chat4U_Protocol::remote('events', ['installation_id' => $state['scope'],
            'topic' => 'visibility', 'removed' => [], 'delivery_id' => $delivery['delivery_id'], 'placement' => $delivery['placement']], $state);
        if (!is_wp_error($result)) {
            if (get_option('chat4u_placement_delivery') === $delivery) { delete_option('chat4u_placement_delivery'); }
        } else { wp_schedule_single_event(time() + 60, 'chat4u_deliver_placement'); }
    }

    public static function public_state(): WP_REST_Response {
        $state = Chat4U_Protocol::connection();
        $connected = ($state['state'] ?? '') === 'connected' && ($state['site_url'] ?? '') === untrailingslashit(get_option('home'));
        $value = self::snapshot($state);
        $response = new WP_REST_Response($connected ? $value + ['installation_id' => $state['scope'], 'generation' => $state['generation']] : ['enabled' => false]);
        $response->header('Cache-Control', 'no-store, max-age=0');
        return $response;
    }

    private static function invalidate_home(): void {
        // Only the affected public homepage; never flush unrelated site/CDN data.
        $front = (int) get_option('page_on_front');
        if ($front) { clean_post_cache($front); }
        do_action('litespeed_purge_url', home_url('/'));
        if (function_exists('rocket_clean_files')) { rocket_clean_files([home_url('/')]); }
    }
}