<?php
defined('ABSPATH') || exit();
final class APEARI_Conversations
{
    public static function key(): string
    {
        return 'apeari_conversations_' . get_current_blog_id();
    }
    public static function restore(): array
    {
        $data = get_user_meta(get_current_user_id(), self::key(), true);
        if (!is_array($data)) {
            delete_user_meta(get_current_user_id(), self::key());
            return [];
        }
        $data['conversations'] = self::prune($data['conversations'] ?? []);
        if (!$data['conversations']) {
            delete_user_meta(get_current_user_id(), self::key());
            return [];
        }
        return $data;
    }
    public static function prune(array $threads): array
    {
        $now = time();
        $cutoff = $now - 7 * DAY_IN_SECONDS;
        foreach ($threads as $key => $messages) {
            $threads[$key] = array_values(
                array_filter(
                    is_array($messages) ? $messages : [],
                    static fn($message) => is_array($message) &&
                        is_int($message['createdAt'] ?? null) &&
                        $message['createdAt'] > $cutoff &&
                        $message['createdAt'] <= $now,
                ),
            );
            if (!$threads[$key]) {
                unset($threads[$key]);
            }
        }
        return $threads;
    }
    public static function clean(array $messages, bool $timestamps = false): array
    {
        $result = [];
        foreach (array_slice($messages, -100) as $message) {
            if (
                is_int($message['createdAt'] ?? null) &&
                $message['createdAt'] <= time() - 7 * DAY_IN_SECONDS
            ) {
                continue;
            }
            if (
                in_array($message['role'] ?? '', ['user', 'assistant'], true) &&
                is_string($message['content'] ?? null)
            ) {
                $result[] = [
                    'role' => $message['role'],
                    'content' => sanitize_textarea_field(mb_substr($message['content'], 0, 6000)),
                ];
                if ($timestamps && is_int($message['createdAt'] ?? null) && $message['createdAt'] <= time()) {
                    $result[array_key_last($result)]['createdAt'] = $message['createdAt'];
                }
            }
        }
        return $result;
    }
    public static function store(array &$data, string $thread, array $messages): void
    {
        $existing = [];
        foreach (self::prune($data['conversations'] ?? [])[$thread] ?? [] as $message) {
            $fingerprint = hash('sha256', $message['role'] . '|' . $message['content']);
            $existing[$fingerprint][] = $message['createdAt'];
        }
        $clean = self::clean($messages, true);
        foreach ($clean as &$message) {
            $fingerprint = hash('sha256', $message['role'] . '|' . $message['content']);
            $message['createdAt'] = !empty($existing[$fingerprint])
                ? array_shift($existing[$fingerprint])
                : $message['createdAt'] ?? time();
        }
        unset($message);
        $data['conversations'][$thread] = $clean;
        $data['conversations'] = array_slice($data['conversations'], -30, null, true);
    }
    public static function remember(string $id, array $data): void
    {
        if (!empty($data['remember'])) {
            $threads = self::prune($data['conversations'] ?? []);
            if (!$threads) {
                self::clear();
                return;
            }
            $latest = max(
                array_map(static fn($messages) => max(array_column($messages, 'createdAt')), $threads),
            );
            update_user_meta(
                get_current_user_id(),
                self::key(),
                wp_slash([
                    'sessionId' => $id,
                    'lastPage' => $data['lastPage'],
                    'conversations' => $threads,
                    'expires' => $latest + 7 * DAY_IN_SECONDS,
                ]),
            );
        }
    }
    public static function clear(): void
    {
        delete_user_meta(get_current_user_id(), self::key());
    }
}