//! Time Sync

use std::time::Duration;
use chrono::{DateTime, Utc};
use tracing::{debug, warn, error};

const TIME_SYNC_URL: &str = "https://core.telegram.org/getProxySecret";
const MAX_TIME_SKEW_SECS: i64 = 30;

/// Time sync result
#[derive(Debug, Clone)]
pub struct TimeSyncResult {
    pub server_time: DateTime<Utc>,
    pub local_time: DateTime<Utc>,
    pub skew_secs: i64,
    pub is_skewed: bool,
}

/// Check time synchronization with Telegram servers
pub async fn check_time_sync() -> Option<TimeSyncResult> {
    let client = reqwest::Client::builder()
        .timeout(Duration::from_secs(10))
        .build()
        .ok()?;
    
    let response = client.get(TIME_SYNC_URL).send().await.ok()?;
    
    // Get Date header
    let date_header = response.headers().get("date")?;
    let date_str = date_header.to_str().ok()?;
    
    // Parse date
    let server_time = DateTime::parse_from_rfc2822(date_str)
        .ok()?
        .with_timezone(&Utc);
    
    let local_time = Utc::now();
    let skew_secs = (local_time - server_time).num_seconds();
    let is_skewed = skew_secs.abs() > MAX_TIME_SKEW_SECS;
    
    let result = TimeSyncResult {
        server_time,
        local_time,
        skew_secs,
        is_skewed,
    };
    
    if is_skewed {
        warn!(
            server = %server_time,
            local = %local_time,
            skew = skew_secs,
            "Time skew detected"
        );
    } else {
        debug!(skew = skew_secs, "Time sync OK");
    }
    
    Some(result)
}

/// Background time sync task
pub async fn time_sync_task(check_interval: Duration) -> ! {
    loop {
        if let Some(result) = check_time_sync().await {
            if result.is_skewed {
                error!(
                    "System clock is off by {} seconds. Please sync your clock.",
                    result.skew_secs
                );
            }
        }
        
        tokio::time::sleep(check_interval).await;
    }
}