use redis::AsyncCommands;
use rocket_db_pools::Connection;

use crate::{
    db::{Postgres, Redis},
    messenger::ChatMsg,
};

// Helper function to cache message in Redis
pub async fn insert(
    cache: &mut Connection<Redis>,
    channel_id: i32,
    msg: &super::ChatMsg,
) -> Result<(), redis::RedisError> {
    let key = format!("messages:{}", channel_id);
    let msg_json = serde_json::to_string(msg).unwrap();

    redis::pipe()
        .atomic()
        .lpush(&key, &msg_json)
        .ltrim(&key, 0, 99)
        .expire(&key, 86400) // 24h expiry
        .query_async(&mut ***cache)
        .await
}

// Helper function to get cached messages from Redis
pub async fn get(
    redis: &mut Connection<Redis>,
    channel_id: i32,
) -> Result<Vec<super::ChatMsg>, redis::RedisError> {
    let key = format!("messages:{}", channel_id);

    // query last 100 messages
    let messages: Vec<ChatMsg> = redis
        .lrange::<_, Vec<String>>(&key, 0, 99)
        .await?
        .into_iter()
        .rev() // Reverse because LPUSH adds to front, so newest is first
        .filter_map(|msg_str| serde_json::from_str(&msg_str).ok())
        .collect();

    Ok(messages)
}

// Helper function to initialize cache from Postgres if empty
pub async fn initialise(
    cache: &mut Connection<Redis>,
    db: &mut Connection<Postgres>,
    channel_id: i32,
) -> Result<(), Box<dyn std::error::Error>> {
    let key = format!("messages:{}", channel_id);

    // less than 100 messages in cache?
    if cache.llen::<_, i32>(&key).await? < 100 {
        // Fetch from Postgres
        let messages = sqlx::query!(
            "SELECT u.username, u.display_name, u.id, m.content, m.created_at
             FROM messages m
             JOIN users u ON m.user_id = u.id
             WHERE m.channel_id = $1
             ORDER BY m.created_at DESC
             LIMIT 100",
            channel_id
        )
        .fetch_all(&mut ***db)
        .await?;

        // Populate cache (in reverse order so oldest is at the end)
        for msg in messages.into_iter().rev() {
            let msg_json = serde_json::to_string(&ChatMsg {
                display_name: Some(msg.display_name.unwrap_or(msg.username)),
                user_id: msg.id as usize,
                text: msg.content,
                timestamp: (msg.created_at.unwrap().unix_timestamp_nanos() / 1_000_000) as usize,
            })?;

            cache.lpush::<_, _, ()>(&key, &msg_json).await?;
        }

        cache.expire::<_, ()>(&key, 86400).await?;
    }

    Ok(())
}