use serde::Serialize;
use serde::de::DeserializeOwned;
use sqlx::SqlitePool;

use crate::errors::*;


pub async fn save<T>(pool: &SqlitePool, name: &str, value: &T) -> Result<(), sqlx::Error>
    where T: Serialize
{
    let bytes = serde_json::to_vec(value).unwrap();
    save_bytes(pool, name, &bytes).await
}


pub async fn save_bytes(pool: &SqlitePool, name: &str, bytes: &[u8]) -> Result<(), sqlx::Error> {
    sqlx::query!(
        "INSERT INTO kv (name, value) VALUES (?, ?)
        ON CONFLICT(name) DO UPDATE SET value = excluded.value;",
        name,
        bytes,
    ).execute(pool).await?;
    Ok(())
}


pub async fn load<T>(pool: &SqlitePool, name: &str) -> Result<Option<T>, LoadKvError>
    where T: DeserializeOwned
{
    let v = load_bytes(pool, name)
        .await?
        .map(|bytes| serde_json::from_slice(&bytes))
        .transpose()?;
    Ok(v)
}


pub async fn load_bytes(pool: &SqlitePool, name: &str) -> Result<Option<Vec<u8>>, sqlx::Error> {
    sqlx::query!("SELECT name, value FROM kv WHERE name = ?", name)
        .map(|row| row.value)
        .fetch_optional(pool)
        .await
        .map(|o| o.flatten())
}


macro_rules! load_bytes_multi {
    (
        $pool:ident,
        $($name:literal),*
    ) => {
        // wrap everything up in an async block for easy short-circuiting...
        async {
            // ...returning a Result...
            Ok::<_, sqlx::Error>(
                //containing an Option...
                Some(
                    // containing a tuple...
                    (
                        // ...with one item for each repetition of $name
                        $(
                            // load_bytes returns Result<Option<_>>, the Result is handled by 
                            // the ? and we match on the Option
                            match crate::kv::load_bytes($pool, $name).await? {
                                Some(v) => v,
                                None => return Ok(None)
                            },
                        )*
                    )
                )
            )
        }
    }
}

pub(crate) use load_bytes_multi;


// macro_rules! load_multi {
//     (
//         $pool:ident,
//         $($name:literal),*
//     ) => {
//         (|| {
//             (
//                 $(
//                     match load(pool, $name)? {
//                         Some(v) => v,
//                         None => return Ok(None)
//                     },
//                 )*
//             )
//         })()
//     }
// }