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use std::{ops::Deref, sync::Arc};

use r2d2::Pool;
use uuid::Uuid;

use super::backend::{r#trait::Backend, Error as BackendError};

struct ConnectionPool<B: Backend> {
    backend: Arc<B>,
    db_id: Uuid,
    conn_pool: Option<Pool<B::ConnectionManager>>,
    is_restricted: bool,
}

impl<B: Backend> Deref for ConnectionPool<B> {
    type Target = Pool<B::ConnectionManager>;

    fn deref(&self) -> &Self::Target {
        self.conn_pool
            .as_ref()
            .expect("conn_pool must always contain a [Some] value")
    }
}

impl<B: Backend> Drop for ConnectionPool<B> {
    fn drop(&mut self) {
        self.conn_pool = None;
        (*self.backend).drop(self.db_id, self.is_restricted).ok();
    }
}

/// Reusable connection pool wrapper
pub struct ReusableConnectionPool<B: Backend>(ConnectionPool<B>);

impl<B: Backend> ReusableConnectionPool<B> {
    pub(crate) fn new(
        backend: Arc<B>,
    ) -> Result<Self, BackendError<B::ConnectionError, B::QueryError>> {
        let db_id = Uuid::new_v4();
        let conn_pool = backend.create(db_id, true)?;

        Ok(Self(ConnectionPool {
            backend,
            db_id,
            conn_pool: Some(conn_pool),
            is_restricted: true,
        }))
    }

    pub(crate) fn clean(&mut self) -> Result<(), BackendError<B::ConnectionError, B::QueryError>> {
        self.0.backend.clean(self.0.db_id)
    }
}

impl<B: Backend> Deref for ReusableConnectionPool<B> {
    type Target = Pool<B::ConnectionManager>;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

/// Single-use connection pool wrapper
pub struct SingleUseConnectionPool<B: Backend>(ConnectionPool<B>);

impl<B: Backend> SingleUseConnectionPool<B> {
    pub(crate) fn new(
        backend: Arc<B>,
    ) -> Result<Self, BackendError<B::ConnectionError, B::QueryError>> {
        let db_id = Uuid::new_v4();
        let conn_pool = backend.create(db_id, false)?;

        Ok(Self(ConnectionPool {
            backend,
            db_id,
            conn_pool: Some(conn_pool),
            is_restricted: false,
        }))
    }
}

impl<B: Backend> Deref for SingleUseConnectionPool<B> {
    type Target = Pool<B::ConnectionManager>;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}