use tokio_postgres::{config::Config as PgConfig, row::Row};
use deadpool_postgres::{Manager, Object, ManagerConfig, Pool, Transaction,
                        RecyclingMethod};
use std::error::Error;
use std::str::FromStr;
use ouroboros::self_referencing;
use uuid::Uuid;
use tokio_postgres::NoTls;
use crate::message_handler::ListenerSession;
use crate::DResult;
use crate::models::{session::Session, user::User, item::Item};

use serde_json;
use futures::FutureExt;

#[derive(Clone, Debug)]
pub struct DBPool {
    pool: Pool
}

#[self_referencing]
pub struct DBTrans {
    conn: Object,
    #[borrows(mut conn)]
    #[covariant]
    pub trans: Option<Transaction<'this>>
}

#[derive(Clone, Debug)]
pub struct SendqueueItem {
    pub item: i64,
    pub session: ListenerSession,
    pub message: Option<String>
}
impl From<Row> for SendqueueItem {
    fn from(row: Row) -> Self {
        SendqueueItem {
            item: row.get("item"),
            session: ListenerSession {
                session: row.get("session"),
                listener: row.get("listener")
            },
            message: row.get("message")
        }
    }
}

impl DBPool {
    pub async fn record_listener_ping(self: &DBPool, listener: Uuid) -> DResult<()> {
        self.get_conn().await?.execute(
            "INSERT INTO listeners (listener, last_seen) \
             VALUES ($1, NOW()) \
             ON CONFLICT (listener) \
             DO UPDATE SET last_seen = EXCLUDED.last_seen", &[&listener]).await?;
        Ok(())
    }

    pub async fn get_dead_listeners(self: &Self) -> DResult<Vec<Uuid>> {
        Ok(self.get_conn().await?
           .query("SELECT listener FROM listeners WHERE last_seen < NOW() - \
                   INTERVAL '2 minutes'", &[])
           .await?.into_iter().map(|r| r.get(0)).collect())
    }

    pub async fn cleanup_listener(self: &Self, listener: Uuid) -> DResult<()> {
        let mut conn = self.get_conn().await?;
        let tx = conn.transaction().await?;
        tx.execute("UPDATE users SET current_session = NULL, \
                    current_listener = NULL WHERE current_listener = $1",
                   &[&listener]).await?;
        tx.execute("DELETE FROM sendqueue WHERE listener = $1",
                   &[&listener]).await?;
        tx.execute("DELETE FROM sessions WHERE listener = $1",
                   &[&listener]).await?;
        tx.execute("DELETE FROM listeners WHERE listener = $1",
                   &[&listener]).await?;
        tx.commit().await?;
        Ok(())
    }

    pub async fn start_session(self: &Self, session: &ListenerSession, details: &Session) -> DResult<()> {
        self.get_conn().await?.execute(
            "INSERT INTO sessions (session, listener, details) \
               VALUES ($1, $2, $3) ON CONFLICT (session) DO NOTHING",
            &[&session.session, &session.listener, &serde_json::to_value(details)?]
        ).await?;
        Ok(())
    }

    pub async fn end_session(self: &Self, session: ListenerSession) -> DResult<()> {
        let mut conn = self.get_conn().await?;
        let tx = conn.transaction().await?;
        tx.execute("UPDATE users SET current_session = NULL, \
                    current_listener = NULL WHERE current_session = $1",
                   &[&session.session]).await?;
        tx.execute("DELETE FROM sendqueue WHERE session = $1",
                   &[&session.session]).await?;
        tx.execute("DELETE FROM sessions WHERE session = $1",
                   &[&session.session]).await?;
        tx.commit().await?;
        Ok(())
    }

    pub async fn start_transaction(self: &Self) -> DResult<DBTrans> {
        let conn = self.get_conn().await?;
        Ok(DBTransAsyncSendTryBuilder {
            conn,
            trans_builder: |conn| Box::pin(conn.transaction().map(|r| r.map(Some)))
        }.try_build().await?)
    }
    
    pub async fn queue_for_session(self: &Self,
                                       session: &ListenerSession,
                                       message: Option<&str>) -> DResult<()> {
        let conn = self.get_conn().await?;
        conn.execute("INSERT INTO sendqueue (session, listener, message) VALUES ($1, $2, $3)",
                     &[&session.session, &session.listener, &message]).await?;
        Ok(())
    }

    pub async fn get_from_sendqueue(self: &Self) -> DResult<Vec<SendqueueItem>> {
        let conn = self.get_conn().await?;
        Ok(conn.query("SELECT item, session, listener, message FROM sendqueue ORDER BY item ASC LIMIT 10",
                      &[])
           .await?.into_iter().map(SendqueueItem::from).collect())
        
    }

    pub async fn delete_from_sendqueue(self: &DBPool, item: &SendqueueItem) -> DResult<()> {
        let conn = self.get_conn().await?;
        conn.execute("DELETE FROM sendqueue WHERE item=$1", &[&item.item]).await?;
        Ok(())
    }
    
    pub async fn get_conn(self: &DBPool) ->
        DResult<Object> {
            let conn = self.pool.get().await?;
            conn.execute("SET synchronous_commit=off", &[]).await?;
            Ok(conn)
        }

    pub fn start(connstr: &str) -> DResult<DBPool> {
        let mgr_config = ManagerConfig {
            recycling_method: RecyclingMethod::Fast
        };
        let mgr = Manager::from_config(
            PgConfig::from_str(connstr)
                .map_err(|e| Box::new(e) as Box<dyn Error + Send + Sync>)?,
            NoTls, mgr_config
        );
        
        Pool::builder(mgr).max_size(4).build()
            .map_err(|e| Box::new(e) as Box<dyn Error + Send + Sync>)
            .map(|pool| Self { pool })
    }
}

impl DBTrans {
    pub async fn queue_for_session(self: &Self,
                                   session: &ListenerSession,
                                   message: Option<&str>) -> DResult<()> {
        self.pg_trans()?
            .execute("INSERT INTO sendqueue (session, listener, message) VALUES ($1, $2, $3)",
                     &[&session.session, &session.listener, &message]).await?;
        Ok(())
    }

    pub async fn get_session_user_model(self: &Self, session: &ListenerSession) -> DResult<Option<(Session, Option<User>)>> {
        match self.pg_trans()?
               .query_opt("SELECT s.details AS sess_details, \
                          u.details AS user_details FROM sessions s \
                          LEFT JOIN users u ON u.current_session = s.session \
                          WHERE s.session = $1", &[&session.session])
               .await? {
            None => Ok(None),
            Some(row) =>
                       Ok(Some(
                           (serde_json::from_value(
                               row.get("sess_details"))?,
                            match row.get::<&str, Option<serde_json::Value>>("user_details") {
                                None => None,
                                Some(v) => serde_json::from_value(v)?
                            })
                       ))
        }
    }

    pub async fn save_session_model(self: &Self, session: &ListenerSession, details: &Session)
                                    -> DResult<()> {
        self.pg_trans()?
            .execute("UPDATE sessions SET details = $1 WHERE session = $2",
                     &[&serde_json::to_value(details)?, &session.session]).await?;
        Ok(())
    }

    pub async fn find_by_username(self: &Self, username: &str) -> DResult<Option<User>> {
        if let Some(details_json) = self.pg_trans()?
            .query_opt("SELECT details FROM users WHERE username=$1",
                       &[&username.to_lowercase()]).await? {
                return Ok(Some(serde_json::from_value(details_json.get("details"))?))
            }
        Ok(None)
    }

    pub async fn create_item(self: &Self, item: &Item) -> DResult<i64> {
        Ok(self.pg_trans()?.query_one("INSERT INTO items (details) VALUES ($1) RETURNING item_id",
                                   &[&serde_json::to_value(item)?]).await?
           .get("item_id"))
    }
    
    pub async fn create_user(self: &Self, session: &ListenerSession, user_dat: &User) -> DResult<()> {
        self.pg_trans()?.execute("INSERT INTO users (\
              username, current_session, current_listener, details\
              ) VALUES ($1, $2, $3, $4)", &[&user_dat.username.to_lowercase(),
                                            &session.session,
                                            &session.listener,
                                            &serde_json::to_value(user_dat)?]).await?;
        Ok(())
    }

    pub async fn save_user_model(self: &Self, details: &User)
                                 -> DResult<()> {
        self.pg_trans()?
            .execute("UPDATE users SET details = $1 WHERE username = $2",
                     &[&serde_json::to_value(details)?,
                       &details.username.to_lowercase()]).await?;
        Ok(())
    }
    
    pub async fn commit(mut self: Self) -> DResult<()> {
        let trans_opt = self.with_trans_mut(|t| std::mem::replace(t, None));
        if let Some(trans) = trans_opt {
            trans.commit().await?;
        }
        Ok(())
    }

    pub fn pg_trans(self: &Self) -> DResult<&Transaction> {
        self.borrow_trans().as_ref().ok_or("Transaction already closed".into())
    }
}