use async_trait::async_trait;
use protocol::bridge_engine::{self, GameState, Player};
use serde_json::json;
use sqlx::{query, PgPool};
use uuid::Uuid;

use crate::error::BridgeError;

#[async_trait]
pub trait Journal {
    // Next sequence number to use.
    fn next(&self) -> i64;

    // Append payload to the journal at sequence number `seq`.
    async fn append(&mut self, seq: i64, payload: serde_json::Value) -> Result<(), BridgeError>;

    // Fetch all journal entries with sequence number greater or equal to `seq`.
    async fn replay(&mut self, seq: i64) -> Result<Vec<serde_json::Value>, BridgeError>;
}

pub struct DbJournal {
    db: PgPool,
    id: Uuid,
    seq: i64
}

impl DbJournal {
    pub fn new(db: PgPool, id: Uuid) -> Self {
        Self { db, id, seq: -1 }
    }
}

#[async_trait]
impl Journal for DbJournal {
    async fn append(&mut self, seq: i64, payload: serde_json::Value) -> Result<(), BridgeError> {
        query!(
            r#"
              insert into object_journal (id, seq, payload)
              values ($1, $2, $3)
            "#,
            self.id,
            seq,
            payload,
        )
        .execute(&self.db)
        .await?;
        Ok(())
    }

    async fn replay(&mut self, seq: i64) -> Result<Vec<serde_json::Value>, BridgeError> {
        let results = query!(
            r#"
              select payload from object_journal
              where id = $1 and seq >= $2
              order by seq
            "#,
            self.id,
            seq
        )
        .fetch_all(&self.db)
        .await?;
        Ok(results.into_iter().map(|v| v.payload).collect())
    }

    fn next(&self) -> i64 {
        self.seq + 1
    }
}

pub struct Table<J>
where
    J: Journal,
{
    journal: J,
    game: GameState,
}

impl<J: Journal> Table<J> {
    pub fn game(&self) -> &GameState { &self.game }
}

impl<J: Journal> Table<J> {
    pub async fn new(mut journal: J) -> Result<Self, BridgeError> {
        let game = GameState::Bidding {
            dealer: Player::East,
            deal: bridge_engine::deal(),
        };
        journal.append(0, json!(game)).await?;
        Ok(Table { journal, game })
    }

    pub async fn replay(mut journal: J) -> Result<Self, BridgeError> {
        let games = journal.replay(0).await?;
        if games.is_empty() {
            return Err(BridgeError::NotFound("table journal missing".to_string()));
        }
        let game = serde_json::from_value(games[games.len() - 1].clone())?;
        Ok(Table { journal, game } )
    }

    pub async fn new_or_replay(mut journal: J) -> Result<Self, BridgeError> {
        let games = journal.replay(0).await?;
        if games.is_empty() {
            return Self::new(journal).await;
        }
        let game = serde_json::from_value(games[games.len() - 1].clone())?;
        Ok(Table { journal, game } )
    }
}

#[cfg(test)]
mod test {
    use super::*;

    #[derive(Default)]
    pub struct TestJournal {
        log: Vec<Option<serde_json::Value>>,
    }

    #[async_trait]
    impl Journal for TestJournal {
        async fn append(
            &mut self,
            seq: i64,
            payload: serde_json::Value,
        ) -> Result<(), BridgeError> {
            if seq != self.log.len() as i64 {
                return Err(BridgeError::UpdateConflict(self.log.len() as i64, seq));
            }
            self.log.push(Some(payload));
            Ok(())
        }

        async fn replay(&mut self, seq: i64) -> Result<Vec<serde_json::Value>, BridgeError> {
            Ok(self.log[seq as usize..]
                .into_iter()
                .filter_map(|e| e.clone())
                .collect())
        }

        fn next(&self) -> i64 {
            self.log.len() as i64
        }
    }

    #[tokio::test]
    async fn test_journal() {
        let mut jnl: TestJournal = Default::default();
        let seq = jnl.next();
        assert_eq!(jnl.next(), 0);
        assert_eq!(jnl.append(seq, json!(10)).await.unwrap(), ());
        assert_eq!(jnl.next(), 1);
        assert!(jnl.append(0, json!(0)).await.is_err());
        let seq = jnl.next();
        assert_eq!(jnl.append(seq, json!(20)).await.unwrap(), ());
        assert_eq!(jnl.replay(1).await.unwrap(), vec!(json!(20)));
    }

    #[tokio::test]
    async fn test_new_table() {
        let t1: Table<TestJournal> = Table::new(Default::default()).await.unwrap();
        match t1.game {
            GameState::Bidding { dealer, deal } => (),
            _ => panic!("should be Bidding"),
        };
    }

    #[tokio::test]
    async fn test_replay_table() {
        let t1: Table<TestJournal> = Table::new(Default::default()).await.unwrap();
        let game = t1.game;
        let journal = t1.journal;

        let t2 = Table::replay(journal).await.unwrap();
        assert_eq!(game, t2.game);
    }
}