use sqlx::{sqlite::Sqlite, SqliteConnection, Transaction};

use crate::{
    clock::DateTime,
    repo::{
        channel::Channel,
        login::{self, Login},
        message,
    },
};

pub trait Provider {
    fn broadcast(&mut self) -> Broadcast;
}

impl<'c> Provider for Transaction<'c, Sqlite> {
    fn broadcast(&mut self) -> Broadcast {
        Broadcast(self)
    }
}

pub struct Broadcast<'t>(&'t mut SqliteConnection);

#[derive(Clone, Debug, Eq, PartialEq, serde::Serialize)]
pub struct Message {
    pub id: message::Id,
    pub sequence: Sequence,
    pub sender: Login,
    pub body: String,
    pub sent_at: DateTime,
}

impl<'c> Broadcast<'c> {
    pub async fn create(
        &mut self,
        sender: &Login,
        channel: &Channel,
        body: &str,
        sent_at: &DateTime,
    ) -> Result<Message, sqlx::Error> {
        let sequence = self.next_sequence_for(channel).await?;

        let id = message::Id::generate();

        let message = sqlx::query!(
            r#"
				insert into message
					(id, channel, sequence, sender, body, sent_at)
				values ($1, $2, $3, $4, $5, $6)
				returning
					id as "id: message::Id",
                    sequence as "sequence: Sequence",
					sender as "sender: login::Id",
					body,
					sent_at as "sent_at: DateTime"
			"#,
            id,
            channel.id,
            sequence,
            sender.id,
            body,
            sent_at,
        )
        .map(|row| Message {
            id: row.id,
            sequence: row.sequence,
            sender: sender.clone(),
            body: row.body,
            sent_at: row.sent_at,
        })
        .fetch_one(&mut *self.0)
        .await?;

        Ok(message)
    }

    async fn next_sequence_for(&mut self, channel: &Channel) -> Result<Sequence, sqlx::Error> {
        let Sequence(current) = sqlx::query_scalar!(
            r#"
                -- `max` never returns null, but sqlx can't detect that
                select max(sequence) as "sequence!: Sequence"
                from message
                where channel = $1
            "#,
            channel.id,
        )
        .fetch_one(&mut *self.0)
        .await?;

        Ok(Sequence(current + 1))
    }

    pub async fn expire(&mut self, expire_at: &DateTime) -> Result<(), sqlx::Error> {
        sqlx::query!(
            r#"
                delete from message
                where sent_at < $1
            "#,
            expire_at,
        )
        .execute(&mut *self.0)
        .await?;

        Ok(())
    }

    pub async fn replay(
        &mut self,
        channel: &Channel,
        resume_at: Option<Sequence>,
    ) -> Result<Vec<Message>, sqlx::Error> {
        let messages = sqlx::query!(
            r#"
				select
					message.id as "id: message::Id",
                    sequence as "sequence: Sequence",
					login.id as "sender_id: login::Id",
					login.name as sender_name,
					message.body,
					message.sent_at as "sent_at: DateTime"
				from message
					join login on message.sender = login.id
				where channel = $1
					and coalesce(sequence > $2, true)
				order by sequence asc
			"#,
            channel.id,
            resume_at,
        )
        .map(|row| Message {
            id: row.id,
            sequence: row.sequence,
            sender: Login {
                id: row.sender_id,
                name: row.sender_name,
            },
            body: row.body,
            sent_at: row.sent_at,
        })
        .fetch_all(&mut *self.0)
        .await?;

        Ok(messages)
    }
}

#[derive(
    Debug,
    Eq,
    Ord,
    PartialEq,
    PartialOrd,
    Clone,
    Copy,
    serde::Serialize,
    serde::Deserialize,
    sqlx::Type,
)]
#[serde(transparent)]
#[sqlx(transparent)]
pub struct Sequence(i64);