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

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

pub trait Provider {
    fn message_events(&mut self) -> Events;
}

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

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

impl<'c> Events<'c> {
    pub async fn create(
        &mut self,
        sender: &Login,
        channel: &Channel,
        body: &str,
        sent_at: &DateTime,
    ) -> Result<types::ChannelEvent, 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| types::ChannelEvent {
            sequence: row.sequence,
            at: row.sent_at,
            channel: channel.clone(),
            data: types::MessageEvent {
                id: row.id,
                sender: sender.clone(),
                body: row.body,
            }
            .into(),
        })
        .fetch_one(&mut *self.0)
        .await?;

        Ok(message)
    }

    async fn next_sequence_for(&mut self, channel: &Channel) -> Result<Sequence, sqlx::Error> {
        let 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(current.next())
    }

    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<types::ChannelEvent>, sqlx::Error> {
        let events = 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| types::ChannelEvent {
            sequence: row.sequence,
            at: row.sent_at,
            channel: channel.clone(),
            data: types::MessageEvent {
                id: row.id,
                sender: login::Login {
                    id: row.sender_id,
                    name: row.sender_name,
                },
                body: row.body,
            }
            .into(),
        })
        .fetch_all(&mut *self.0)
        .await?;

        Ok(events)
    }
}