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

use crate::{
    clock::DateTime,
    db::NotFound,
    event::{Instant, Sequence},
    login::{self, History, Login},
    name::{self, Name},
    token::{Id, Secret},
};

pub trait Provider {
    fn tokens(&mut self) -> Tokens;
}

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

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

impl<'c> Tokens<'c> {
    // Issue a new token for an existing login. The issued_at timestamp will
    // be used to control expiry, until the token is actually used.
    pub async fn issue(
        &mut self,
        login: &History,
        issued_at: &DateTime,
    ) -> Result<Secret, sqlx::Error> {
        let id = Id::generate();
        let secret = Uuid::new_v4().to_string();
        let login = login.id();

        let secret = sqlx::query_scalar!(
            r#"
                insert
                into token (id, secret, login, issued_at, last_used_at)
                values ($1, $2, $3, $4, $4)
                returning secret as "secret!: Secret"
            "#,
            id,
            secret,
            login,
            issued_at,
        )
        .fetch_one(&mut *self.0)
        .await?;

        Ok(secret)
    }

    pub async fn require(&mut self, token: &Id) -> Result<(), sqlx::Error> {
        sqlx::query_scalar!(
            r#"
                select id as "id: Id"
                from token
                where id = $1
            "#,
            token,
        )
        .fetch_one(&mut *self.0)
        .await?;

        Ok(())
    }

    // Revoke a token by its secret.
    pub async fn revoke(&mut self, token: &Id) -> Result<(), sqlx::Error> {
        sqlx::query_scalar!(
            r#"
                delete
                from token
                where id = $1
                returning id as "id: Id"
            "#,
            token,
        )
        .fetch_one(&mut *self.0)
        .await?;

        Ok(())
    }

    // Revoke tokens for a login
    pub async fn revoke_all(&mut self, login: &login::History) -> Result<Vec<Id>, sqlx::Error> {
        let login = login.id();
        let tokens = sqlx::query_scalar!(
            r#"
                delete
                from token
                where login = $1
                returning id as "id: Id"
            "#,
            login,
        )
        .fetch_all(&mut *self.0)
        .await?;

        Ok(tokens)
    }

    // Expire and delete all tokens that haven't been used more recently than
    // `expire_at`.
    pub async fn expire(&mut self, expire_at: &DateTime) -> Result<Vec<Id>, sqlx::Error> {
        let tokens = sqlx::query_scalar!(
            r#"
                delete
                from token
                where last_used_at < $1
                returning id as "id: Id"
            "#,
            expire_at,
        )
        .fetch_all(&mut *self.0)
        .await?;

        Ok(tokens)
    }

    // Validate a token by its secret, retrieving the associated Login record.
    // Will return an error if the token is not valid. If successful, the
    // retrieved token's last-used timestamp will be set to `used_at`.
    pub async fn validate(
        &mut self,
        secret: &Secret,
        used_at: &DateTime,
    ) -> Result<(Id, History), LoadError> {
        // I would use `update … returning` to do this in one query, but
        // sqlite3, as of this writing, does not allow an update's `returning`
        // clause to reference columns from tables joined into the update. Two
        // queries is fine, but it feels untidy.
        let (token, login) = sqlx::query!(
            r#"
                update token
                set last_used_at = $1
                where secret = $2
                returning
                    id as "token: Id",
                    login as "login: login::Id"
            "#,
            used_at,
            secret,
        )
        .map(|row| (row.token, row.login))
        .fetch_one(&mut *self.0)
        .await?;

        let login = sqlx::query!(
            r#"
                select
                    id as "id: login::Id",
                    display_name as "display_name: String",
                    canonical_name as "canonical_name: String",
                    created_sequence as "created_sequence: Sequence",
                    created_at as "created_at: DateTime"
                from login
                where id = $1
            "#,
            login,
        )
        .map(|row| {
            Ok::<_, name::Error>(History {
                login: Login {
                    id: row.id,
                    name: Name::new(row.display_name, row.canonical_name)?,
                },
                created: Instant::new(row.created_at, row.created_sequence),
            })
        })
        .fetch_one(&mut *self.0)
        .await??;

        Ok((token, login))
    }
}

#[derive(Debug, thiserror::Error)]
#[error(transparent)]
pub enum LoadError {
    Database(#[from] sqlx::Error),
    Name(#[from] name::Error),
}

impl<T> NotFound for Result<T, LoadError> {
    type Ok = T;
    type Error = LoadError;

    fn optional(self) -> Result<Option<T>, LoadError> {
        match self {
            Ok(value) => Ok(Some(value)),
            Err(LoadError::Database(sqlx::Error::RowNotFound)) => Ok(None),
            Err(other) => Err(other),
        }
    }
}