use futures_core::future::BoxFuture;

use crate::database::{Database, HasRow};

use crate::executor::Execute;

use crate::pool::Pool;

/// Represents a result set, which is generated by executing a query against the database.

///

/// A `Cursor` can be created by either [`Executor::execute`](trait.Execute.html) or

/// [`Query::fetch`](struct.Query.html).

///

/// Initially the `Cursor` is positioned before the first row. The `next` method moves the cursor

/// to the next row, and because it returns `None` when there are no more rows, it can be used

/// in a `while` loop to iterate through all returned rows.

pub trait Cursor<'c, 'q>

where

Self: Send,

{

type Database: Database;

fn from_pool<E>(pool: &Pool<<Self::Database as Database>::Connection>, query: E) -> Self

where

Self: Sized,

E: Execute<'q, Self::Database>;

fn from_connection<E>(

connection: &'c mut <Self::Database as Database>::Connection,

query: E,

) -> Self

where

Self: Sized,

E: Execute<'q, Self::Database>;

/// Fetch the next row in the result. Returns `None` if there are no more rows.

fn next<'cur>(

&'cur mut self,

) -> BoxFuture<'cur, crate::Result<Option<<Self::Database as HasRow<'cur>>::Row>>>;

}