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// Copyright (c) 2016 Anatoly Ikorsky
//
// Licensed under the Apache License, Version 2.0
// <LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0> or the MIT
// license <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. All files in the project carrying such notice may not be copied,
// modified, or distributed except according to those terms.

use conn::futures::query_result::InnerQueryResult;
use conn::futures::query_result::UnconsumedQueryResult;
use either::Left;
use either::Right;
use errors::*;
use lib_futures::Async::Ready;
use lib_futures::Future;
use lib_futures::Poll;
use proto::Row;
use std::mem;


/// Future that calls `F: FnMut(Row) -> U` on each Row of a `QueryResult`.
///
/// It resolves to a pair of `Vec<U>` an output of corresponding `ResultKind`.
pub struct Map<F, U, T> {
    query_result: T,
    fun: F,
    acc: Vec<U>,
}

pub fn new_new<F, U, T>(query_result: T, fun: F) -> Map<F, U, T>
    where F: FnMut(Row) -> U,
{
    Map {
        query_result: query_result,
        fun: fun,
        acc: Vec::new(),
    }
}

impl<F, U, T> Future for Map<F, U, T>
    where F: FnMut(Row) -> U,
          T: InnerQueryResult,
          T: UnconsumedQueryResult,
{
    type Item = (Vec<U>, T::Output);
    type Error = Error;

    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
        match try_ready!(self.query_result.poll()) {
            Left(row) => {
                let val = (&mut self.fun)(row);
                self.acc.push(val);
                self.poll()
            },
            Right(output) => {
                let acc = mem::replace(&mut self.acc, Vec::new());
                Ok(Ready((acc, output)))
            },
        }
    }
}