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// Copyright 2016 MaidSafe.net limited.
//
// This SAFE Network Software is licensed to you under (1) the MaidSafe.net Commercial License,
// version 1.0 or later, or (2) The General Public License (GPL), version 3, depending on which
// licence you accepted on initial access to the Software (the "Licences").
//
// By contributing code to the SAFE Network Software, or to this project generally, you agree to be
// bound by the terms of the MaidSafe Contributor Agreement.  This, along with the Licenses can be
// found in the root directory of this project at LICENSE, COPYING and CONTRIBUTOR.
//
// Unless required by applicable law or agreed to in writing, the SAFE Network Software distributed
// under the GPL Licence is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.
//
// Please review the Licences for the specific language governing permissions and limitations
// relating to use of the SAFE Network Software.

use client::Client;
use crypto::shared_secretbox;
use futures::Future;
use nfs::{File, NfsError, NfsFuture, data_map};
use self_encryption::SelfEncryptor;
use self_encryption_storage::SelfEncryptionStorage;
use utils::FutureExt;

/// Reader is used to read contents of a File. It can read in chunks if the
/// file happens to be very large
#[allow(dead_code)]
pub struct Reader<T> {
    client: Client<T>,
    self_encryptor: SelfEncryptor<SelfEncryptionStorage<T>>,
}

impl<T: 'static> Reader<T> {
    /// Create a new instance of Reader
    pub fn new(
        client: Client<T>,
        storage: SelfEncryptionStorage<T>,
        file: &File,
        encryption_key: Option<shared_secretbox::Key>,
    ) -> Box<NfsFuture<Reader<T>>> {
        data_map::get(&client, file.data_map_name(), encryption_key)
            .and_then(move |data_map| {
                let self_encryptor = SelfEncryptor::new(storage, data_map)?;

                Ok(Reader {
                    client: client,
                    self_encryptor: self_encryptor,
                })
            })
            .into_box()
    }

    /// Returns the total size of the file/blob
    pub fn size(&self) -> u64 {
        self.self_encryptor.len()
    }

    /// Read data from file/blob
    pub fn read(&self, position: u64, length: u64) -> Box<NfsFuture<Vec<u8>>> {
        trace!(
            "Reader reading from pos: {} and size: {}.",
            position,
            length
        );

        if (position + length) > self.size() {
            err!(NfsError::InvalidRange)
        } else {
            debug!(
                "Reading {len} bytes of data from file starting at offset of {pos} bytes ...",
                len = length,
                pos = position
            );
            self.self_encryptor
                .read(position, length)
                .map_err(From::from)
                .into_box()
        }
    }
}