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use std::{io, fs};
use std::sync::Arc;

use oid::ObjectId;
use bson;

use db::{Database, ThreadDatabase};
use coll::Collection;
use coll::options::FindOptions;
use cursor::Cursor;
use error::Error::{self, ArgumentError};
use error::Result;

use self::file::{File, Mode};

pub mod file;

/// A default cursor wrapper that maps bson documents into GridFS file representations.
pub struct FileCursor {
    store: Store,
    cursor: Cursor,
    err: Option<Error>,
}

impl Iterator for FileCursor {
    type Item = File;

    fn next(&mut self) -> Option<File> {
        match self.cursor.next() {
            Some(Ok(bdoc)) => Some(File::with_doc(self.store.clone(), bdoc)),
            Some(Err(err)) => {
                self.err = Some(err);
                None
            }
            None => None,
        }
    }
}

impl FileCursor {
    /// Returns the next n files.
    pub fn next_n(&mut self, n: i32) -> Result<Vec<File>> {
        let docs = self.cursor.next_n(n)?;
        Ok(docs.into_iter()
            .map(|doc| File::with_doc(self.store.clone(), doc.clone()))
            .collect())
    }

    /// Returns the next batch of files.
    pub fn drain_current_batch(&mut self) -> Result<Vec<File>> {
        let docs = self.cursor.drain_current_batch()?;
        Ok(docs.into_iter()
            .map(|doc| File::with_doc(self.store.clone(), doc))
            .collect())
    }
}

/// Alias for a thread-safe GridFS instance.
pub type Store = Arc<StoreInner>;

/// Interfaces with a GridFS instance.
pub struct StoreInner {
    files: Collection,
    chunks: Collection,
}

pub trait ThreadedStore {
    /// A new GridFS store within the database with prefix 'fs'.
    fn with_db(db: Database) -> Store;
    /// A new GridFS store within the database with a specified prefix.
    fn with_prefix(db: Database, prefix: String) -> Store;
    /// Creates a new file.
    fn create(&self, name: String) -> Result<File>;
    /// Opens a file by filename.
    fn open(&self, name: String) -> Result<File>;
    /// Opens a file by object ID.
    fn open_id(&self, id: ObjectId) -> Result<File>;
    /// Returns a cursor to all file documents matching the provided filter.
    fn find(&self,
            filter: Option<bson::Document>,
            options: Option<FindOptions>)
            -> Result<FileCursor>;
    /// Removes a file from GridFS by filename.
    fn remove(&self, name: String) -> Result<()>;
    /// Removes a file from GridFS by object ID.
    fn remove_id(&self, id: ObjectId) -> Result<()>;
    /// Inserts a new file from local into GridFS.
    fn put(&self, name: String) -> Result<()>;
    /// Retrieves a file from GridFS into local storage.
    fn get(&self, name: String) -> Result<()>;
}

impl ThreadedStore for Store {
    fn with_db(db: Database) -> Store {
        Store::with_prefix(db, String::from("fs"))
    }

    fn with_prefix(db: Database, prefix: String) -> Store {
        Arc::new(StoreInner {
            files: db.collection(&format!("{}.files", prefix)[..]),
            chunks: db.collection(&format!("{}.chunks", prefix)[..]),
        })
    }

    fn create(&self, name: String) -> Result<File> {
        Ok(File::with_name(self.clone(), name, ObjectId::new()?, Mode::Write))
    }

    fn open(&self, name: String) -> Result<File> {
        let mut options = FindOptions::new();
        options.sort = Some(doc!{ "uploadDate" => 1 });

        match self.files.find_one(Some(doc!{ "filename" => name }), Some(options))? {
            Some(bdoc) => Ok(File::with_doc(self.clone(), bdoc)),
            None => Err(ArgumentError(String::from("File does not exist."))),
        }
    }

    fn open_id(&self, id: ObjectId) -> Result<File> {
        match self.files.find_one(Some(doc!{ "_id" => id }), None)? {
            Some(bdoc) => Ok(File::with_doc(self.clone(), bdoc)),
            None => Err(ArgumentError(String::from("File does not exist."))),
        }
    }

    fn find(&self, filter: Option<bson::Document>, options: Option<FindOptions>) -> Result<FileCursor> {
        Ok(FileCursor {
            store: self.clone(),
            cursor: self.files.find(filter, options)?,
            err: None,
        })
    }

    fn remove(&self, name: String) -> Result<()> {
        let mut options = FindOptions::new();
        options.projection = Some(doc!{ "_id" => 1 });

        let cursor = self.find(Some(doc!{ "filename" => name }), Some(options))?;
        for doc in cursor {
            self.remove_id(doc.id.clone())?;
        }

        Ok(())
    }

    fn remove_id(&self, id: ObjectId) -> Result<()> {
        self.files.delete_many(doc!{ "_id" => (id.clone()) }, None)?;
        self.chunks.delete_many(doc!{ "files_id" => (id.clone()) }, None)?;
        Ok(())
    }

    fn put(&self, name: String) -> Result<()> {
        let mut file = self.create(name.clone())?;
        let mut f = fs::File::open(name)?;
        io::copy(&mut f, &mut file)?;
        file.close()?;
        Ok(())
    }

    fn get(&self, name: String) -> Result<()> {
        let mut f = fs::File::create(name.clone())?;
        let mut file = self.open(name)?;
        io::copy(&mut file, &mut f)?;
        file.close()?;
        Ok(())
    }
}