use std::fs::File;
use std::path::{Path, PathBuf};
use std::io;
use std::ops::{Deref, DerefMut};

use crate::request::Request;
use crate::response::{self, Responder};
use crate::http::ContentType;

/// A file with an associated name; responds with the Content-Type based on the
/// file extension.
#[derive(Debug)]
pub struct NamedFile(PathBuf, File);

impl NamedFile {
    /// Attempts to open a file in read-only mode.
    ///
    /// # Errors
    ///
    /// This function will return an error if path does not already exist. Other
    /// errors may also be returned according to
    /// [`OpenOptions::open()`](std::fs::OpenOptions::open()).
    ///
    /// # Examples
    ///
    /// ```rust
    /// use rocket::response::NamedFile;
    ///
    /// # #[allow(unused_variables)]
    /// let file = NamedFile::open("foo.txt");
    /// ```
    pub fn open<P: AsRef<Path>>(path: P) -> io::Result<NamedFile> {
        let file = File::open(path.as_ref())?;
        Ok(NamedFile(path.as_ref().to_path_buf(), file))
    }

    /// Retrieve the underlying `File`.
    #[inline(always)]
    pub fn file(&self) -> &File {
        &self.1
    }

    /// Take the underlying `File`.
    #[inline(always)]
    pub fn take_file(self) -> File {
        self.1
    }

    /// Retrieve a mutable borrow to the underlying `File`.
    #[inline(always)]
    pub fn file_mut(&mut self) -> &mut File {
        &mut self.1
    }

    /// Retrieve the path of this file.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use std::io;
    /// use rocket::response::NamedFile;
    ///
    /// # #[allow(dead_code)]
    /// # fn demo_path() -> io::Result<()> {
    /// let file = NamedFile::open("foo.txt")?;
    /// assert_eq!(file.path().as_os_str(), "foo.txt");
    /// # Ok(())
    /// # }
    /// ```
    #[inline(always)]
    pub fn path(&self) -> &Path {
        self.0.as_path()
    }
}

/// Streams the named file to the client. Sets or overrides the Content-Type in
/// the response according to the file's extension if the extension is
/// recognized. See [`ContentType::from_extension()`] for more information. If
/// you would like to stream a file with a different Content-Type than that
/// implied by its extension, use a [`File`] directly.
impl<'r> Responder<'r> for NamedFile {
    fn respond_to(self, req: &'r Request<'_>) -> response::ResultFuture<'r> {
        Box::pin(async move {
            let mut response = self.1.respond_to(req).await?;
            if let Some(ext) = self.0.extension() {
                if let Some(ct) = ContentType::from_extension(&ext.to_string_lossy()) {
                    response.set_header(ct);
                }
            }

            Ok(response)
        })
    }
}

impl Deref for NamedFile {
    type Target = File;

    fn deref(&self) -> &File {
        &self.1
    }
}

impl DerefMut for NamedFile {
    fn deref_mut(&mut self) -> &mut File {
        &mut self.1
    }
}

impl io::Read for NamedFile {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        self.file().read(buf)
    }

    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
        self.file().read_to_end(buf)
    }
}

impl io::Write for NamedFile {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.file().write(buf)
    }

    fn flush(&mut self) -> io::Result<()> {
        self.file().flush()
    }
}

impl io::Seek for NamedFile {
    fn seek(&mut self, pos: io::SeekFrom) -> io::Result<u64> {
        self.file().seek(pos)
    }
}

impl io::Read for &NamedFile {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        self.file().read(buf)
    }

    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
        self.file().read_to_end(buf)
    }
}

impl io::Write for &NamedFile {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.file().write(buf)
    }

    fn flush(&mut self) -> io::Result<()> {
        self.file().flush()
    }
}

impl io::Seek for &NamedFile {
    fn seek(&mut self, pos: io::SeekFrom) -> io::Result<u64> {
        self.file().seek(pos)
    }
}