use std::io;
use std::path::{Path, PathBuf};

use crate::{Metadata, ReadDir, VfsBackend, VfsEvent};

/// `VfsBackend` that returns an error on every operation.
#[non_exhaustive]
pub struct NoopBackend;

impl NoopBackend {
    pub fn new() -> Self {
        Self
    }
}

impl VfsBackend for NoopBackend {
    fn read(&mut self, _path: &Path) -> io::Result<Vec<u8>> {
        Err(io::Error::other("NoopBackend doesn't do anything"))
    }

    fn write(&mut self, _path: &Path, _data: &[u8]) -> io::Result<()> {
        Err(io::Error::other("NoopBackend doesn't do anything"))
    }

    fn exists(&mut self, _path: &Path) -> io::Result<bool> {
        Err(io::Error::other("NoopBackend doesn't do anything"))
    }

    fn read_dir(&mut self, _path: &Path) -> io::Result<ReadDir> {
        Err(io::Error::other("NoopBackend doesn't do anything"))
    }

    fn create_dir(&mut self, _path: &Path) -> io::Result<()> {
        Err(io::Error::other("NoopBackend doesn't do anything"))
    }

    fn create_dir_all(&mut self, _path: &Path) -> io::Result<()> {
        Err(io::Error::other("NoopBackend doesn't do anything"))
    }

    fn remove_file(&mut self, _path: &Path) -> io::Result<()> {
        Err(io::Error::other("NoopBackend doesn't do anything"))
    }

    fn remove_dir_all(&mut self, _path: &Path) -> io::Result<()> {
        Err(io::Error::other("NoopBackend doesn't do anything"))
    }

    fn metadata(&mut self, _path: &Path) -> io::Result<Metadata> {
        Err(io::Error::other("NoopBackend doesn't do anything"))
    }

    fn canonicalize(&mut self, _path: &Path) -> io::Result<PathBuf> {
        Err(io::Error::other("NoopBackend doesn't do anything"))
    }

    fn event_receiver(&self) -> crossbeam_channel::Receiver<VfsEvent> {
        crossbeam_channel::never()
    }

    fn watch(&mut self, _path: &Path) -> io::Result<()> {
        Err(io::Error::other("NoopBackend doesn't do anything"))
    }

    fn unwatch(&mut self, _path: &Path) -> io::Result<()> {
        Err(io::Error::other("NoopBackend doesn't do anything"))
    }
}

impl Default for NoopBackend {
    fn default() -> Self {
        Self::new()
    }
}