use futures_io::{AsyncRead, AsyncWrite};
use futures_lite::Stream;

use crate::io::{
    get_meta_path, AssetReader, AssetReaderError, AssetWriter, AssetWriterError, PathStream,
    Reader, Writer,
};
use bevy_utils::BoxedFuture;

use std::{
    fs::{read_dir, File},
    io::{Read, Write},
    path::{Path, PathBuf},
    pin::Pin,
    task::Poll,
};

use super::{FileAssetReader, FileAssetWriter};

struct FileReader(File);

impl AsyncRead for FileReader {
    fn poll_read(
        self: Pin<&mut Self>,
        _cx: &mut std::task::Context<'_>,
        buf: &mut [u8],
    ) -> Poll<std::io::Result<usize>> {
        let this = self.get_mut();
        let read = this.0.read(buf);
        Poll::Ready(read)
    }
}

struct FileWriter(File);

impl AsyncWrite for FileWriter {
    fn poll_write(
        self: Pin<&mut Self>,
        _cx: &mut std::task::Context<'_>,
        buf: &[u8],
    ) -> Poll<std::io::Result<usize>> {
        let this = self.get_mut();
        let wrote = this.0.write(buf);
        Poll::Ready(wrote)
    }

    fn poll_flush(
        self: Pin<&mut Self>,
        _cx: &mut std::task::Context<'_>,
    ) -> Poll<std::io::Result<()>> {
        let this = self.get_mut();
        let flushed = this.0.flush();
        Poll::Ready(flushed)
    }

    fn poll_close(
        self: Pin<&mut Self>,
        _cx: &mut std::task::Context<'_>,
    ) -> Poll<std::io::Result<()>> {
        Poll::Ready(Ok(()))
    }
}

struct DirReader(Vec<PathBuf>);

impl Stream for DirReader {
    type Item = PathBuf;

    fn poll_next(
        self: Pin<&mut Self>,
        _cx: &mut std::task::Context<'_>,
    ) -> Poll<Option<Self::Item>> {
        let this = self.get_mut();
        Poll::Ready(this.0.pop())
    }
}

impl AssetReader for FileAssetReader {
    fn read<'a>(
        &'a self,
        path: &'a Path,
    ) -> BoxedFuture<'a, Result<Box<Reader<'a>>, AssetReaderError>> {
        Box::pin(async move {
            let full_path = self.root_path.join(path);
            match File::open(&full_path) {
                Ok(file) => {
                    let reader: Box<Reader> = Box::new(FileReader(file));
                    Ok(reader)
                }
                Err(e) => {
                    if e.kind() == std::io::ErrorKind::NotFound {
                        Err(AssetReaderError::NotFound(full_path))
                    } else {
                        Err(e.into())
                    }
                }
            }
        })
    }

    fn read_meta<'a>(
        &'a self,
        path: &'a Path,
    ) -> BoxedFuture<'a, Result<Box<Reader<'a>>, AssetReaderError>> {
        let meta_path = get_meta_path(path);
        Box::pin(async move {
            let full_path = self.root_path.join(meta_path);
            match File::open(&full_path) {
                Ok(file) => {
                    let reader: Box<Reader> = Box::new(FileReader(file));
                    Ok(reader)
                }
                Err(e) => {
                    if e.kind() == std::io::ErrorKind::NotFound {
                        Err(AssetReaderError::NotFound(full_path))
                    } else {
                        Err(e.into())
                    }
                }
            }
        })
    }

    fn read_directory<'a>(
        &'a self,
        path: &'a Path,
    ) -> BoxedFuture<'a, Result<Box<PathStream>, AssetReaderError>> {
        Box::pin(async move {
            let full_path = self.root_path.join(path);
            match read_dir(&full_path) {
                Ok(read_dir) => {
                    let root_path = self.root_path.clone();
                    let mapped_stream = read_dir.filter_map(move |f| {
                        f.ok().and_then(|dir_entry| {
                            let path = dir_entry.path();
                            // filter out meta files as they are not considered assets
                            if let Some(ext) = path.extension().and_then(|e| e.to_str()) {
                                if ext.eq_ignore_ascii_case("meta") {
                                    return None;
                                }
                            }
                            let relative_path = path.strip_prefix(&root_path).unwrap();
                            Some(relative_path.to_owned())
                        })
                    });
                    let read_dir: Box<PathStream> = Box::new(DirReader(mapped_stream.collect()));
                    Ok(read_dir)
                }
                Err(e) => {
                    if e.kind() == std::io::ErrorKind::NotFound {
                        Err(AssetReaderError::NotFound(full_path))
                    } else {
                        Err(e.into())
                    }
                }
            }
        })
    }

    fn is_directory<'a>(
        &'a self,
        path: &'a Path,
    ) -> BoxedFuture<'a, std::result::Result<bool, AssetReaderError>> {
        Box::pin(async move {
            let full_path = self.root_path.join(path);
            let metadata = full_path
                .metadata()
                .map_err(|_e| AssetReaderError::NotFound(path.to_owned()))?;
            Ok(metadata.file_type().is_dir())
        })
    }
}

impl AssetWriter for FileAssetWriter {
    fn write<'a>(
        &'a self,
        path: &'a Path,
    ) -> BoxedFuture<'a, Result<Box<Writer>, AssetWriterError>> {
        Box::pin(async move {
            let full_path = self.root_path.join(path);
            if let Some(parent) = full_path.parent() {
                std::fs::create_dir_all(parent)?;
            }
            let file = File::create(&full_path)?;
            let writer: Box<Writer> = Box::new(FileWriter(file));
            Ok(writer)
        })
    }

    fn write_meta<'a>(
        &'a self,
        path: &'a Path,
    ) -> BoxedFuture<'a, Result<Box<Writer>, AssetWriterError>> {
        Box::pin(async move {
            let meta_path = get_meta_path(path);
            let full_path = self.root_path.join(meta_path);
            if let Some(parent) = full_path.parent() {
                std::fs::create_dir_all(parent)?;
            }
            let file = File::create(&full_path)?;
            let writer: Box<Writer> = Box::new(FileWriter(file));
            Ok(writer)
        })
    }

    fn remove<'a>(
        &'a self,
        path: &'a Path,
    ) -> BoxedFuture<'a, std::result::Result<(), AssetWriterError>> {
        Box::pin(async move {
            let full_path = self.root_path.join(path);
            std::fs::remove_file(full_path)?;
            Ok(())
        })
    }

    fn remove_meta<'a>(
        &'a self,
        path: &'a Path,
    ) -> BoxedFuture<'a, std::result::Result<(), AssetWriterError>> {
        Box::pin(async move {
            let meta_path = get_meta_path(path);
            let full_path = self.root_path.join(meta_path);
            std::fs::remove_file(full_path)?;
            Ok(())
        })
    }

    fn remove_directory<'a>(
        &'a self,
        path: &'a Path,
    ) -> BoxedFuture<'a, std::result::Result<(), AssetWriterError>> {
        Box::pin(async move {
            let full_path = self.root_path.join(path);
            std::fs::remove_dir_all(full_path)?;
            Ok(())
        })
    }

    fn remove_empty_directory<'a>(
        &'a self,
        path: &'a Path,
    ) -> BoxedFuture<'a, std::result::Result<(), AssetWriterError>> {
        Box::pin(async move {
            let full_path = self.root_path.join(path);
            std::fs::remove_dir(full_path)?;
            Ok(())
        })
    }

    fn remove_assets_in_directory<'a>(
        &'a self,
        path: &'a Path,
    ) -> BoxedFuture<'a, std::result::Result<(), AssetWriterError>> {
        Box::pin(async move {
            let full_path = self.root_path.join(path);
            std::fs::remove_dir_all(&full_path)?;
            std::fs::create_dir_all(&full_path)?;
            Ok(())
        })
    }

    fn rename<'a>(
        &'a self,
        old_path: &'a Path,
        new_path: &'a Path,
    ) -> BoxedFuture<'a, std::result::Result<(), AssetWriterError>> {
        Box::pin(async move {
            let full_old_path = self.root_path.join(old_path);
            let full_new_path = self.root_path.join(new_path);
            if let Some(parent) = full_new_path.parent() {
                std::fs::create_dir_all(parent)?;
            }
            std::fs::rename(full_old_path, full_new_path)?;
            Ok(())
        })
    }

    fn rename_meta<'a>(
        &'a self,
        old_path: &'a Path,
        new_path: &'a Path,
    ) -> BoxedFuture<'a, std::result::Result<(), AssetWriterError>> {
        Box::pin(async move {
            let old_meta_path = get_meta_path(old_path);
            let new_meta_path = get_meta_path(new_path);
            let full_old_path = self.root_path.join(old_meta_path);
            let full_new_path = self.root_path.join(new_meta_path);
            if let Some(parent) = full_new_path.parent() {
                std::fs::create_dir_all(parent)?;
            }
            std::fs::rename(full_old_path, full_new_path)?;
            Ok(())
        })
    }
}