use anyhow::Result;
use std::fs::File;
use std::io;
use std::io::{Read,Write};
use std::path::PathBuf;
use log::*;

use flate2::Compression;
use flate2::read::GzDecoder;
use flate2::write::GzEncoder;

use crate::compression::CompressionEngine;

#[derive(Debug, Eq, PartialEq, Clone, Default)]
pub struct CompressionEngineGZip {}

impl CompressionEngineGZip {
    pub fn new() -> CompressionEngineGZip {
        CompressionEngineGZip {}
    }
}

impl CompressionEngine for CompressionEngineGZip {
    fn is_supported(&self) -> bool {
        true
    }

    fn open(&self, file_path: PathBuf) -> Result<Box<dyn Read>> {
        debug!("COMPRESSION: Opening {:?} using {:?}", file_path, *self);

        let file = File::open(file_path)?;
        Ok(Box::new(GzDecoder::new(file)))
    }

    fn create(&self, file_path: PathBuf) -> Result<Box<dyn Write>> {
        debug!("COMPRESSION: Writting to {:?} using {:?}", file_path, *self);

        let file = File::create(file_path)?;
        let gzip_write = GzEncoder::new(file, Compression::default());

        Ok(Box::new(AutoFinishGzEncoder::new(gzip_write)))
    }

}

pub struct AutoFinishGzEncoder<W: Write> {
    encoder: Option<GzEncoder<W>>,
}

impl<W: Write> AutoFinishGzEncoder<W> {
    fn new(gz_encoder: GzEncoder<W>) -> AutoFinishGzEncoder<W> {
        AutoFinishGzEncoder {
            encoder: Some(gz_encoder),
        }
    }
}

impl<W: Write> Drop for AutoFinishGzEncoder<W> {
    fn drop(&mut self) {
        if let Some(encoder) = self.encoder.take() {
            debug!("COMPRESSION: Finishing");
            let _ = encoder.finish();
        }
    }
}

impl<W: Write> Write for AutoFinishGzEncoder<W> {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.encoder.as_mut().unwrap().write(buf)
    }

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