use std::{
    fs::File,
    io::{BufReader, Read, Write},
    path::Path,
};

use anyhow::Context;
use bgzip::{BGZFReader, BGZFWriter, Compression};
use log::debug;

pub fn get_reader(path: &str) -> anyhow::Result<Box<dyn std::io::Read>> {
    debug!("Reading: {path}");
    let file_type = *path
        .split(".")
        .collect::<Vec<&str>>()
        .last()
        .context(format!("Can't parse {path}"))?;
    assert!(file_type == "gz" || file_type == "vcf" || file_type == "bed" || file_type == "tsv");

    let raw_reader: Box<dyn std::io::Read> = Box::new(File::open(path)?);

    match file_type {
        "gz" => {
            let reader = Box::new(BGZFReader::new(raw_reader)?);
            Ok(Box::new(BufReader::new(reader)))
        }
        "vcf" | "bed" | "tsv" => Ok(Box::new(BufReader::new(raw_reader))),
        t => {
            panic!("unknown file type: {}", t)
        }
    }
}

pub fn get_gz_reader(path: &str) -> anyhow::Result<BGZFReader<File>> {
    debug!("Reading: {path}");
    let file_type = *path
        .split(".")
        .collect::<Vec<&str>>()
        .last()
        .context("Can't parse {path}.")?;

    let path = if file_type != "gz" {
        compress_to_bgzip(path)?
    } else {
        path.to_string()
    };

    let reader = File::open(path)?;
    Ok(BGZFReader::new(reader)?)
}

pub fn compress_to_bgzip(input_path: &str) -> anyhow::Result<String> {
    let output_path = format!("{}.gz", input_path);

    if Path::new(&output_path).exists() {
        return Ok(output_path);
    }

    debug!("Compressing {input_path}");
    let input_file = File::open(input_path)?;
    let mut reader = BufReader::new(input_file);

    let output_file = File::create(&output_path)?;
    let mut writer = BGZFWriter::new(output_file, Compression::default());

    let mut buffer = [0; 8192];
    loop {
        let bytes_read = reader.read(&mut buffer)?;
        if bytes_read == 0 {
            break;
        }
        writer.write_all(&buffer[..bytes_read])?;
    }

    writer.close()?;
    Ok(output_path)
}