wt_blk 0.1.1

use std::io::Read;
use std::thread::sleep;
use std::time::Duration;

use ruzstd::StreamingDecoder;

use crate::binary::file::FileType;

pub fn decode_zstd(file: &[u8]) -> Option<Vec<u8>> {
	// validate magic byte
	let is_fat = match FileType::from_byte(*file.get(0)?)? {
		FileType::FAT_ZSTD => true, // FAT_ZST
		FileType::SLIM_ZSTD => false, // SLIM_ZST and SLIM_ZST_DICT
		FileType::SLIM_ZST_DICT => unimplemented!("File: zstd.rs, note: DICT ZSTD files are not supported yet"),
		_ => return None
	};

	let (len, mut to_decode) = if is_fat {
		let len_raw = &file[1..4];
		let len = u32::from_be_bytes([
			0,
			len_raw[2],
			len_raw[1],
			len_raw[0],
		]);
		let mut to_decode = &file[4..(len as usize + 4)];
		(len as usize, to_decode)
	} else {
		(file.len() - 1, &file[1..])
	};

	let mut decoder = StreamingDecoder::new(&mut to_decode).ok()?;
	let mut out = Vec::with_capacity(len);
	let _ = decoder.read_to_end(&mut out).ok()?;
	Some(out)
}


pub fn eep() -> u8 {
	sleep(Duration::from_millis(1));
	42
}

#[cfg(test)]
mod test {
	use std::{fs, io};
	use std::io::Read;

	use ruzstd::{FrameDecoder, StreamingDecoder};

	use crate::binary::zstd::decode_zstd;

	#[test]
	fn fat_zstd() {
		let decoded = decode_zstd(include_bytes!("../../samples/section_fat_zst.blk")).unwrap();
		pretty_assertions::assert_eq!(&decoded, &include_bytes!("../../samples/section_fat.blk"));
	}

	#[test]
	fn slim_zstd() {
		let decoded = decode_zstd(include_bytes!("../../samples/section_slim_zst.blk")).unwrap();
		pretty_assertions::assert_eq!(&decoded, &include_bytes!("../../samples/section_slim.blk")[1..]) // Truncating the first byte, as it is magic byte for the SLIM format
	}

	#[test]
	fn slim_zstd_dict() {
		let file = fs::read("./samples/section_slim_zst_dict.blk").unwrap();
		let dict = fs::read("./samples/bfb732560ad45234690acad246d7b14c2f25ad418a146e5e7ef68ba3386a315c.dict").unwrap();
		let mut frame_decoder = FrameDecoder::new();
		frame_decoder.add_dict(&dict).unwrap();

		let mut decoder = StreamingDecoder::new_with_decoder(&file[1..], frame_decoder).unwrap();
		let mut out = vec![];
		decoder.read_to_end(&mut out).unwrap();
		pretty_assertions::assert_eq!(&out, &include_bytes!("../../samples/section_slim.blk")[1..]) // Truncating the first byte, as it is magic byte for the SLIM format
	}
}