build.rs for fetching dat tests

build.rs

//! Build script for DAT

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

use flate2::read::GzDecoder;
use tar::Archive;

const DAT_EXISTS_FILE_CHECK: &str = "tests/dat/.done";
const OUTPUT_FOLDER: &str = "tests/dat";
const VERSION: &str = "0.0.2";

fn main() {
    if dat_exists() {
        return;
    }

    let tarball_data = download_dat_files();
    extract_tarball(tarball_data);
    write_done_file();
}

fn dat_exists() -> bool {
    Path::new(DAT_EXISTS_FILE_CHECK).exists()
}

fn download_dat_files() -> Vec<u8> {
    let tarball_url = format!(
        "https://github.com/delta-incubator/dat/releases/download/v{version}/deltalake-dat-v{version}.tar.gz",
        version = VERSION
    );

    let response = ureq::get(&tarball_url).call().unwrap();
    let mut tarball_data: Vec<u8> = Vec::new();
    response
        .into_reader()
        .read_to_end(&mut tarball_data)
        .unwrap();

    tarball_data
}
  
fn extract_tarball(tarball_data: Vec<u8>) {
    let tarball = GzDecoder::new(BufReader::new(&tarball_data[..]));
    let mut archive = Archive::new(tarball);
    std::fs::create_dir_all(OUTPUT_FOLDER).expect("Failed to create output directory");
    archive
        .unpack(OUTPUT_FOLDER)
        .expect("Failed to unpack tarball");
}

fn write_done_file() {
    let mut done_file =
        BufWriter::new(File::create(DAT_EXISTS_FILE_CHECK).expect("Failed to create .done file"));
    write!(done_file, "done").expect("Failed to write .done file");
}