extern crate structview;
use structview::{u32_be, View};

#[derive(Clone, Copy, View)]
#[repr(C)]
pub struct MlHeader {
    magic: [u8; 8], /* '\0', 'm', 'l', 'o', 'c', 'a', 't', 'e' */
    conf_size: u32_be,
    version: u8,
    check_visibility: u8,
    pad: [u8; 2],
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::fs::File;
    use std::io::{BufRead, BufReader};

    #[test]
    fn can_read_header() -> Result<(), String> {
        let db = File::open("/var/lib/mlocate/mlocate.db").expect("Unable to open file");
        let mut reader = BufReader::new(db);
        match reader.fill_buf() {
            Ok(buffer) => match MlHeader::view(&buffer[0..32]) {
                Ok(header) => {
                    let text = &header.magic[1..8];
                    assert_eq!(text, *b"mlocate");
                    assert_eq!(header.version, 0);
                    let magic = std::str::from_utf8(text).unwrap_or("ERROR");
                    println!(
                        "magic: {}\nversion: {}\nconf_size: {}\nvisibility: {}",
                        magic, header.version, header.conf_size, header.check_visibility
                    );
                    Ok(())
                }
                Err(_) => Err("The header did not unpack.".to_owned()),
            },
            Err(_) => Err("The header could not be read".to_owned()),
        }
    }
}