Reformats domain blocklist from ABP format to HOST format

abp_to_host.rs

/*

build with cargo build --release

to run, do ./abp_to_host <path_to_abp_blocklist>

*/


use std::{fs, env};
use std::io::{BufRead, BufReader, BufWriter, Write};

fn main() {
    let args: Vec<String> = env::args().collect();
    if args.len() != 3 || &args[1] == "-h" || &args[1] == "--help" {
        println!("Two arguments are required:\n\
        \t1. path of the ABP blocklist file\n\
        \t2. path of the output file\n\n\
        Usage:\n\
        \t./abp_to_host <path_to_abp_blocklist> <path_to_output_file>");
        return
    }
    let path_to_abp = &args[1];
    let path_to_host = &args[2];
    
    let mut abp_f = BufReader::new(
        fs::File::open(path_to_abp).expect("Unable to open file")
        ).lines();

    let mut host_f = BufWriter::new(
        fs::OpenOptions::new()
            .write(true)
            .create(true)
            .open(path_to_host)
            .expect("Unable to create new file")
        );

    
    {
        let found_date = false;
        let mut date = String::new();

        for line in abp_f.by_ref() {
            let line = line.expect("Unable to read line");

            if line.starts_with("! Version: ") {
                date.push_str(&line[11..].trim_end());
                break
            } else if line.starts_with("||") && !found_date {
                panic!("No date found in ABP file")
            }
        }

        host_f.write_all("# Title: EU US most prevalent ads & trackers HOST format\n\
            # Expires: 30 days\n\
            #\n".as_bytes())
            .expect("Unable to write to file");
        host_f.write_all(format!("# Updated: {}\n", date).as_bytes())
            .expect("Unable to write to file");
        host_f.write_all("# Please report issues related to website breakage at github\n\
            # Kees1958/W3C_annual_most_used_survey_blocklist/issues\n\
            #\n\
            #\n\
            #\n".as_bytes())
            .expect("Unable to write to file");
    }


    for line in abp_f {
        let line = line.expect("Unable to read line");

        if line.starts_with("||") {
            if let Some(end) = line.find("$") {
                let mut domain = &line[2..end];

                if domain.contains("*") {
                    continue
                } else {
                    domain = domain.trim_end_matches(',');
                }

                host_f.write_all(format!("0.0.0.0 {}\n", domain).as_bytes())
                    .expect("Unable to write to file");
            }
        }  
    }

    host_f.flush().expect("Unable to flush data to file");

}