use std::env;
use std::fs;
use std::io;
use std::process::exit;

const DATA_PATH: &str = env!("DATA_PATH");

fn main() {
    let args: Vec<String> = env::args().collect();
    let license_index;
    let outfile: &str;
    if args.len() < 2 || args[1] == "-h" {
        print_help();
        return;
    } else if args[1] == "-o" {
        outfile = get_outfile(&args).unwrap_or_else(|| exit(1));
        license_index = 3;
    } else {
        outfile = "LICENSE";
        license_index = 1;
    }
    if args.len() <= license_index {
        print_help();
        return;
    }
    copy_license(&args[license_index], outfile);
}

fn copy_license(license: &str, outfile: &str) {
    let license_path = DATA_PATH.to_owned() + "/" + license;
    let license_content = fs::read_to_string(license_path).unwrap_or_else(|_| {
        eprintln!("error: could not open license for reading: '{}'", license);
        exit(1);
    });
    let _ = fs::write(outfile, license_content).or_else(|_| -> io::Result<()> {
        eprintln!("error: could not write license: '{}'", outfile);
        exit(1);
    });
}

fn get_outfile(args: &Vec<String>) -> Option<&str> {
    if args.len() < 3 {
        eprintln!("error: -o requires an option");
        return None;
    }
    return Some(&args[2]);
}

fn print_help() {
    println!("license-tool [-h] [-o OUTFILE] <license>");
    println!("Licenses:");
    let dirs = fs::read_dir(DATA_PATH);
    if dirs.is_err() {
        eprintln!("error: could not open data directory");
        exit(1);
    }
    for file in dirs.unwrap() {
        if file.is_err() {
            eprintln!("error: error reading data directory");
            exit(1);
        }
        println!("  {}", file.as_ref().unwrap().file_name().to_string_lossy());
    }
}