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

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

fn main() {
    let user_data_file = get_user_data_file();
    let args: Vec<String> = env::args().collect();
    let license_index;
    let outfile: &str;
    if args.len() < 2 || args[1] == "-h" {
        print_help(&user_data_file);
        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(&user_data_file);
        return
    }
    let license_name = &args[license_index];
    if license_name.contains("/") {
        eprintln!("error: malformatted license name: '{}'", license_name);
        exit(1)
    }
    copy_license(&license_name, outfile, &user_data_file);
}

fn copy_license(license: &str, outfile: &str, user_data_file: &String) {
    let user_path = user_data_file.to_owned() + "/" + license;
    let license_content = fs::read_to_string(user_path).unwrap_or_else(|_| {
        let global_path = GLOBAL_DATA_PATH.to_owned() + "/" + license;
        fs::read_to_string(global_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
    }
    Some(&args[2])
}

fn print_help(user_data_file: &String) {
    println!("license-tool [-h] [-o OUTFILE] <license>");
    println!("User License Dir: {}", user_data_file);
    let mut user_dirs = HashSet::<String>::new();
    let user_dir = fs::read_dir(user_data_file);
    if user_dir.is_ok() {
        println!("User Licenses:");
        let user_error_fun = |_| {
            eprintln!("error: could not read user data directory");
            exit(1)
        };
        for file in user_dir.unwrap() {
            let file_name = file.unwrap_or_else(user_error_fun).file_name()
                .to_string_lossy().to_string();
            println!("  {}", file_name);
            user_dirs.insert(file_name);
        }
    }
    let global_dir = fs::read_dir(GLOBAL_DATA_PATH);
    if global_dir.is_ok() {
        println!("Global Licenses:");
        let global_error_fun = |_| {
            eprintln!("error: error reading data directory");
            exit(1)
        };
        for file in global_dir.unwrap() {
            let file_name = file.unwrap_or_else(global_error_fun).file_name()
                .to_string_lossy().to_string();
            if user_dirs.contains(&file_name) {
                println!("  {} [Overridden]", file_name);
            } else {
                println!("  {}", file_name);
            }
        }
    }
}

fn get_user_data_file() -> String {
    let xdg_config = env::var("XDG_CONFIG_HOME").unwrap_or_else(|_| {
        let home_dir = env::var("HOME").unwrap_or_else(|_| {
            eprintln!("error: '$HOME' not set");
            exit(1)
        });
        home_dir + "/.config"
    });
    xdg_config + "/license-tool"
}