use std::time::{SystemTime, UNIX_EPOCH};

use base32::Alphabet;
use clap::{Parser, Subcommand};
use totp_rfc6238::{HashAlgorithm, TotpGenerator};

/// Get the current time since epoch
pub fn time() -> u64 {
    SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .unwrap()
        .as_secs()
}

/// TOTP - One Time Password generator
#[derive(Parser, Debug)]
#[clap(author, version, about, long_about = None)]
struct Args {
    #[clap(subcommand)]
    command: SubCommands,
}

#[derive(Subcommand, Debug)]
enum SubCommands {
    /// Setup configuration
    Setup,

    /// Get a TOTP code
    #[clap(arg_required_else_help = true)]
    Code {
        /// The secret to use
        #[clap(short, long)]
        secret: String,

        /// Interval between two numbers generation
        #[clap(short, long, default_value_t = 30)]
        topt_step: u64,

        /// Size of generated secret
        #[clap(short, long, default_value_t = 6)]
        len: usize,
    },
}

fn main() {
    let args: Args = Args::parse();

    match args.command {
        SubCommands::Setup => {
            println!("To configure TOPT :");
            println!("1. Please open https://mysignins.microsoft.com/security-info");
            println!("2. Click on \"Add method\"");
            println!(
                "3. On the popup that appears, choose \"Authenticator app\" and click \"Add\"."
            );
            println!(
                "4. Click on \"I want to use a different authenticator app\" and click \"Next\""
            );
            println!("5. Click on \"Can't save image ?\" and copy the \"Secret key\"");
            println!(
                "6. Re-run this program running {} code --secret <SECRET>",
                std::env::args().next().unwrap()
            );
            println!("7. Back on the browser, click Next and paste copied code");
        }

        SubCommands::Code {
            secret,
            topt_step,
            len,
        } => {
            let totp_generator = TotpGenerator::new()
                .set_digit(len)
                .unwrap()
                .set_step(topt_step)
                .unwrap()
                .set_hash_algorithm(HashAlgorithm::SHA1)
                .build();

            let key = base32::decode(Alphabet::RFC4648 { padding: true }, &secret).unwrap();

            let code = totp_generator.get_code(&key);
            let next_update = totp_generator.get_next_update_time().unwrap();

            println!("Secret = {}", code);
            println!("Next update = {} seconds", next_update - time());
        }
    }
}

#[cfg(test)]
mod test {
    use crate::Args;

    #[test]
    fn verify_cli() {
        use clap::CommandFactory;
        Args::command().debug_assert()
    }
}