use std::{env, process::ExitCode, str::FromStr};

use keyfork_derive_path_data::paths;
use keyfork_derive_util::{DerivationPath, ExtendedPrivateKey, PathError};
use keyforkd_client::Client;

use ed25519_dalek::SigningKey;

type XPrv = ExtendedPrivateKey<SigningKey>;

/// Any error that can occur while deriving a key.
#[derive(Debug, thiserror::Error)]
pub enum Error {
    /// The given path could not be parsed.
    #[error("Could not parse the given path: {0}")]
    PathFormat(#[from] PathError),

    /// The request to derive data failed.
    #[error("Unable to perform key derivation request: {0}")]
    KeyforkdClient(#[from] keyforkd_client::Error),
}

#[allow(missing_docs)]
pub type Result<T, E = Error> = std::result::Result<T, E>;

fn validate(path: &str) -> Result<DerivationPath> {
    let index = paths::AGE.inner().first().unwrap();

    let path = DerivationPath::from_str(path)?;
    assert!(
        path.len() >= 2,
        "Expected path of at least m/{index}/account_id'"
    );

    let given_index = path.iter().next().expect("checked .len() above");
    assert_eq!(
        index, given_index,
        "Expected derivation path starting with m/{index}, got: {given_index}",
    );

    Ok(path)
}

fn run() -> Result<(), Box<dyn std::error::Error>> {
    let mut args = env::args();
    let program_name = args.next().expect("program name");
    let args = args.collect::<Vec<_>>();
    let path = match args.as_slice() {
        [path] => validate(path)?,
        _ => panic!("Usage: {program_name} path"),
    };

    let mut client = Client::discover_socket()?;
    // TODO: should this key be clamped to Curve25519 specs?
    let xprv: XPrv = client.request_xprv(&path)?;
    let hrp = bech32::Hrp::parse("AGE-SECRET-KEY-")?;
    let age_key = bech32::encode::<bech32::Bech32>(hrp, &xprv.private_key().to_bytes())?;
    println!("{}", age_key.to_uppercase());
    Ok(())
}

fn main() -> ExitCode {
    if let Err(e) = run() {
        eprintln!("Error: {e}");
        ExitCode::FAILURE
    } else {
        ExitCode::SUCCESS
    }
}