use std::{
    env,
    fs::File,
    path::{Path, PathBuf},
    process::ExitCode,
};

use keyfork_shard::openpgp::{decrypt, discover_certs, openpgp::Cert, parse_messages};

type Result<T, E = Box<dyn std::error::Error>> = std::result::Result<T, E>;

fn validate<'a>(
    messages_file: impl AsRef<Path>,
    key_discovery: impl Into<Option<&'a str>>,
) -> Result<(File, Vec<Cert>)> {
    let key_discovery = key_discovery.into().map(PathBuf::from);
    key_discovery.as_ref().map(std::fs::metadata).transpose()?;

    // Load certs from path
    let certs = key_discovery
        .map(discover_certs)
        .transpose()?
        .unwrap_or(vec![]);

    Ok((File::open(messages_file)?, certs))
}

fn run() -> Result<()> {
    let mut args = env::args();
    let program_name = args.next().expect("program name");
    let args = args.collect::<Vec<_>>();
    let (messages_file, cert_list) = match args.as_slice() {
        [messages_file, key_discovery] => validate(messages_file, key_discovery.as_str())?,
        [messages_file] => validate(messages_file, None)?,
        _ => panic!("Usage: {program_name} messages_file [key_discovery]"),
    };

    let mut encrypted_messages = parse_messages(messages_file)?;

    let encrypted_metadata = encrypted_messages
        .pop_front()
        .expect("any pgp encrypted message");

    decrypt(
        &cert_list,
        encrypted_metadata,
        encrypted_messages.make_contiguous(),
    )?;

    Ok(())
}

fn main() -> ExitCode {
    let result = run();
    if let Err(e) = result {
        eprintln!("Error: {e}");
        let mut source = e.source();
        while let Some(new_error) = source.take() {
            eprintln!("Source: {new_error}");
            source = new_error.source();
        }
        return ExitCode::FAILURE;
    }
    ExitCode::SUCCESS
}