// SPDX-License-Identifier: EUPL-1.2+
// SPDX-FileCopyrightText: 2025 Alyssa Ross <hi@alyssa.is>

mod keyfile;

use std::env::args_os;
use std::ffi::OsString;
use std::fs::File;
use std::io::{read_to_string, stderr, Write};
use std::os::fd::OwnedFd;
use std::os::unix::prelude::*;
use std::process::exit;

use keyfile::parse;

fn extract_runtime(mut metadata: File) -> Result<String, String> {
    let metadata = read_to_string(&mut metadata).map_err(|e| e.to_string())?;
    let group = parse(&metadata).map_err(|e| e.to_string())?;
    let application = group
        .get("Application")
        .ok_or_else(|| "Application group missing".to_string())?;
    Ok(application
        .get("runtime")
        .ok_or_else(|| "runtime property missing".to_string())?
        .clone())
}

// SAFETY: we do not expect "extract_runtime" to collide with another symbol.
#[unsafe(export_name = "extract_runtime")]
pub extern "C" fn extract_runtime_c(metadata: OwnedFd, out: &mut [u8; 256]) {
    let error = match extract_runtime(metadata.into()) {
        Err(e) => e,
        Ok(runtime) if runtime.len() >= out.len() => "runtime name too long".to_string(),
        Ok(runtime) => {
            out[..runtime.len()].copy_from_slice(runtime.as_bytes());
            out[runtime.len()] = 0;
            return;
        }
    };

    let prog_name = args_os()
        .next()
        .unwrap_or_else(|| OsString::from("mount-flatpak"));
    stderr().write_all(prog_name.as_bytes()).unwrap();
    eprintln!(": {error}");
    exit(1);
}