apeirogond 0.15.1

Daemon for Apeirogon, a cross-platform software KVM
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// SPDX-License-Identifier: GPL-3.0-or-later

//! Durable validated settings snapshot; an unusable file never blocks startup.

use std::fs::File;
use std::io::{self, Read};
use std::path::{Path, PathBuf};

use a7n_core::settings::Settings;
use a7n_platform::fs::write_user_only;
use a7n_proto::{limits, v1};
use prost::Message;

pub(crate) struct SettingsStore {
    path: PathBuf,
    pub(crate) state: Option<Settings>,
}

impl SettingsStore {
    pub(crate) fn load(path: &Path) -> Self {
        let state = read_settings(path).unwrap_or_else(|()| {
            crate::log::event!("kind=settings_file_invalid");
            None
        });
        Self {
            path: path.to_owned(),
            state,
        }
    }

    pub(crate) fn persist(&mut self, state: Settings) -> io::Result<()> {
        write_user_only(&self.path, &state.to_proto().encode_to_vec())?;
        self.state = Some(state);
        Ok(())
    }
}

fn read_settings(path: &Path) -> Result<Option<Settings>, ()> {
    let file = match File::open(path) {
        Ok(file) => file,
        Err(error) if error.kind() == io::ErrorKind::NotFound => return Ok(None),
        Err(_) => return Err(()),
    };
    let mut bytes = Vec::new();
    file.take((limits::CONTROL_FRAME_MAX + 1) as u64)
        .read_to_end(&mut bytes)
        .map_err(|_| ())?;
    if bytes.len() > limits::CONTROL_FRAME_MAX {
        return Err(());
    }
    let wire = v1::SettingsSync::decode(bytes.as_slice()).map_err(|_| ())?;
    Settings::try_from(&wire).map(Some).map_err(|_| ())
}