//! Registry: local storage of built VM artifacts under
//! `$XDG_DATA_HOME/boco/registry/<image>/`.

use anyhow::{Context, Result, anyhow, bail};
use std::{fs, io, path::PathBuf};

/// Validate a user-supplied image name before it is used in a registry path.
///
/// The name becomes a directory under `$XDG_DATA_HOME/boco/registry/`, so
/// path separators and `.`/`..` would allow escaping that directory.
/// Allow-list: ASCII alphanumerics plus `.`, `_`, `:`, `-` (covers image
/// refs like `alpine:3.15`).
pub(crate) fn validate_image_name(name: &str) -> Result<()> {
    let valid = !name.is_empty()
        && name != "."
        && name != ".."
        && name
            .chars()
            .all(|c| c.is_ascii_alphanumeric() || matches!(c, '.' | '_' | ':' | '-'));
    if !valid {
        bail!(
            "invalid image name '{name}': must be non-empty and contain only \
             alphanumerics, '.', '_', ':' and '-' (no path separators or '..')"
        );
    }
    Ok(())
}

pub(crate) fn vmlinuz_path() -> Result<PathBuf> {
    let base = xdg::BaseDirectories::with_prefix("boco");
    base.place_data_file("vmlinuz")
        .context("Failed to create XDG_DATA_HOME subdirectory")
}

pub(crate) fn registry_base_dir() -> Result<PathBuf> {
    let base = xdg::BaseDirectories::with_prefix("boco");
    base.create_data_directory("registry")
        .context("Failed to create XDG_DATA_HOME subdirectory")
}

pub(crate) fn init_binary_path() -> Result<PathBuf> {
    let base = xdg::BaseDirectories::with_prefix("boco");
    base.get_data_file("boco-init")
        .context("boco-init not found in XDG data dir")
}

pub(crate) fn registry_dir(image: &str) -> Result<PathBuf> {
    validate_image_name(image)?;
    let base = registry_base_dir()?;

    let reg_dir = base.join(image);
    fs::create_dir(&reg_dir)
        .or_else(|e| {
            (e.kind() == io::ErrorKind::AlreadyExists)
                .then_some(())
                .ok_or(e)
        })
        .with_context(|| anyhow!("Failed to create {reg_dir:?}"))?;

    Ok(reg_dir)
}

#[cfg(test)]
mod tests {
    use super::validate_image_name;

    #[test]
    fn accepts_valid_image_names() {
        for name in [
            "alpine:3.15",
            "boco",
            "mock-vm",
            "my_vm",
            "a.b.c",
            "vm-1.2.3",
        ] {
            validate_image_name(name).unwrap_or_else(|e| panic!("{name} rejected: {e}"));
        }
    }

    #[test]
    fn rejects_traversal_and_separators() {
        for name in [
            "",
            ".",
            "..",
            "../evil",
            "../../tmp/evil",
            "a/b",
            "/abs",
            "a\\b",
            "foo bar",
            "vm;rm",
            "vm\n",
        ] {
            assert!(
                validate_image_name(name).is_err(),
                "{name:?} should be rejected"
            );
        }
    }
}