dynix/src/lib.rs

// SPDX-FileCopyrightText: 2026 Qyriad <qyriad@qyriad.me>
//
// SPDX-License-Identifier: EUPL-1.1

use std::{
    iter,
    sync::{Arc, LazyLock},
};

pub(crate) mod prelude {
    #![allow(unused_imports)]

    pub use std::{
        error::Error as StdError,
        ffi::{OsStr, OsString},
        fmt::{Display, Formatter, Result as FmtResult},
        io::{Error as IoError, Read, Seek, SeekFrom, Write},
        path::{Path, PathBuf},
        process::{Command, ExitCode},
        str::FromStr,
    };

    #[cfg(unix)]
    pub use std::os::{
        fd::AsRawFd,
        unix::ffi::{OsStrExt, OsStringExt},
    };

    pub type BoxDynError = Box<dyn StdError + Send + Sync + 'static>;

    pub use command_error::{CommandExt, OutputLike};
    pub use fs_err::File;
    #[cfg(unix)]
    pub use fs_err::os::unix::fs::{FileExt, OpenOptionsExt};

    pub use tap::{Pipe, Tap};

    pub use tracing::{Level, debug, error, info, trace, warn};
}

use prelude::*;

pub mod args;
pub use args::{AppendCmd, Args};
mod color;
pub use color::{_CLI_ENABLE_COLOR, SHOULD_COLOR};
pub mod line;
mod nixcmd;
pub use line::Line;
pub mod source;
pub use source::{SourceFile, SourceLine};

#[cfg(all(not(feature = "regex-full"), not(feature = "regex-lite")))]
compile_error!("At least one of features `regex-full` or `regex-lite` must be used");

#[cfg(feature = "regex-full")]
use regex as _regex;

// Having both `regex-full` and `regex-lite` isn't an error; it's just wasteful.
#[cfg(not(feature = "regex-full"))]
use regex_lite as _regex;

use _regex::Regex;

use itertools::Itertools;
use serde::{Deserialize, Serialize};

pub const ASCII_WHITESPACE: &[char] = &['\t', '\n', '\x0C', '\r', ' '];

/// Regex pattern to extract the priority in a `lib.mkOverride` call.
static MK_OVERRIDE_RE: LazyLock<Regex> = LazyLock::new(|| {
    // Named capture group: priority
    // - Word boundary
    // - Literal `mkOverride`
    // - One or more whitespace characters
    // - Literal open parenthesis
    // - Named capture group "priority"
    //   - One or more of: digit characters, or literal `-`
    // - Literal close parenthesis
    Regex::new(r"(?-u)\bmkOverride\s+\((?<priority>[\d-]+)\)").unwrap()
});

#[tracing::instrument(level = "debug")]
pub fn do_append(args: Arc<Args>, append_args: AppendCmd) -> Result<(), BoxDynError> {
    let filepath = Path::new(&args.file);
    let filepath: PathBuf = if filepath.is_relative() && !filepath.starts_with("./") {
        iter::once(OsStr::new("./"))
            .chain(filepath.iter())
            .collect()
    } else {
        filepath.to_path_buf()
    };

    let mut opts = File::options();
    opts.read(true)
        .write(true)
        .create(false)
        .custom_flags(libc::O_CLOEXEC);

    let source_file = SourceFile::open_from(Arc::from(filepath), opts)?;
    let pri = get_where(source_file.clone())?;

    let new_pri = pri - 1;

    let new_pri_line = get_next_prio_line(
        source_file.clone(),
        append_args.name,
        new_pri,
        append_args.value,
    )?;

    debug!("new_pri_line={new_pri_line}");

    write_next_prio(source_file, new_pri_line)?;

    Ok(())
}

#[derive(Debug, Clone, PartialEq, Hash, Serialize, Deserialize)]
pub struct DefinitionWithLocation {
    pub file: Box<Path>,
    pub value: Box<serde_json::Value>,
}

pub fn expr_for_configuration(source_file: &Path) -> OsString {
    [
        OsStr::new("import <nixpkgs/nixos> { configuration = "),
        source_file.as_os_str(),
        OsStr::new("; }"),
    ]
    .into_iter()
    .collect()
}

fn maybe_extract_prio_from_line(line: &SourceLine) -> Option<i64> {
    MK_OVERRIDE_RE
        .captures(line.text_ref())
        .map(|caps| caps.name("priority").unwrap().as_str())
        .map(|prio_str| {
            i64::from_str(prio_str).unwrap_or_else(|e| {
                panic!(
                    "lib.mkOverride called with non-integer {}: {}. Nix source code is wrong!\n{}",
                    prio_str, e, line,
                );
            })
        })
}

pub fn get_where(dynamic_nix: SourceFile) -> Result<i64, BoxDynError> {
    let lines = dynamic_nix.lines()?;
    let prio = lines
        .iter()
        .filter_map(maybe_extract_prio_from_line)
        .sorted_unstable()
        .next() // Priorities with lower integer values are "stronger" priorities.
        .unwrap_or(0);

    Ok(prio)
}

pub fn get_next_prio_line(
    source: SourceFile,
    option_name: Arc<str>,
    new_prio: i64,
    new_value: Arc<str>,
) -> Result<SourceLine, BoxDynError> {
    let source_lines = source.lines()?;
    let penultimate = source_lines.get(source_lines.len() - 2);
    // FIXME: don't rely on whitespace lol
    debug_assert_eq!(penultimate.map(SourceLine::text).as_deref(), Some("  ];"));
    let penultimate = penultimate.unwrap();

    let new_generation = 0 - new_prio;

    let new_line = SourceLine {
        line: penultimate.line,
        path: source.path(),
        text: Arc::from(format!(
            "      {} = lib.mkOverride ({}) ({}); # DYNIX GENERATION {}",
            option_name, new_prio, new_value, new_generation,
        )),
    };

    Ok(new_line)
}

pub fn write_next_prio(mut source: SourceFile, new_line: SourceLine) -> Result<(), BoxDynError> {
    let new_mod_start = SourceLine {
        line: new_line.line.prev(),
        path: source.path(),
        text: Arc::from("    {"),
    };
    let new_mod_end = SourceLine {
        line: new_line.line.next(),
        path: source.path(),
        text: Arc::from("    }"),
    };

    source.insert_lines(&[new_mod_start, new_line, new_mod_end])?;

    Ok(())
}