PoC

src/lib.rs

@@ -1,4 +1,4 @@
-use std::sync::Arc;
+use std::sync::{Arc, LazyLock};
 
 pub(crate) mod prelude {
     #![allow(unused_imports)]
@@ -43,6 +43,8 @@ use serde::{Deserialize, Serialize};
 
 use crate::source::SourceFile;
 
+pub const ASCII_WHITESPACE: &[char] = &['\t', '\n', '\x0C', '\r', ' '];
+
 #[derive(Debug, Clone, PartialEq, Hash, Serialize, Deserialize)]
 pub struct DefinitionWithLocation {
     pub file: Box<Path>,
@@ -75,8 +77,8 @@ pub fn get_where(option_name: &str, configuration_nix: &Path) -> Result<Box<Path
 
 pub fn get_highest_prio(
     option_name: &str,
-    mut source: SourceFile,
-) -> Result<SourceLine, BoxDynError> {
+    source: SourceFile,
+) -> Result<(i64, SourceLine), BoxDynError> {
     // Get the current highest priority.
 
     let expr: OsString = [
@@ -93,7 +95,7 @@ pub fn get_highest_prio(
         .into_command()
         .output_checked_utf8()?;
     let stdout = output.stdout();
-    let highest_prio = stdout.trim();
+    let highest_prio = i64::from_str(stdout.trim())?;
 
     let needle = format!("lib.mkOverride ({})", highest_prio);
 
@@ -111,27 +113,77 @@ pub fn get_highest_prio(
             )
         });
 
-    Ok(line.clone())
+    Ok((highest_prio, line.clone()))
+}
+
+pub fn get_next_prio_line(
+    source: SourceFile,
+    option_name: Arc<str>,
+    last_line_def: SourceLine,
+    new_prio: i64,
+    new_value: Arc<str>,
+) -> Result<SourceLine, BoxDynError> {
+    if !last_line_def.text.ends_with(';') {
+        todo!();
+    }
+    let next_line = source.line(last_line_def.line.next())?;
+    if next_line.text.trim() != "}" {
+        todo!();
+    }
+
+    let (indentation, _rest) = last_line_def.text.split_at(
+        last_line_def
+            .text
+            .find(|ch: char| !ch.is_ascii_whitespace())
+            .unwrap_or_default(),
+    );
+    // FIXME: fix indentation
+    let new_text = format!("{indentation}{option_name} = lib.mkOverride ({new_prio}) ({new_value});",);
+
+    let new_line = SourceLine {
+        line: next_line.line.next(),
+        path: source.path(),
+        text: Arc::from(new_text),
+    };
+
+    Ok(new_line)
 }
 
 pub fn write_next_prio(
     mut source: SourceFile,
     last_line_def: SourceLine,
-    last_pri: i64,
-    new_prio: i64,
+    new_text: Arc<str>,
 ) -> Result<(), BoxDynError> {
     //let lines = source.lines()?;
 
-    let old_text = last_line_def.text();
-    let new_text = old_text.replace(last_pri.to_string().as_str(), new_prio.to_string().as_str());
+    let open_brace_line = source.line(last_line_def.line.prev())?.text();
+    let close_brace_line = source.line(last_line_def.line.next())?.text();
 
+    let new_mod_start = SourceLine {
+        line: last_line_def.line.next(),
+        path: source.path(),
+        text: open_brace_line,
+    };
     let new_line = SourceLine {
-        line: Line::from_index(last_line_def.line.index() + 1),
+        line: new_mod_start.line.next(),
         path: source.path(),
         text: Arc::from(new_text),
     };
+    let new_mod_end = SourceLine {
+        line: new_line.line.next(),
+        path: source.path(),
+        text: close_brace_line,
+    };
 
-    source.insert_line(new_line.line, new_line.text())?;
+    dbg!(&new_mod_start.text());
+
+    source.insert_lines(&[
+        new_mod_start,
+        new_line,
+        new_mod_end,
+    ])?;
+
+    //source.insert_line(new_line.line, new_line.text())?;
 
     Ok(())
 }

src/line.rs

@@ -9,24 +9,35 @@ pub struct Line(pub u64);
 
 /// Constructors.
 impl Line {
-    pub fn from_index(index: u64) -> Self {
+    pub const fn from_index(index: u64) -> Self {
         Self(index)
     }
 
-    pub fn from_linenr(linenr: NonZeroU64) -> Self {
+    pub const fn from_linenr(linenr: NonZeroU64) -> Self {
         Self(linenr.get() - 1)
     }
+
+    pub const fn next(self) -> Self {
+        Self::from_index(self.index() + 1)
+    }
+
+    /// Panics if self is line index 0.
+    pub const fn prev(self) -> Self {
+        Self::from_index(self.index() - 1)
+    }
 }
 
 /// Getters.
 impl Line {
     /// 0-indexed
-    pub fn index(self) -> u64 {
+    pub const fn index(self) -> u64 {
         self.0
     }
 
     /// 1-indexed
-    pub fn linenr(self) -> u64 {
+    pub const fn linenr(self) -> u64 {
         self.0 + 1
     }
 }
+
+pub struct Lines(Vec<Line>);

src/main.rs

@@ -1,8 +1,7 @@
-use std::{error::Error as StdError, sync::Arc};
 use std::io::{self, IsTerminal};
 use std::path::Path;
 use std::process::ExitCode;
-
+use std::{error::Error as StdError, sync::Arc};
 
 use append_override::source::SourceFile;
 use clap::{ColorChoice, Parser as _};
@@ -28,31 +27,28 @@ fn main_wrapped() -> Result<(), Box<dyn StdError + Send + Sync + 'static>> {
     let def_path = append_override::get_where(&args.name, filepath)?;
     let def_path = Arc::from(def_path);
     let mut opts = File::options();
-    opts
-        .read(true)
+    opts.read(true)
         .write(true)
         .create(false)
         .custom_flags(libc::O_CLOEXEC);
     let source_file = SourceFile::open_from(Arc::clone(&def_path), opts)?;
 
-    let last_def_line = append_override::get_highest_prio(&args.name, source_file.clone())?;
-    let pri: i64 = {
-        let text = last_def_line.text();
-        let pat = "lib.mkOverride (";
-        let start = text.find(pat).unwrap();
-        let substr = &text[start..];
-        let substr = substr.strip_prefix(pat).unwrap();
-        let end_paren = substr.find(")").unwrap();
-        let final_num = &substr[..end_paren];
-
-        final_num.parse().unwrap()
-    };
+    let (pri, last_def_line) = append_override::get_highest_prio(&args.name, source_file.clone())?;
+    let new_pri = pri - 1;
 
     eprintln!("{last_def_line}");
 
-    dbg!(&pri);
+    let new_pri_line = append_override::get_next_prio_line(
+        source_file.clone(),
+        args.name.into(),
+        last_def_line.clone(),
+        new_pri,
+        args.value.into(),
+    )?;
 
-    append_override::write_next_prio(source_file, last_def_line, pri, pri - 1)?;
+    eprintln!("new_pri_line={new_pri_line}");
+
+    append_override::write_next_prio(source_file, last_def_line, new_pri_line.text())?;
 
     Ok(())
 }

src/source.rs

@@ -48,6 +48,8 @@ pub struct SourcePath {
 pub struct SourceFile {
     path: Arc<Path>,
     file: Arc<Mutex<File>>,
+    /// References to `SourceFile` do not prevent mutating `lines`.
+    /// Also `lines` is lazily initialized.
     lines: Arc<OnceLock<RefCell<Vec<SourceLine>>>>,
 }
 
@@ -119,6 +121,75 @@ impl SourceFile {
         Ref::map(self.lines.get().unwrap().borrow(), |lines| lines.as_slice())
     }
 
+    /// With debug assertions, panics if `lines` are not contiguous.
+    pub fn insert_lines(&mut self, new_lines: &[SourceLine]) -> Result<(), IoError> {
+        if new_lines.is_empty() {
+            return Ok(());
+        }
+
+        debug_assert!(new_lines.is_sorted_by(|lhs, rhs| lhs.line.next() == rhs.line));
+
+        let path = self.path();
+        let cur_lines = self.lines()?;
+        let first_half = cur_lines
+            .iter()
+            .take(new_lines.last().unwrap().line.prev().index() as usize)
+            .map(SourceLine::text);
+        let middle = new_lines.iter().map(SourceLine::text);
+        let second_half = cur_lines
+            .iter()
+            .skip(new_lines.last().unwrap().line.prev().index() as usize)
+            .map(SourceLine::text);
+
+        let final_lines: Vec<SourceLine> = first_half
+            .chain(middle)
+            .chain(second_half)
+            .enumerate()
+            .map(|(idx, text)| SourceLine {
+                line: Line::from_index(idx as u64),
+                text,
+                path: self.path(),
+            })
+            .collect();
+
+        // Assert lines are continuous.
+        debug_assert!(final_lines.is_sorted_by(|lhs, rhs| lhs.line.next() == rhs.line));
+        debug_assert_eq!(cur_lines.len() + new_lines.len(), final_lines.len());
+
+        drop(cur_lines);
+
+        // Write it to a file in the same directory.
+        let new_name: OsString = [
+            // foo
+            path.file_name().unwrap(),
+            OsStr::new(".tmp"),
+        ]
+        .into_iter()
+        .collect::<OsString>();
+        let tmp_path = path.with_file_name(&new_name);
+        let tmp_file = File::options()
+            .create(true)
+            .write(true)
+            .truncate(true)
+            .custom_flags(libc::O_EXCL | libc::O_CLOEXEC)
+            .open(&tmp_path)?;
+
+        let mut writer = BufWriter::new(tmp_file);
+        for line in final_lines.iter() {
+            writer.write_all(line.text().as_bytes())?;
+            writer.write_all(b"\n")?;
+        }
+        writer.flush()?;
+        drop(writer);
+        // Rename the temporary file to the new file, which is atomic (TODO: I think).
+        fs_err::rename(&tmp_path, &path)?;
+
+        // Finally, update state.
+        self.lines.get().unwrap().replace(final_lines);
+
+        Ok(())
+    }
+
     pub fn insert_line(&mut self, at: Line, text: Arc<str>) -> Result<(), IoError> {
         self.lines()?;
         let path = self.path();