factor out do_append in prep for delta subcommands

src/lib.rs

@@ -1,4 +1,4 @@
-use std::sync::Arc;
+use std::{iter, sync::Arc};
 
 pub(crate) mod prelude {
     #![allow(unused_imports)]
@@ -32,7 +32,7 @@ pub(crate) mod prelude {
 use prelude::*;
 
 pub mod args;
-pub use args::Parser;
+pub use args::{AppendCmd, Args};
 mod color;
 pub use color::{CLI_ENABLE_COLOR, SHOULD_COLOR};
 pub mod line;
@@ -47,6 +47,43 @@ use crate::source::SourceFile;
 
 pub const ASCII_WHITESPACE: &[char] = &['\t', '\n', '\x0C', '\r', ' '];
 
+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()
+    };
+
+    // Get what file that thing is defined in.
+    let def_path = get_where(&append_args.name, &filepath)?;
+
+    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(def_path), opts)?;
+
+    let pri = get_highest_prio(&append_args.name, source_file.clone())?;
+    let new_pri = pri - 1;
+
+    let new_pri_line = get_next_prio_line(
+        source_file.clone(),
+        append_args.name.into(),
+        new_pri,
+        append_args.value.into(),
+    )?;
+
+    eprintln!("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>,