print, main, error: cleanup, add docs

src/error.rs

@@ -38,9 +38,6 @@ pub enum AppError {
 
     #[error("Database error: {source}")]
     DatabaseError { source: rusqlite::Error },
-
-    #[error("Nix store error: {message} for path: {store_path}")]
-    NixStoreError { message: String, store_path: String },
 }
 
 // Implement From traits to support the ? operator
@@ -123,12 +120,4 @@ impl AppError {
             context: context.into(),
         }
     }
-
-    /// Create a Nix store error
-    pub fn nix_store_error<M: Into<String>, P: Into<String>>(message: M, store_path: P) -> Self {
-        Self::NixStoreError {
-            message: message.into(),
-            store_path: store_path.into(),
-        }
-    }
 }

src/main.rs

@@ -1,11 +1,10 @@
 mod print;
 use clap::Parser;
 use core::str;
-use log::{debug, error, warn};
+use log::{debug, error};
 use regex::Regex;
 use std::{
     collections::{HashMap, HashSet},
-    process::Command,
     string::ToString,
     sync::OnceLock,
     thread,
@@ -93,11 +92,9 @@ fn main() {
         .format_timestamp(Some(env_logger::fmt::TimestampPrecision::Seconds))
         .init();
 
-    debug!("Nix available: {}", check_nix_available()); // XXX: is this supposed to be user-facing?
     println!("<<< {}", args.path.to_string_lossy());
     println!(">>> {}", args.path2.to_string_lossy());
 
-
     // handles to the threads collecting closure size information
     // We do this as early as possible because nix is slow.
     let closure_size_handles = if args.closure_size {
@@ -222,9 +219,9 @@ fn main() {
         .max()
         .unwrap_or_default();
 
-    print::print_added(added, &post, col_width);
-    print::print_removed(removed, &pre, col_width);
-    print::print_changes(changed, &pre, &post, col_width);
+    print::print_added(&added, &post, col_width);
+    print::print_removed(&removed, &pre, col_width);
+    print::print_changes(&changed, &pre, &post, col_width);
 
     if let Some((pre_handle, post_handle)) = closure_size_handles {
         match (pre_handle.join(), post_handle.join()) {
@@ -261,7 +258,14 @@ fn store_path_regex() -> &'static Regex {
     })
 }
 
-// Parse the nix store path to extract package name and version
+/// Parses a nix store path to extract the packages name and version
+///
+/// This function first drops the inputs first 44 chars, since that is exactly the length of the /nix/store/... prefix. Then it matches that against our store path regex.
+///
+/// # Returns
+///
+/// * Result<(&'a str, &'a str)> - The Package's name and version, or an error if
+///   one or both cannot be retrieved.
 fn get_version<'a>(pack: impl Into<&'a str>) -> Result<(&'a str, &'a str)> {
     let path = pack.into();
 
@@ -294,17 +298,3 @@ fn get_version<'a>(pack: impl Into<&'a str>) -> Result<(&'a str, &'a str)> {
         source: None,
     })
 }
-
-fn check_nix_available() -> bool {
-    // Check if nix is available on the host system.
-    debug!("Checking nix command availability");
-    let nix_available = Command::new("nix").arg("--version").output().ok();
-    let nix_query_available = Command::new("nix-store").arg("--version").output().ok();
-
-    let result = nix_available.is_some() && nix_query_available.is_some();
-    if !result {
-        warn!("Nix commands not available, functionality may be limited");
-    }
-
-    result
-}

src/print.rs

@@ -2,6 +2,12 @@ use core::str;
 use std::collections::{HashMap, HashSet};
 use yansi::Paint;
 
+/// diffs two strings character by character, and returns a tuple of strings
+/// colored in a way to represent the differences between the two input strings.
+///
+/// # Returns:
+///
+/// * (String, String) - The differing chars being red in the left, and green in the right one.
 fn diff_versions(left: &str, right: &str) -> (String, String) {
     let mut prev = String::new();
     let mut post = String::new();
@@ -31,7 +37,8 @@ fn diff_versions(left: &str, right: &str) -> (String, String) {
     (prev, post)
 }
 
-pub fn print_added(set: HashSet<&str>, post: &HashMap<&str, HashSet<&str>>, col_width: usize) {
+/// print the packages added between two closures.
+pub fn print_added(set: &HashSet<&str>, post: &HashMap<&str, HashSet<&str>>, col_width: usize) {
     println!("{}", "Packages added:".underline().bold());
 
     // Use sorted outpu
@@ -57,7 +64,8 @@ pub fn print_added(set: HashSet<&str>, post: &HashMap<&str, HashSet<&str>>, col_
     }
 }
 
-pub fn print_removed(set: HashSet<&str>, pre: &HashMap<&str, HashSet<&str>>, col_width: usize) {
+/// print the packages removed between two closures.
+pub fn print_removed(set: &HashSet<&str>, pre: &HashMap<&str, HashSet<&str>>, col_width: usize) {
     println!("{}", "Packages removed:".underline().bold());
 
     // Use sorted output for more predictable and readable results
@@ -84,7 +92,7 @@ pub fn print_removed(set: HashSet<&str>, pre: &HashMap<&str, HashSet<&str>>, col
 }
 
 pub fn print_changes(
-    set: HashSet<&str>,
+    set: &HashSet<&str>,
     pre: &HashMap<&str, HashSet<&str>>,
     post: &HashMap<&str, HashSet<&str>>,
     col_width: usize,