finish review

src/backend/backend_trait.rs

@@ -1,7 +1,5 @@
 use std::collections::HashMap;
 use std::fmt::Debug;
-use std::fs::{read_to_string, File};
-use std::io::Write;
 use std::process::Command;
 use std::rc::Rc;
 use std::{collections::HashSet, process::ExitStatus};
@@ -32,66 +30,12 @@ pub(crate) trait Backend: Debug {
     /// Get all packages that were installed in the system explicitly.
     fn get_explicitly_installed_packages(&self) -> Result<HashSet<Package>>;
 
-    // TODO continue here
     fn assign_group(&self, to_assign: Vec<(Package, Rc<Group>)>) {
-        todo!();
-        let mut group_package_map = HashMap::new();
-
-        for (p, group) in to_assign {
-            if !group_package_map.contains_key(&group) {
-                group_package_map.insert(group.clone(), vec![]);
-            }
-
-            let inner = group_package_map.get_mut(&group).unwrap();
-            inner.push(p);
-        }
-
-        for vecs in group_package_map.values_mut() {
-            vecs.sort();
-        }
+        let group_package_map = get_group_packages_map(to_assign);
+        let section_header = format!("[{}]", self.get_section());
 
         for (group, packages) in group_package_map {
-            let group_file_content = read_to_string(&group.path).unwrap();
-            let old_length = dbg!(group_file_content.len());
-            let mut must_write_section_header = false;
-
-            let mut lines = group_file_content.lines();
-
-            lines.find(|line| line.contains(&format!("[{}]", self.get_section())));
-            lines.next().unwrap();
-
-            // let start_of_section = if let Some(start_of_section) = group_file_content.find() {
-            //     start_of_section
-            // } else {
-            //     must_write_section_header = true;
-            //     old_length
-            // };
-
-            // dbg!(&start_of_section);
-
-            // let mut new_file_content = group_file_content
-            //     .get(..start_of_section)
-            //     .unwrap()
-            //     .to_owned();
-
-            // dbg!(&new_file_content);
-
-            // todo!();
-
-            // if dbg!(must_write_section_header) {
-            //     new_file_content.push_str(&format!("\n[{}]", self.get_section()));
-            // }
-            // for package in packages {
-            //     new_file_content.push_str(&format!("\n{package}"));
-            // }
-            // new_file_content.push('\n');
-
-            // if old_length > start_of_section {
-            //     new_file_content.push_str(group_file_content.get(old_length..).unwrap());
-            // }
-
-            // let mut file = File::create(&group.path).unwrap();
-            // write!(file, "{new_file_content}").unwrap();
+            group.save_packages(&section_header, packages);
         }
     }
 
@@ -170,3 +114,23 @@ pub(crate) trait Backend: Debug {
         Ok(diff)
     }
 }
+
+fn get_group_packages_map(
+    to_assign: Vec<(Package, Rc<Group>)>,
+) -> HashMap<Rc<Group>, Vec<Package>> {
+    let mut group_package_map = HashMap::new();
+
+    for (p, group) in to_assign {
+        if !group_package_map.contains_key(&group) {
+            group_package_map.insert(group.clone(), vec![]);
+        }
+
+        let inner = group_package_map.get_mut(&group).unwrap();
+        inner.push(p);
+    }
+
+    for vecs in group_package_map.values_mut() {
+        vecs.sort();
+    }
+    group_package_map
+}

src/grouping/group.rs

@@ -1,12 +1,13 @@
-use std::fmt::Write;
-use std::fs::read_to_string;
+use std::fmt::Write as FmtWrite;
+use std::fs::{read_to_string, File};
 use std::hash::Hash;
+use std::io::Write as IoWrite;
 use std::path::{Path, PathBuf};
 use std::{collections::HashSet, fmt::Display};
 
 use anyhow::{Context, Result};
 
-use super::Section;
+use super::{Package, Section};
 
 use crate::Config;
 
@@ -110,6 +111,19 @@ impl Group {
             path,
         })
     }
+
+    pub(crate) fn save_packages(&self, section_header: &str, packages: Vec<Package>) {
+        let mut content = read_to_string(&self.path).unwrap();
+
+        if content.contains(section_header) {
+            write_packages_to_existing_section(&mut content, section_header, &packages);
+        } else {
+            add_new_section_with_packages(&mut content, section_header, &packages);
+        }
+
+        let mut file = File::create(&self.path).unwrap();
+        write!(file, "{content}").unwrap();
+    }
 }
 
 impl Display for Group {
@@ -128,3 +142,40 @@ impl Display for Group {
         Ok(())
     }
 }
+
+fn write_packages_to_existing_section(
+    group_file_content: &mut String,
+    section_header: &str,
+    packages: &[Package],
+) {
+    let idx_of_first_package_line_in_section =
+        find_first_package_line_in_section(group_file_content, section_header);
+
+    let after = group_file_content.split_off(idx_of_first_package_line_in_section);
+
+    for p in packages {
+        group_file_content.push_str(&format!("{p}\n"));
+    }
+
+    group_file_content.push_str(&after);
+}
+
+fn find_first_package_line_in_section(group_file_content: &str, section_header: &str) -> usize {
+    let section_start = group_file_content.find(section_header).unwrap();
+    let distance_to_next_newline = group_file_content[section_start..].find('\n').unwrap();
+
+    section_start + distance_to_next_newline + 1 // + 1 to be after the newline
+}
+
+fn add_new_section_with_packages(
+    group_file_content: &mut String,
+    section_header: &str,
+    packages: &[Package],
+) {
+    group_file_content.push('\n');
+    group_file_content.push_str(section_header);
+    group_file_content.push('\n');
+    for p in packages {
+        group_file_content.push_str(&format!("{p}\n"));
+    }
+}