First rough parsing of alias file to hashmap

.gitignore

@@ -25,3 +25,7 @@ testdata/mathebau.aliases
 
 # might contain private mailadresses as well
 testdata/virt_aliases
+
+
+# Added by cargo
+/target

Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "alias_to_sieve"
+version = "0.1.0"

Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "alias_to_sieve"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+
+[[bin]]
+name = "alias_to_sieve"
+path = "main.rs"

main.rs

@@ -0,0 +1,69 @@
+use std::fs::File;
+use std::io::{self, BufRead};
+use std::path::Path;
+use std::env;
+use std::collections::HashMap;
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+
+    let file_path = &args[1];
+
+    // File must exist in the current path
+    if let Ok(lines) = read_lines(file_path) {
+        // Consumes the iterator, returns an (Optional) String
+        let mut redirect_map : HashMap<String, Vec<String>> = HashMap::new();
+        let mut destinations : Vec<String> = Vec::new();
+        for line in lines.flatten() {
+            let line = String::from(line.split_at(line.find("#").unwrap_or(line.len())).0);
+            let destination = line.split_at(line.find(char::is_whitespace).unwrap_or(0)).0;
+            if destination == "" {
+                continue;
+            }
+            let redirects: Vec<String> = line.split_at(line.find(char::is_whitespace).unwrap_or(0)).1.split(", ")
+              .map(|address| to_mailaddress(address)).collect();
+            if redirects.len() == 0 {
+                continue;
+            }
+            destinations.push(to_mailaddress(destination));
+            redirect_map.insert(to_mailaddress(destination), redirects);
+        }
+        let mut changed = true; 
+        while changed {
+            changed = false;
+            let mut all_new_redirects : HashMap<String, Vec<String>> = HashMap::new();
+            for destination in destinations.iter() {
+                for forward_to in redirect_map.get(destination).unwrap().iter() {
+                    if let Some(new_redirects) = redirect_map.get(forward_to) {
+                        changed = true;
+                        all_new_redirects.entry(destination.clone()).or_insert(redirect_map.get(destination).unwrap().clone())
+                        .retain(|dest| *dest != *forward_to);
+                        all_new_redirects.entry(destination.clone()).and_modify(|d| d.extend(new_redirects.iter().map(|x| x.clone())));
+                    }
+                }
+                
+            }
+            
+            for (destination, new_redirect) in all_new_redirects {
+                *redirect_map.get_mut(&destination).unwrap() = new_redirect;
+            }
+        }
+        println!("{:#?}", redirect_map);
+    }
+}
+
+fn to_mailaddress(local_part: &str) -> String {
+    let local_part = local_part.trim();
+    if local_part.contains("@") {
+        return String::from(local_part);
+    }
+    return local_part.to_string() + "@mathebau.de";
+}
+
+// The output is wrapped in a Result to allow matching on errors.
+// Returns an Iterator to the Reader of the lines of the file.
+fn read_lines<P>(filename: P) -> io::Result<io::Lines<io::BufReader<File>>>
+where P: AsRef<Path>, {
+    let file = File::open(filename)?;
+    Ok(io::BufReader::new(file).lines())
+}