Reorder and comment

src/main.rs

@@ -36,6 +36,8 @@ fn main() {
         print_help();
         return;
     }
+
+    // Collect alias files and their default domains
     let mut alias_files: Vec<AliasFile> = Vec::new();
     for i in (1..args.len()).step_by(2) {
         if let Ok(lines) = read_lines(&args[i]) {
@@ -48,6 +50,82 @@ fn main() {
     println!("{}", generate_sieve_script(parse_alias_to_map(alias_files)));
 }
 
+/// Read a virtual alias file (http://www.postfix.org/virtual.5.html)
+/// and convert it to a map of destination addresses to a list of their final forwarding addresses.
+fn parse_alias_to_map(alias_files: Vec<AliasFile>) -> AliasMap {
+    // File must exist in the current path
+    let mut redirect_map: AliasMap = AliasMap::new();
+    let mut destinations: Vec<OrdEmailAddress> = Vec::new();
+
+    // Extract all pairs (destination to redirect addresses) from the alias files
+    for alias_file in alias_files {
+        for line in alias_file.content {
+            let line = line.unwrap();
+
+            // Ignore comments in the alias file
+            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.is_empty() {
+                continue;
+            }
+
+            let redirects: Vec<OrdEmailAddress> = line
+                .split_at(line.find(char::is_whitespace).unwrap_or(0))
+                .1
+                .split(' ')
+                .filter(|address| address.trim().to_string().replace(',', "") != "")
+                .map(|addr| to_mailaddress(addr, &alias_file.default_domain))
+                .collect();
+
+            if redirects.is_empty() {
+                continue;
+            }
+            destinations.push(to_mailaddress(destination, &alias_file.default_domain));
+            redirect_map.insert(
+                to_mailaddress(destination, &alias_file.default_domain),
+                redirects,
+            );
+        }
+    }
+
+    // Replace redirects that are again forwarded elsewhere by that.
+    // Break after depth max_iterations and assume infinite recursion afterwards.
+    let mut changed = true;
+    let mut iterations = 0;
+    let max_iterations = 100;
+    while changed && iterations < max_iterations {
+        changed = false;
+        iterations += 1;
+        let mut all_new_redirects: AliasMap = AliasMap::new();
+        for destination in &destinations {
+            for forward_to in redirect_map.get(destination).unwrap() {
+                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().cloned()));
+                }
+            }
+        }
+        for (destination, new_redirect) in all_new_redirects {
+            *redirect_map.get_mut(&destination).unwrap() = new_redirect;
+        }
+    }
+    if iterations == max_iterations {
+        panic!("Possibly infinite recursion detected in parse_alias_map. Did not terminate after {max_iterations} rounds.");
+    }
+    redirect_map
+}
+
+/// Generate a Sieve script (https://en.wikipedia.org/wiki/Sieve_(mail_filtering_language))
+/// from a map of destination addresses to a list of their forwarding addresses.
+///
+/// Addresses are sorted according to the order on OrdEmailAddress.
 fn generate_sieve_script(redirects: AliasMap) -> String {
     let mut script: String = "require [\"envelope\", \"copy\"];\n\n".to_string();
     for (redirect, mut destinations) in redirects {
@@ -69,62 +147,10 @@ fn generate_sieve_script(redirects: AliasMap) -> String {
     script
 }
 
-fn parse_alias_to_map(alias_files: Vec<AliasFile>) -> AliasMap {
-    // File must exist in the current path
-    let mut redirect_map: AliasMap = AliasMap::new();
-    let mut destinations: Vec<OrdEmailAddress> = Vec::new();
-    for alias_file in alias_files {
-        for line in alias_file.content {
-            let line = line.unwrap();
-            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.is_empty() {
-                continue;
-            }
-            let redirects: Vec<OrdEmailAddress> = line
-                .split_at(line.find(char::is_whitespace).unwrap_or(0))
-                .1
-                .split(' ')
-                .filter(|address| address.trim().to_string().replace(',', "") != "")
-                .map(|addr| to_mailaddress(addr, &alias_file.default_domain))
-                .collect();
-            if redirects.is_empty() {
-                continue;
-            }
-            destinations.push(to_mailaddress(destination, &alias_file.default_domain));
-            redirect_map.insert(
-                to_mailaddress(destination, &alias_file.default_domain),
-                redirects,
-            );
-        }
-    }
-    let mut changed = true;
-    while changed {
-        changed = false;
-        let mut all_new_redirects: AliasMap = AliasMap::new();
-        for destination in &destinations {
-            for forward_to in redirect_map.get(destination).unwrap() {
-                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().cloned()));
-                }
-            }
-        }
-        for (destination, new_redirect) in all_new_redirects {
-            *redirect_map.get_mut(&destination).unwrap() = new_redirect;
-        }
-    }
-    redirect_map
-}
-
-fn to_mailaddress(local_part: &str, default_domain: &FQDN) -> OrdEmailAddress {
-    let mut addr = local_part.trim().to_string();
+/// Create an OrdEmailAddress from some alias entry.
+/// Return parameter for complete mail addresses and append the default domain for local parts.
+fn to_mailaddress(alias_entry: &str, default_domain: &FQDN) -> OrdEmailAddress {
+    let mut addr = alias_entry.trim().to_string();
     addr = addr.replace(',', "");
     if addr.contains('@') {
         return OrdEmailAddress(EmailAddress::parse(&addr, None).unwrap());

testdata/infiniterec.aliases

@@ -0,0 +1,2 @@
+# This creates an infinite recursion
+orga orga