Add --refresh to repair stale device IDs, and rename to audioswitch

Windows gives a device a new endpoint ID when it reappears as another
instance, typically a DAC moved to a different USB port, which also
gains a "2- " name prefix. The old config line then silently dropped out
of the cycle. --refresh re-points each stale line at the present output
with the same name (ignoring that prefix), keeps order and comments, adds
unmentioned outputs as commented-out lines, and keeps a .bak of the
previous file.

Also replace every remaining "win-audio-output-switcher" with
"audioswitch": the config now lives in %APPDATA%\audioswitch, and the
autostart Run value and single-instance mutex use the new name.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

README.md

@@ -1,4 +1,4 @@
-# win-audio-output-switcher
+# audioswitch
 
 A global hotkey that cycles the Windows 11 default audio output, and a flyout that tells
 you where you landed.
@@ -76,6 +76,7 @@ $old = [Environment]::GetEnvironmentVariable('Path', 'User')
 audioswitch                  Run in the background (single instance)
 audioswitch --list           List outputs and their endpoint IDs
 audioswitch --config         Create/open the config file
+audioswitch --refresh        Update config device IDs to match current outputs
 audioswitch --quit           Stop the running instance
 audioswitch --autostart on   Start with Windows (off to undo)
 ```
@@ -89,7 +90,7 @@ GUI-subsystem binary, a shell may hand back the prompt before the output arrives
 
 ## Config
 
-`%APPDATA%\win-audio-output-switcher\config.ini`, created by `--config` already populated
+`%APPDATA%\audioswitch\config.ini`, created by `--config` already populated
 with the outputs you have right now. Edits apply on the next hotkey press — no restart.
 
 ```ini
@@ -106,6 +107,13 @@ osd_fade = false
 {0.0.0.00000000}.{ff879682-...} = Haut-parleurs (Focusrite USB Audio)
 ```
 
+Windows sometimes gives a device a new endpoint ID. Plugging a DAC into a different USB
+port is the usual cause, and its name gains a `2- ` prefix as well. The old line then
+silently drops out of the cycle. `audioswitch --refresh` fixes this. It moves each stale
+line to the present output with the same name (ignoring that prefix), keeps your order and
+comments, and adds outputs the file doesn't mention yet as commented-out lines. The
+previous file is kept as `config.ini.bak`.
+
 `osd_fade` is off by default. Fading needs `WS_EX_LAYERED`, which on some builds suppresses
 the acrylic backdrop that makes the flyout look like part of the shell. Turn it on and see
 which you prefer on your machine.

src/cli.rs

@@ -23,7 +23,7 @@ use windows::Win32::UI::WindowsAndMessaging::SW_SHOWNORMAL;
 use crate::{audio, config};
 
 const RUN_KEY: windows::core::PCWSTR = w!(r"Software\Microsoft\Windows\CurrentVersion\Run");
-const RUN_VALUE: windows::core::PCWSTR = w!("win-audio-output-switcher");
+const RUN_VALUE: windows::core::PCWSTR = w!("audioswitch");
 
 /// True when another instance already holds the single-instance mutex.
 ///
@@ -102,6 +102,59 @@ pub fn config() -> i32 {
     0
 }
 
+pub fn refresh() -> i32 {
+    attach_console();
+
+    let Ok(enumerator) = audio::enumerator() else {
+        eprintln!("Could not reach the audio device enumerator.");
+        return 1;
+    };
+    let outputs = audio::outputs(&enumerator).unwrap_or_default();
+
+    let path = config::path();
+    let Ok(text) = std::fs::read_to_string(&path) else {
+        // Nothing to refresh, but a fresh template is exactly what a refresh would produce.
+        return match config::write_template(&outputs) {
+            Ok(path) => {
+                println!("No config yet - created {}", path.display());
+                0
+            }
+            Err(error) => {
+                eprintln!("Could not write the config file: {error}");
+                1
+            }
+        };
+    };
+
+    let pairs: Vec<(&str, &str)> = outputs
+        .iter()
+        .map(|output| (output.id.as_str(), output.name.as_str()))
+        .collect();
+    let Some(refreshed) = config::refresh(&text, &pairs) else {
+        println!("No [devices] section - every active output is already in the cycle.");
+        return 0;
+    };
+
+    for change in &refreshed.changes {
+        println!("  {change}");
+    }
+    if refreshed.text == text {
+        println!("Config already up to date: {}", path.display());
+        return 0;
+    }
+
+    // One level of undo, in case a name match picked the wrong device.
+    let backup = path.with_extension("ini.bak");
+    if let Err(error) = std::fs::write(&backup, &text)
+        .and_then(|()| std::fs::write(&path, &refreshed.text))
+    {
+        eprintln!("Could not update the config file: {error}");
+        return 1;
+    }
+    println!("\nUpdated {} (previous version in {})", path.display(), backup.display());
+    0
+}
+
 pub fn quit() -> i32 {
     attach_console();
 
@@ -158,12 +211,13 @@ fn print_usage() {
         .unwrap_or_else(|_| "audioswitch.exe".to_string());
 
     println!(
-        "win-audio-output-switcher - cycle the default audio output from a global hotkey\n\
+        "audioswitch - cycle the default audio output from a global hotkey\n\
          \n\
          Usage ({exe}):\n\
          \x20 <exe>                  Run in the background (single instance)\n\
          \x20 <exe> --list           List outputs and their endpoint IDs\n\
          \x20 <exe> --config         Create/open the config file\n\
+         \x20 <exe> --refresh        Update config device IDs to match current outputs\n\
          \x20 <exe> --quit           Stop the running instance\n\
          \x20 <exe> --autostart on   Start with Windows (off to undo)\n\
          \x20 <exe> --help           This text\n\

src/config.rs

@@ -1,4 +1,4 @@
-//! The config file: `%APPDATA%\win-audio-output-switcher\config.ini`.
+//! The config file: `%APPDATA%\audioswitch\config.ini`.
 //!
 //! Deliberately hand-parsed. The whole file is a handful of `key = value` lines plus one
 //! `[devices]` section, which is not worth a serde + toml dependency — and endpoint IDs
@@ -52,7 +52,7 @@ impl Default for Config {
 pub fn path() -> PathBuf {
     let base = std::env::var("APPDATA").unwrap_or_default();
     PathBuf::from(base)
-        .join("win-audio-output-switcher")
+        .join("audioswitch")
         .join("config.ini")
 }
 
@@ -158,7 +158,7 @@ pub fn write_template(outputs: &[crate::audio::Endpoint]) -> std::io::Result<Pat
     }
 
     let mut text = String::from(
-        "; win-audio-output-switcher\n\
+        "; audioswitch\n\
          ; Edits take effect on the next hotkey press - no restart needed.\n\
          \n\
          hotkey = ctrl+alt+a\n\
@@ -183,3 +183,140 @@ pub fn write_template(outputs: &[crate::audio::Endpoint]) -> std::io::Result<Pat
     fs::write(&path, text)?;
     Ok(path)
 }
+
+/// Outcome of [`refresh`]: the rewritten file and a line per change, for the user.
+pub struct Refresh {
+    pub text: String,
+    pub changes: Vec<String>,
+}
+
+/// Rewrite the `[devices]` section against the outputs present right now.
+///
+/// Windows hands a device a new endpoint ID when it reappears as a different instance -
+/// typically the same DAC in another USB port, which also gains a `2- ` in its name. The
+/// old ID then silently drops out of the cycle. This re-points each stale line at the
+/// present output with the same name, keeping the user's order and comments, and lists
+/// outputs the file does not mention yet as commented-out lines.
+///
+/// `outputs` is `(id, name)` pairs. Returns `None` when there is no `[devices]` section,
+/// since then every output is already cycled and there is nothing to refresh.
+pub fn refresh(text: &str, outputs: &[(&str, &str)]) -> Option<Refresh> {
+    struct Entry {
+        line: usize,
+        /// Everything before the ID: empty, or the comment marker that disabled the line.
+        prefix: String,
+        id: String,
+        label: String,
+    }
+
+    let mut lines: Vec<String> = text.lines().map(str::to_string).collect();
+    let mut section: Option<(usize, usize)> = None;
+    let mut entries = Vec::new();
+
+    for (index, raw) in lines.iter().enumerate() {
+        let line = raw.trim();
+        if line.starts_with('[') && line.ends_with(']') {
+            if let Some((_, end)) = section.as_mut() {
+                if *end == usize::MAX {
+                    *end = index;
+                }
+            }
+            if line[1..line.len() - 1].trim().eq_ignore_ascii_case("devices") {
+                section = Some((index, usize::MAX));
+            }
+            continue;
+        }
+        if !matches!(section, Some((_, usize::MAX))) {
+            continue;
+        }
+
+        // A disabled device line is still a device line: remap it too, or it would be
+        // listed again below as a new output.
+        let body = line.trim_start_matches([';', '#']).trim_start();
+        let commented = body.len() != line.len();
+        let Some((key, value)) = body.split_once('=') else {
+            continue;
+        };
+        let key = key.trim();
+        if key.is_empty() || (commented && !key.starts_with('{')) {
+            continue;
+        }
+        entries.push(Entry {
+            line: index,
+            prefix: line[..line.len() - body.len()].to_string(),
+            id: key.to_string(),
+            label: value.trim().to_string(),
+        });
+    }
+
+    let (header, end) = section?;
+    let end = end.min(lines.len());
+
+    let present = |id: &str| outputs.iter().find(|(output, _)| *output == id);
+    let mut claimed: Vec<&str> = entries
+        .iter()
+        .filter_map(|entry| present(&entry.id).map(|(id, _)| *id))
+        .collect();
+    let mut changes = Vec::new();
+
+    for entry in &entries {
+        let (id, name) = match present(&entry.id) {
+            Some(&(id, name)) => (id, name),
+            None => {
+                let wanted = normalize(&entry.label);
+                let found = outputs
+                    .iter()
+                    .find(|(id, name)| !claimed.contains(id) && normalize(name) == wanted);
+                let Some(&(id, name)) = found else {
+                    changes.push(format!("not present, left as is: {}", entry.label));
+                    continue;
+                };
+                claimed.push(id);
+                changes.push(format!("new ID for {name}: {} -> {id}", entry.id));
+                (id, name)
+            }
+        };
+
+        let rewritten = format!("{}{id} = {name}", entry.prefix);
+        if lines[entry.line] != rewritten {
+            if entry.id == id && entry.label != name {
+                changes.push(format!("renamed: {} -> {name}", entry.label));
+            }
+            lines[entry.line] = rewritten;
+        }
+    }
+
+    // New outputs go at the end of the section, disabled, so refreshing never changes
+    // what the hotkey cycles through beyond fixing stale IDs.
+    let insert_at = (header + 1..end)
+        .rev()
+        .find(|&index| !lines[index].trim().is_empty())
+        .map_or(header + 1, |index| index + 1);
+    let added: Vec<String> = outputs
+        .iter()
+        .filter(|(id, _)| !claimed.contains(id))
+        .map(|(id, name)| {
+            changes.push(format!("added (commented out): {name}"));
+            format!("; {id} = {name}")
+        })
+        .collect();
+    lines.splice(insert_at..insert_at, added);
+
+    let newline = if text.contains("\r\n") { "\r\n" } else { "\n" };
+    let mut text = lines.join(newline);
+    text.push_str(newline);
+    Some(Refresh { text, changes })
+}
+
+/// A device name without the instance number Windows inserts for a second copy of the
+/// same hardware: `Casque (2- FiiO USB DAC-E07K)` -> `casque (fiio usb dac-e07k)`.
+fn normalize(name: &str) -> String {
+    if let Some(open) = name.find('(') {
+        let rest = &name[open + 1..];
+        let digits = rest.len() - rest.trim_start_matches(|c: char| c.is_ascii_digit()).len();
+        if digits > 0 && rest[digits..].starts_with("- ") {
+            return format!("{}{}", &name[..=open], &rest[digits + 2..]).to_lowercase();
+        }
+    }
+    name.to_lowercase()
+}

src/main.rs

@@ -1,4 +1,4 @@
-//! win-audio-output-switcher
+//! audioswitch
 //!
 //! A global hotkey that cycles the Windows default audio output, and a flyout that says
 //! which one you landed on. One hidden window, one message loop, no polling: the process
@@ -41,7 +41,7 @@ mod cli;
 /// Asks a running instance to exit.
 const WM_QUIT_REQUEST: u32 = WM_APP + 2;
 
-const MUTEX_NAME: PCWSTR = w!("Local\\win-audio-output-switcher");
+const MUTEX_NAME: PCWSTR = w!("Local\\audioswitch");
 
 struct App {
     enumerator: IMMDeviceEnumerator,
@@ -71,6 +71,7 @@ fn main() {
     let code = match args.first().map(String::as_str) {
         Some("--list" | "-l") => cli::list(),
         Some("--config" | "-c") => cli::config(),
+        Some("--refresh" | "-r") => cli::refresh(),
         Some("--quit" | "-q") => cli::quit(),
         Some("--autostart") => cli::autostart(args.get(1).map(String::as_str)),
         Some("--help" | "-h") => cli::help(),