ctl: show the candidates when completion is ambiguousmain

Tab now behaves like bash: it extends the word to the longest common prefix
and prints every candidate as a column list, instead of quietly cycling
through them one per press. Above completion_prompt_limit (100) it asks before
dumping the list.

Candidates are inserted with their spaces escaped, so a completed track name
stays one argument after Enter; the list itself shows the plain name.

1 files changed, 39 insertions, 20 deletions

diff --git a/src/ctl.rs b/src/ctl.rs
index 5cb2f3b..882982e 100644
--- a/src/ctl.rs
+++ b/src/ctl.rs
@@ -16,6 +16,7 @@
 use crate::cli::Cli;
 use clap::{CommandFactory, Parser};
 use rustyline::completion::{Completer, Pair};
+use rustyline::config::{CompletionType, Config};
 use rustyline::error::ReadlineError;
 use rustyline::highlight::Highlighter;
 use rustyline::hint::Hinter;
@@ -110,16 +111,31 @@ fn complete_music(prefix: &str) -> Vec<Pair> {
         .lines()
         .map(str::trim)
         .filter(|candidate| !candidate.is_empty())
-        // The CLI escapes spaces for shells; the shell's own reader needs the
-        // real text back and re-quotes it below.
-        .map(unescape)
-        .map(|candidate| Pair {
-            display: candidate.clone(),
-            replacement: quote(&candidate),
+        // Show the real name, but insert it escaped: the editor replaces the
+        // word with this text, and an unescaped space would turn one argument
+        // into two on the next Enter.
+        .map(|candidate| {
+            let name = unescape(candidate);
+            Pair {
+                display: name.clone(),
+                replacement: escape(&name),
+            }
         })
         .collect()
 }
 
+/// Escape a candidate so it stays one argument when inserted into the line.
+fn escape(candidate: &str) -> String {
+    let mut out = String::with_capacity(candidate.len());
+    for c in candidate.chars() {
+        if matches!(c, ' ' | '\\' | '\'' | '"') {
+            out.push('\\');
+        }
+        out.push(c);
+    }
+    out
+}
+
 /// Undo the shell escaping `rsp db-complete` applies.
 fn unescape(candidate: &str) -> String {
     let mut out = String::with_capacity(candidate.len());
@@ -136,15 +152,6 @@ fn unescape(candidate: &str) -> String {
     out
 }
 
-/// Quote a candidate that contains spaces, so it stays one argument.
-fn quote(candidate: &str) -> String {
-    if candidate.contains(char::is_whitespace) {
-        format!("'{}'", candidate.replace('\'', r"'\''"))
-    } else {
-        candidate.to_string()
-    }
-}
-
 /// Split a command line into arguments, honouring quotes and backslash
 /// escapes so that track names with spaces survive.
 fn split_args(line: &str) -> Vec<String> {
@@ -257,7 +264,14 @@ pub fn run() -> Result<(), Box<dyn std::error::Error>> {
     }
 
     let history_path = crate::config::runtime_dir().join("ctl_history");
-    let mut editor: Editor<CtlHelper, DefaultHistory> = Editor::default()?;
+    // Bash-style completion: extend to the longest common prefix and print the
+    // candidates when the word stays ambiguous, instead of silently cycling
+    // through them (which hides what is actually available).
+    let config = Config::builder()
+        .completion_type(CompletionType::List)
+        .completion_show_all_if_ambiguous(true)
+        .build();
+    let mut editor: Editor<CtlHelper, DefaultHistory> = Editor::with_default(config)?;
     let _ = editor.load_history(&history_path);
 
     if !crate::config::Config::get_socket_path().exists() {
@@ -337,11 +351,16 @@ mod tests {
     }
 
     #[test]
-    fn quotes_single_word_arguments_only_when_needed() {
-        assert_eq!(quote("AFX"), "AFX");
+    fn escapes_candidates_before_inserting_them() {
+        assert_eq!(escape("AFX"), "AFX");
+        assert_eq!(escape("Analogue Bubblebath/"), r"Analogue\ Bubblebath/");
+        assert_eq!(escape(r"a\\b"), r"a\\\\b");
+
+        // What the editor inserts must come back as a single argument.
+        let line = format!("play {}", escape("AFX/Analogue Bubblebath, Vol 3.1/"));
         assert_eq!(
-            quote("Analogue Bubblebath, Vol 3.1"),
-            "'Analogue Bubblebath, Vol 3.1'"
+            split_args(&line),
+            vec!["play", "AFX/Analogue Bubblebath, Vol 3.1/"]
         );
     }