Add diy command completor example

examples/diy_completer.rs

@@ -0,0 +1,123 @@
+use rustyline::completion::{extract_word, Completer, FilenameCompleter, Pair};
+use rustyline::error::ReadlineError;
+use rustyline::{CompletionType, Config, Context, EditMode, Editor};
+use rustyline_derive::{Helper, Highlighter, Hinter, Validator};
+use std::collections::HashSet;
+
+const DEFAULT_BREAK_CHARS: [u8; 3] = [b' ', b'\t', b'\n'];
+
+#[derive(Hash, Debug, PartialEq, Eq)]
+struct Command {
+    cmd: String,
+    pre_cmd: String,
+}
+
+impl Command {
+    fn new(cmd: &str, pre_cmd: &str) -> Self {
+        Self {
+            cmd: cmd.into(),
+            pre_cmd: pre_cmd.into(),
+        }
+    }
+}
+struct CommandCompleter {
+    cmds: HashSet<Command>,
+}
+
+impl CommandCompleter {
+    pub fn find_matches(&self, line: &str, pos: usize) -> rustyline::Result<(usize, Vec<Pair>)> {
+        let (start, word) = extract_word(line, pos, None, &DEFAULT_BREAK_CHARS);
+        let pre_cmd = line[..start].trim();
+
+        let matches = self
+            .cmds
+            .iter()
+            .filter_map(|hint| {
+                if hint.cmd.starts_with(word) && pre_cmd == &hint.pre_cmd {
+                    let mut replacement = hint.cmd.clone();
+                    replacement += " ";
+                    Some(Pair {
+                        display: hint.cmd.to_string(),
+                        replacement: replacement.to_string(),
+                    })
+                } else {
+                    None
+                }
+            })
+            .collect();
+        Ok((start, matches))
+    }
+}
+
+#[derive(Helper, Hinter, Validator, Highlighter)]
+struct MyHelper {
+    file_completer: FilenameCompleter,
+    cmd_completer: CommandCompleter,
+}
+
+impl Completer for MyHelper {
+    type Candidate = Pair;
+
+    fn complete(
+        &self,
+        line: &str,
+        pos: usize,
+        ctx: &Context<'_>,
+    ) -> Result<(usize, Vec<Pair>), ReadlineError> {
+        match self.cmd_completer.find_matches(line, pos) {
+            Ok((start, matches)) => {
+                if matches.is_empty() {
+                    self.file_completer.complete(line, pos, ctx)
+                } else {
+                    Ok((start, matches))
+                }
+            }
+            Err(e) => Err(e),
+        }
+    }
+}
+
+fn cmd_sets() -> HashSet<Command> {
+    let mut set = HashSet::new();
+    set.insert(Command::new("helper", "about"));
+    set.insert(Command::new("hinter", "about"));
+    set.insert(Command::new("highlighter", "about"));
+    set.insert(Command::new("validator", "about"));
+    set.insert(Command::new("completer", "about"));
+
+    set.insert(Command::new("release", "dev"));
+    set.insert(Command::new("deploy", "dev"));
+    set.insert(Command::new("compile", "dev"));
+    set.insert(Command::new("test", "dev"));
+
+    set.insert(Command::new("history", ""));
+    set.insert(Command::new("about", ""));
+    set.insert(Command::new("help", ""));
+    set.insert(Command::new("dev", ""));
+    set
+}
+
+// To debug rustyline:
+// RUST_LOG=rustyline=debug cargo run --example example 2> debug.log
+fn main() -> rustyline::Result<()> {
+    env_logger::init();
+    let config = Config::builder()
+        .history_ignore_space(true)
+        .completion_type(CompletionType::List)
+        .edit_mode(EditMode::Emacs)
+        .build();
+    let h = MyHelper {
+        file_completer: FilenameCompleter::new(),
+        cmd_completer: CommandCompleter { cmds: cmd_sets() },
+    };
+    let mut rl: Editor<MyHelper> = Editor::with_config(config)?;
+    rl.set_helper(Some(h));
+
+    let mut count = 1;
+    loop {
+        let p = format!("{}> ", count);
+        let readline = rl.readline(&p)?;
+        println!("Line: {}", readline);
+        count += 1;
+    }
+}