use thiserror::Error;
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum CommandId {
Login,
Logout,
Model,
TitleModel,
Resume,
Config,
Skills,
Exit,
}
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct CommandSpec {
pub id: CommandId,
pub name: &'static str,
pub usage: &'static str,
pub description: &'static str,
}
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct CommandInvocation {
pub id: CommandId,
pub name: String,
pub raw_args: String,
pub args: String,
}
#[derive(Clone, Debug, Error, PartialEq, Eq)]
pub enum CommandParseError {
#[error("unknown command '/{0}'")]
Unknown(String),
}
pub static COMMANDS: &[CommandSpec] = &[
CommandSpec {
id: CommandId::Login,
name: "login",
usage: "/login [provider]",
description: "log in to a provider",
},
CommandSpec {
id: CommandId::Logout,
name: "logout",
usage: "/logout [provider]",
description: "delete provider credentials",
},
CommandSpec {
id: CommandId::Model,
name: "model",
usage: "/model [model]",
description: "show or switch model",
},
CommandSpec {
id: CommandId::TitleModel,
name: "title-model",
usage: "/title-model [model]",
description: "show or switch session title model",
},
CommandSpec {
id: CommandId::Resume,
name: "resume",
usage: "/resume [id]",
description: "resume a saved session",
},
CommandSpec {
id: CommandId::Config,
name: "config",
usage: "/config",
description: "open configuration picker",
},
CommandSpec {
id: CommandId::Skills,
name: "skills",
usage: "/skills",
description: "show loaded skills and descriptions",
},
CommandSpec {
id: CommandId::Exit,
name: "exit",
usage: "/exit",
description: "quit rho",
},
];
pub fn command_prefix(input: &str) -> Option<&str> {
let token_end = input
.char_indices()
.find_map(|(index, ch)| ch.is_whitespace().then_some(index))
.unwrap_or(input.len());
let prefix = input[..token_end].strip_prefix('/')?;
if prefix.starts_with('/') {
None
} else {
Some(prefix)
}
}
pub fn matching_commands(prefix: &str) -> Vec<&'static CommandSpec> {
let prefix = prefix
.strip_prefix('/')
.unwrap_or(prefix)
.to_ascii_lowercase();
COMMANDS
.iter()
.filter(|command| command.name.starts_with(&prefix))
.collect()
}
pub fn parse_command(input: &str) -> Result<Option<CommandInvocation>, CommandParseError> {
let input = input.trim_end();
let Some(rest) = input.strip_prefix('/') else {
return Ok(None);
};
if rest.starts_with('/') {
return Ok(None);
}
let name_end = rest
.char_indices()
.find_map(|(index, ch)| ch.is_whitespace().then_some(index))
.unwrap_or(rest.len());
let name = &rest[..name_end];
let raw_args = rest[name_end..].to_string();
let args = raw_args.trim().to_string();
let spec = COMMANDS
.iter()
.find(|command| command.name.eq_ignore_ascii_case(name))
.ok_or_else(|| CommandParseError::Unknown(name.to_string()))?;
Ok(Some(CommandInvocation {
id: spec.id,
name: spec.name.to_string(),
raw_args,
args,
}))
}
pub fn complete_command(input: &str, cursor: usize, spec: &CommandSpec) -> (String, usize) {
let token_end = first_token_end_byte(input);
let token_len = input[..token_end].chars().count();
let args = input[token_end..].trim_start();
let completed_prefix = format!("/{} ", spec.name);
let completed_prefix_len = completed_prefix.chars().count();
let completed = if args.is_empty() {
completed_prefix
} else {
format!("{completed_prefix}{args}")
};
let new_cursor = if cursor <= token_len {
completed_prefix_len
} else {
completed
.chars()
.count()
.min(completed_prefix_len.saturating_add(cursor.saturating_sub(token_len)))
};
(completed, new_cursor)
}
fn first_token_end_byte(input: &str) -> usize {
input
.char_indices()
.find_map(|(index, ch)| ch.is_whitespace().then_some(index))
.unwrap_or(input.len())
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn matches_all_commands_for_empty_slash_prefix() {
let matches = matching_commands(command_prefix("/").unwrap());
assert_eq!(matches.len(), COMMANDS.len());
assert!(matches.iter().any(|command| command.name == "model"));
}
#[test]
fn additional_leading_slashes_are_literal_text() {
assert_eq!(command_prefix("//"), None);
assert_eq!(parse_command("//literal").unwrap(), None);
}
#[test]
fn slash_must_be_first_character_to_parse_as_command() {
assert_eq!(command_prefix(" /model"), None);
assert_eq!(parse_command(" /model").unwrap(), None);
}
#[test]
fn matches_commands_by_case_insensitive_prefix() {
let matches = matching_commands(command_prefix("/M").unwrap());
assert_eq!(matches.len(), 1);
assert_eq!(matches[0].name, "model");
}
#[test]
fn matches_full_command_name() {
let matches = matching_commands(command_prefix("/model").unwrap());
assert_eq!(matches.len(), 1);
assert_eq!(matches[0].id, CommandId::Model);
}
#[test]
fn matching_unknown_command_returns_no_matches() {
let matches = matching_commands(command_prefix("/nope").unwrap());
assert!(matches.is_empty());
}
#[test]
fn parses_skills_command() {
let invocation = parse_command("/skills").unwrap().unwrap();
assert_eq!(invocation.id, CommandId::Skills);
assert_eq!(invocation.name, "skills");
}
#[test]
fn parses_model_command_with_arguments() {
let invocation = parse_command("/model gpt-5.5").unwrap().unwrap();
assert_eq!(invocation.id, CommandId::Model);
assert_eq!(invocation.name, "model");
assert_eq!(invocation.raw_args, " gpt-5.5");
assert_eq!(invocation.args, "gpt-5.5");
}
#[test]
fn parses_non_command_as_none() {
assert_eq!(parse_command("hello /model").unwrap(), None);
}
#[test]
fn rejects_unknown_command() {
let err = parse_command("/nope").unwrap_err();
assert_eq!(err, CommandParseError::Unknown("nope".into()));
}
#[test]
fn parses_logout_command_with_provider_argument() {
let invocation = parse_command("/logout openai-codex").unwrap().unwrap();
assert_eq!(invocation.id, CommandId::Logout);
assert_eq!(invocation.args, "openai-codex");
}
#[test]
fn login_usage_accepts_provider_argument() {
let login = COMMANDS
.iter()
.find(|command| command.name == "login")
.unwrap();
assert_eq!(login.usage, "/login [provider]");
}
#[test]
fn completes_command_and_preserves_args() {
let spec = COMMANDS
.iter()
.find(|command| command.name == "model")
.unwrap();
let (input, cursor) = complete_command("/m gpt-5.5", 2, spec);
assert_eq!(input, "/model gpt-5.5");
assert_eq!(cursor, 7);
}
}