//! Slash-command parser that maps TUI `/foo` input lines into `Command`
//! variants for the action dispatch system.

/// A parsed slash command from the TUI input buffer.
#[derive(Debug, Clone, PartialEq)]
pub enum Command {
    Help,
    Quit,
    McpOpen,
    Clear,
    ClearConfirm,
    Login { provider: String },
    Edit(String),
    McpAdd { name: String, command: String },
    ModelList,
    Compact,
    TodoOpen,
    UsageOpen,
    Unknown(String),
}

/// Parse a slash-prefixed input line into a `Command` value.
///
/// Flow: trim -> check for leading `/` -> split on space (max 3 parts) ->
/// match the first token against known commands -> extract arguments from
/// the remaining parts.
///
/// Why: early return `Unknown` for non-slash lines so the caller can treat
/// them as regular chat input.
pub fn parse_command(text: &str) -> Command {
    let text = text.trim();
    if !text.starts_with('/') {
        return Command::Unknown(text.to_string());
    }
    let parts: Vec<&str> = text.splitn(3, ' ').collect();
    let cmd = parts[0];
    let arg1 = parts.get(1).copied().unwrap_or("");
    let arg2 = parts.get(2).copied().unwrap_or("");
    match cmd {
        "/help" => Command::Help,
        "/quit" => Command::Quit,
        "/clear" if arg1.is_empty() => Command::ClearConfirm,
        "/clear" => Command::Clear,
        "/login" if arg1.is_empty() => Command::Login {
            provider: String::new(),
        },
        "/login" if !arg1.is_empty() => Command::Login {
            provider: arg1.to_string(),
        },
        "/edit" if !arg1.is_empty() => Command::Edit(arg1.to_string()),
        "/edit" => Command::Edit(".".to_string()),
        "/mcp" if arg1.is_empty() => Command::McpOpen,
        "/mcp" if arg1 == "add" && !arg2.is_empty() => {
            let rest = arg2.trim();
            if let Some(space) = rest.find(' ') {
                let name = rest[..space].to_string();
                let command = rest[space + 1..].trim().to_string();
                Command::McpAdd { name, command }
            } else {
                Command::McpAdd {
                    name: rest.to_string(),
                    command: String::new(),
                }
            }
        }
        "/model" => Command::ModelList,
        "/compact" => Command::Compact,
        "/todo" => Command::TodoOpen,
        "/usage" => Command::UsageOpen,
        _ => Command::Unknown(cmd.to_string()),
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn parses_todo_open() {
        assert_eq!(parse_command("/todo"), Command::TodoOpen);
    }

    #[test]
    fn parses_usage_open() {
        assert_eq!(parse_command("/usage"), Command::UsageOpen);
    }
}