use super::Repl;

pub type BoxedCommandFunction = Box<(fn(&mut Repl, &[&str]) -> Option<String>)>;

/// A CommandTree is either a `Terminal` or a `NonTerminal`. When command parsing reaches the first
/// Terminal, it will execute the `BoxedCommandFunction` found there with any remaining arguments
#[derive(Clone)]
pub enum CommandTree {
  Terminal {
    name: String,
    children: Vec<CommandTree>,
    help_msg: Option<String>,
    function: BoxedCommandFunction,
  },
  NonTerminal {
    name: String,
    children: Vec<CommandTree>,
    help_msg: Option<String>,
  },
  Top(Vec<CommandTree>),
}

impl CommandTree {
  pub fn nonterm_no_further_tab_completions(s: &str, help: Option<&str>) -> CommandTree {
    CommandTree::NonTerminal {name: s.to_string(), help_msg: help.map(|x| x.to_string()), children: vec![] }
  }

  pub fn terminal(s: &str, help: Option<&str>, children: Vec<CommandTree>, function: BoxedCommandFunction) -> CommandTree {
    CommandTree::Terminal {name: s.to_string(), help_msg: help.map(|x| x.to_string()), function, children }
  }

  pub fn nonterm(s: &str, help: Option<&str>, children: Vec<CommandTree>) -> CommandTree {
    CommandTree::NonTerminal {
      name: s.to_string(),
      help_msg: help.map(|x| x.to_string()),
      children,
    }
  }

  /*
  pub fn nonterm_with_function(s: &str, help: Option<&str>, children: Vec<CommandTree>, func: BoxedCommandFunction) -> CommandTree {
    CommandTree::NonTerminal {
      name: s.to_string(),
      help_msg: help.map(|x| x.to_string()),
      children,
      function: Some(func),
    }
  }
  */

  pub fn get_cmd(&self) -> &str {
    match self {
      CommandTree::Terminal { name, .. } => name.as_str(),
      CommandTree::NonTerminal {name, ..} => name.as_str(),
      CommandTree::Top(_) => "",
    }
  }
  pub fn get_help(&self) -> &str {
    match self {
      CommandTree::Terminal { help_msg, ..} => help_msg.as_ref().map(|s| s.as_str()).unwrap_or(""),
      CommandTree::NonTerminal { help_msg, .. } => help_msg.as_ref().map(|s| s.as_str()).unwrap_or(""),
      CommandTree::Top(_) => ""
    }
  }
  pub fn get_children(&self) -> Vec<&str> {
    use CommandTree::*;
    match self {
      Terminal { children, .. } |
      NonTerminal { children, .. } |
      Top(children) => children.iter().map(|x| x.get_cmd()).collect()
    }
  }
}