You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: argparse.rs
    path of file: ./repos/sad/src
    
    the code of the file until where you have to start completion: use {
  super::{subprocess::SubprocCommand, types::Fail},
  aho_corasick::{AhoCorasick, AhoCorasickBuilder},
  clap::Parser,
  regex::{Regex, RegexBuilder},
  shlex::split,
  std::{
    collections::HashMap,
    env::{args_os, current_dir, var_os},
    ffi::OsString,
    io::{stderr, stdout, IsTerminal},
    path::PathBuf,
  },
  which::which,
};

#[derive(Debug)]
pub enum Mode {
  Initial,
  Preview(PathBuf),
  Patch(PathBuf),
}

impl Mode {
  pub const ARGV: &'static str = env!("SAD_ARGV_UUID");
  pub const PREVIEW: &'static str = env!("SAD_PREVIEW_UUID");
  pub const PATCH: &'static str = env!("SAD_PATCH_UUID");
}

#[derive(Debug, Parser)]
#[clap(about, version)]
pub struct Arguments {
  /// Search pattern
  #[clap()]
  pub pattern: String,

  ///
    
pub fn parse_opts(mode: Mode, args: Arguments) -> Result<Options, Fail> {
  let mut flagset = p_auto_flags(args.exact, &args.pattern);
  flagset.extend(
    args
      .flags
      .unwrap_or_default()
      .split_terminator("")
      .skip(1)
      .map(String::from),
  );

  let engine = {
    let replace = args.replace.unwrap_or_default();
    if args.exact {
      Engine::AhoCorasick(p_aho_corasick(&args.pattern, flagset)?, replace)
    } else {
      Engine::Regex(p_regex(&args.pattern, flagset)?, replace)
    }
  };

  let action = match (args.commit, mode, p_fzf(&args.fzf)) {
    (true, _, _) | (_, Mode::Patch(_), _) => Action::Commit,
    (_, Mode::Initial, Some((bin, args))) => Action::FzfPreview(bin, args),
    _ => Action::Preview,
  };

  let printer = p_pager(&args.pager).map_or(Printer::Stdout, Printer::Pager);

  Ok(Options {
    cwd: current_dir().ok(),
    action,
    engine,
    printer,
    unified: args.unified.unwrap_or(3),
  })
}