//! Argument handling and output plumbing shared by the subcommands.

use std::io::Write;

/// Where a subcommand writes: `o` for results, `e` for diagnostics.
pub struct Out<'a> {
    pub o: &'a mut dyn Write,
    pub e: &'a mut dyn Write,
}

/// The arguments after the subcommand name.
pub struct Args {
    cmd: &'static str,
    rest: std::collections::VecDeque<String>,
}

impl Args {
    pub fn new(cmd: &'static str, rest: Vec<String>) -> Self {
        Self {
            cmd,
            rest: rest.into(),
        }
    }

    #[allow(clippy::should_implement_trait)]
    pub fn next(&mut self) -> Option<String> {
        self.rest.pop_front()
    }

    /// Put an option and its value back, to be read next (for the
    /// `--name=value` form).
    pub fn push_front(&mut self, name: String, value: String) {
        self.rest.push_front(value);
        self.rest.push_front(name);
    }

    /// The value after an option such as `--max-bytes`.
    pub fn value(&mut self) -> Option<String> {
        self.rest.pop_front()
    }

    /// A numeric option value.
    pub fn number<T: std::str::FromStr>(&mut self) -> Option<T> {
        self.rest.pop_front().and_then(|s| s.parse().ok())
    }

    /// Report a usage problem; exit status 2.
    pub fn usage_error(&self, out: &mut Out, msg: &str, usage: &str) -> std::io::Result<i32> {
        writeln!(out.e, "h5rs {}: {msg}\n\n{usage}", self.cmd)?;
        Ok(2)
    }
}