//! This module implements basic `rustfmt` code formatting.

use anyhow::{anyhow, Result};
use std::io::Write;
use std::process::{Command, Stdio};

/// Format the raw input source string and return formatted output.
pub fn format<S>(source: S) -> Result<String>
where
    S: AsRef<str>,
{
    let mut rustfmt = Command::new("rustfmt")
        .args(&["--edition", "2018"])
        .stdin(Stdio::piped())
        .stdout(Stdio::piped())
        .spawn()?;

    {
        let stdin = rustfmt
            .stdin
            .as_mut()
            .ok_or_else(|| anyhow!("stdin was not created for `rustfmt` child process"))?;
        stdin.write_all(source.as_ref().as_bytes())?;
    }

    let output = rustfmt.wait_with_output()?;
    if !output.status.success() {
        return Err(anyhow!(
            "`rustfmt` exited with code {}:\n{}",
            output.status,
            String::from_utf8_lossy(&output.stderr),
        ));
    }

    let stdout = String::from_utf8(output.stdout)?;
    Ok(stdout)
}
