figcraft/apps/figcraft-cli/src/args.rs

//! Minimal std-only argument parsing: positionals, `--key value` / `--key=value` / `-o value`
//! options, and boolean `--flag`s. Unknown options are usage errors.

use std::collections::BTreeMap;

use crate::{CliError, CliResult};

#[derive(Debug, Default)]
pub struct Args {
    pub positional: Vec<String>,
    values: BTreeMap<String, String>,
    flags: Vec<String>,
}

impl Args {
    pub fn parse(argv: &[String], valued: &[&str], flags: &[&str]) -> CliResult<Self> {
        let mut a = Args::default();
        let mut it = argv.iter();
        while let Some(arg) = it.next() {
            let name = if let Some(n) = arg.strip_prefix("--") {
                n
            } else if let Some(n) = arg.strip_prefix('-').filter(|n| n.len() == 1 && !n.starts_with(|c: char| c.is_ascii_digit())) {
                n
            } else {
                a.positional.push(arg.clone());
                continue;
            };
            let (name, inline) = match name.split_once('=') {
                Some((n, v)) => (n, Some(v.to_string())),
                None => (name, None),
            };
            if valued.contains(&name) {
                let v = match inline {
                    Some(v) => v,
                    None => it.next().cloned().ok_or_else(|| CliError::Usage(format!("`{arg}` needs a value")))?,
                };
                a.values.insert(name.to_string(), v);
            } else if flags.contains(&name) && inline.is_none() {
                a.flags.push(name.to_string());
            } else {
                return Err(CliError::Usage(format!("unknown option `{arg}`")));
            }
        }
        Ok(a)
    }

    pub fn value(&self, k: &str) -> Option<String> {
        self.values.get(k).cloned()
    }

    pub fn flag(&self, k: &str) -> bool {
        self.flags.iter().any(|f| f == k)
    }

    pub fn one_positional(&self, usage: &str) -> CliResult<String> {
        match self.positional.as_slice() {
            [one] => Ok(one.clone()),
            _ => Err(CliError::Usage(format!("expected: {usage}"))),
        }
    }

    pub fn scale(&self) -> CliResult<f64> {
        match self.values.get("scale") {
            None => Ok(1.0),
            Some(s) => s
                .trim_end_matches('x')
                .parse::<f64>()
                .ok()
                .filter(|v| v.is_finite() && *v > 0.0 && *v <= 64.0)
                .ok_or_else(|| CliError::Usage(format!("--scale must be a number in (0, 64], got `{s}`"))),
        }
    }

    pub fn usize(&self, k: &str, default: usize) -> CliResult<usize> {
        match self.values.get(k) {
            None => Ok(default),
            Some(s) => s.replace('_', "").parse::<usize>().map_err(|_| CliError::Usage(format!("--{k} must be a whole number, got `{s}`"))),
        }
    }
}

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

    fn v(s: &[&str]) -> Vec<String> {
        s.iter().map(|x| x.to_string()).collect()
    }

    #[test]
    fn parses_options_and_flags() {
        let a = Args::parse(&v(&["in.figcraft", "-o", "out", "--scale=2", "--json"]), &["o", "scale"], &["json"]).unwrap();
        assert_eq!(a.positional, ["in.figcraft"]);
        assert_eq!(a.value("o").as_deref(), Some("out"));
        assert_eq!(a.scale().unwrap(), 2.0);
        assert!(a.flag("json"));
    }

    #[test]
    fn rejects_bad_input() {
        assert!(matches!(Args::parse(&v(&["--nope"]), &[], &[]), Err(CliError::Usage(_))));
        assert!(matches!(Args::parse(&v(&["-o"]), &["o"], &[]), Err(CliError::Usage(_))));
        assert!(matches!(Args::parse(&v(&["--json=1"]), &[], &["json"]), Err(CliError::Usage(_))));
        let a = Args::parse(&v(&["--scale", "abc"]), &["scale"], &[]).unwrap();
        assert!(a.scale().is_err());
        let a = Args::parse(&v(&["--scale", "-3"]), &["scale"], &[]).unwrap();
        assert!(a.scale().is_err());
        // Negative numbers are positionals, not options.
        let a = Args::parse(&v(&["-5"]), &[], &[]).unwrap();
        assert_eq!(a.positional, ["-5"]);
    }
}