Implement basic functions to generate recipes for R and Python

[wolfv]

cc @nichmor @tdejager and @marcelotrevisani :)

This is just using rip to extract source dist & wheel informations for a given package name. Doesn't write a recipe at all yet, but this could be a good starting point. One more thing we'd have to do is use the conda mapping that pixi & grayskull use to get the conda-forge package name based on the PyPI package name. Do we have a good API for that, @baszalmstra?

[marcelotrevisani]

Hey, I have been doing something similar. But it is only on my computer. Due to some personal and work obligations I'm a bit slow on that 😅

[baszalmstra]

The entire "API" can be found here: https://github.com/prefix-dev/pixi/blob/main/src/lock_file/pypi_name_mapping.rs

It's pretty straightforward.

[wolfv]

@marcelotrevisani I also just implemented a good chunk of PyPI recipe generation :) Would love your feedback.

E.g. I don't know how to decide wether a package can be noarch...

[wolfv]

I started some implementation for evaluating & transforming the marker tree, but I am postponing that for now:

fn rhs_to_string(marker_value: &MarkerValue) -> &str {
    match marker_value {
        MarkerValue::MarkerEnvVersion(_) => "",
        MarkerValue::MarkerEnvString(_) => "",
        MarkerValue::Extra => "",
        MarkerValue::QuotedString(s) => s,
    }
}

fn translate_marker(marker: &MarkerTree, out: &mut String) {
    match marker {
        MarkerTree::Expression(expr) => {
            if expr.l_value == MarkerValue::MarkerEnvVersion(MarkerValueVersion::PythonVersion) {
                out.push_str(&format!("cmp(python, \"{}{}\")", expr.operator, rhs_to_string(&expr.r_value)));
            } else {
                out.push_str(&expr.l_value.to_string());
            }
        }
        MarkerTree::And(exprs) => {
            out.push_str("(");
            for (i, expr) in exprs.iter().enumerate() {
                translate_marker(expr, out);
                if i != exprs.len() - 1 {
                    out.push_str(", ");
                }
            }
            out.push_str(")");
        }
        MarkerTree::Or(exprs) => {
            out.push_str("(");
            for (i, expr) in exprs.iter().enumerate() {
                translate_marker(expr, out);
                if i != exprs.len() - 1 {
                    out.push_str(" || ");
                }
            }
            out.push_str(")");
        }
    }
}