pipa-lang 1.0.0-alpha.1

A tiny template language
Documentation 
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// SPDX-FileCopyrightText: Copyright 2026 olav@occy.org
// SPDX-License-Identifier: MPL-2.0

use crate::lang::adapter::Adapter;
use crate::lang::args::eval_unary_arg;
use crate::lang::args::take_thunk_arg;
use crate::lang::args::thunk_as_pipe;
use crate::lang::arity::Arity;
use crate::lang::arity::assert_func_arity;
use crate::lang::error::Error;
use crate::lang::eval::eval_node_list;
use crate::lang::machine::Machine;
use crate::lang::node::Node;
use crate::value::Value;
use crate::value::list::List;
use crate::value::map::Map;

pub(crate) fn group(
    adapter: &impl Adapter,
    machine: &mut Machine<'_>,
    stdin: Option<&Value>,
    mut node: Node,
) -> Result<Value, Error> {
    assert_func_arity(adapter, machine, stdin, &node, &Arity::new(2))?;

    let thunk = take_thunk_arg(adapter, machine, &mut node)?;
    let thunk = thunk_as_pipe(adapter, machine, thunk)?;
    let value = eval_unary_arg(adapter, machine, stdin, node)?;
    let value = value.unwrap_or_default();
    let call = |v: &Value| eval_node_list(adapter, machine, Some(v), thunk.clone());

    let value = match value {
        v @ Value::Bytes(_) => group_impl([v].into_iter(), call),
        Value::List(v) => group_impl(v.data.into_iter(), call),
        Value::Map(v) => group_impl(v.into_iter().map(|(_, v)| v), call),
    };

    Ok(value.unwrap_or_default())
}

fn group_impl(
    values: impl Iterator<Item = Value>,
    mut key: impl FnMut(&Value) -> Result<Option<Value>, Error>,
) -> Result<Value, Error> {
    let mut map = Map::default();

    for value in values {
        let k = key(&value)?.unwrap_or_default().join();
        if let Some(Value::List(list)) = map.get_mut(&k) {
            list.push(value);
        } else {
            map.fold_key(k, List::from(value));
        }
    }

    Ok(map.into())
}