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;

pub(crate) fn reduce(
    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 mut call = |v: &Value| eval_node_list(adapter, machine, Some(v), thunk.clone());

    let value = match value {
        v @ Value::Bytes(_) => call(&List::from(vec![Value::default(), v]).into())?,
        Value::List(v) => Some(v.into_iter().fold(Value::default(), |a, v| {
            call(&List::from(vec![a, v]).into())
                .unwrap_or_default()
                .unwrap_or_default()
        })),
        Value::Map(v) => Some(
            v.into_iter()
                .map(|(_, v)| v)
                .fold(Value::default(), |a, v| {
                    call(&List::from(vec![a, v]).into())
                        .unwrap_or_default()
                        .unwrap_or_default()
                }),
        ),
    };

    Ok(value.unwrap_or_default())
}