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::arg_into_string;
use crate::lang::args::eval_unary_arg;
use crate::lang::arity::Arity;
use crate::lang::arity::assert_func_arity;
use crate::lang::error::Error;
use crate::lang::machine::Machine;
use crate::lang::node::Node;
use crate::value::Value;

const PARAGRAPH_START: &str = "<p>";
const PARAGRAPH_END: &str = "</p>";
const PARAGRAPH_BREAK: &str = "<br>";

pub(crate) fn format_paragraphs(
    adapter: &impl Adapter,
    machine: &mut Machine<'_>,
    stdin: Option<&Value>,
    node: Node,
) -> Result<Value, Error> {
    assert_func_arity(adapter, machine, stdin, &node, &Arity::new(1))?;

    let value = eval_unary_arg(adapter, machine, stdin, node)?;
    let value = arg_into_string(value).unwrap_or_default();

    let mut lines = value.trim().lines().peekable();
    let mut paras = new_paragraph_string(&value);
    paras.push_str(PARAGRAPH_START);

    while let Some(line) = lines.next() {
        if line.is_empty() && lines.peek().is_some() {
            paras.push_str(PARAGRAPH_END);
            paras.push_str(PARAGRAPH_START);
        } else if lines.peek().is_some_and(|l| !l.is_empty()) {
            paras.push_str(line);
            paras.push_str(PARAGRAPH_BREAK);
        } else {
            paras.push_str(line);
        }
    }

    paras.push_str(PARAGRAPH_END);
    Ok(paras.into())
}

fn new_paragraph_string(value: &str) -> String {
    String::with_capacity(value.len() + PARAGRAPH_START.len() + PARAGRAPH_END.len())
}