calepin 0.0.7

A Rust CLI for preprocessing Typst documents with executable code chunks
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// Shell engine session via a persistent /bin/sh subprocess.
//
// A single sh process runs for the lifetime of the document render. Variables,
// cd, and other shell state persist across chunks — same semantics as R/Python.
//
// No figure support: shell chunks produce only text output and errors.
//
// ## Functions
//
// - ShSession::init()            — Spawn /bin/sh with the bootstrap read-eval loop.
// - ShSession::capture()         — Execute a shell code chunk and capture output.
// - ShSession::evaluate_inline() — Evaluate a single shell expression and return trimmed output.

use anyhow::Result;

use super::make_sentinel;
use super::subprocess::{spawn_script, SubprocessSession};

/// Bootstrap shell script sent once at startup.
/// Reads sentinel-delimited code blocks from stdin, executes them with eval,
/// and writes sentinel-tagged results to stdout.
const SH_BOOTSTRAP: &str = r#"
_calepin_tmpfile=$(mktemp)
trap 'rm -f "$_calepin_tmpfile"' EXIT
while IFS= read -r _line; do
    case "$_line" in
        *_BEGIN)
            _sentinel="${_line%_BEGIN}"
            _code=""
            while IFS= read -r _line; do
                case "$_line" in
                    "${_sentinel}_END") break ;;
                    *) _code="${_code}${_line}
" ;;
                esac
            done
            _exit=0
            eval "$_code" > "$_calepin_tmpfile" 2>&1 || _exit=$?
            _output=$(cat "$_calepin_tmpfile")
            if [ "$_exit" -ne 0 ]; then
                printf '%s' "${_sentinel}_ERROR:${_output}"
                printf '\n'
            elif [ -n "$_output" ]; then
                printf '%s' "${_sentinel}_OUTPUT:${_output}"
                printf '\n'
            fi
            printf '%s' "${_sentinel}_DONE"
            printf '\n'
            ;;
    esac
done
"#;

pub struct ShSession {
    session: SubprocessSession,
    _bootstrap_file: tempfile::NamedTempFile,
}

impl ShSession {
    pub fn init_with_program(
        program: &str,
        cwd: Option<&std::path::Path>,
        timeout: Option<std::time::Duration>,
    ) -> Result<Self> {
        let (session, bootstrap_file) =
            spawn_script(program, &[], SH_BOOTSTRAP, "sh", cwd, timeout)?;
        Ok(ShSession {
            session,
            _bootstrap_file: bootstrap_file,
        })
    }

    /// Execute a shell code chunk and return sentinel-tagged output.
    pub fn capture(&mut self, code: &str) -> Result<String> {
        let sentinel = make_sentinel();
        self.session.execute(&sentinel, code)
    }
}