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1d3f990 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 | //! M4 Engine — GNU M4 wrapper with sandboxing and feedback
use crate::sandbox::{SandboxConfig, SandboxLimits};
use crate::feedback::FeedbackBuffer;
use anyhow::{Result, anyhow, Context};
use std::process::{Command, Stdio};
use std::io::Write;
use tracing::{debug, trace};
/// M4 Engine with sandboxing
pub struct M4Engine {
config: SandboxConfig,
feedback: FeedbackBuffer,
expansion_count: usize,
}
impl M4Engine {
pub fn new(config: SandboxConfig) -> Result<Self> {
// Verify M4 exists
Command::new("m4")
.arg("--version")
.output()
.context("GNU M4 not found in PATH")?;
Ok(Self {
config,
feedback: FeedbackBuffer::new(),
expansion_count: 0,
})
}
pub fn default_sandbox() -> Result<Self> {
Self::new(SandboxConfig::default())
}
pub fn permissive_sandbox() -> Result<Self> {
Self::new(SandboxConfig::permissive())
}
pub fn strict_sandbox() -> Result<Self> {
Self::new(SandboxConfig::strict())
}
/// Expand M4 input with current feedback state
pub fn expand(&mut self, input: &str) -> Result<String> {
self.expansion_count += 1;
debug!(count = self.expansion_count, input_len = input.len(), "M4 expansion");
// Check recursion depth limit
if self.expansion_count > self.config.limits.max_expansion_depth {
return Err(anyhow!(
"M4 recursion depth exceeded: {} > {}",
self.expansion_count,
self.config.limits.max_expansion_depth
));
}
// Construct full M4 input with feedback
let full_input = self.construct_input(input)?;
// Execute M4
let output = self.execute_m4(&full_input)?;
// Validate output size
if output.len() > self.config.limits.max_output_size {
return Err(anyhow!(
"M4 output too large: {} > {}",
output.len(),
self.config.limits.max_output_size
));
}
trace!("M4 expansion succeeded");
Ok(output)
}
/// Construct M4 input with sandbox prelude and feedback
fn construct_input(&self, user_input: &str) -> Result<String> {
let mut input = String::new();
// 1. Sandbox prelude (deny dangerous builtins)
for builtin in &self.config.limits.denied_builtins {
input.push_str(&format!("define(`{}', `')\n", builtin));
}
// 2. Set recursion limit
input.push_str(&format!(
"define(`__M4_RECURSION_LIMIT', `{}')\n",
self.config.limits.max_call_stack
));
// 3. Feedback definitions from previous cells
input.push_str(&self.feedback.get_definitions_code());
// 4. User input
input.push_str(user_input);
input.push('\n');
Ok(input)
}
/// Execute M4 via subprocess
fn execute_m4(&self, input: &str) -> Result<String> {
let mut child = Command::new("m4")
.arg("-P") // Prefix builtins
.arg("-E") // Fatal warnings
.stdin(Stdio::piped())
.stdout(Stdio::piped())
.stderr(Stdio::piped())
.spawn()
.context("Failed to spawn M4 process")?;
// Write input
{
let stdin = child.stdin.as_mut().context("Failed to open M4 stdin")?;
stdin.write_all(input.as_bytes()).context("Failed to write to M4")?;
}
// Wait for completion
let output = child.wait_with_output().context("Failed to wait for M4")?;
if !output.status.success() {
let stderr = String::from_utf8_lossy(&output.stderr);
return Err(anyhow!("M4 expansion failed: {}", stderr));
}
Ok(String::from_utf8_lossy(&output.stdout).to_string())
}
/// Record output as feedback for next cell
pub fn push_feedback(&mut self, output: String) {
self.feedback.push_output(output);
}
/// Define a macro for next cell
pub fn define(&mut self, name: String, value: String) {
let def = format!("{}={}", name, value);
self.feedback.push_definition(def);
}
/// Clear feedback buffer (reset for new execution ring)
pub fn clear_feedback(&mut self) {
self.feedback.clear();
}
pub fn expansion_count(&self) -> usize {
self.expansion_count
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_engine_creation() {
let result = M4Engine::default_sandbox();
// May fail if M4 not installed in test environment
let _ = result;
}
#[test]
fn test_construct_input() {
let engine = M4Engine {
config: SandboxConfig::default(),
feedback: FeedbackBuffer::new(),
expansion_count: 0,
};
let input = engine.construct_input("test input").unwrap();
assert!(input.contains("test input"));
}
#[test]
fn test_feedback_integration() {
let mut engine = M4Engine {
config: SandboxConfig::default(),
feedback: FeedbackBuffer::new(),
expansion_count: 0,
};
engine.define("VAR".into(), "42".into());
engine.push_feedback("output: 42".into());
assert_eq!(engine.expansion_count(), 0);
}
#[test]
fn test_recursion_limit() {
let mut engine = M4Engine {
config: SandboxConfig::strict(),
feedback: FeedbackBuffer::new(),
expansion_count: 0,
};
engine.expansion_count = 50;
let result = engine.expand("test");
// Will fail due to recursion limit
assert!(result.is_err());
}
}
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