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//! Token-efficient renderer for AI/LLM consumption.
//!
//! This renderer produces compact output optimized for LLM processing, similar to the MCP
//! server output format. It uses comment-style formatting (`Name // description`) to keep
//! tokens to a minimum while maintaining readability and semantic information.
use std::fmt::{Result, Write};
use crate::styled_string::{
Document, DocumentNode, HeadingLevel, ListItem, ShowWhen, Span, TruncationLevel,
};
/// AI-friendly renderer state
struct AiRenderer<'w, W: Write> {
output: &'w mut W,
indent: String,
}
/// Render a document in AI-friendly format
pub fn render(document: &Document, output: &mut impl Write) -> Result {
let mut renderer = AiRenderer::new(output);
renderer.render_block_sequence(&document.nodes)
}
impl<'w, W: Write> AiRenderer<'w, W> {
fn new(output: &'w mut W) -> Self {
Self {
output,
indent: String::new(),
}
}
fn write_indent(&mut self) -> Result {
write!(self.output, "{}", self.indent)
}
/// Render a sequence of block nodes with blank lines between top-level blocks
fn render_block_sequence(&mut self, nodes: &[DocumentNode]) -> Result {
for (idx, node) in nodes.iter().enumerate() {
if idx > 0 {
writeln!(self.output)?; // Blank line between top-level blocks
}
self.render_node(node)?;
}
Ok(())
}
fn render_nodes(&mut self, nodes: &[DocumentNode]) -> Result {
for node in nodes {
self.render_node(node)?;
}
Ok(())
}
fn render_node(&mut self, node: &DocumentNode) -> Result {
match node {
DocumentNode::Paragraph { spans } => {
self.write_indent()?;
self.render_spans(spans)?;
writeln!(self.output)?;
Ok(())
}
DocumentNode::Heading { level, spans } => {
self.write_indent()?;
self.render_spans(spans)?;
writeln!(self.output)?;
// Add underlines for headings (similar to plain renderer but compact)
self.write_indent()?;
match level {
HeadingLevel::Title => {
for _ in 0..80 {
write!(self.output, "=")?;
}
writeln!(self.output)?;
}
HeadingLevel::Section => {
for _ in 0..80 {
write!(self.output, "-")?;
}
writeln!(self.output)?;
}
}
Ok(())
}
DocumentNode::Section { title, nodes } => {
if let Some(title_spans) = title {
self.write_indent()?;
self.render_spans(title_spans)?;
writeln!(self.output)?;
}
// Render section items compactly
for node in nodes {
self.render_node(node)?;
}
Ok(())
}
DocumentNode::List { items } => {
// Render list items with blank lines between them
for (idx, item) in items.iter().enumerate() {
if idx > 0 {
writeln!(self.output)?; // Blank line between items
}
self.render_list_item(item)?;
}
Ok(())
}
DocumentNode::CodeBlock { code, .. } => {
self.write_indent()?;
writeln!(self.output, "```")?;
for line in code.lines() {
self.write_indent()?;
writeln!(self.output, "{line}")?;
}
if !code.ends_with('\n') && !code.is_empty() {
writeln!(self.output)?;
}
self.write_indent()?;
writeln!(self.output, "```")?;
Ok(())
}
DocumentNode::GeneratedCode { spans } => {
self.write_indent()?;
self.render_spans(spans)?;
writeln!(self.output)?;
Ok(())
}
DocumentNode::HorizontalRule => {
self.write_indent()?;
for _ in 0..80 {
write!(self.output, "─")?;
}
writeln!(self.output)?;
Ok(())
}
DocumentNode::BlockQuote { nodes } => {
for node in nodes {
self.write_indent()?;
write!(self.output, "> ")?;
let saved_indent = self.indent.clone();
self.indent.push_str(" ");
self.render_node(node)?;
self.indent = saved_indent;
}
Ok(())
}
DocumentNode::Table { header, rows } => {
let row_count = rows.len();
let col_count = header
.as_ref()
.map_or_else(|| rows.first().map_or(0, |r| r.len()), |h| h.len());
self.write_indent()?;
writeln!(
self.output,
"[Table: {} columns × {} rows]",
col_count, row_count
)?;
Ok(())
}
DocumentNode::TruncatedBlock { nodes, level } => {
match level {
TruncationLevel::SingleLine => {
if let Some(first_node) = nodes.first() {
match first_node {
DocumentNode::Paragraph { spans } => {
self.write_indent()?;
self.render_spans(spans)?;
}
DocumentNode::Heading { spans, .. } => {
self.write_indent()?;
self.render_spans(spans)?;
}
_ => {
self.render_node(first_node)?;
}
}
if nodes.len() > 1 {
write!(self.output, " [+{} more lines]", nodes.len() - 1)?;
}
}
writeln!(self.output)?;
}
TruncationLevel::Brief => {
if let Some(first_node) = nodes.first() {
self.render_node(first_node)?;
if nodes.len() > 1 {
self.write_indent()?;
write!(self.output, "[+{} more lines]", nodes.len() - 1)?;
writeln!(self.output)?;
}
}
}
TruncationLevel::Full => {
self.render_block_sequence(nodes)?;
}
}
Ok(())
}
DocumentNode::Conditional { show_when, nodes } => {
let should_show = match show_when {
ShowWhen::Always => true,
ShowWhen::Interactive => false,
ShowWhen::NonInteractive => true,
};
if should_show {
for node in nodes {
self.render_node(node)?;
}
}
Ok(())
}
}
}
fn render_spans(&mut self, spans: &[Span]) -> Result {
for span in spans {
self.render_span(span)?;
}
Ok(())
}
fn render_span(&mut self, Span { text, .. }: &Span) -> Result {
for (idx, line) in text.split('\n').enumerate() {
if idx > 0 {
writeln!(self.output)?;
self.write_indent()?;
}
write!(self.output, "{line}")?;
}
Ok(())
}
fn render_list_item(&mut self, item: &ListItem) -> Result {
self.write_indent()?;
// Render first node (typically the name) to a temporary string to control formatting
let mut first_node_output = String::new();
if let Some(first) = item.content.first() {
let mut temp_renderer = AiRenderer {
output: &mut first_node_output,
indent: String::new(),
};
temp_renderer.render_node(first)?;
}
// Strip trailing whitespace from first node
let first_text = first_node_output.trim_end();
write!(self.output, "{}", first_text)?;
// If there are more nodes, render them as comment-style description
if item.content.len() > 1 {
write!(self.output, " // ")?;
// Render subsequent content inline or as brief description
for node in item.content.iter().skip(1) {
match node {
DocumentNode::Paragraph { spans } => {
self.render_spans(spans)?;
}
DocumentNode::TruncatedBlock {
nodes,
level: TruncationLevel::Brief,
} => {
if let Some(desc) = nodes.first() {
match desc {
DocumentNode::Paragraph { spans } => {
self.render_spans(spans)?;
}
_ => {
self.render_node(desc)?;
}
}
}
if nodes.len() > 1 {
write!(self.output, " [+{} more lines]", nodes.len() - 1)?;
}
}
_ => {
self.render_node(node)?;
}
}
}
}
writeln!(self.output)?;
Ok(())
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_render_heading() {
let doc = Document::with_nodes(vec![DocumentNode::heading(
HeadingLevel::Title,
vec![Span::plain("Item: "), Span::type_name("Vec")],
)]);
let mut output = String::new();
render(&doc, &mut output).unwrap();
assert!(output.contains("Item: Vec"));
assert!(output.contains("===="));
}
#[test]
fn test_render_list() {
let doc = Document::with_nodes(vec![DocumentNode::list(vec![
ListItem::new(vec![
DocumentNode::paragraph(vec![Span::plain("First")]),
DocumentNode::paragraph(vec![Span::plain("description")]),
]),
ListItem::new(vec![
DocumentNode::paragraph(vec![Span::plain("Second")]),
DocumentNode::paragraph(vec![Span::plain("more description")]),
]),
])]);
let mut output = String::new();
render(&doc, &mut output).unwrap();
// Should have comment-style format
assert!(output.contains("First // "));
assert!(output.contains("Second // "));
// Should not have bullet points
assert!(!output.contains("◦"));
}
}