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pub type DocRef<'a> = &'a Doc<'a>;
pub fn pretty_print(doc_ref: DocRef, max_width: u32) -> String {
let mut printer = PrettyPrinter::new(doc_ref, max_width);
printer.print()
}
#[derive(PartialEq, Debug)]
pub enum Doc<'a> {
Newline,
NewlineWithNoIndent,
ForceBreak, // immediately use multi-line mode in choice(x, y) or group()
Text(String, u32), // The given text should not contain line breaks
Softline, // a space or a newline
Maybeline, // empty or a newline
Flat(DocRef<'a>),
Indent(u32, DocRef<'a>),
Dedent(u32, DocRef<'a>),
Concat(Vec<DocRef<'a>>),
Choice(DocRef<'a>, DocRef<'a>),
//Align(u32, DocRef<'a>),
}
struct PrettyPrinter<'a> {
max_width: u32,
col: u32,
chunks: Vec<Chunk<'a>>,
}
pub struct PrettyConfig {
pub indent_size: u32,
}
impl PrettyConfig {
pub fn new(indent_size: u32) -> Self {
if indent_size == 0 {
panic!("indent_size must be greater than 0")
} else {
Self { indent_size }
}
}
}
#[derive(Debug, Clone, Copy)]
struct Chunk<'a> {
doc_ref: DocRef<'a>,
indent: u32,
flat: bool,
//align: u32,
}
impl<'a> Chunk<'a> {
fn with_doc(self, doc_ref: DocRef<'a>) -> Self {
Chunk { doc_ref, ..self }
}
fn indented(self, indent: u32, doc_ref: DocRef<'a>) -> Self {
Chunk {
doc_ref,
indent: self.indent + indent,
..self
}
}
fn dedented(self, indent: u32, doc_ref: DocRef<'a>) -> Self {
Chunk {
doc_ref,
indent: self.indent.saturating_sub(indent),
..self
}
}
fn flat(self, doc_ref: DocRef<'a>) -> Self {
Chunk {
doc_ref,
flat: true,
..self
}
}
}
impl<'a> PrettyPrinter<'a> {
fn new(doc_ref: DocRef<'a>, max_width: u32) -> Self {
let chunk = Chunk {
doc_ref,
indent: 0,
flat: false,
};
Self {
max_width,
col: 0,
chunks: vec![chunk],
}
}
fn print(&mut self) -> String {
let mut result = String::new();
// Initialize the Doc::Newline buffer with clear state
let mut newline_buffer = NewlineBuffer::new();
while let Some(chunk) = self.chunks.pop() {
match chunk.doc_ref {
Doc::Newline => {
// Set a pending newline with the current indent
newline_buffer.set_pending(chunk.indent);
}
Doc::NewlineWithNoIndent => {
// Clear any pending newline and insert a newline without indent
newline_buffer.clear();
result.push('\n');
self.col = 0;
}
Doc::Softline => {
if chunk.flat {
result.push(' ');
self.col += 1;
} else {
newline_buffer.set_pending(chunk.indent);
}
}
Doc::Maybeline => {
if !chunk.flat {
newline_buffer.set_pending(chunk.indent);
}
}
Doc::ForceBreak => {
// TODO: still needed after line_comment refinement?
// Handle ForceBreak if necessary
}
Doc::Text(text, width) => {
// Before printing text, flush any pending newline
if newline_buffer.is_pending() {
self.insert_newline_with_indent(&mut result, newline_buffer.get_indent());
newline_buffer.clear();
}
if text == " " && result.ends_with(' ') {
// TODO: better way to handle this challenge?
// do nothing to avoid "double spacing" in comment node handling
} else {
result.push_str(text);
self.col += width;
}
}
Doc::Flat(x) => self.chunks.push(chunk.flat(x)),
Doc::Indent(i, x) => self.chunks.push(chunk.indented(*i, x)),
Doc::Dedent(i, x) => self.chunks.push(chunk.dedented(*i, x)),
Doc::Concat(seq) => {
for n in seq.iter().rev() {
self.chunks.push(chunk.with_doc(n));
}
}
Doc::Choice(x, y) => {
if newline_buffer.is_pending() {
self.insert_newline_with_indent(&mut result, newline_buffer.get_indent());
newline_buffer.clear();
}
if chunk.flat {
// 1. Already forced single-line by a parent
self.chunks.push(chunk.with_doc(x));
} else {
// 2. Let's see if x fits
if self.fits(chunk.with_doc(x)) {
self.chunks.push(chunk.with_doc(x));
} else {
// 3. x not fits, use the fall-back y (usually the multi-line version)
self.chunks.push(chunk.with_doc(y));
}
}
}
}
}
// Flush the last element in case buffer has a newline
if newline_buffer.is_pending() {
self.insert_newline_with_indent(&mut result, newline_buffer.get_indent());
newline_buffer.clear();
}
result
}
fn insert_newline_with_indent(&mut self, result: &mut String, indent: u32) {
result.push('\n');
for _ in 0..indent {
result.push(' ');
}
self.col = indent;
}
//fn insert_newline_with_indent(&mut self, result: &mut String, chunk: &Chunk) {
// result.push('\n');
// let total_indent = chunk.indent;
// for _ in 0..total_indent {
// result.push(' ');
// }
// self.col = total_indent;
//}
fn fits(&self, chunk: Chunk<'a>) -> bool {
let mut remaining_width = self.max_width.saturating_sub(self.col);
let mut stack = vec![chunk];
let mut chunks = &self.chunks as &[Chunk];
loop {
let chunk = if let Some(chunk) = stack.pop() {
chunk
} else if let Some((chunk, more_chunks)) = chunks.split_last() {
chunks = more_chunks;
*chunk
} else {
return true;
};
match chunk.doc_ref {
Doc::Newline | Doc::NewlineWithNoIndent => return true,
Doc::ForceBreak => return false,
Doc::Softline => {
if chunk.flat {
if remaining_width >= 1 {
remaining_width -= 1;
} else {
return false;
}
} else {
return true;
}
}
Doc::Maybeline => {
if !chunk.flat {
return true;
}
}
Doc::Text(_, text_width) => {
if *text_width <= remaining_width {
remaining_width -= text_width;
} else {
return false;
}
}
Doc::Flat(x) => stack.push(chunk.flat(x)),
Doc::Indent(i, x) => stack.push(chunk.indented(*i, x)),
Doc::Dedent(i, x) => stack.push(chunk.dedented(*i, x)),
//Doc::Align(relative_align_col, x) => {
// let new_align = chunk.align + relative_align_col;
// stack.push(chunk.align(new_align, x));
//}
Doc::Concat(seq) => {
for n in seq.iter().rev() {
stack.push(chunk.with_doc(n));
}
}
Doc::Choice(x, y) => {
if chunk.flat {
stack.push(chunk.with_doc(x));
} else {
// With assumption: for every choice `x | y`,
// the first line of `y` is no longer than the first line of `x`.
stack.push(chunk.with_doc(y));
}
}
}
}
}
}
struct NewlineBuffer {
has_pending_newline: bool,
indent_level: u32,
}
impl NewlineBuffer {
fn new() -> Self {
Self {
has_pending_newline: false,
indent_level: 0,
}
}
fn set_pending(&mut self, indent: u32) {
self.has_pending_newline = true;
self.indent_level = indent;
}
fn clear(&mut self) {
self.has_pending_newline = false;
self.indent_level = 0;
}
fn is_pending(&self) -> bool {
self.has_pending_newline
}
fn get_indent(&self) -> u32 {
self.indent_level
}
}