sasso 0.8.0

//! Serialize the flattened output tree to CSS.

use crate::ast::SrcLines;
use crate::eval::{OutItem, OutNode};
use crate::sourcemap::SmCollector;
use crate::OutputStyle;

pub(crate) fn emit(nodes: &[OutNode], style: OutputStyle, charset: bool) -> String {
    // The default path collects nothing: `&mut None` makes every `record_*`
    // call inert, so the output is byte-for-byte the historical CSS.
    emit_inner(nodes, style, &mut None, charset).0
}

/// Like [`emit`], but also records a source map. Returns the final CSS, the
/// byte length of the `@charset`/BOM prefix that shifts every body offset, and
/// the populated collector (raw body offsets, not yet resolved to lines).
pub(crate) fn emit_with_map(
    nodes: &[OutNode],
    style: OutputStyle,
    charset: bool,
) -> (String, usize, SmCollector) {
    let mut collector = Some(SmCollector::new(matches!(style, OutputStyle::Compressed)));
    let (css, body_off) = emit_inner(nodes, style, &mut collector, charset);
    (css, body_off, collector.expect("collector present"))
}

/// Shared serializer. `collector = Some` records mapped-token body offsets;
/// `None` records nothing (the default path). Returns `(css, body_off)` where
/// `body_off` is the length of the prepended `@charset`/BOM prefix (0 when the
/// body is pure ASCII).
fn emit_inner(
    nodes: &[OutNode],
    style: OutputStyle,
    collector: &mut Option<SmCollector>,
    charset: bool,
) -> (String, usize) {
    let mut body = match style {
        OutputStyle::Expanded => emit_expanded(nodes, collector),
        OutputStyle::Compressed => emit_compressed(nodes, collector),
    };
    // The library API (`compile`/`compile_with_source_map`, and thus the wasm
    // `compileString().css` and the Ruby gem) returns the serialized stylesheet
    // with NO trailing newline — byte-for-byte what dart-sass's library API
    // returns. The expanded emitter terminates each statement with "\n", which
    // leaves exactly one trailing newline; drop it. (Compressed never emits a
    // trailing newline, so this is a no-op there.) The CLI front-ends
    // (src/main.rs, wasm cli.mjs) re-append the single newline dart-sass's CLI
    // adds. Stripping after emit keeps every recorded source-map offset valid:
    // nothing maps to the final newline.
    if body.ends_with('\n') {
        body.pop();
    }
    // dart-sass declares UTF-8 when the output contains any non-ASCII code
    // point: expanded output gets a leading `@charset "UTF-8";`, compressed
    // output gets a UTF-8 byte-order mark instead. The prefix shifts every
    // recorded body offset by its byte length (reported as `body_off`).
    // `charset: false` (dart-sass `--no-charset`) suppresses it entirely.
    if !charset || body.is_ascii() {
        return (body, 0);
    }
    match style {
        OutputStyle::Expanded => {
            const PREFIX: &str = "@charset \"UTF-8\";\n";
            (format!("{PREFIX}{body}"), PREFIX.len())
        }
        OutputStyle::Compressed => {
            let prefix = "\u{FEFF}";
            (format!("{prefix}{body}"), prefix.len())
        }
    }
}

/// Record a mapped token at the current end of `out` if collecting. Reads only
/// `out.len()` and the SrcLines — never mutates the output.
fn record(out: &str, lines: SrcLines, collector: &mut Option<SmCollector>) {
    if let Some(c) = collector {
        // A bubbled-selector wrapper carries its mapping in the source-map-only
        // override fields (so `file`/`start` stay 0 and the trailing-comment
        // heuristic stays disabled); everything else maps from `file`/`start`.
        let file = if lines.map_file != 0 {
            lines.map_file
        } else {
            lines.file
        };
        let line = if lines.map_line != 0 {
            lines.map_line
        } else {
            lines.start
        };
        // `line` is the 1-based source line; 0 means "unknown" — skip it.
        if line == 0 {
            return;
        }
        c.record(out.len(), file, line - 1, lines.start_col);
    }
}

fn emit_expanded(nodes: &[OutNode], collector: &mut Option<SmCollector>) -> String {
    let mut out = String::new();
    let mut prev = SrcLines::default();
    for node in nodes {
        emit_node_expanded(&mut out, node, 0, &mut prev, collector);
    }
    out
}

/// dart `_isTrailingComment` (expanded style only): a comment joins the
/// previous line when it starts on the line the previous construct ended —
/// or, for a block's first child, on the parent's opening-brace line — and
/// both come from the same source file. `prev.end` always holds the
/// comparison line; a zero file id disables the rule.
///
/// A `previous` whose span is IDENTICAL to the comment's is a clone of the
/// same comment (the same file imported twice): dart's span-containment
/// branch then walks back for a `{`, finds `searchFrom < 0`, and rejects it.
fn is_trailing(comment: SrcLines, prev: SrcLines) -> bool {
    comment.file != 0 && comment.file == prev.file && comment.start == prev.end && comment != prev
}

/// The previous-sibling seed for a block's children: the first child compares
/// against the block's opening-brace line (dart walks back to the `{`).
fn block_start(lines: SrcLines) -> SrcLines {
    SrcLines {
        file: lines.file,
        start: lines.start,
        end: lines.start,
        col: 0,
        start_col: 0,
        // The trailing-comment seed never feeds source-map output; map overrides
        // are irrelevant here.
        map_file: 0,
        map_line: 0,
    }
}

/// Append a trailing comment to the line already in `out`: drop the pending
/// newline(s) — at the root a group blank line may sit between — then write
/// ` /*…*/` with continuation lines at indentation 0 (dart saves and zeroes
/// `_indentation` for trailing comments).
fn push_trailing_comment(out: &mut String, text: &str, lines: SrcLines, collector: &mut Option<SmCollector>) {
    while out.ends_with('\n') {
        out.pop();
    }
    out.push(' ');
    // Source-map: the joined comment's `/*`.
    record(out, lines, collector);
    out.push_str("/*");
    push_comment_text(out, text, "", lines.start_col as usize);
    out.push_str("*/\n");
}

/// Close an expanded block opened with `" {\n"`. When its only child was a
/// trailing comment the whole block stays on one line (dart: ` }`, e.g.
/// `@font-face { /**/ }`); otherwise the `}` gets its own indented line.
fn close_block(out: &mut String, indent: &str, children: usize, last_joined: bool) {
    if children == 1 && last_joined {
        out.pop(); // the trailing comment's newline
        out.push_str(" }\n");
    } else {
        out.push_str(indent);
        out.push_str("}\n");
    }
}

/// Indentation for a nesting depth (two spaces per level) without allocating:
/// `"  ".repeat(depth)` ran once per emitted node/item, which is tens of
/// thousands of short-lived Strings on a large output. Depths beyond the
/// precomputed pad (rare) fall back to an owned String.
fn indent_for(depth: usize) -> std::borrow::Cow<'static, str> {
    const PAD: &str = "                                                                "; // 32 levels
    match PAD.get(..depth * 2) {
        Some(s) => std::borrow::Cow::Borrowed(s),
        None => std::borrow::Cow::Owned("  ".repeat(depth)),
    }
}

/// Render one node at the given nesting `depth` (0 = document root). Each
/// extra level adds two spaces of indentation. `prev` carries the previous
/// sibling's source lines for the trailing-comment rule (its `end` is the
/// comparison line); returns whether THIS node was emitted as a trailing
/// comment joined onto the previous line.
fn emit_node_expanded(
    out: &mut String,
    node: &OutNode,
    depth: usize,
    prev: &mut SrcLines,
    collector: &mut Option<SmCollector>,
) -> bool {
    let indent = indent_for(depth);
    let indent = indent.as_ref();
    match node {
        // A module-scope wrapper is transparent: emit its contents in place
        // (the previous-sibling line state flows through the boundary).
        OutNode::ModuleScope { nodes, .. } => {
            let mut joined = false;
            for n in nodes {
                joined = emit_node_expanded(out, n, depth, prev, collector);
            }
            return joined;
        }
        OutNode::Rule {
            selectors,
            linebreaks,
            items,
            lines,
            ..
        } => {
            // `Parsed` selectors render to their final strings here (byte-
            // identical to the strings the extend engine used to materialize);
            // `Raw` selectors borrow directly.
            let selectors = selectors.to_strings();
            out.push_str(indent);
            // Source-map: the selector list's first character.
            record(out, *lines, collector);
            // A complex selector flagged with a source line break starts on its
            // own line (aligned to the rule's indent); others are `, `-joined.
            for (i, sel) in selectors.iter().enumerate() {
                if i > 0 {
                    out.push(',');
                    if linebreaks.get(i).copied().unwrap_or(false) {
                        out.push('\n');
                        out.push_str(indent);
                    } else {
                        out.push(' ');
                    }
                }
                // A line break INSIDE the selector (a pseudo arg's preserved
                // source line) continues at the rule's indent, like dart's
                // _writeIndentation after every line feed.
                if sel.contains('\n') && !indent.is_empty() {
                    let mut first = true;
                    for line in sel.split('\n') {
                        if !first {
                            out.push('\n');
                            out.push_str(indent);
                        }
                        out.push_str(line);
                        first = false;
                    }
                } else {
                    out.push_str(sel);
                }
            }
            out.push_str(" {\n");
            let mut inner = block_start(*lines);
            let mut joined = false;
            for item in items {
                joined = emit_item_expanded(out, item, depth + 1, &mut inner, collector);
            }
            close_block(out, indent, items.len(), joined);
            *prev = *lines;
        }
        OutNode::Comment(text, lines) => {
            if is_trailing(*lines, *prev) {
                // Source-map: the joined `/*` (after the dropped newline + space).
                push_trailing_comment(out, text, *lines, collector);
                *prev = *lines;
                return true;
            }
            out.push_str(indent);
            // Source-map: the comment's `/*`.
            record(out, *lines, collector);
            out.push_str("/*");
            push_comment_text(out, text, indent, lines.start_col as usize);
            out.push_str("*/\n");
            *prev = *lines;
        }
        OutNode::Raw(s) => {
            out.push_str(indent);
            out.push_str(s);
            out.push('\n');
            *prev = SrcLines::default();
        }
        // Control-only hoist markers (consumed by the bubbling passes) never
        // reach the output and don't disturb the previous-sibling line state.
        OutNode::GroupEnd | OutNode::MediaHoist | OutNode::AtRootHoist { .. } | OutNode::AtRootPackTight => {
            return false;
        }
        OutNode::Blank => {
            // A synthetic group separator: dart has no such node, so it leaves
            // the previous-sibling line state alone (a trailing comment after
            // it joins across, swallowing the blank like dart does).
            out.push('\n');
        }
        OutNode::AtDecl {
            prop,
            value,
            important,
            custom,
            lines,
        } => {
            out.push_str(indent);
            // Source-map: the declaration property name.
            record(out, *lines, collector);
            out.push_str(prop);
            emit_decl_value_expanded(out, value, *important, *custom, lines.col as usize, indent);
            out.push_str(";\n");
            *prev = *lines;
        }
        OutNode::AtRule {
            name,
            prelude,
            body,
            has_block,
            lines,
        } => {
            out.push_str(indent);
            // Source-map: the at-rule's `@` keyword.
            record(out, *lines, collector);
            out.push('@');
            out.push_str(name);
            if !prelude.is_empty() {
                out.push(' ');
                out.push_str(prelude);
            }
            *prev = *lines;
            if !has_block {
                out.push_str(";\n");
                return false;
            }
            if body.is_empty() {
                out.push_str(" {}\n");
                return false;
            }
            out.push_str(" {\n");
            let mut inner = block_start(*lines);
            let mut children = 0usize;
            let mut joined = false;
            for child in body {
                let before = out.len();
                let j = emit_node_expanded(out, child, depth + 1, &mut inner, collector);
                // Sentinels emit nothing and don't count as children.
                if out.len() > before {
                    children += 1;
                    joined = j;
                }
            }
            close_block(out, indent, children, joined);
        }
    }
    false
}

/// Render one rule-block item; same `prev`/return contract as
/// [`emit_node_expanded`].
fn emit_item_expanded(
    out: &mut String,
    item: &OutItem,
    depth: usize,
    prev: &mut SrcLines,
    collector: &mut Option<SmCollector>,
) -> bool {
    let indent = indent_for(depth);
    let indent = indent.as_ref();
    match item {
        OutItem::Decl {
            prop,
            value,
            important,
            custom,
            lines,
        } => {
            out.push_str(indent);
            // Source-map: the declaration property name.
            record(out, *lines, collector);
            out.push_str(prop);
            emit_decl_value_expanded(out, value, *important, *custom, lines.col as usize, indent);
            out.push_str(";\n");
            *prev = *lines;
        }
        OutItem::Comment(text, lines) => {
            if is_trailing(*lines, *prev) {
                push_trailing_comment(out, text, *lines, collector);
                *prev = *lines;
                return true;
            }
            out.push_str(indent);
            // Source-map: the comment's `/*`.
            record(out, *lines, collector);
            out.push_str("/*");
            push_comment_text(out, text, indent, lines.start_col as usize);
            out.push_str("*/\n");
            *prev = *lines;
        }
        OutItem::ChildlessAtRule { name, prelude, lines } => {
            out.push_str(indent);
            // Source-map: the at-rule's `@` keyword.
            record(out, *lines, collector);
            out.push('@');
            out.push_str(name);
            if !prelude.is_empty() {
                out.push(' ');
                out.push_str(prelude);
            }
            out.push_str(";\n");
            *prev = *lines;
        }
        OutItem::NestedRule { selectors, items } => {
            out.push_str(indent);
            out.push_str(&selectors.join(", "));
            out.push_str(" {\n");
            let mut inner = SrcLines::default();
            let mut joined = false;
            for child in items {
                joined = emit_item_expanded(out, child, depth + 1, &mut inner, collector);
            }
            close_block(out, indent, items.len(), joined);
            *prev = SrcLines::default();
        }
        OutItem::NestedAtRule { name, prelude, items } => {
            out.push_str(indent);
            out.push('@');
            out.push_str(name);
            if !prelude.is_empty() {
                out.push(' ');
                out.push_str(prelude);
            }
            out.push_str(" {\n");
            let mut inner = SrcLines::default();
            let mut joined = false;
            for child in items {
                joined = emit_item_expanded(out, child, depth + 1, &mut inner, collector);
            }
            close_block(out, indent, items.len(), joined);
            *prev = SrcLines::default();
        }
    }
    false
}

/// Append the `: value [!important]` portion of an expanded declaration. A
/// custom property emits its value verbatim right after the colon (its leading
/// whitespace is part of `value`, dart-sass adds no space) and never appends an
/// `!important` flag; a normal declaration uses the canonical `: ` separator.
/// A multi-line custom value is re-indented (dart `_writeReindentedValue`):
/// `name_col` is the declaration name's 0-based source column and `indent`
/// the current output indentation.
fn emit_decl_value_expanded(
    out: &mut String,
    value: &str,
    important: bool,
    custom: bool,
    name_col: usize,
    indent: &str,
) {
    if custom {
        out.push(':');
        match minimum_indentation(value) {
            MinIndent::SingleLine => out.push_str(value),
            MinIndent::Trailing => {
                out.push_str(trim_ascii_right_exclude_escape(value));
                out.push(' ');
            }
            MinIndent::Min(m) => write_with_indent(out, value, m.min(name_col), indent),
        }
        return;
    }
    out.push_str(": ");
    out.push_str(value);
    if important {
        out.push_str(" !important");
    }
}

/// dart `_minimumIndentation`: the minimum indentation of `text`'s
/// continuation lines, skipping blank lines.
enum MinIndent {
    /// `text` has no newline — emit verbatim.
    SingleLine,
    /// Every continuation line is blank (dart's `-1`) — trim right + space.
    Trailing,
    /// The least indented non-blank continuation line starts at this column.
    Min(usize),
}

fn minimum_indentation(text: &str) -> MinIndent {
    let bytes = text.as_bytes();
    let mut i = match text.find('\n') {
        None => return MinIndent::SingleLine,
        Some(p) => p + 1,
    };
    if i >= bytes.len() {
        return MinIndent::Trailing;
    }
    let mut min: Option<usize> = None;
    while i < bytes.len() {
        let start = i;
        while i < bytes.len() && (bytes[i] == b' ' || bytes[i] == b'\t') {
            i += 1;
        }
        if i >= bytes.len() {
            break; // a trailing all-whitespace line is not counted
        }
        if bytes[i] == b'\n' {
            i += 1; // blank line: not counted
            continue;
        }
        let col = i - start;
        min = Some(min.map_or(col, |m| m.min(col)));
        while i < bytes.len() && bytes[i] != b'\n' {
            i += 1;
        }
        i += 1;
    }
    match min {
        None => MinIndent::Trailing,
        Some(m) => MinIndent::Min(m),
    }
}

/// dart `trimAsciiRight(value, excludeEscape: true)`: strip trailing ASCII
/// whitespace, but keep one character after a terminating backslash so an
/// escaped trailing space survives.
fn trim_ascii_right_exclude_escape(s: &str) -> &str {
    let bytes = s.as_bytes();
    let mut end = bytes.len();
    while end > 0 && matches!(bytes[end - 1], b' ' | b'\t' | b'\n' | b'\r' | b'\x0c') {
        end -= 1;
    }
    if end != 0 && end != bytes.len() && bytes[end - 1] == b'\\' {
        end += 1;
    }
    &s[..end]
}

/// dart `_writeWithIndent`: write the first line verbatim, then each
/// continuation line stripped of `min_indent` characters and prefixed with
/// the current output indentation. Blank lines stay blank; a trailing
/// all-whitespace line folds to a single space.
fn write_with_indent(out: &mut String, text: &str, min_indent: usize, indent: &str) {
    let first_end = text.find('\n').unwrap_or(text.len());
    out.push_str(&text[..first_end]);
    if first_end == text.len() {
        return;
    }
    let mut i = first_end + 1;
    loop {
        let mut line_start = i;
        let mut newlines = 1usize;
        // Scan the whitespace run, counting blank lines; `i` settles on the
        // first non-whitespace character (the run's indentation is ASCII, so
        // byte stepping stays on char boundaries).
        loop {
            if i >= text.len() {
                out.push(' ');
                return;
            }
            match text.as_bytes()[i] {
                b' ' | b'\t' => i += 1,
                b'\n' => {
                    i += 1;
                    line_start = i;
                    newlines += 1;
                }
                _ => break,
            }
        }
        for _ in 0..newlines {
            out.push('\n');
        }
        out.push_str(indent);
        let line_end = text[i..].find('\n').map(|p| i + p).unwrap_or(text.len());
        out.push_str(&text[line_start + min_indent..line_end]);
        if line_end == text.len() {
            return;
        }
        i = line_end + 1;
    }
}

fn emit_compressed(nodes: &[OutNode], collector: &mut Option<SmCollector>) -> String {
    let mut out = String::new();
    for node in nodes {
        emit_node_compressed(&mut out, node, collector);
    }
    out
}

/// Render `nodes` joined for compressed output. A declaration is terminated by
/// `;` before whatever follows it, but a preceding rule/at-rule `}` is its own
/// separator, so no `;` is inserted after it (matching dart-sass).
fn emit_compressed_body(out: &mut String, nodes: &[OutNode], collector: &mut Option<SmCollector>) {
    let mut prev_was_decl = false;
    for node in nodes {
        // Comments and blanks produce no compressed output; don't let them
        // reset the separator state.
        if matches!(node, OutNode::Comment(..) | OutNode::Blank) {
            continue;
        }
        if prev_was_decl {
            out.push(';');
        }
        emit_node_compressed(out, node, collector);
        prev_was_decl = matches!(node, OutNode::AtDecl { .. });
    }
}

/// Serialize a plain-CSS nested rule for compressed output (a rare, untested
/// path — plain CSS is normally emitted expanded).
fn compressed_nested_rule(selectors: &[String], items: &[OutItem]) -> String {
    let inner: Vec<String> = items
        .iter()
        .filter_map(|it| match it {
            OutItem::Decl {
                prop,
                value,
                important,
                custom,
                ..
            } => {
                let imp = if *important && !*custom { "!important" } else { "" };
                let value = fold_value_compressed(value, *custom);
                Some(format!("{prop}:{value}{imp}"))
            }
            OutItem::Comment(..) => None,
            OutItem::ChildlessAtRule { name, prelude, .. } if prelude.is_empty() => Some(format!("@{name}")),
            OutItem::ChildlessAtRule { name, prelude, .. } => Some(format!("@{name} {prelude}")),
            OutItem::NestedRule { selectors, items } => Some(compressed_nested_rule(selectors, items)),
            OutItem::NestedAtRule { name, prelude, items } => {
                Some(compressed_nested_at_rule(name, prelude, items))
            }
        })
        .collect();
    format!("{}{{{}}}", selectors.join(","), inner.join(";"))
}

/// dart `_writeFoldedValue` (compressed custom properties): each newline
/// becomes a single space and the whitespace run following it is dropped.
/// Non-custom values pass through untouched.
fn fold_value_compressed<'v>(value: &'v str, custom: bool) -> std::borrow::Cow<'v, str> {
    if !custom || !value.contains('\n') {
        return std::borrow::Cow::Borrowed(value);
    }
    let mut out = String::with_capacity(value.len());
    let mut chars = value.chars().peekable();
    while let Some(c) = chars.next() {
        if c != '\n' {
            out.push(c);
            continue;
        }
        out.push(' ');
        while matches!(chars.peek(), Some(' ' | '\t' | '\n' | '\r' | '\x0c')) {
            chars.next();
        }
    }
    std::borrow::Cow::Owned(out)
}

/// dart-sass omits the space between the at-rule name and a prelude that begins
/// with `(` in compressed output, but ONLY for `@media`
/// (`visitCssMediaRule`) and `@supports` (`visitCssSupportsRule`). Every other
/// at-rule keeps the space even before `(` — e.g. `@container (min-width:1px)`.
fn compressed_at_rule_omits_space(name: &str, prelude: &str) -> bool {
    matches!(name, "media" | "supports") && prelude.starts_with('(')
}

/// Serialize a plain-CSS nested at-rule for compressed output (rare path; see
/// [`compressed_nested_rule`]).
fn compressed_nested_at_rule(name: &str, prelude: &str, items: &[OutItem]) -> String {
    let body = compressed_nested_rule(&[], items);
    // `compressed_nested_rule` with no selectors renders `{...}`; reuse its body.
    if prelude.is_empty() {
        format!("@{name}{body}")
    } else if compressed_at_rule_omits_space(name, prelude) {
        format!("@{name}{prelude}{body}")
    } else {
        format!("@{name} {prelude}{body}")
    }
}

fn emit_node_compressed(out: &mut String, node: &OutNode, collector: &mut Option<SmCollector>) {
    match node {
        OutNode::ModuleScope { nodes, .. } => {
            for n in nodes {
                emit_node_compressed(out, n, collector);
            }
        }
        OutNode::Rule {
            selectors,
            linebreaks: _,
            items,
            lines,
            ..
        } => {
            // Pre-render each visible item to a string, keeping its source lines
            // for the source map (`None` = no usable mapping, e.g. a plain-CSS
            // nested rule whose leading token is a selector we don't map here).
            let decls: Vec<(String, Option<SrcLines>)> = items
                .iter()
                .filter_map(|it| match it {
                    OutItem::Decl {
                        prop,
                        value,
                        important,
                        custom,
                        lines,
                    } => {
                        // A custom property emits its value verbatim (its
                        // leading whitespace is part of `value`) and never gains
                        // an `!important` flag.
                        let imp = if *important && !*custom { "!important" } else { "" };
                        let value = fold_value_compressed(value, *custom);
                        Some((format!("{prop}:{value}{imp}"), Some(*lines)))
                    }
                    OutItem::Comment(..) => None,
                    OutItem::ChildlessAtRule { name, prelude, lines } => {
                        let s = if prelude.is_empty() {
                            format!("@{name}")
                        } else {
                            format!("@{name} {prelude}")
                        };
                        Some((s, Some(*lines)))
                    }
                    OutItem::NestedRule { selectors, items } => {
                        Some((compressed_nested_rule(selectors, items), None))
                    }
                    OutItem::NestedAtRule { name, prelude, items } => {
                        Some((compressed_nested_at_rule(name, prelude, items), None))
                    }
                })
                .collect();
            if decls.is_empty() {
                return;
            }
            // Source-map: the selector list's first character.
            record(out, *lines, collector);
            out.push_str(&selectors.to_strings().join(","));
            out.push('{');
            for (i, (s, dlines)) in decls.iter().enumerate() {
                if i > 0 {
                    out.push(';');
                }
                if let Some(l) = dlines {
                    // Source-map: the item's leading token (property name / `@`).
                    record(out, *l, collector);
                }
                out.push_str(s);
            }
            out.push('}');
        }
        // Loud comments are dropped in compressed output (the slice does
        // not yet special-case `/*!` important comments).
        OutNode::Comment(..) => {}
        OutNode::Raw(s) => out.push_str(s),
        OutNode::Blank => {}
        // Control-only hoist markers never reach the output.
        OutNode::GroupEnd | OutNode::MediaHoist | OutNode::AtRootHoist { .. } | OutNode::AtRootPackTight => {}
        OutNode::AtDecl {
            prop,
            value,
            important,
            custom,
            lines,
        } => {
            let imp = if *important && !*custom { "!important" } else { "" };
            // Source-map: the declaration property name.
            record(out, *lines, collector);
            out.push_str(prop);
            out.push(':');
            out.push_str(&fold_value_compressed(value, *custom));
            out.push_str(imp);
        }
        OutNode::AtRule {
            name,
            prelude,
            body,
            has_block,
            lines,
        } => {
            // Source-map: the at-rule's `@` keyword.
            record(out, *lines, collector);
            out.push('@');
            out.push_str(name);
            if !prelude.is_empty() {
                // Compressed `@media`/`@supports` omit the space before a prelude
                // that begins with `(` (dart `visitCssMediaRule`/`visitCssSupportsRule`).
                if !compressed_at_rule_omits_space(name, prelude) {
                    out.push(' ');
                }
                out.push_str(prelude);
            }
            if !has_block {
                out.push(';');
                return;
            }
            out.push('{');
            emit_compressed_body(out, body, collector);
            out.push('}');
        }
    }
}

/// Write a loud comment's text with dart's continuation-line handling
/// (`_minimumIndentation` + `_writeWithIndent`, run on the EVALUATED text so
/// interpolated comments dedent too): continuation lines lose
/// `min(<minimum indentation across them>, <the comment's own source start
/// column>)` leading whitespace and gain the CURRENT output indentation;
/// whitespace-only interior lines collapse to bare newlines. The final line
/// always counts as content — the `*/` closer follows this text.
fn push_comment_text(out: &mut String, text: &str, indent: &str, start_col: usize) {
    if !text.contains('\n') {
        out.push_str(text);
        return;
    }
    let lines: Vec<&str> = text.split('\n').collect();
    let mut min: Option<usize> = None;
    for (i, line) in lines.iter().enumerate().skip(1) {
        if i + 1 != lines.len() && line.trim().is_empty() {
            continue;
        }
        let ind = line.len() - line.trim_start_matches([' ', '\t']).len();
        min = Some(min.map_or(ind, |m| m.min(ind)));
    }
    let strip = min.map_or(0, |m| m.min(start_col));
    out.push_str(lines[0]);
    for (i, line) in lines.iter().enumerate().skip(1) {
        out.push('\n');
        if i + 1 != lines.len() && line.trim().is_empty() {
            continue;
        }
        let ind = line.len() - line.trim_start_matches([' ', '\t']).len();
        out.push_str(indent);
        out.push_str(&line[strip.min(ind)..]);
    }
}