lini 0.3.0

//! Canonical source formatter (SPEC §14). Parses to the AST and re-emits a
//! normalized form: the three phases in order (stylesheet → instances → wires),
//! `key: value;` declarations in `{ }` blocks, `name::base` defines, 2-space
//! indent, space-separated value groups (comma between groups). Comments and
//! blank-line groupings are preserved; sibling nodes align their id/type
//! columns. Idempotent: `fmt(fmt(x)) == fmt(x)`.

use crate::ast::{Side, WireOp};
use crate::error::Error;
use crate::lexer;
use crate::span::Span;
use crate::syntax::ast::{
    Block, Child, Decl, Define, Endpoint, File, Node, Rule, SelPart, Selector, StyleItem, Value,
    Wire, WireBlock,
};
use crate::syntax::parser;

mod trivia;
use trivia::{Trivia, TriviaToken, scan_trivia};

const INDENT: &str = "  ";

/// A declarations-only block collapses onto one line (`.hot { stroke: red; }`)
/// when the whole line fits within this budget; past it, or once the block holds
/// a child node/wire, it breaks across lines. Prettier's print-width, give or take.
const MAX_LINE: usize = 80;

pub fn format(src: &str) -> Result<String, Error> {
    let tokens = lexer::lex(src)?;
    let file = parser::parse(&tokens)?;
    let trivia = scan_trivia(src);
    let mut out = String::new();
    Emitter {
        trivia: &trivia,
        cursor: 0,
        out: &mut out,
        align: true,
        terse: true,
    }
    .emit_file(&file, src.len());
    Ok(out)
}

/// Emit an AST with no source to draw trivia from — for a synthesized `File`
/// (the desugar pass), whose nodes carry no real spans. Same emitter, empty
/// trivia: clean output, comments dropped.
pub(crate) fn print_file(file: &File) -> String {
    let mut out = String::new();
    Emitter {
        trivia: &[],
        cursor: 0,
        out: &mut out,
        align: false,
        terse: false,
    }
    .emit_file(file, 0);
    out
}

struct Emitter<'a> {
    trivia: &'a [TriviaToken],
    cursor: usize,
    out: &'a mut String,
    /// Column-align sibling id/type columns. On for canonical `fmt`; off for
    /// `print_file` (synthesized ASTs, where mixing anonymous sugar children
    /// with named nodes would pad oddly).
    align: bool,
    /// Contract a text-only block to trailing labels (`api |box| "API"`). On for
    /// `fmt`; off for `print_file` (desugar), which expands sugar to the block.
    terse: bool,
}

impl Emitter<'_> {
    fn emit_file(&mut self, file: &File, src_len: usize) {
        let mut phases_emitted = 0;
        if !file.stylesheet.is_empty() {
            // Root config declarations group on one line like a block's, the same
            // CSS-shaped style (SPEC §20); rules, defines, and `--var`s each take
            // their own line.
            let items = &file.stylesheet;
            let mut i = 0;
            while i < items.len() {
                if matches!(items[i], StyleItem::RootDecl(_)) {
                    let start = i;
                    while i < items.len() && matches!(items[i], StyleItem::RootDecl(_)) {
                        i += 1;
                    }
                    let run: Vec<&Decl> = items[start..i]
                        .iter()
                        .map(|it| match it {
                            StyleItem::RootDecl(d) => d,
                            _ => unreachable!(),
                        })
                        .collect();
                    self.emit_grouped_decls(&run, 0);
                } else {
                    self.emit_trivia_before(style_item_span(&items[i]).start, 0);
                    self.emit_style_item(&items[i], 0);
                    self.cursor = style_item_span(&items[i]).end;
                    i += 1;
                }
            }
            phases_emitted += 1;
        }
        if !file.instances.is_empty() {
            self.section_break(phases_emitted);
            self.emit_children(&file.instances, 0);
            phases_emitted += 1;
        }
        if !file.wires.is_empty() {
            self.section_break(phases_emitted);
            for w in &file.wires {
                self.emit_trivia_before(w.span.start, 0);
                self.emit_wire(w, 0);
                self.out.push('\n');
                self.cursor = w.span.end;
            }
        }
        self.emit_trivia_before(src_len, 0);
        if self.out.is_empty() {
            return;
        }
        if !self.out.ends_with('\n') {
            self.out.push('\n');
        }
    }

    /// One blank line between two non-empty phases (only once any phase has been
    /// written), unless the running output already ends in one.
    fn section_break(&mut self, phases_emitted: usize) {
        if phases_emitted > 0 && !self.out.is_empty() && !self.out.ends_with("\n\n") {
            self.out.push('\n');
        }
    }

    // ───────── Stylesheet ─────────

    fn emit_style_item(&mut self, item: &StyleItem, depth: usize) {
        match item {
            StyleItem::RootDecl(d) => {
                self.indent(depth);
                self.emit_decl(d, false);
                self.out.push('\n');
            }
            StyleItem::Var(d) => {
                self.indent(depth);
                self.emit_decl(d, true);
                self.out.push('\n');
            }
            StyleItem::Rule(r) => self.emit_rule(r, depth),
            StyleItem::Define(d) => self.emit_define(d, depth),
        }
    }

    fn emit_rule(&mut self, rule: &Rule, depth: usize) {
        self.indent(depth);
        self.emit_selector(&rule.selector);
        self.emit_decl_block(&rule.decls, rule.span.end, depth);
        self.out.push('\n');
    }

    fn emit_define(&mut self, def: &Define, depth: usize) {
        self.indent(depth);
        self.out.push_str(&def.name);
        self.out.push_str("::");
        self.out.push_str(&def.base);
        self.emit_block(&def.body, def.span.end, depth);
        self.out.push('\n');
    }

    fn emit_selector(&mut self, sel: &Selector) {
        // The wire-defaults rule carries the reserved `wire` selector internally
        // but is written with the wire glyph.
        if let [SelPart::Type(t)] = sel.parts.as_slice()
            && t == "wire"
        {
            self.out.push_str("->");
            return;
        }
        for (i, part) in sel.parts.iter().enumerate() {
            if i > 0 {
                self.out.push(' ');
            }
            match part {
                SelPart::Type(t) => self.out.push_str(t),
                SelPart::Class(c) => {
                    self.out.push('.');
                    self.out.push_str(c);
                }
            }
        }
    }

    // ───────── Instances ─────────

    fn emit_children(&mut self, children: &[Child], depth: usize) {
        let widths = if self.align {
            align::child_widths(children, self.trivia)
        } else {
            vec![align::NodeWidths::default(); children.len()]
        };
        for (i, c) in children.iter().enumerate() {
            let span = child_span(c);
            self.emit_trivia_before(span.start, depth);
            match c {
                Child::Box(n) => self.emit_node(n, depth, widths[i]),
                Child::Text(t) => {
                    self.indent(depth);
                    self.emit_string(&t.text);
                }
            }
            self.out.push('\n');
            self.cursor = span.end;
        }
    }

    /// The column count if this block is a grid whose children are *all* bare
    /// text (a `|table|`) and no comment sits between the cells — then the cells
    /// align into columns (SPEC §8/§14). Any box cell or interleaved comment
    /// returns `None`, falling the body back to one child per line.
    fn table_cols(&self, block: &Block) -> Option<usize> {
        let cells = &block.children;
        if cells.is_empty() || !cells.iter().all(|c| matches!(c, Child::Text(_))) {
            return None;
        }
        let start = child_span(&cells[0]).start;
        let end = child_span(cells.last().unwrap()).end;
        if self.has_trivia_between(start, end) {
            return None;
        }
        count_columns(&block.decls)
    }

    /// Emit bare-text cells as aligned rows: each column padded to its widest
    /// cell, a single space between columns, `columns` cells per row.
    fn emit_aligned_cells(&mut self, cells: &[Child], cols: usize, depth: usize) {
        let texts: Vec<String> = cells
            .iter()
            .map(|c| match c {
                Child::Text(t) => quoted(&t.text),
                Child::Box(_) => String::new(), // table_cols guarantees all-text
            })
            .collect();
        let mut widths = vec![0usize; cols];
        for (i, s) in texts.iter().enumerate() {
            widths[i % cols] = widths[i % cols].max(s.len());
        }
        for (i, s) in texts.iter().enumerate() {
            let col = i % cols;
            if col == 0 {
                self.indent(depth);
            } else {
                self.out.push(' ');
            }
            self.out.push_str(s);
            if col == cols - 1 || i == texts.len() - 1 {
                self.out.push('\n');
            } else {
                pad(self.out, widths[col] - s.len());
            }
        }
        self.cursor = child_span(cells.last().unwrap()).end;
    }

    fn emit_node(&mut self, node: &Node, depth: usize, w: align::NodeWidths) {
        self.indent(depth);
        // Head tokens — `id |type| "labels" .classes` — each separated from the
        // last by one space, with the alignment widths padding the id/type
        // columns out to the group's max. `wrote` tracks whether any token (or a
        // reserved-but-empty column) precedes, so the separator never leads.
        let mut wrote = false;
        if let Some(id) = &node.id {
            self.out.push_str(id);
            pad(self.out, w.id.saturating_sub(id.len()));
            wrote = true;
        } else if w.id > 0 {
            pad(self.out, w.id);
            wrote = true;
        }
        if let Some(ty) = &node.ty {
            self.space_if(wrote);
            let t = format!("|{}|", ty);
            self.out.push_str(&t);
            pad(self.out, w.ty.saturating_sub(t.len()));
            wrote = true;
        } else if w.ty > 0 {
            self.space_if(wrote);
            pad(self.out, w.ty);
            wrote = true;
        }
        for class in &node.classes {
            self.space_if(wrote);
            self.out.push('.');
            self.out.push_str(class);
            wrote = true;
        }
        if let Some(block) = &node.block
            && !self.try_trailing_labels(
                &block.children,
                block.decls.is_empty() && block.wires.is_empty(),
                node.span.end,
            )
        {
            self.emit_block(block, node.span.end, depth);
        }
    }

    /// In terse mode, a block that is only text (≥1 child, no decls / boxes /
    /// wires / comment) is written as trailing labels — `… "a" "b"`, no braces.
    /// Returns whether it did so (and advanced the cursor).
    fn try_trailing_labels(&mut self, children: &[Child], no_config: bool, end: usize) -> bool {
        let text_only =
            !children.is_empty() && children.iter().all(|c| matches!(c, Child::Text(_)));
        if !self.terse || !no_config || !text_only || self.has_trivia_between(self.cursor, end) {
            return false;
        }
        for c in children {
            if let Child::Text(t) = c {
                self.out.push(' ');
                self.emit_string(&t.text);
            }
        }
        self.cursor = end;
        true
    }

    fn space_if(&mut self, cond: bool) {
        if cond {
            self.out.push(' ');
        }
    }

    /// Emit a run of declarations grouped onto as few lines as the source's
    /// trivia allows (SPEC §20): consecutive decls with nothing between them
    /// share one line (`cell: 1 2; layout: column; gap: 16;`), and a comment or
    /// blank line starts a fresh one. They never share the opening brace's line.
    fn emit_grouped_decls(&mut self, decls: &[&Decl], depth: usize) {
        let mut mid_line = false;
        for d in decls {
            if mid_line && self.has_trivia_between(self.cursor, d.span.start) {
                self.out.push('\n');
                mid_line = false;
            }
            self.emit_trivia_before(d.span.start, depth);
            if mid_line {
                self.out.push(' ');
            } else {
                self.indent(depth);
            }
            self.emit_decl(d, false);
            self.cursor = d.span.end;
            mid_line = true;
        }
        if mid_line {
            self.out.push('\n');
        }
    }

    fn has_trivia_between(&self, start: usize, end: usize) -> bool {
        self.trivia.iter().any(|t| t.pos >= start && t.pos < end)
    }

    /// Try to collapse a body of declarations + bare-text labels onto the current
    /// line — ` { cell: 1 1; "Cat" }`. Restores and returns `false` if there's a
    /// comment/blank inside or the finished line exceeds [`MAX_LINE`], so the
    /// caller falls through to the multi-line form. A box child or internal wire
    /// is the caller's cue never to try.
    fn try_inline(&mut self, decls: &[Decl], texts: &[&str], end: usize) -> bool {
        if self.has_trivia_between(self.cursor, end) {
            return false;
        }
        let line_start = self.out.rfind('\n').map_or(0, |i| i + 1);
        let saved = self.out.len();
        self.out.push_str(" { ");
        let mut first = true;
        for d in decls {
            if !first {
                self.out.push(' ');
            }
            self.emit_decl(d, false);
            first = false;
        }
        for t in texts {
            if !first {
                self.out.push(' ');
            }
            self.emit_string(t);
            first = false;
        }
        self.out.push_str(" }");
        if self.out.len() - line_start <= MAX_LINE {
            self.cursor = end;
            true
        } else {
            self.out.truncate(saved);
            false
        }
    }

    fn emit_block(&mut self, block: &Block, end: usize, depth: usize) {
        let empty = block.decls.is_empty() && block.children.is_empty() && block.wires.is_empty();
        if empty && !self.has_comment_in(self.cursor, end) {
            self.out.push_str(" {}");
            self.cursor = end;
            return;
        }
        // A box child or internal wire forces the multi-line form, as does a
        // multi-row table (it always breaks into aligned rows); otherwise a body
        // of only declarations and bare text may collapse onto one line.
        let has_box = block.children.iter().any(|c| matches!(c, Child::Box(_)));
        let table = self.table_cols(block);
        let multi_row = matches!(table, Some(cols) if block.children.len() > cols);
        if !has_box && block.wires.is_empty() && !multi_row {
            let texts = text_strs(&block.children);
            if self.try_inline(&block.decls, &texts, end) {
                return;
            }
        }
        self.out.push_str(" {\n");
        let decls: Vec<&Decl> = block.decls.iter().collect();
        self.emit_grouped_decls(&decls, depth + 1);
        // A grid of bare-text cells (a `|table|`) aligns into columns; any other
        // cell kind, or a comment between cells, falls back to one-per-line.
        match table {
            Some(cols) => self.emit_aligned_cells(&block.children, cols, depth + 1),
            None => self.emit_children(&block.children, depth + 1),
        }
        for wire in &block.wires {
            self.emit_trivia_before(wire.span.start, depth + 1);
            self.emit_wire(wire, depth + 1);
            self.out.push('\n');
            self.cursor = wire.span.end;
        }
        self.emit_trivia_before(end, depth + 1);
        self.indent(depth);
        self.out.push('}');
    }

    /// A rule body: only declarations, same braces.
    fn emit_decl_block(&mut self, decls: &[Decl], end: usize, depth: usize) {
        if decls.is_empty() && !self.has_comment_in(self.cursor, end) {
            self.out.push_str(" {}");
            self.cursor = end;
            return;
        }
        if self.try_inline(decls, &[], end) {
            return;
        }
        self.out.push_str(" {\n");
        let refs: Vec<&Decl> = decls.iter().collect();
        self.emit_grouped_decls(&refs, depth + 1);
        self.emit_trivia_before(end, depth + 1);
        self.indent(depth);
        self.out.push('}');
    }

    // ───────── Wires ─────────

    fn emit_wire(&mut self, w: &Wire, depth: usize) {
        self.indent(depth);
        for (i, group) in w.chain.iter().enumerate() {
            if i > 0 {
                self.out.push(' ');
                self.out.push_str(&wire_op_str(w.op));
                self.out.push(' ');
            }
            for (j, ep) in group.endpoints.iter().enumerate() {
                if j > 0 {
                    self.out.push_str(" & ");
                }
                self.emit_endpoint(ep);
            }
        }
        for class in &w.classes {
            self.out.push_str(" .");
            self.out.push_str(class);
        }
        if let Some(block) = &w.block
            && !self.try_trailing_labels(&block.labels, block.decls.is_empty(), w.span.end)
        {
            self.emit_wire_block(block, w.span.end, depth);
        }
    }

    fn emit_endpoint(&mut self, ep: &Endpoint) {
        self.out.push_str(&ep.path.join("."));
        if let Some(side) = ep.side {
            self.out.push('.');
            self.out.push_str(side_str(side));
        }
    }

    fn emit_wire_block(&mut self, block: &WireBlock, end: usize, depth: usize) {
        let empty = block.decls.is_empty() && block.labels.is_empty();
        if empty && !self.has_comment_in(self.cursor, end) {
            self.out.push_str(" {}");
            self.cursor = end;
            return;
        }
        let has_box = block.labels.iter().any(|c| matches!(c, Child::Box(_)));
        if !has_box {
            let texts = text_strs(&block.labels);
            if self.try_inline(&block.decls, &texts, end) {
                return;
            }
        }
        self.out.push_str(" {\n");
        let decls: Vec<&Decl> = block.decls.iter().collect();
        self.emit_grouped_decls(&decls, depth + 1);
        self.emit_children(&block.labels, depth + 1);
        self.emit_trivia_before(end, depth + 1);
        self.indent(depth);
        self.out.push('}');
    }

    // ───────── Declarations & values ─────────

    fn emit_decl(&mut self, decl: &Decl, is_var: bool) {
        if is_var {
            self.out.push_str("--");
        }
        self.out.push_str(&decl.name);
        self.out.push_str(": ");
        for (i, group) in decl.groups.iter().enumerate() {
            if i > 0 {
                self.out.push_str(", ");
            }
            for (j, v) in group.iter().enumerate() {
                if j > 0 {
                    self.out.push(' ');
                }
                self.emit_value(v);
            }
        }
        self.out.push(';');
    }

    fn emit_value(&mut self, v: &Value) {
        match v {
            Value::Number(n) => self.out.push_str(&format_number(*n)),
            Value::String(s) => self.emit_string(s),
            Value::Hex(h) => {
                self.out.push('#');
                self.out.push_str(h);
            }
            Value::Ident(s) => self.out.push_str(s),
            Value::Var(name) => {
                self.out.push_str("--");
                self.out.push_str(name);
            }
            Value::Call(c) => {
                self.out.push_str(&c.name);
                self.out.push('(');
                for (i, arg) in c.args.iter().enumerate() {
                    if i > 0 {
                        self.out.push_str(", ");
                    }
                    self.emit_value(arg);
                }
                self.out.push(')');
            }
        }
    }

    fn emit_string(&mut self, s: &str) {
        self.out.push_str(&quoted(s));
    }

    // ───────── Trivia ─────────

    fn indent(&mut self, depth: usize) {
        for _ in 0..depth {
            self.out.push_str(INDENT);
        }
    }

    fn has_comment_in(&self, start: usize, end: usize) -> bool {
        self.trivia
            .iter()
            .any(|t| matches!(t.kind, Trivia::Comment(_)) && t.pos >= start && t.pos < end)
    }

    fn emit_trivia_before(&mut self, until: usize, depth: usize) {
        let mut last_was_blank = false;
        for t in self.trivia {
            if t.pos < self.cursor {
                continue;
            }
            if t.pos >= until {
                break;
            }
            match &t.kind {
                Trivia::Comment(text) => {
                    self.indent(depth);
                    self.out.push_str(text);
                    self.out.push('\n');
                    last_was_blank = false;
                }
                Trivia::BlankLine => {
                    if !last_was_blank && !self.out.is_empty() && !self.out.ends_with("\n\n") {
                        self.out.push('\n');
                        last_was_blank = true;
                    }
                }
            }
        }
        self.cursor = until;
    }
}

// ─────────────────────────── Spans & token helpers ───────────────────────────

fn style_item_span(item: &StyleItem) -> Span {
    match item {
        StyleItem::RootDecl(d) | StyleItem::Var(d) => d.span,
        StyleItem::Rule(r) => r.span,
        StyleItem::Define(d) => d.span,
    }
}

fn wire_op_str(op: WireOp) -> String {
    format!(
        "{}{}{}",
        op.start.start_str(),
        op.line.as_str(),
        op.end.end_str()
    )
}

fn side_str(s: Side) -> &'static str {
    match s {
        Side::Top => "top",
        Side::Bottom => "bottom",
        Side::Left => "left",
        Side::Right => "right",
    }
}

fn pad(out: &mut String, n: usize) {
    for _ in 0..n {
        out.push(' ');
    }
}

fn child_span(c: &Child) -> Span {
    match c {
        Child::Box(n) => n.span,
        Child::Text(t) => t.span,
    }
}

/// A string as a Lini double-quoted literal, with the four escapes.
fn quoted(s: &str) -> String {
    let mut out = String::with_capacity(s.len() + 2);
    out.push('"');
    for c in s.chars() {
        match c {
            '"' => out.push_str("\\\""),
            '\\' => out.push_str("\\\\"),
            '\n' => out.push_str("\\n"),
            '\t' => out.push_str("\\t"),
            _ => out.push(c),
        }
    }
    out.push('"');
    out
}

/// The grid column count from a `columns:` declaration — a track list where
/// `repeat(N)` counts as N and every other entry as one. `None` if absent.
fn count_columns(decls: &[Decl]) -> Option<usize> {
    let d = decls.iter().find(|d| d.name == "columns")?;
    let n: usize = d
        .groups
        .iter()
        .flatten()
        .map(|v| match v {
            Value::Call(c) if c.name == "repeat" => c
                .args
                .first()
                .and_then(|a| match a {
                    Value::Number(x) if *x >= 1.0 => Some(*x as usize),
                    _ => None,
                })
                .unwrap_or(1),
            _ => 1,
        })
        .sum();
    (n > 0).then_some(n)
}

/// The bare-text labels among a body's children, in order — used to test whether
/// the body fits inline (boxes are checked separately by the caller).
fn text_strs(children: &[Child]) -> Vec<&str> {
    children
        .iter()
        .filter_map(|c| match c {
            Child::Text(t) => Some(t.text.as_str()),
            Child::Box(_) => None,
        })
        .collect()
}

fn format_number(n: f64) -> String {
    if n.fract() == 0.0 && n.is_finite() && n.abs() < 1e15 {
        format!("{}", n as i64)
    } else {
        format!("{}", n)
    }
}

mod align;

#[cfg(test)]
mod tests;