drawlang-syntax 0.1.2

//! Canonical formatter. One statement per line, two-space indent, comments
//! preserved, at most one consecutive blank line. Idempotent:
//! `fmt(fmt(x)) == fmt(x)`.
//!
//! Leaf values (strings, numbers, expressions, paths) are reprinted from
//! their source spans, so escapes and interpolations round-trip exactly.

use crate::ast::*;
use crate::span::Span;

const INLINE_MAX: usize = 80;

pub fn format(file: &File, src: &str) -> String {
    let f = Formatter { src };
    let mut out = String::new();
    let version = file
        .header
        .as_ref()
        .map(|h| h.version.as_str())
        .unwrap_or("0.1");
    out.push_str(&format!("drawl {version}\n"));

    let mut first = true;
    for stmt in &file.stmts {
        // Top-level statements get a blank line between them by default;
        // consecutive property-like lines stay together if the author had
        // no blank line and no comments.
        let want_blank = if first {
            true
        } else {
            stmt.trivia.blank_before || !stmt.trivia.leading.is_empty() || is_block_stmt(stmt)
        };
        if want_blank {
            out.push('\n');
        }
        first = false;
        f.write_stmt(&mut out, stmt, 0);
    }
    // Exactly one trailing newline.
    while out.ends_with("\n\n") {
        out.pop();
    }
    if !out.ends_with('\n') {
        out.push('\n');
    }
    out
}

fn is_block_stmt(stmt: &Stmt) -> bool {
    matches!(
        stmt.kind,
        StmtKind::Canvas(_)
            | StmtKind::Def(_)
            | StmtKind::Group(_)
            | StmtKind::Class(_)
            | StmtKind::Constrain(_)
            | StmtKind::For(_)
    )
}

struct Formatter<'a> {
    src: &'a str,
}

impl<'a> Formatter<'a> {
    fn snip(&self, span: Span) -> &str {
        let s = span.start.min(self.src.len());
        let e = span.end.min(self.src.len());
        self.src[s..e].trim()
    }

    fn write_stmt(&self, out: &mut String, stmt: &Stmt, depth: usize) {
        let indent = "  ".repeat(depth);
        for c in &stmt.trivia.leading {
            out.push_str(&indent);
            if c.is_empty() {
                out.push_str("//\n");
            } else {
                out.push_str(&format!("// {c}\n"));
            }
        }
        // Orphan-comment sentinel: comments only, no statement.
        if let StmtKind::Prop(p) = &stmt.kind {
            if p.key.is_empty() {
                return;
            }
        }

        let trailing = stmt
            .trivia
            .trailing
            .as_ref()
            .map(|c| format!(" // {c}"))
            .unwrap_or_default();

        match &stmt.kind {
            StmtKind::Canvas(block) => {
                out.push_str(&format!("{indent}canvas {{\n"));
                self.write_block_stmts(out, block, depth + 1);
                out.push_str(&format!("{indent}}}{trailing}\n"));
            }
            StmtKind::Def(d) => {
                let params: Vec<&str> = d.params.iter().map(|p| p.name.as_str()).collect();
                out.push_str(&format!(
                    "{indent}def {}({}) {{\n",
                    d.name.name,
                    params.join(", ")
                ));
                self.write_block_stmts(out, &d.body, depth + 1);
                out.push_str(&format!("{indent}}}{trailing}\n"));
            }
            StmtKind::Group(g) => {
                let label = g
                    .label
                    .as_ref()
                    .map(|l| format!(" {}", self.snip(l.span)))
                    .unwrap_or_default();
                out.push_str(&format!("{indent}group {}{label} {{\n", g.name.name));
                self.write_block_stmts(out, &g.body, depth + 1);
                out.push_str(&format!("{indent}}}{trailing}\n"));
            }
            StmtKind::Class(c) => {
                if let Some(line) = self.inline_block(&c.body) {
                    out.push_str(&format!("{indent}class {} {line}{trailing}\n", c.name.name));
                } else {
                    out.push_str(&format!("{indent}class {} {{\n", c.name.name));
                    self.write_block_stmts(out, &c.body, depth + 1);
                    out.push_str(&format!("{indent}}}{trailing}\n"));
                }
            }
            StmtKind::Constrain(cs) => {
                out.push_str(&format!("{indent}constrain {{\n"));
                let inner = "  ".repeat(depth + 1);
                for c in cs {
                    for lc in &c.trivia.leading {
                        out.push_str(&format!("{inner}// {lc}\n"));
                    }
                    let t = c
                        .trivia
                        .trailing
                        .as_ref()
                        .map(|x| format!(" // {x}"))
                        .unwrap_or_default();
                    out.push_str(&format!("{inner}{}{t}\n", self.snip(c.span)));
                }
                out.push_str(&format!("{indent}}}{trailing}\n"));
            }
            StmtKind::Pin(p) => {
                out.push_str(&format!(
                    "{indent}pin {} at ({}, {}){trailing}\n",
                    self.snip(p.target.span),
                    self.snip(p.x.span),
                    self.snip(p.y.span)
                ));
            }
            StmtKind::For(f) => {
                if let Some(line) = self.inline_for(f) {
                    if indent.len() + line.len() <= INLINE_MAX {
                        out.push_str(&format!("{indent}{line}{trailing}\n"));
                        return;
                    }
                }
                out.push_str(&format!(
                    "{indent}for {} in {}..{} {{\n",
                    f.var.name,
                    self.snip(f.start.span),
                    self.snip(f.end.span)
                ));
                self.write_block_stmts(out, &f.body, depth + 1);
                out.push_str(&format!("{indent}}}{trailing}\n"));
            }
            StmtKind::Port(p) => {
                if let Some(line) = self.inline_block(&p.body) {
                    out.push_str(&format!("{indent}port {} {line}{trailing}\n", p.name.name));
                } else {
                    out.push_str(&format!("{indent}port {} {{\n", p.name.name));
                    self.write_block_stmts(out, &p.body, depth + 1);
                    out.push_str(&format!("{indent}}}{trailing}\n"));
                }
            }
            StmtKind::Prop(p) => {
                out.push_str(&format!("{indent}{}{trailing}\n", self.prop_line(p)));
            }
            StmtKind::Node(n) => {
                if let Some(line) = self.inline_node(n) {
                    if indent.len() + line.len() <= INLINE_MAX {
                        out.push_str(&format!("{indent}{line}{trailing}\n"));
                        return;
                    }
                }
                self.write_node_multiline(out, n, depth, &trailing);
            }
            StmtKind::Edge(e) => {
                let op = match e.op {
                    EdgeOp::Forward => "->",
                    EdgeOp::Bidirectional => "<->",
                };
                let label = e
                    .label
                    .as_ref()
                    .map(|l| format!(" : {}", self.snip(l.span)))
                    .unwrap_or_default();
                let props = match &e.props {
                    Some(b) => match self.inline_block(b) {
                        Some(line) => format!(" {line}"),
                        None => format!(" {}", self.snip(b.span)),
                    },
                    None => String::new(),
                };
                out.push_str(&format!(
                    "{indent}{} {op} {}{label}{props}{trailing}\n",
                    self.snip(e.from.span),
                    self.snip(e.to.span)
                ));
            }
        }
    }

    fn write_block_stmts(&self, out: &mut String, block: &Block, depth: usize) {
        let mut first = true;
        for stmt in &block.stmts {
            if !first && (stmt.trivia.blank_before || !stmt.trivia.leading.is_empty()) {
                out.push('\n');
            }
            first = false;
            self.write_stmt(out, stmt, depth);
        }
    }

    fn write_node_multiline(&self, out: &mut String, n: &Node, depth: usize, trailing: &str) {
        let indent = "  ".repeat(depth);
        match &n.kind {
            NodeKind::Plain { body } => {
                let name = n.name.as_ref().expect("plain nodes are named");
                if body.stmts.is_empty() {
                    out.push_str(&format!("{indent}{}{trailing}\n", name.name));
                    return;
                }
                out.push_str(&format!("{indent}{} {{\n", name.name));
                self.write_block_stmts(out, body, depth + 1);
                out.push_str(&format!("{indent}}}{trailing}\n"));
            }
            NodeKind::Container { ctype, body, .. } => {
                let name = n.name.as_ref().expect("containers are named");
                let kw = match ctype {
                    ContainerType::Row => "row".to_string(),
                    ContainerType::Column => "column".to_string(),
                    ContainerType::Grid { cols, rows } => format!("grid {cols}x{rows}"),
                };
                out.push_str(&format!("{indent}{}: {kw} {{\n", name.name));
                self.write_block_stmts(out, body, depth + 1);
                out.push_str(&format!("{indent}}}{trailing}\n"));
            }
            NodeKind::Call { callee, args, body } => {
                let args: Vec<&str> = args.iter().map(|a| self.snip(a.span)).collect();
                let head = match &n.name {
                    Some(name) => format!("{}: {}({})", name.name, callee.name, args.join(", ")),
                    None => format!("{}({})", callee.name, args.join(", ")),
                };
                match body {
                    Some(b) if !b.stmts.is_empty() => {
                        out.push_str(&format!("{indent}{head} {{\n"));
                        self.write_block_stmts(out, b, depth + 1);
                        out.push_str(&format!("{indent}}}{trailing}\n"));
                    }
                    _ => out.push_str(&format!("{indent}{head}{trailing}\n")),
                }
            }
        }
    }

    fn prop_line(&self, p: &Prop) -> String {
        let key: Vec<&str> = p.key.iter().map(|k| k.name.as_str()).collect();
        format!("{}: {}", key.join("."), self.snip(p.value.span()))
    }

    /// `{ a: 1; b: 2 }` if the block is only 1–2 comment-free properties.
    fn inline_block(&self, block: &Block) -> Option<String> {
        if block.stmts.is_empty() {
            return None;
        }
        if block.stmts.len() > 2 {
            return None;
        }
        let mut parts = Vec::new();
        for s in &block.stmts {
            if !s.trivia.leading.is_empty() || s.trivia.trailing.is_some() {
                return None;
            }
            match &s.kind {
                StmtKind::Prop(p) if !p.key.is_empty() => parts.push(self.prop_line(p)),
                _ => return None,
            }
        }
        let line = format!("{{ {} }}", parts.join("; "));
        (line.len() <= INLINE_MAX - 10).then_some(line)
    }

    /// `name { label: "x" }`, `name`, `gpu(i)`, or `g0: gpu(0)`.
    fn inline_node(&self, n: &Node) -> Option<String> {
        match &n.kind {
            NodeKind::Plain { body } => {
                let name = n.name.as_ref()?;
                if body.stmts.is_empty() {
                    return Some(name.name.clone());
                }
                // Inline only when every stmt is a prop or a port that fits.
                if body.stmts.len() > 2 {
                    return None;
                }
                let mut parts = Vec::new();
                for s in &body.stmts {
                    if !s.trivia.leading.is_empty() || s.trivia.trailing.is_some() {
                        return None;
                    }
                    match &s.kind {
                        StmtKind::Prop(p) if !p.key.is_empty() => parts.push(self.prop_line(p)),
                        StmtKind::Port(p) => {
                            let inner = self.inline_block(&p.body)?;
                            parts.push(format!("port {} {inner}", p.name.name));
                        }
                        _ => return None,
                    }
                }
                Some(format!("{} {{ {} }}", name.name, parts.join("; ")))
            }
            NodeKind::Container { ctype, body, .. } => {
                let name = n.name.as_ref()?;
                if body.stmts.len() != 1 {
                    return None;
                }
                let inner_stmt = &body.stmts[0];
                if !inner_stmt.trivia.leading.is_empty() || inner_stmt.trivia.trailing.is_some() {
                    return None;
                }
                let inner = match &inner_stmt.kind {
                    StmtKind::For(f) => self.inline_for(f)?,
                    StmtKind::Node(inner_n) => self.inline_node(inner_n)?,
                    _ => return None,
                };
                let kw = match ctype {
                    ContainerType::Row => "row".to_string(),
                    ContainerType::Column => "column".to_string(),
                    ContainerType::Grid { cols, rows } => format!("grid {cols}x{rows}"),
                };
                Some(format!("{}: {kw} {{ {inner} }}", name.name))
            }
            NodeKind::Call { callee, args, body } => {
                let args: Vec<&str> = args.iter().map(|a| self.snip(a.span)).collect();
                let head = match &n.name {
                    Some(name) => format!("{}: {}({})", name.name, callee.name, args.join(", ")),
                    None => format!("{}({})", callee.name, args.join(", ")),
                };
                match body {
                    None => Some(head),
                    Some(b) if b.stmts.is_empty() => Some(head),
                    Some(b) => {
                        let inner = self.inline_block(b)?;
                        Some(format!("{head} {inner}"))
                    }
                }
            }
        }
    }

    fn inline_for(&self, f: &For) -> Option<String> {
        if f.body.stmts.len() != 1 {
            return None;
        }
        let s = &f.body.stmts[0];
        if !s.trivia.leading.is_empty() || s.trivia.trailing.is_some() {
            return None;
        }
        let inner = match &s.kind {
            StmtKind::Node(n) => self.inline_node(n)?,
            StmtKind::Edge(e) => {
                let op = match e.op {
                    EdgeOp::Forward => "->",
                    EdgeOp::Bidirectional => "<->",
                };
                let label = e
                    .label
                    .as_ref()
                    .map(|l| format!(" : {}", self.snip(l.span)))
                    .unwrap_or_default();
                let props = match &e.props {
                    Some(b) => format!(" {}", self.inline_block(b)?),
                    None => String::new(),
                };
                format!(
                    "{} {op} {}{label}{props}",
                    self.snip(e.from.span),
                    self.snip(e.to.span)
                )
            }
            _ => return None,
        };
        Some(format!(
            "for {} in {}..{} {{ {inner} }}",
            f.var.name,
            self.snip(f.start.span),
            self.snip(f.end.span)
        ))
    }
}