Make compute functions possible 💻

Ships with the amazing new `rgb` function!

9 files changed, 189 insertions, 115 deletions

diff --git a/src/compute/scope.rs b/src/compute/scope.rs
index 1c297fde..3ab56561 100644
--- a/src/compute/scope.rs
+++ b/src/compute/scope.rs
@@ -8,16 +8,14 @@ use super::value::FuncValue;
 /// A map from identifiers to functions.
 pub struct Scope {
     functions: HashMap<String, FuncValue>,
-    fallback: FuncValue,
 }
 
 impl Scope {
     // Create a new empty scope with a fallback function that is invoked when no
     // match is found.
-    pub fn new(fallback: FuncValue) -> Self {
+    pub fn new() -> Self {
         Self {
             functions: HashMap::new(),
-            fallback,
         }
     }
 
@@ -30,11 +28,6 @@ impl Scope {
     pub fn func(&self, name: &str) -> Option<&FuncValue> {
         self.functions.get(name)
     }
-
-    /// Return the fallback function.
-    pub fn fallback(&self) -> &FuncValue {
-        &self.fallback
-    }
 }
 
 impl Debug for Scope {
diff --git a/src/compute/table.rs b/src/compute/table.rs
index e8c4b307..bb71d4f2 100644
--- a/src/compute/table.rs
+++ b/src/compute/table.rs
@@ -115,6 +115,17 @@ impl<V> Table<V> {
         self.lowest_free += 1;
     }
 
+    /// Iterator over all borrowed keys and values.
+    pub fn iter(&self) -> impl Iterator<Item = (BorrowedKey, &V)> {
+        self.nums().map(|(&k, v)| (BorrowedKey::Num(k), v))
+            .chain(self.strs().map(|(k, v)| (BorrowedKey::Str(k), v)))
+    }
+
+    /// Iterate over all values in the table.
+    pub fn values(&self) -> impl Iterator<Item = &V> {
+        self.nums().map(|(_, v)| v).chain(self.strs().map(|(_, v)| v))
+    }
+
     /// Iterate over the number key-value pairs.
     pub fn nums(&self) -> std::collections::btree_map::Iter<u64, V> {
         self.nums.iter()
@@ -125,9 +136,16 @@ impl<V> Table<V> {
         self.strs.iter()
     }
 
-    /// Iterate over all values in the table.
-    pub fn values(&self) -> impl Iterator<Item = &V> {
-        self.nums().map(|(_, v)| v).chain(self.strs().map(|(_, v)| v))
+    /// Move into an owned iterator over owned keys and values.
+    pub fn into_iter(self) -> impl Iterator<Item = (OwnedKey, V)> {
+        self.nums.into_iter().map(|(k, v)| (OwnedKey::Num(k), v))
+            .chain(self.strs.into_iter().map(|(k, v)| (OwnedKey::Str(k), v)))
+    }
+
+    /// Move into an owned iterator over all values in the table.
+    pub fn into_values(self) -> impl Iterator<Item = V> {
+        self.nums.into_iter().map(|(_, v)| v)
+            .chain(self.strs.into_iter().map(|(_, v)| v))
     }
 
     /// Iterate over the number key-value pairs.
@@ -139,12 +157,6 @@ impl<V> Table<V> {
     pub fn into_strs(self) -> std::collections::btree_map::IntoIter<String, V> {
         self.strs.into_iter()
     }
-
-    /// Move into an owned iterator over all values in the table.
-    pub fn into_values(self) -> impl Iterator<Item = V> {
-        self.nums.into_iter().map(|(_, v)| v)
-            .chain(self.strs.into_iter().map(|(_, v)| v))
-    }
 }
 
 impl<'a, K, V> Index<K> for Table<V>
@@ -168,7 +180,7 @@ impl<V: Eq> Eq for Table<V> {}
 
 impl<V: PartialEq> PartialEq for Table<V> {
     fn eq(&self, other: &Self) -> bool {
-        self.nums().eq(other.nums()) && self.strs().eq(other.strs())
+        self.iter().eq(other.iter())
     }
 }
 
@@ -218,6 +230,15 @@ pub enum OwnedKey {
     Str(String),
 }
 
+impl From<BorrowedKey<'_>> for OwnedKey {
+    fn from(key: BorrowedKey<'_>) -> Self {
+        match key {
+            BorrowedKey::Num(num) => Self::Num(num),
+            BorrowedKey::Str(string) => Self::Str(string.to_string()),
+        }
+    }
+}
+
 impl From<u64> for OwnedKey {
     fn from(num: u64) -> Self {
         Self::Num(num)
diff --git a/src/compute/value.rs b/src/compute/value.rs
index 32f2778b..c11a3d31 100644
--- a/src/compute/value.rs
+++ b/src/compute/value.rs
@@ -7,11 +7,11 @@ use std::rc::Rc;
 use fontdock::{FontStyle, FontWeight, FontWidth};
 
 use crate::color::RgbaColor;
-use crate::layout::{Commands, Dir, LayoutContext, SpecAlign};
+use crate::layout::{Command, Commands, Dir, LayoutContext, SpecAlign};
 use crate::length::{Length, ScaleLength};
 use crate::paper::Paper;
 use crate::syntax::span::{Span, Spanned};
-use crate::syntax::tree::SyntaxTree;
+use crate::syntax::tree::{SyntaxTree, SyntaxNode};
 use crate::syntax::Ident;
 use crate::{DynFuture, Feedback, Pass};
 use super::table::{SpannedEntry, Table};
@@ -61,6 +61,47 @@ impl Value {
     }
 }
 
+impl Spanned<Value> {
+    /// Transform this value into something layoutable.
+    ///
+    /// If this is already a command-value, it is simply unwrapped, otherwise
+    /// the value is represented as layoutable content in a reasonable way.
+    pub fn into_commands(self) -> Commands {
+        match self.v {
+            Value::Commands(commands) => commands,
+            Value::Tree(tree) => vec![Command::LayoutSyntaxTree(tree)],
+
+            // Forward to each entry, separated with spaces.
+            Value::Table(table) => {
+                let mut commands = vec![];
+                let mut end = None;
+                for entry in table.into_values() {
+                    if let Some(last_end) = end {
+                        let span = Span::new(last_end, entry.key.start);
+                        commands.push(Command::LayoutSyntaxTree(vec![
+                            Spanned::new(SyntaxNode::Spacing, span)
+                        ]));
+                    }
+
+                    end = Some(entry.val.span.end);
+                    commands.extend(entry.val.into_commands());
+                }
+                commands
+            }
+
+            // Format with debug.
+            val => vec![
+                Command::LayoutSyntaxTree(vec![
+                    Spanned::new(
+                        SyntaxNode::Text(format!("{:?}", val)),
+                        self.span,
+                    )
+                ])
+            ],
+        }
+    }
+}
+
 impl Debug for Value {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         use Value::*;
diff --git a/src/layout/mod.rs b/src/layout/mod.rs
index 837c19ec..efb2f169 100644
--- a/src/layout/mod.rs
+++ b/src/layout/mod.rs
@@ -45,7 +45,7 @@ pub struct BoxLayout {
 }
 
 /// The context for layouting.
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct LayoutContext<'a> {
     /// The font loader to query fonts from when typesetting text.
     pub loader: &'a SharedFontLoader,
diff --git a/src/layout/tree.rs b/src/layout/tree.rs
index f132a8cb..e500c4ba 100644
--- a/src/layout/tree.rs
+++ b/src/layout/tree.rs
@@ -1,6 +1,5 @@
 //! Layouting of syntax trees.
 
-use crate::compute::value::Value;
 use crate::style::LayoutStyle;
 use crate::syntax::decoration::Decoration;
 use crate::syntax::span::{Span, Spanned};
@@ -62,12 +61,7 @@ impl<'a> TreeLayouter<'a> {
         };
 
         match &node.v {
-            SyntaxNode::Spacing => {
-                self.layouter.add_primary_spacing(
-                    self.style.text.word_spacing(),
-                    SpacingKind::WORD,
-                );
-            }
+            SyntaxNode::Spacing => self.layout_space(),
             SyntaxNode::Linebreak => self.layouter.finish_line(),
 
             SyntaxNode::ToggleItalic => {
@@ -93,45 +87,11 @@ impl<'a> TreeLayouter<'a> {
         }
     }
 
-    async fn layout_par(&mut self, par: &SyntaxTree) {
-        self.layouter.add_secondary_spacing(
-            self.style.text.paragraph_spacing(),
-            SpacingKind::PARAGRAPH,
+    fn layout_space(&mut self) {
+        self.layouter.add_primary_spacing(
+            self.style.text.word_spacing(),
+            SpacingKind::WORD,
         );
-
-        self.layout_tree(par).await;
-    }
-
-    async fn layout_call(&mut self, call: Spanned<&CallExpr>) {
-        let name = call.v.name.v.as_str();
-        let span = call.v.name.span;
-
-        let (func, deco) = if let Some(func) = self.ctx.scope.func(name) {
-            (func, Decoration::Resolved)
-        } else {
-            error!(@self.feedback, span, "unknown function");
-            (self.ctx.scope.fallback(), Decoration::Unresolved)
-        };
-
-        self.feedback.decorations.push(Spanned::new(deco, span));
-
-        let args = call.v.args.eval();
-        let pass = func(span, args, LayoutContext {
-            style: &self.style,
-            spaces: self.layouter.remaining(),
-            root: true,
-            ..self.ctx
-        }).await;
-
-        self.feedback.extend(pass.feedback);
-
-        if let Value::Commands(commands) = pass.output {
-            for command in commands {
-                self.execute_command(command, call.span).await;
-            }
-        } else {
-            self.layout_raw(&[format!("{:?}", pass.output)]).await;
-        }
     }
 
     async fn layout_text(&mut self, text: &str) {
@@ -154,24 +114,44 @@ impl<'a> TreeLayouter<'a> {
         self.style.text.fallback
             .list_mut()
             .insert(0, "monospace".to_string());
-
         self.style.text.fallback.flatten();
 
-        // Layout the first line.
-        let mut iter = lines.iter();
-        if let Some(line) = iter.next() {
-            self.layout_text(line).await;
-        }
-
-        // Put a newline before each following line.
-        for line in iter {
-            self.layouter.finish_line();
+        let mut first = true;
+        for line in lines {
+            if !first {
+                self.layouter.finish_line();
+            }
+            first = false;
             self.layout_text(line).await;
         }
 
         self.style.text.fallback = fallback;
     }
 
+    async fn layout_par(&mut self, par: &SyntaxTree) {
+        self.layout_tree(par).await;
+        self.layouter.add_secondary_spacing(
+            self.style.text.paragraph_spacing(),
+            SpacingKind::PARAGRAPH,
+        );
+    }
+
+    async fn layout_call(&mut self, call: Spanned<&CallExpr>) {
+        let ctx = LayoutContext {
+            style: &self.style,
+            spaces: self.layouter.remaining(),
+            root: false,
+            ..self.ctx
+        };
+
+        let val = call.v.eval(&ctx, &mut self.feedback).await;
+        let commands = Spanned::new(val, call.span).into_commands();
+
+        for command in commands {
+            self.execute_command(command, call.span).await;
+        }
+    }
+
     async fn execute_command(&mut self, command: Command, span: Span) {
         use Command::*;
 
diff --git a/src/library/color.rs b/src/library/color.rs
new file mode 100644
index 00000000..eab84fd0
--- /dev/null
+++ b/src/library/color.rs
@@ -0,0 +1,26 @@
+use crate::color::RgbaColor;
+use super::*;
+
+/// `rgb`: Create an RGB(A) color.
+pub async fn rgb(span: Span, mut args: TableValue, _: LayoutContext<'_>) -> Pass<Value> {
+    let mut f = Feedback::new();
+
+    let color = RgbaColor::new(
+        clamp(args.expect::<Spanned<f64>>("red value", span, &mut f), &mut f),
+        clamp(args.expect::<Spanned<f64>>("green value", span, &mut f), &mut f),
+        clamp(args.expect::<Spanned<f64>>("blue value", span, &mut f), &mut f),
+        clamp(args.take::<Spanned<f64>>(), &mut f),
+    );
+
+    args.unexpected(&mut f);
+    Pass::new(Value::Color(color), f)
+}
+
+fn clamp(component: Option<Spanned<f64>>, f: &mut Feedback) -> u8 {
+    component.map(|c| {
+        if c.v < 0.0 || c.v > 255.0 {
+            error!(@f, c.span, "should be between 0 and 255")
+        }
+        c.v.min(255.0).max(0.0).round() as u8
+    }).unwrap_or_default()
+}
diff --git a/src/library/mod.rs b/src/library/mod.rs
index eaab72fc..7d266eb5 100644
--- a/src/library/mod.rs
+++ b/src/library/mod.rs
@@ -2,12 +2,14 @@
 
 mod align;
 mod boxed;
+mod color;
 mod font;
 mod page;
 mod spacing;
 
 pub use align::*;
 pub use boxed::*;
+pub use color::*;
 pub use font::*;
 pub use page::*;
 pub use spacing::*;
@@ -18,10 +20,10 @@ use crate::compute::scope::Scope;
 use crate::prelude::*;
 
 macro_rules! std {
-    (fallback: $fallback:expr $(, $name:literal => $func:expr)* $(,)?) => {
+    ($($name:literal => $func:expr),* $(,)?) => {
         /// Create a scope with all standard library functions.
         pub fn _std() -> Scope {
-            let mut std = Scope::new(wrap!(val));
+            let mut std = Scope::new();
             $(std.insert($name, wrap!($func));)*
             std
         }
@@ -35,32 +37,12 @@ macro_rules! wrap {
 }
 
 std! {
-    fallback: val,
     "align" => align,
     "box" => boxed,
-    "dump" => dump,
     "font" => font,
     "h" => h,
     "page" => page,
     "pagebreak" => pagebreak,
+    "rgb" => rgb,
     "v" => v,
-    "val" => val,
-}
-
-/// `val`: Layouts its body flatly, ignoring other arguments.
-///
-/// This is also the fallback function, which is used when a function name
-/// cannot be resolved.
-pub async fn val(_: Span, mut args: TableValue, _: LayoutContext<'_>) -> Pass<Value> {
-    let commands = match args.take::<SyntaxTree>() {
-        Some(tree) => vec![LayoutSyntaxTree(tree)],
-        None => vec![],
-    };
-
-    Pass::commands(commands, Feedback::new())
-}
-
-/// `dump`: Dumps its arguments into the document.
-pub async fn dump(_: Span, args: TableValue, _: LayoutContext<'_>) -> Pass<Value> {
-    Pass::okay(Value::Table(args))
 }
diff --git a/src/syntax/tokens.rs b/src/syntax/tokens.rs
index 2d371bf8..a27ef982 100644
--- a/src/syntax/tokens.rs
+++ b/src/syntax/tokens.rs
@@ -252,10 +252,9 @@ impl<'s> Iterator for Tokens<'s> {
                 let text = self.read_string_until(|n| {
                     let val = match n {
                         c if c.is_whitespace() => true,
-                        '['  | ']' | '/' | '*' => true,
+                        '['  | ']' | '{' | '}' | '/' | '*' => true,
                         '\\' | '_' | '`' if body => true,
-                        ':'  | '=' | ',' | '"' |
-                        '('  | ')' | '{' | '}' if !body => true,
+                        ':'  | '=' | ',' | '"' | '('  | ')' if !body => true,
                         '+'  | '-' if !body && !last_was_e => true,
                         _ => false,
                     };
diff --git a/src/syntax/tree.rs b/src/syntax/tree.rs
index e7a1eaf1..47c79117 100644
--- a/src/syntax/tree.rs
+++ b/src/syntax/tree.rs
@@ -5,7 +5,10 @@ use std::fmt::{self, Debug, Formatter};
 use crate::color::RgbaColor;
 use crate::compute::table::{SpannedEntry, Table};
 use crate::compute::value::{TableValue, Value};
+use crate::layout::LayoutContext;
 use crate::length::Length;
+use crate::{DynFuture, Feedback};
+use super::decoration::Decoration;
 use super::span::{Spanned, SpanVec};
 use super::Ident;
 
@@ -91,7 +94,11 @@ impl Expr {
     }
 
     /// Evaluate the expression to a value.
-    pub fn eval(&self) -> Value {
+    pub async fn eval(
+        &self,
+        ctx: &LayoutContext<'_>,
+        f: &mut Feedback,
+    ) -> Value {
         use Expr::*;
         match self {
             Ident(i) => Value::Ident(i.clone()),
@@ -100,9 +107,9 @@ impl Expr {
             &Number(n) => Value::Number(n),
             &Length(s) => Value::Length(s),
             &Color(c) => Value::Color(c),
-            Table(t) => Value::Table(t.eval()),
+            Table(t) => Value::Table(t.eval(ctx, f).await),
             Tree(t) => Value::Tree(t.clone()),
-            Call(_) => todo!("eval call"),
+            Call(call) => call.eval(ctx, f).await,
             Neg(_) => todo!("eval neg"),
             Add(_, _) => todo!("eval add"),
             Sub(_, _) => todo!("eval sub"),
@@ -144,18 +151,23 @@ pub type TableExpr = Table<SpannedEntry<Expr>>;
 
 impl TableExpr {
     /// Evaluate the table expression to a table value.
-    pub fn eval(&self) -> TableValue {
-        let mut table = TableValue::new();
+    pub fn eval<'a>(
+        &'a self,
+        ctx: &'a LayoutContext<'a>,
+        f: &'a mut Feedback,
+    ) -> DynFuture<'a, TableValue> {
+        Box::pin(async move {
+            let mut table = TableValue::new();
 
-        for (&key, entry) in self.nums() {
-            table.insert(key, entry.as_ref().map(|val| val.eval()));
-        }
-
-        for (key, entry) in self.strs() {
-            table.insert(key.clone(), entry.as_ref().map(|val| val.eval()));
-        }
+            for (key, entry) in self.iter() {
+                let val = entry.val.v.eval(ctx, f).await;
+                let spanned = Spanned::new(val, entry.val.span);
+                let entry = SpannedEntry::new(entry.key, spanned);
+                table.insert(key, entry);
+            }
 
-        table
+            table
+        })
     }
 }
 
@@ -165,3 +177,23 @@ pub struct CallExpr {
     pub name: Spanned<Ident>,
     pub args: TableExpr,
 }
+
+impl CallExpr {
+    /// Evaluate the call expression to a value.
+    pub async fn eval(&self, ctx: &LayoutContext<'_>, f: &mut Feedback) -> Value {
+        let name = self.name.v.as_str();
+        let span = self.name.span;
+        let args = self.args.eval(ctx, f).await;
+
+        if let Some(func) = ctx.scope.func(name) {
+            let pass = func(span, args, ctx.clone()).await;
+            f.extend(pass.feedback);
+            f.decorations.push(Spanned::new(Decoration::Resolved, span));
+            pass.output
+        } else {
+            error!(@f, span, "unknown function");
+            f.decorations.push(Spanned::new(Decoration::Unresolved, span));
+            Value::Table(args)
+        }
+    }
+}