Non-fatal argument parsing 🌋

1 files changed, 121 insertions, 0 deletions

diff --git a/src/syntax/func/keys.rs b/src/syntax/func/keys.rs
new file mode 100644
index 00000000..dff97bde
--- /dev/null
+++ b/src/syntax/func/keys.rs
@@ -0,0 +1,121 @@
+use crate::layout::prelude::*;
+use super::*;
+
+use AxisKey::*;
+use PaddingKey::*;
+use AlignmentValue::*;
+
+
+pub trait Key {
+    type Output: Eq;
+
+    fn parse(key: Spanned<&str>) -> Option<Self::Output>;
+}
+
+impl<K: Key> Key for Spanned<K> {
+    type Output = Spanned<K::Output>;
+
+    fn parse(key: Spanned<&str>) -> Option<Self::Output> {
+        K::parse(key).map(|v| Spanned { v, span: key.span })
+    }
+}
+
+macro_rules! key {
+    ($type:ty, $output:ty, $($($p:pat)|* => $r:expr),* $(,)?) => {
+        impl Key for $type {
+            type Output = $output;
+
+            fn parse(key: Spanned<&str>) -> Option<Self::Output> {
+                match key.v {
+                    $($($p)|* => Some($r)),*,
+                    other => None,
+                }
+            }
+        }
+    };
+}
+
+/// An argument key which identifies a layouting axis.
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+pub enum AxisKey {
+    Generic(GenericAxis),
+    Specific(SpecificAxis),
+}
+
+impl AxisKey {
+    /// The generic version of this axis key in the given system of axes.
+    pub fn to_generic(self, axes: LayoutAxes) -> GenericAxis {
+        match self {
+            Generic(axis) => axis,
+            Specific(axis) => axis.to_generic(axes),
+        }
+    }
+
+    /// The specific version of this axis key in the given system of axes.
+    pub fn to_specific(self, axes: LayoutAxes) -> SpecificAxis {
+        match self {
+            Generic(axis) => axis.to_specific(axes),
+            Specific(axis) => axis,
+        }
+    }
+}
+
+key!(AxisKey, Self,
+    "horizontal" | "h" => Specific(Horizontal),
+    "vertical"   | "v" => Specific(Vertical),
+    "primary"    | "p" => Generic(Primary),
+    "secondary"  | "s" => Generic(Secondary),
+);
+
+pub struct ExtentKey;
+
+key!(ExtentKey, AxisKey,
+    "width"          | "w"  => Specific(Horizontal),
+    "height"         | "h"  => Specific(Vertical),
+    "primary-size"   | "ps" => Generic(Primary),
+    "secondary-size" | "ss" => Generic(Secondary),
+);
+
+/// An argument key which identifies an axis, but allows for positional
+/// arguments with unspecified axes.
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+pub enum PosAxisKey {
+    /// The first positional argument.
+    First,
+    /// The second positional argument.
+    Second,
+    /// An axis keyword argument.
+    Keyword(AxisKey),
+}
+
+/// An argument key which identifies a margin or padding target.
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+pub enum PaddingKey<Axis> {
+    /// All four sides should have the specified padding.
+    All,
+    /// Both sides of the given axis should have the specified padding.
+    Both(Axis),
+    /// Only the given side of the given axis should have the specified padding.
+    Side(Axis, AlignmentValue),
+}
+
+key!(PaddingKey<AxisKey>, Self,
+    "horizontal" | "h" => Both(Specific(Horizontal)),
+    "vertical"   | "v" => Both(Specific(Vertical)),
+    "primary"    | "p" => Both(Generic(Primary)),
+    "secondary"  | "s" => Both(Generic(Secondary)),
+
+    "left"   => Side(Specific(Horizontal), Left),
+    "right"  => Side(Specific(Horizontal), Right),
+    "top"    => Side(Specific(Vertical),   Top),
+    "bottom" => Side(Specific(Vertical),   Bottom),
+
+    "primary-origin"    => Side(Generic(Primary),     Align(Origin)),
+    "primary-end"       => Side(Generic(Primary),     Align(End)),
+    "secondary-origin"  => Side(Generic(Secondary),   Align(Origin)),
+    "secondary-end"     => Side(Generic(Secondary),   Align(End)),
+    "horizontal-origin" => Side(Specific(Horizontal), Align(Origin)),
+    "horizontal-end"    => Side(Specific(Horizontal), Align(End)),
+    "vertical-origin"   => Side(Specific(Vertical),   Align(Origin)),
+    "vertical-end"      => Side(Specific(Vertical),   Align(End)),
+);