1 files changed, 152 insertions, 0 deletions
diff --git a/src/model/symbol.rs b/src/model/symbol.rs
new file mode 100644
index 00000000..ac1d2b10
--- /dev/null
+++ b/src/model/symbol.rs
@@ -0,0 +1,152 @@
+use std::cmp::Reverse;
+use std::collections::BTreeSet;
+use std::fmt::{self, Debug, Formatter, Write};
+
+use crate::diag::StrResult;
+use crate::util::EcoString;
+
+/// Define a list of symbols.
+#[macro_export]
+#[doc(hidden)]
+macro_rules! __symbols {
+    ($func:ident, $($name:ident: $value:tt),* $(,)?) => {
+        pub(super) fn $func(scope: &mut $crate::model::Scope) {
+            $(scope.define(stringify!($name), $crate::model::symbols!(@one $value));)*
+        }
+    };
+    (@one $c:literal) => { $crate::model::Symbol::new($c) };
+    (@one [$($first:literal $(: $second:literal)?),* $(,)?]) => {
+        $crate::model::Symbol::list(&[
+            $($crate::model::symbols!(@pair $first $(: $second)?)),*
+        ])
+    };
+    (@pair $first:literal) => { ("", $first) };
+    (@pair $first:literal: $second:literal) => { ($first, $second) };
+}
+
+#[doc(inline)]
+pub use crate::__symbols as symbols;
+
+/// A symbol.
+#[derive(Clone, Eq, PartialEq, Hash)]
+pub struct Symbol {
+    repr: Repr,
+    modifiers: EcoString,
+}
+
+/// A collection of symbols.
+#[derive(Clone, Eq, PartialEq, Hash)]
+enum Repr {
+    Single(char),
+    List(&'static [(&'static str, char)]),
+}
+
+impl Symbol {
+    /// Create a new symbol from a single character.
+    pub fn new(c: char) -> Self {
+        Self { repr: Repr::Single(c), modifiers: EcoString::new() }
+    }
+
+    /// Create a symbol with variants.
+    #[track_caller]
+    pub fn list(list: &'static [(&'static str, char)]) -> Self {
+        debug_assert!(!list.is_empty());
+        Self {
+            repr: Repr::List(list),
+            modifiers: EcoString::new(),
+        }
+    }
+
+    /// Get the symbol's text.
+    pub fn get(&self) -> char {
+        match self.repr {
+            Repr::Single(c) => c,
+            Repr::List(list) => find(list, &self.modifiers).unwrap(),
+        }
+    }
+
+    /// Apply a modifier to the symbol.
+    pub fn modified(mut self, modifier: &str) -> StrResult<Self> {
+        if !self.modifiers.is_empty() {
+            self.modifiers.push('.');
+        }
+        self.modifiers.push_str(modifier);
+        if match self.repr {
+            Repr::Single(_) => true,
+            Repr::List(list) => find(list, &self.modifiers).is_none(),
+        } {
+            Err("unknown modifier")?
+        }
+        Ok(self)
+    }
+
+    /// The characters that are covered by this symbol.
+    pub fn chars(&self) -> impl Iterator<Item = char> {
+        let (first, slice) = match self.repr {
+            Repr::Single(c) => (Some(c), [].as_slice()),
+            Repr::List(list) => (None, list),
+        };
+        first.into_iter().chain(slice.iter().map(|&(_, c)| c))
+    }
+
+    /// Possible modifiers.
+    pub fn modifiers(&self) -> impl Iterator<Item = &str> + '_ {
+        let mut set = BTreeSet::new();
+        if let Repr::List(list) = self.repr {
+            for modifier in list.iter().flat_map(|(name, _)| name.split('.')) {
+                if !modifier.is_empty() && !contained(&self.modifiers, modifier) {
+                    set.insert(modifier);
+                }
+            }
+        }
+        set.into_iter()
+    }
+}
+
+impl Debug for Symbol {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        f.write_char(self.get())
+    }
+}
+
+/// Find the best symbol from the list.
+fn find(list: &[(&str, char)], modifiers: &str) -> Option<char> {
+    let mut best = None;
+    let mut best_score = None;
+
+    // Find the best table entry with this name.
+    'outer: for candidate in list {
+        for modifier in parts(modifiers) {
+            if !contained(candidate.0, modifier) {
+                continue 'outer;
+            }
+        }
+
+        let mut matching = 0;
+        let mut total = 0;
+        for modifier in parts(candidate.0) {
+            if contained(modifiers, modifier) {
+                matching += 1;
+            }
+            total += 1;
+        }
+
+        let score = (matching, Reverse(total));
+        if best_score.map_or(true, |b| score > b) {
+            best = Some(candidate.1);
+            best_score = Some(score);
+        }
+    }
+
+    best
+}
+
+/// Split a modifier list into its parts.
+fn parts(modifiers: &str) -> impl Iterator<Item = &str> {
+    modifiers.split('.').filter(|s| !s.is_empty())
+}
+
+/// Whether the modifier string contains the modifier `m`.
+fn contained(modifiers: &str, m: &str) -> bool {
+    parts(modifiers).any(|part| part == m)
+}