From 0620b103e1c9a8eaa71a7bc9e5c1b75ee2d5aef0 Mon Sep 17 00:00:00 2001
From: Sean Olson <olson.sean.k@gmail.com>
Date: Fri, 29 Mar 2024 17:44:34 -0700
Subject: [PATCH] Consider adjacent tokens when constructing a HIR.

---
 src/hir.rs        | 34 ++++++++++++++++++++--------------
 src/lib.rs        |  4 ++++
 src/token/walk.rs | 20 +++++++++++++++++---
 3 files changed, 41 insertions(+), 17 deletions(-)

diff --git a/src/hir.rs b/src/hir.rs
index d689909..a6f09c9 100644
--- a/src/hir.rs
+++ b/src/hir.rs
@@ -128,11 +128,12 @@ where
             term
         }
 
-        fn term(&mut self, _: impl FoldPosition<'t, A>, leaf: &LeafKind<'t>) -> Self::Term {
+        fn term(&mut self, position: impl FoldPosition<'t, A>, leaf: &LeafKind<'t>) -> Self::Term {
             use token::Wildcard::{One, Tree, ZeroOrMore};
             use Archetype::{Character, Range};
             use LeafKind::{Class, Literal, Separator, Wildcard};
 
+            let adjacency = position.adjacency();
             match leaf {
                 Class(ref class) => {
                     let is_negated = class.is_negated();
@@ -161,11 +162,17 @@ where
                         Hir::literal(literal.text().as_bytes())
                     }
                 },
-                // TODO: Separators should probably also match the end of text when they are at the
-                //       end of a glob expression. This may not be possible in a fold with simple
-                //       terms though, since that positional information isn't available until
-                //       reaching the root of the token tree.
-                Separator(_) => self::separator().into_hir(),
+                Separator(_) => {
+                    if adjacency.right.is_some() {
+                        self::separator().into_hir()
+                    }
+                    else {
+                        Hir::alternation(vec![
+                            self::separator().into_hir(),
+                            Hir::look(hir::Look::End),
+                        ])
+                    }
+                },
                 Wildcard(ref wildcard) => match wildcard {
                     One => Hir::class(hir::Class::Unicode(self::not_separator())),
                     Tree { has_root } => Hir::alternation(vec![
@@ -190,12 +197,13 @@ where
                         self::separator().into_hir(),
                         Hir::empty(),
                     ]),
-                    // TODO: Zero or more wildcards should match **one** or more if they comprise
-                    //       the entirety of a component, such as in `a/*/b`. This may not be
-                    //       possible in a fold with simple terms though, since adjacency
-                    //       information isn't available until reaching the root of the token tree.
                     ZeroOrMore(ref evaluation) => Hir::repetition(hir::Repetition {
-                        min: 0,
+                        min: if adjacency.is_open() || adjacency.is_closed_boundary() {
+                            1
+                        }
+                        else {
+                            0
+                        },
                         max: None,
                         greedy: evaluation.is_eager(),
                         sub: Box::new(self::not_separator().into_hir()),
@@ -215,9 +223,7 @@ where
                     .iter()
                     .adjacent()
                     .map(|token| {
-                        let hir = token
-                            .fold_with_adjacent(Compile::default())
-                            .unwrap_or_else(Hir::empty);
+                        let hir = token.fold_with_adjacent(Compile).unwrap_or_else(Hir::empty);
                         if token.into_item().is_capturing() {
                             let index = capture_group_index;
                             capture_group_index = capture_group_index
diff --git a/src/lib.rs b/src/lib.rs
index 1e3d411..7f44172 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -268,6 +268,10 @@ pub trait SliceProjection: Index<usize, Output = Self::Item> {
     fn get(&self, index: usize) -> Option<&Self::Item>;
 
     fn len(&self) -> usize;
+
+    fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
 }
 
 impl<T> SliceProjection for [T] {
diff --git a/src/token/walk.rs b/src/token/walk.rs
index e4876c3..5c40b55 100644
--- a/src/token/walk.rs
+++ b/src/token/walk.rs
@@ -38,7 +38,7 @@ impl<'i, 't, A> ParentToken<'i, 't, A> for &'i BranchKind<'t, A> {
     type Child = &'i Token<'t, A>;
 
     fn as_ref(&self) -> &BranchKind<'t, A> {
-        *self
+        self
     }
 
     fn into_tokens(self) -> impl DoubleEndedIterator<Item = Self::Child> {
@@ -67,8 +67,8 @@ impl<'t, A> ChildToken<'t, A> for Token<'t, A> {
 
 #[derive(Debug)]
 pub struct Adjacency<'i, 't, A> {
-    left: Option<&'i Token<'t, A>>,
-    right: Option<&'i Token<'t, A>>,
+    pub left: Option<&'i Token<'t, A>>,
+    pub right: Option<&'i Token<'t, A>>,
 }
 
 impl<'i, 't, A> Adjacency<'i, 't, A> {
@@ -80,6 +80,20 @@ impl<'i, 't, A> Adjacency<'i, 't, A> {
             right: right.or(self.right),
         }
     }
+
+    pub fn is_open(&self) -> bool {
+        self.left.is_none() && self.right.is_none()
+    }
+
+    pub fn is_closed(&self) -> bool {
+        self.left.is_some() && self.right.is_some()
+    }
+
+    pub fn is_closed_boundary(&self) -> bool {
+        let is_boundary =
+            |token: Option<&Token<'_, _>>| token.map_or(false, |token| token.boundary().is_some());
+        is_boundary(self.left) && is_boundary(self.right)
+    }
 }
 
 impl<'i, 't, A> Clone for Adjacency<'i, 't, A> {