4 files changed, 74 insertions, 18 deletions

diff --git a/crates/libeditor/src/code_actions.rs b/crates/libeditor/src/code_actions.rs
index b3305be2a..f53a8f9c6 100644
--- a/crates/libeditor/src/code_actions.rs
+++ b/crates/libeditor/src/code_actions.rs
@@ -3,7 +3,7 @@ use std::{
 };
 
 use libsyntax2::{
-    File,
+    File, TextUnit,
     ast::{self, AstNode, AttrsOwner, TypeParamsOwner, NameOwner},
     SyntaxKind::COMMA,
     SyntaxNodeRef,
@@ -13,7 +13,7 @@ use libsyntax2::{
     },
 };
 
-use {TextUnit, EditBuilder, Edit};
+use {EditBuilder, Edit, find_node_at_offset};
 
 #[derive(Debug)]
 pub struct ActionResult {
@@ -39,7 +39,7 @@ pub fn flip_comma<'a>(file: &'a File, offset: TextUnit) -> Option<impl FnOnce()
 }
 
 pub fn add_derive<'a>(file: &'a File, offset: TextUnit) -> Option<impl FnOnce() -> ActionResult + 'a> {
-    let nominal = find_node::<ast::NominalDef>(file.syntax(), offset)?;
+    let nominal = find_node_at_offset::<ast::NominalDef>(file.syntax(), offset)?;
     Some(move || {
         let derive_attr = nominal
             .attrs()
@@ -66,7 +66,7 @@ pub fn add_derive<'a>(file: &'a File, offset: TextUnit) -> Option<impl FnOnce()
 }
 
 pub fn add_impl<'a>(file: &'a File, offset: TextUnit) -> Option<impl FnOnce() -> ActionResult + 'a> {
-    let nominal = find_node::<ast::NominalDef>(file.syntax(), offset)?;
+    let nominal = find_node_at_offset::<ast::NominalDef>(file.syntax(), offset)?;
     let name = nominal.name()?;
 
     Some(move || {
@@ -105,16 +105,6 @@ fn non_trivia_sibling(node: SyntaxNodeRef, direction: Direction) -> Option<Synta
         .find(|node| !node.kind().is_trivia())
 }
 
-pub fn find_node<'a, N: AstNode<'a>>(syntax: SyntaxNodeRef<'a>, offset: TextUnit) -> Option<N> {
-    let leaves = find_leaf_at_offset(syntax, offset);
-    let leaf = leaves.clone()
-        .find(|leaf| !leaf.kind().is_trivia())
-        .or_else(|| leaves.right_biased())?;
-    ancestors(leaf)
-        .filter_map(N::cast)
-        .next()
-}
-
 fn comma_list(buf: &mut String, bra: &str, ket: &str, items: impl Iterator<Item=impl fmt::Display>) {
     buf.push_str(bra);
     let mut first = true;
diff --git a/crates/libeditor/src/completion.rs b/crates/libeditor/src/completion.rs
new file mode 100644
index 000000000..cf61ec784
--- /dev/null
+++ b/crates/libeditor/src/completion.rs
@@ -0,0 +1,31 @@
+use libsyntax2::{
+    File, TextUnit,
+    ast,
+    algo::find_leaf_at_offset,
+};
+
+use {
+    AtomEdit, find_node_at_offset,
+};
+
+#[derive(Debug)]
+pub struct CompletionItem {
+    name: String,
+}
+
+pub fn scope_completion(file: &File, offset: TextUnit) -> Option<Vec<CompletionItem>> {
+    // Insert a fake ident to get a valid parse tree
+    let file = {
+        let edit = AtomEdit::insert(offset, "intellijRulezz".to_string());
+        // Don't bother with completion if incremental reparse fails
+        file.incremental_reparse(&edit)?
+    };
+    let name_ref = find_node_at_offset::<ast::NameRef>(file.syntax(), offset)?;
+    Some(complete(name_ref))
+}
+
+fn complete(name_ref: ast::NameRef) -> Vec<CompletionItem> {
+    vec![CompletionItem {
+        name: "foo".to_string()
+    }]
+}
diff --git a/crates/libeditor/src/lib.rs b/crates/libeditor/src/lib.rs
index 55302265f..60489f7e3 100644
--- a/crates/libeditor/src/lib.rs
+++ b/crates/libeditor/src/lib.rs
@@ -8,11 +8,12 @@ mod line_index;
 mod edit;
 mod code_actions;
 mod typing;
+mod completion;
 
 use libsyntax2::{
-    File, TextUnit, TextRange,
+    File, TextUnit, TextRange, SyntaxNodeRef,
     ast::{AstNode, NameOwner},
-    algo::{walk, find_leaf_at_offset},
+    algo::{walk, find_leaf_at_offset, ancestors},
     SyntaxKind::{self, *},
 };
 pub use libsyntax2::AtomEdit;
@@ -22,10 +23,11 @@ pub use self::{
     symbols::{StructureNode, file_structure, FileSymbol, file_symbols},
     edit::{EditBuilder, Edit},
     code_actions::{
-        ActionResult, find_node,
+        ActionResult,
         flip_comma, add_derive, add_impl,
     },
     typing::join_lines,
+    completion::scope_completion,
 };
 
 #[derive(Debug)]
@@ -138,3 +140,16 @@ pub fn runnables(file: &File) -> Vec<Runnable> {
         })
         .collect()
 }
+
+pub fn find_node_at_offset<'a, N: AstNode<'a>>(
+    syntax: SyntaxNodeRef<'a>,
+    offset: TextUnit,
+) -> Option<N> {
+    let leaves = find_leaf_at_offset(syntax, offset);
+    let leaf = leaves.clone()
+        .find(|leaf| !leaf.kind().is_trivia())
+        .or_else(|| leaves.right_biased())?;
+    ancestors(leaf)
+        .filter_map(N::cast)
+        .next()
+}
diff --git a/crates/libeditor/tests/test.rs b/crates/libeditor/tests/test.rs
index c8882c94d..9d59f4cdf 100644
--- a/crates/libeditor/tests/test.rs
+++ b/crates/libeditor/tests/test.rs
@@ -9,7 +9,7 @@ use libeditor::{
     ActionResult,
     highlight, runnables, extend_selection, file_structure,
     flip_comma, add_derive, add_impl, matching_brace,
-    join_lines,
+    join_lines, scope_completion,
 };
 
 #[test]
@@ -244,6 +244,26 @@ struct Foo { f: u32 }
 ");
 }
 
+// #[test]
+// fn test_completion() {
+//     fn do_check(code: &str, expected_completions: &str) {
+//         let (off, code) = extract_offset(&code);
+//         let file = file(&code);
+//         let completions = scope_completion(&file, off).unwrap();
+//         assert_eq_dbg(expected_completions, &completions);
+//     }
+
+//     do_check(r"
+// fn foo(foo: i32) {
+//     let bar = 92;
+//     1 + <|>
+// }
+// ", r#"
+// CompletionItem { name: "bar" },
+// CompletionItem { name: "foo" },
+// "#);
+// }
+
 fn file(text: &str) -> File {
     File::parse(text)
 }