1 files changed, 61 insertions, 0 deletions

diff --git a/crates/ra_analysis/src/completion.rs b/crates/ra_analysis/src/completion.rs
new file mode 100644
index 000000000..a0fd6828d
--- /dev/null
+++ b/crates/ra_analysis/src/completion.rs
@@ -0,0 +1,61 @@
+use ra_editor::{CompletionItem, find_node_at_offset, complete_module_items};
+use ra_syntax::{
+    AtomEdit, File, TextUnit, AstNode,
+    ast::{self, ModuleItemOwner},
+};
+
+use crate::{
+    FileId, Cancelable,
+    db::{self, SyntaxDatabase},
+    descriptors::module::{ModulesDatabase, ModuleTree, ModuleId},
+};
+
+pub(crate) fn resolve_based_completion(db: &db::RootDatabase, file_id: FileId, offset: TextUnit) -> Cancelable<Option<Vec<CompletionItem>>> {
+    let file = db.file_syntax(file_id);
+    let module_tree = db.module_tree()?;
+    let file = {
+        let edit = AtomEdit::insert(offset, "intellijRulezz".to_string());
+        file.reparse(&edit)
+    };
+    let target_file = match find_target_module(&module_tree, file_id, &file, offset) {
+        None => return Ok(None),
+        Some(target_module) => {
+            let file_id = target_module.file_id(&module_tree);
+            db.file_syntax(file_id)
+        }
+    };
+    let mut res = Vec::new();
+    complete_module_items(target_file.ast().items(), None, &mut res);
+    Ok(Some(res))
+}
+
+pub(crate) fn find_target_module(module_tree: &ModuleTree, file_id: FileId, file: &File, offset: TextUnit) -> Option<ModuleId> {
+    let name_ref: ast::NameRef = find_node_at_offset(file.syntax(), offset)?;
+    let mut crate_path = crate_path(name_ref)?;
+    let module_id = module_tree.any_module_for_file(file_id)?;
+    crate_path.pop();
+    let mut target_module = module_id.root(&module_tree);
+    for name in crate_path {
+        target_module = target_module.child(module_tree, name.text().as_str())?;
+    }
+    Some(target_module)
+}
+
+fn crate_path(name_ref: ast::NameRef) -> Option<Vec<ast::NameRef>> {
+    let mut path = name_ref.syntax()
+        .parent().and_then(ast::PathSegment::cast)?
+        .parent_path();
+    let mut res = Vec::new();
+    loop {
+        let segment = path.segment()?;
+        match segment.kind()? {
+            ast::PathSegmentKind::Name(name) => res.push(name),
+            ast::PathSegmentKind::CrateKw => break,
+            ast::PathSegmentKind::SelfKw | ast::PathSegmentKind::SuperKw =>
+                return None,
+        }
+        path = path.qualifier()?;
+    }
+    res.reverse();
+    Some(res)
+}