From bd2b2f1b48f86d59c3b746b72a14192f75419a84 Mon Sep 17 00:00:00 2001
From: "Jeremy A. Kolb" <jkolb@ara.com>
Date: Sun, 23 Sep 2018 11:13:27 -0400
Subject: Implement folding ranges

---
 crates/ra_lsp_server/src/main_loop/handlers.rs | 90 +++++++++++++++++++++++++-
 crates/ra_lsp_server/src/main_loop/mod.rs      |  1 +
 2 files changed, 90 insertions(+), 1 deletion(-)

diff --git a/crates/ra_lsp_server/src/main_loop/handlers.rs b/crates/ra_lsp_server/src/main_loop/handlers.rs
index 2d9391859..36cdeda38 100644
--- a/crates/ra_lsp_server/src/main_loop/handlers.rs
+++ b/crates/ra_lsp_server/src/main_loop/handlers.rs
@@ -1,15 +1,18 @@
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
 
 use languageserver_types::{
     Diagnostic, DiagnosticSeverity, DocumentSymbol,
     CodeActionResponse, Command, TextDocumentIdentifier,
     SymbolInformation, Position, Location, TextEdit,
     CompletionItem, InsertTextFormat, CompletionItemKind,
+    FoldingRange, FoldingRangeParams, FoldingRangeKind
 };
 use serde_json::to_value;
 use ra_analysis::{Query, FileId, RunnableKind, JobToken};
 use ra_syntax::{
+    algo::{siblings, walk, Direction},
     text_utils::contains_offset_nonstrict,
+    SyntaxKind, SyntaxNodeRef, TextRange
 };
 
 use ::{
@@ -177,6 +180,7 @@ pub fn handle_workspace_symbol(
                     world, &line_index
                 )?,
                 container_name: None,
+                deprecated: None,
             };
             res.push(info);
         };
@@ -365,6 +369,90 @@ pub fn handle_completion(
     Ok(Some(req::CompletionResponse::Array(items)))
 }
 
+pub fn handle_folding_range(
+    world: ServerWorld,
+    params: FoldingRangeParams,
+    _token: JobToken,
+) -> Result<Option<Vec<FoldingRange>>> {
+    let file_id = params.text_document.try_conv_with(&world)?;
+    let file = world.analysis().file_syntax(file_id);
+    let line_index = world.analysis().file_line_index(file_id);
+    let syntax = file.syntax();
+
+    let mut res = vec![];
+    let mut visited = HashSet::new();
+
+    for node in walk::preorder(syntax) {
+        if visited.contains(&node) {
+            continue;
+        }
+
+        let range_and_kind = match node.kind() {
+            SyntaxKind::COMMENT => (
+                contiguous_range_for(SyntaxKind::COMMENT, node, &mut visited),
+                Some(FoldingRangeKind::Comment),
+            ),
+            SyntaxKind::USE_ITEM => (
+                contiguous_range_for(SyntaxKind::USE_ITEM, node, &mut visited),
+                Some(FoldingRangeKind::Imports),
+            ),
+            _ => (None, None),
+        };
+
+        match range_and_kind {
+            (Some(range), Some(kind)) => {
+                let range = range.conv_with(&line_index);
+                res.push(FoldingRange {
+                    start_line: range.start.line,
+                    start_character: Some(range.start.character),
+                    end_line: range.end.line,
+                    end_character: Some(range.start.character),
+                    kind: Some(kind),
+                });
+            }
+            _ => {}
+        }
+    }
+
+    if res.is_empty() {
+        Ok(None)
+    } else {
+        Ok(Some(res))
+    }
+}
+
+fn contiguous_range_for<'a>(
+    kind: SyntaxKind,
+    node: SyntaxNodeRef<'a>,
+    visited: &mut HashSet<SyntaxNodeRef<'a>>,
+) -> Option<TextRange> {
+    visited.insert(node);
+
+    let left = node;
+    let mut right = node;
+    for node in siblings(node, Direction::Forward) {
+        visited.insert(node);
+        match node.kind() {
+            SyntaxKind::WHITESPACE if !node.leaf_text().unwrap().as_str().contains("\n\n") => (),
+            k => {
+                if k == kind {
+                    right = node
+                } else {
+                    break;
+                }
+            }
+        }
+    }
+    if left != right {
+        Some(TextRange::from_to(
+            left.range().start(),
+            right.range().end(),
+        ))
+    } else {
+        None
+    }
+}
+
 pub fn handle_code_action(
     world: ServerWorld,
     params: req::CodeActionParams,
diff --git a/crates/ra_lsp_server/src/main_loop/mod.rs b/crates/ra_lsp_server/src/main_loop/mod.rs
index 2b2279e97..abc58b70e 100644
--- a/crates/ra_lsp_server/src/main_loop/mod.rs
+++ b/crates/ra_lsp_server/src/main_loop/mod.rs
@@ -253,6 +253,7 @@ fn on_request(
         .on::<req::DecorationsRequest>(handlers::handle_decorations)?
         .on::<req::Completion>(handlers::handle_completion)?
         .on::<req::CodeActionRequest>(handlers::handle_code_action)?
+        .on::<req::FoldingRangeRequest>(handlers::handle_folding_range)?
         .finish();
     match req {
         Ok((id, handle)) => {
-- 
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