From 0511059d604d7544a4af4e8ebd990c755fd1cff2 Mon Sep 17 00:00:00 2001
From: Sam Atkins <atkinssj@serenityos.org>
Date: Thu, 23 Feb 2023 15:35:57 +0000
Subject: [PATCH] LibJS: Assign folding regions for JS files

Each {} block is now treated as a folding region, so that they can be
collapsed and expanded in TextEditor, HackStudio, and anywhere else
that uses the syntax highlighter. :^)
---
 .../Libraries/LibJS/SyntaxHighlighter.cpp     | 25 +++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/Userland/Libraries/LibJS/SyntaxHighlighter.cpp b/Userland/Libraries/LibJS/SyntaxHighlighter.cpp
index 0cd788fb8a..2973773967 100644
--- a/Userland/Libraries/LibJS/SyntaxHighlighter.cpp
+++ b/Userland/Libraries/LibJS/SyntaxHighlighter.cpp
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2020, the SerenityOS developers.
+ * Copyright (c) 2023, Sam Atkins <atkinssj@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -54,6 +55,7 @@ void SyntaxHighlighter::rehighlight(Palette const& palette)
     Lexer lexer(text);
 
     Vector<GUI::TextDocumentSpan> spans;
+    Vector<GUI::TextDocumentFoldingRegion> folding_regions;
     GUI::TextPosition position { 0, 0 };
     GUI::TextPosition start { 0, 0 };
 
@@ -92,16 +94,39 @@ void SyntaxHighlighter::rehighlight(Palette const& palette)
             span.range.end().line(), span.range.end().column());
     };
 
+    struct TokenData {
+        Token token;
+        GUI::TextRange range;
+    };
+    Vector<TokenData> folding_region_start_tokens;
+
     bool was_eof = false;
     for (auto token = lexer.next(); !was_eof; token = lexer.next()) {
         append_token(token.trivia(), token, true);
+
+        auto token_start_position = position;
         append_token(token.value(), token, false);
 
         if (token.type() == TokenType::Eof)
             was_eof = true;
+
+        // Create folding regions for {} blocks
+        if (token.type() == TokenType::CurlyOpen) {
+            folding_region_start_tokens.append({ .token = token,
+                .range = { token_start_position, position } });
+        } else if (token.type() == TokenType::CurlyClose) {
+            if (!folding_region_start_tokens.is_empty()) {
+                auto curly_open = folding_region_start_tokens.take_last();
+                GUI::TextDocumentFoldingRegion region;
+                region.range.set_start(curly_open.range.end());
+                region.range.set_end(token_start_position);
+                folding_regions.append(region);
+            }
+        }
     }
 
     m_client->do_set_spans(move(spans));
+    m_client->do_set_folding_regions(move(folding_regions));
 
     m_has_brace_buddies = false;
     highlight_matching_token_pair();