From 71194e70eb626fe556816df8961146939dda666e Mon Sep 17 00:00:00 2001
From: Yingchi Long <i@lyc.dev>
Date: Thu, 25 May 2023 02:57:16 +0800
Subject: [PATCH] nixd: support hover

---
 lib/nixd/include/nixd/Server.h |  8 ++++++-
 lib/nixd/src/Server.cpp        | 44 ++++++++++++++++++++++++++++++++--
 2 files changed, 49 insertions(+), 3 deletions(-)

diff --git a/lib/nixd/include/nixd/Server.h b/lib/nixd/include/nixd/Server.h
index f7321e856..ca34c97df 100644
--- a/lib/nixd/include/nixd/Server.h
+++ b/lib/nixd/include/nixd/Server.h
@@ -2,10 +2,12 @@
 
 #include "lspserver/Connection.h"
 #include "lspserver/DraftStore.h"
+#include "lspserver/Function.h"
 #include "lspserver/LSPServer.h"
 #include "lspserver/Logger.h"
 #include "lspserver/Protocol.h"
 #include "lspserver/SourceCode.h"
+#include "nixd/EvalDraftStore.h"
 
 #include <llvm/ADT/FunctionExtras.h>
 #include <llvm/Support/JSON.h>
@@ -14,7 +16,8 @@ namespace nixd {
 /// The server instance, nix-related language features goes here
 class Server : public lspserver::LSPServer {
 
-  lspserver::DraftStore DraftMgr;
+  EvalDraftStore DraftMgr;
+  boost::asio::thread_pool Pool;
 
   std::shared_ptr<const std::string> getDraft(lspserver::PathRef File) const;
 
@@ -37,6 +40,7 @@ class Server : public lspserver::LSPServer {
          std::unique_ptr<lspserver::OutboundPort> Out)
       : LSPServer(std::move(In), std::move(Out)) {
     Registry.addMethod("initialize", this, &Server::onInitialize);
+    Registry.addMethod("textDocument/hover", this, &Server::onHover);
     Registry.addNotification("initialized", this, &Server::onInitialized);
 
     // Text Document Synchronization
@@ -61,6 +65,8 @@ class Server : public lspserver::LSPServer {
   void publishStandaloneDiagnostic(lspserver::URIForFile Uri,
                                    std::string Content,
                                    std::optional<int64_t> LSPVersion);
+  void onHover(const lspserver::TextDocumentPositionParams &,
+               lspserver::Callback<llvm::json::Value>);
 };
 
 }; // namespace nixd
diff --git a/lib/nixd/src/Server.cpp b/lib/nixd/src/Server.cpp
index 0c03acfd4..0bd82dfc4 100644
--- a/lib/nixd/src/Server.cpp
+++ b/lib/nixd/src/Server.cpp
@@ -1,9 +1,11 @@
 #include "nixd/Server.h"
+#include "lspserver/Logger.h"
 #include "nixd/Diagnostic.h"
 
 #include "lspserver/Path.h"
 #include "lspserver/Protocol.h"
 
+#include <exception>
 #include <llvm/ADT/StringRef.h>
 #include <llvm/Support/Error.h>
 #include <llvm/Support/JSON.h>
@@ -13,6 +15,9 @@
 #include <nix/store-api.hh>
 
 #include <filesystem>
+#include <sstream>
+#include <string>
+#include <variant>
 namespace fs = std::filesystem;
 namespace nixd {
 
@@ -25,6 +30,7 @@ void Server::onInitialize(const lspserver::InitializeParams &InitializeParams,
            {"change", (int)lspserver::TextDocumentSyncKind::Incremental},
            {"save", true},
        }},
+      {"hoverProvider", true},
   };
 
   llvm::json::Object Result{
@@ -89,8 +95,8 @@ void Server::publishStandaloneDiagnostic(lspserver::URIForFile Uri,
   auto NixState = std::make_unique<nix::EvalState>(nix::Strings{}, NixStore);
   try {
     fs::path Path = Uri.file().str();
-    auto *E =
-        NixState->parseExprFromString(std::move(Content), Path.remove_filename());
+    auto *E = NixState->parseExprFromString(std::move(Content),
+                                            Path.remove_filename());
     nix::Value V;
     NixState->eval(E, V);
   } catch (const nix::Error &PE) {
@@ -104,4 +110,38 @@ void Server::publishStandaloneDiagnostic(lspserver::URIForFile Uri,
       .uri = Uri, .diagnostics = {}, .version = LSPVersion});
 }
 
+void Server::onHover(const lspserver::TextDocumentPositionParams &Paras,
+                     lspserver::Callback<llvm::json::Value> Reply) {
+  std::string HoverFile = Paras.textDocument.uri.file().str();
+  DraftMgr.withEvaluation(
+      Pool, {"--file", HoverFile}, "",
+      [=, Reply = std::move(Reply)](
+          std::variant<std::exception *,
+                       nix::ref<EvalDraftStore::EvaluationResult>>
+              EvalResult) mutable {
+        nix::ref<EvalDraftStore::EvaluationResult> Result =
+            std::get<1>(EvalResult);
+        try {
+          std::get<1>(EvalResult); // w contains int, not float: will throw
+        } catch (const std::bad_variant_access &) {
+          std::exception *Excepts = std::get<0>(EvalResult);
+          lspserver::log(Excepts->what());
+        }
+        auto Forest = Result->EvalASTForest;
+        auto AST = Forest.at(HoverFile);
+        auto *Node = AST->lookupPosition(Paras.position);
+        std::stringstream NodeOut;
+        Node->show(Result->State->symbols, NodeOut);
+        auto Value = AST->getValue(Node);
+        std::stringstream Res{};
+        Value.print(Result->State->symbols, Res);
+        Reply(lspserver::Hover{
+            .contents =
+                {
+                    .value = Res.str(),
+                },
+        });
+      });
+}
+
 } // namespace nixd