chore: preparations for adding flat json support

src/core/json/detail/flat_dfs.cc

@@ -21,19 +21,105 @@ auto FlatDfsItem::Init(const PathSegment& segment) -> AdvanceResult {
 }
 
 auto FlatDfsItem::Advance(const PathSegment& segment) -> AdvanceResult {
-  return AdvanceResult{};
+  if (state_ == kInit) {
+    return Init(segment);
+  }
+
+  if (!ShouldIterateAll(segment.type()))
+    return Exhausted();
+
+  ++state_;
+  auto vec = obj().AsVector();
+  if (state_ >= vec.size())
+    return Exhausted();
+  return Next(vec[state_]);
 }
 
 FlatDfs FlatDfs::Traverse(absl::Span<const PathSegment> path, const flexbuffers::Reference root,
                           const PathFlatCallback& callback) {
   DCHECK(!path.empty());
   FlatDfs dfs;
 
+  if (path.size() == 1) {
+    dfs.PerformStep(path[0], root, callback);
+    return dfs;
+  }
+
+  using ConstItem = FlatDfsItem;
+  vector<ConstItem> stack;
+  stack.emplace_back(root);
+
+  do {
+    unsigned segment_index = stack.back().segment_idx();
+    const auto& path_segment = path[segment_index];
+
+    // init or advance the current object
+    ConstItem::AdvanceResult res = stack.back().Advance(path_segment);
+    if (res && !res->first.IsNull()) {
+      const flexbuffers::Reference next = res->first;
+      DVLOG(2) << "Handling now " << next.GetType() << " " << next.ToString();
+
+      // We descent only if next is object or an array.
+      if (IsRecursive(next.GetType())) {
+        unsigned next_seg_id = res->second;
+
+        if (next_seg_id + 1 < path.size()) {
+          stack.emplace_back(next, next_seg_id);
+        } else {
+          // terminal step
+          // TODO: to take into account MatchStatus
+          // for `json.set foo $.a[10]` or for `json.set foo $.*.b`
+          dfs.PerformStep(path[next_seg_id], next, callback);
+        }
+      }
+    } else {
+      stack.pop_back();
+    }
+  } while (!stack.empty());
+
   return dfs;
 }
 
 auto FlatDfs::PerformStep(const PathSegment& segment, const flexbuffers::Reference node,
                           const PathFlatCallback& callback) -> nonstd::expected<void, MatchStatus> {
+  switch (segment.type()) {
+    case SegmentType::IDENTIFIER: {
+      if (!node.IsMap())
+        return make_unexpected(MISMATCH);
+      auto map = node.AsMap();
+      flexbuffers::Reference value = map[segment.identifier().c_str()];
+      if (!value.IsNull()) {
+        DoCall(callback, string_view{segment.identifier()}, value);
+      }
+    } break;
+    case SegmentType::INDEX: {
+      if (!node.IsVector())
+        return make_unexpected(MISMATCH);
+      auto vec = node.AsVector();
+      if (segment.index() >= vec.size()) {
+        return make_unexpected(OUT_OF_BOUNDS);
+      }
+      DoCall(callback, nullopt, vec[segment.index()]);
+    } break;
+
+    case SegmentType::DESCENT:
+    case SegmentType::WILDCARD: {
+      auto vec = node.AsVector();       // always succeeds
+      auto keys = node.AsMap().Keys();  // always succeeds
+      string str;
+      for (size_t i = 0; i < vec.size(); ++i) {
+        flexbuffers::Reference key = keys[i];
+        optional<string_view> opt_key;
+        if (key.IsString()) {
+          str = key.ToString();
+          opt_key = str;
+        }
+        DoCall(callback, opt_key, vec[i]);
+      }
+    } break;
+    default:
+      LOG(DFATAL) << "Unknown segment " << SegmentName(segment.type());
+  }
   return {};
 }
 

src/core/json/driver.cc

@@ -17,13 +17,8 @@ namespace dfly::json {
 namespace {
 
 class SingleValueImpl : public AggFunction {
-  JsonType GetResultImpl() const final {
-    return visit(Overloaded{
-                     [](monostate) { return JsonType::null(); },
-                     [](double d) { return JsonType(d); },
-                     [](int64_t i) { return JsonType(i); },
-                 },
-                 val_);
+  Result GetResultImpl() const final {
+    return val_;
   }
 
  protected:
@@ -35,7 +30,15 @@ class SingleValueImpl : public AggFunction {
     }
   }
 
-  variant<monostate, double, int64_t> val_;
+  void Init(const flexbuffers::Reference src) {
+    if (src.IsFloat()) {
+      val_.emplace<double>(src.AsDouble());
+    } else {
+      val_.emplace<int64_t>(src.AsInt64());
+    }
+  }
+
+  Result val_;
 };
 
 class MaxImpl : public SingleValueImpl {
@@ -58,6 +61,25 @@ class MaxImpl : public SingleValueImpl {
 
     return true;
   }
+
+  bool ApplyImpl(flexbuffers::Reference src) final {
+    if (!src.IsNumeric()) {
+      return false;
+    }
+
+    visit(Overloaded{
+              [&](monostate) { Init(src); },
+              [&](double d) { val_ = max(d, src.AsDouble()); },
+              [&](int64_t i) {
+                if (src.IsFloat())
+                  val_ = max(double(i), src.AsDouble());
+                else
+                  val_ = max(i, src.AsInt64());
+              },
+          },
+          val_);
+    return true;
+  }
 };
 
 class MinImpl : public SingleValueImpl {
@@ -81,6 +103,25 @@ class MinImpl : public SingleValueImpl {
 
     return true;
   }
+
+  bool ApplyImpl(flexbuffers::Reference src) final {
+    if (!src.IsNumeric()) {
+      return false;
+    }
+
+    visit(Overloaded{
+              [&](monostate) { Init(src); },
+              [&](double d) { val_ = min(d, src.AsDouble()); },
+              [&](int64_t i) {
+                if (src.IsFloat())
+                  val_ = min(double(i), src.AsDouble());
+                else
+                  val_ = min(i, src.AsInt64());
+              },
+          },
+          val_);
+    return true;
+  }
 };
 
 class AvgImpl : public AggFunction {
@@ -95,9 +136,19 @@ class AvgImpl : public AggFunction {
     return true;
   }
 
-  JsonType GetResultImpl() const final {
+  bool ApplyImpl(flexbuffers::Reference src) final {
+    if (!src.IsNumeric()) {
+      return false;
+    }
+    sum_ += src.AsDouble();
+    count_++;
+
+    return true;
+  }
+
+  Result GetResultImpl() const final {
     DCHECK_GT(count_, 0u);  // AggFunction guarantees that
-    return JsonType(sum_ / count_);
+    return Result(double(sum_ / count_));
   }
 
   double sum_ = 0;