1 files changed, 72 insertions, 0 deletions
diff --git a/src/buildtool/common/tree.hpp b/src/buildtool/common/tree.hpp
new file mode 100644
index 00000000..512eda86
--- /dev/null
+++ b/src/buildtool/common/tree.hpp
@@ -0,0 +1,72 @@
+#ifndef INCLUDED_SRC_BUILDTOOL_COMMON_TREE_HPP
+#define INCLUDED_SRC_BUILDTOOL_COMMON_TREE_HPP
+
+#include <string>
+#include <unordered_map>
+
+#include "nlohmann/json.hpp"
+#include "src/buildtool/common/action_description.hpp"
+#include "src/buildtool/common/artifact_description.hpp"
+
+// Describes tree, its inputs, output (tree artifact), and action (tree action).
+class Tree {
+    using inputs_t = ActionDescription::inputs_t;
+
+  public:
+    explicit Tree(inputs_t&& inputs)
+        : id_{ComputeId(inputs)}, inputs_{std::move(inputs)} {}
+
+    [[nodiscard]] auto Id() const& -> std::string const& { return id_; }
+    [[nodiscard]] auto Id() && -> std::string { return std::move(id_); }
+
+    [[nodiscard]] auto ToJson() const -> nlohmann::json {
+        return ComputeDescription(inputs_);
+    }
+
+    [[nodiscard]] auto Inputs() const -> inputs_t { return inputs_; }
+
+    [[nodiscard]] auto Action() const -> ActionDescription {
+        return {
+            {/*unused*/}, {/*unused*/}, Action::CreateTreeAction(id_), inputs_};
+    }
+
+    [[nodiscard]] auto Output() const -> ArtifactDescription {
+        return ArtifactDescription{id_};
+    }
+
+    [[nodiscard]] static auto FromJson(std::string const& id,
+                                       nlohmann::json const& json)
+        -> std::optional<Tree> {
+        auto inputs = inputs_t{};
+        inputs.reserve(json.size());
+        for (auto const& [path, artifact] : json.items()) {
+            auto artifact_desc = ArtifactDescription::FromJson(artifact);
+            if (not artifact_desc) {
+                return std::nullopt;
+            }
+            inputs.emplace(path, std::move(*artifact_desc));
+        }
+        return Tree{id, std::move(inputs)};
+    }
+
+  private:
+    std::string id_;
+    inputs_t inputs_;
+
+    Tree(std::string id, inputs_t&& inputs)
+        : id_{std::move(id)}, inputs_{std::move(inputs)} {}
+
+    static auto ComputeDescription(inputs_t const& inputs) -> nlohmann::json {
+        auto json = nlohmann::json::object();
+        for (auto const& [path, artifact] : inputs) {
+            json[path] = artifact.ToJson();
+        }
+        return json;
+    }
+
+    static auto ComputeId(inputs_t const& inputs) -> std::string {
+        return ComputeHash(ComputeDescription(inputs).dump());
+    }
+};
+
+#endif  // INCLUDED_SRC_BUILDTOOL_COMMON_TREE_HPP