1 files changed, 87 insertions, 0 deletions
diff --git a/src/buildtool/file_system/git_tree.hpp b/src/buildtool/file_system/git_tree.hpp
new file mode 100644
index 00000000..57cb3b52
--- /dev/null
+++ b/src/buildtool/file_system/git_tree.hpp
@@ -0,0 +1,87 @@
+#ifndef INCLUDED_SRC_BUILDTOOL_FILE_SYSTEM_GIT_TREE_HPP
+#define INCLUDED_SRC_BUILDTOOL_FILE_SYSTEM_GIT_TREE_HPP
+
+#include <filesystem>
+#include <optional>
+#include <unordered_map>
+
+#include "gsl-lite/gsl-lite.hpp"
+#include "src/buildtool/file_system/git_cas.hpp"
+#include "src/buildtool/file_system/object_type.hpp"
+#include "src/utils/cpp/atomic.hpp"
+#include "src/utils/cpp/hex_string.hpp"
+
+class GitTreeEntry;
+using GitTreeEntryPtr = std::shared_ptr<GitTreeEntry const>;
+
+class GitTree {
+    friend class GitTreeEntry;
+
+  public:
+    using entries_t =
+        std::unordered_map<std::string, gsl::not_null<GitTreeEntryPtr>>;
+
+    /// \brief Read tree with given id from Git repository.
+    /// \param repo_path  Path to the Git repository.
+    /// \param tree_id    Tree id as as hex string.
+    [[nodiscard]] static auto Read(std::filesystem::path const& repo_path,
+                                   std::string const& tree_id) noexcept
+        -> std::optional<GitTree>;
+
+    /// \brief Read tree with given id from CAS.
+    /// \param cas      Git CAS that contains the tree id.
+    /// \param tree_id  Tree id as as hex string.
+    [[nodiscard]] static auto Read(gsl::not_null<GitCASPtr> const& cas,
+                                   std::string const& tree_id) noexcept
+        -> std::optional<GitTree>;
+
+    /// \brief Lookup by dir entry name. '.' and '..' are not allowed.
+    [[nodiscard]] auto LookupEntryByName(std::string const& name) const noexcept
+        -> GitTreeEntryPtr;
+
+    /// \brief Lookup by relative path. '.' is not allowed.
+    [[nodiscard]] auto LookupEntryByPath(
+        std::filesystem::path const& path) const noexcept -> GitTreeEntryPtr;
+
+    [[nodiscard]] auto begin() const noexcept { return entries_.begin(); }
+    [[nodiscard]] auto end() const noexcept { return entries_.end(); }
+
+  private:
+    gsl::not_null<GitCASPtr> cas_;
+    entries_t entries_;
+
+    GitTree(gsl::not_null<GitCASPtr> cas, entries_t&& entries) noexcept
+        : cas_{std::move(cas)}, entries_{std::move(entries)} {}
+};
+
+class GitTreeEntry {
+  public:
+    GitTreeEntry(gsl::not_null<GitCASPtr> cas,
+                 std::string raw_id,
+                 ObjectType type) noexcept
+        : cas_{std::move(cas)}, raw_id_{std::move(raw_id)}, type_{type} {}
+
+    [[nodiscard]] auto IsBlob() const noexcept { return IsFileObject(type_); }
+    [[nodiscard]] auto IsTree() const noexcept { return IsTreeObject(type_); }
+
+    [[nodiscard]] auto Blob() const noexcept -> std::optional<std::string>;
+    [[nodiscard]] auto Tree() && = delete;
+    [[nodiscard]] auto Tree() const& noexcept -> std::optional<GitTree> const&;
+
+    [[nodiscard]] auto Hash() const noexcept { return ToHexString(raw_id_); }
+    [[nodiscard]] auto Type() const noexcept { return type_; }
+    // Use with care. Implementation might read entire object to obtain size.
+    // Consider using Blob()->size() instead.
+    [[nodiscard]] auto Size() const noexcept -> std::optional<std::size_t>;
+
+  private:
+    gsl::not_null<GitCASPtr> cas_;
+    std::string raw_id_;
+    ObjectType type_;
+    mutable atomic_shared_ptr<std::optional<GitTree>> tree_cached_{nullptr};
+    mutable std::atomic<bool> tree_loading_{false};
+};
+
+using GitTreePtr = std::shared_ptr<GitTree const>;
+
+#endif  // INCLUDED_SRC_BUILDTOOL_FILE_SYSTEM_GIT_TREE_HPP