From 1f344bd93258fac03b6ea82c15dd5dad41ee20fa Mon Sep 17 00:00:00 2001
From: Paul Cristian Sarbu <paul.cristian.sarbu@huawei.com>
Date: Mon, 29 Aug 2022 11:35:15 +0200
Subject: Git CAS: Move Git tree ops to fake repo wrapper class

---
 src/buildtool/file_system/git_repo.hpp | 59 ++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)

(limited to 'src/buildtool/file_system/git_repo.hpp')

diff --git a/src/buildtool/file_system/git_repo.hpp b/src/buildtool/file_system/git_repo.hpp
index ae0c183b..6103d879 100644
--- a/src/buildtool/file_system/git_repo.hpp
+++ b/src/buildtool/file_system/git_repo.hpp
@@ -28,6 +28,25 @@ using git_repository = struct git_repository;
 /// existing ODB, allowing thread-safe operations.
 class GitRepo {
   public:
+    // Stores the data for defining a single Git tree entry, which consists of
+    // a name (flat basename) and an object type (file/executable/tree).
+    struct tree_entry_t {
+        tree_entry_t(std::string n, ObjectType t)
+            : name{std::move(n)}, type{t} {}
+        std::string name;
+        ObjectType type;
+        [[nodiscard]] auto operator==(tree_entry_t const& other) const noexcept
+            -> bool {
+            return name == other.name and type == other.type;
+        }
+    };
+
+    // Tree entries by raw id. The same id might refer to multiple entries.
+    // Note that sharding by id is used as this format enables a more efficient
+    // internal implementation for creating trees.
+    using tree_entries_t =
+        std::unordered_map<std::string, std::vector<tree_entry_t>>;
+
     GitRepo() = delete;  // no default ctor
 
     // allow only move, no copy
@@ -55,6 +74,46 @@ class GitRepo {
 
     [[nodiscard]] auto IsRepoFake() const noexcept -> bool;
 
+    /// \brief Read entries from tree in CAS.
+    /// Reading a tree must be backed by an object database. Therefore, a real
+    /// repository is required.
+    /// \param id         The object id.
+    /// \param is_hex_id  Specify whether `id` is hex string or raw.
+    [[nodiscard]] auto ReadTree(std::string const& id,
+                                bool is_hex_id = false) const noexcept
+        -> std::optional<tree_entries_t>;
+
+    /// \brief Create a flat tree from entries and store tree in CAS.
+    /// Creating a tree must be backed by an object database. Therefore, a real
+    /// repository is required. Furthermore, all entries must be available in
+    /// the underlying object database and object types must correctly reflect
+    /// the type of the object found in the database.
+    /// \param entries  The entries to create the tree from.
+    /// \returns The raw object id as string, if successful.
+    [[nodiscard]] auto CreateTree(GitRepo::tree_entries_t const& entries)
+        const noexcept -> std::optional<std::string>;
+
+    /// \brief Read entries from tree data (without object db).
+    /// \param data       The tree object as plain data.
+    /// \param id         The object id.
+    /// \param is_hex_id  Specify whether `id` is hex string or raw.
+    /// \returns The tree entries.
+    [[nodiscard]] static auto ReadTreeData(std::string const& data,
+                                           std::string const& id,
+                                           bool is_hex_id = false) noexcept
+        -> std::optional<tree_entries_t>;
+
+    /// \brief Create a flat shallow (without objects in db) tree and return it.
+    /// Creates a tree object from the entries without access to the actual
+    /// blobs. Objects are not required to be available in the underlying object
+    /// database. It is sufficient to provide the raw object id and and object
+    /// type for every entry.
+    /// \param entries  The entries to create the tree from.
+    /// \returns A pair of raw object id and the tree object content.
+    [[nodiscard]] static auto CreateShallowTree(
+        GitRepo::tree_entries_t const& entries) noexcept
+        -> std::optional<std::pair<std::string, std::string>>;
+
     ~GitRepo() noexcept;
 
   private:
-- 
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