Split out a new libnixflake

Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>

src/libflake/flake/lockfile.hh

@@ -0,0 +1,95 @@
+#pragma once
+///@file
+
+#include "flakeref.hh"
+
+#include <nlohmann/json_fwd.hpp>
+
+namespace nix {
+class Store;
+class StorePath;
+}
+
+namespace nix::flake {
+
+typedef std::vector<FlakeId> InputPath;
+
+struct LockedNode;
+
+/**
+ * A node in the lock file. It has outgoing edges to other nodes (its
+ * inputs). Only the root node has this type; all other nodes have
+ * type LockedNode.
+ */
+struct Node : std::enable_shared_from_this<Node>
+{
+    typedef std::variant<ref<LockedNode>, InputPath> Edge;
+
+    std::map<FlakeId, Edge> inputs;
+
+    virtual ~Node() { }
+};
+
+/**
+ * A non-root node in the lock file.
+ */
+struct LockedNode : Node
+{
+    FlakeRef lockedRef, originalRef;
+    bool isFlake = true;
+
+    LockedNode(
+        const FlakeRef & lockedRef,
+        const FlakeRef & originalRef,
+        bool isFlake = true)
+        : lockedRef(lockedRef), originalRef(originalRef), isFlake(isFlake)
+    { }
+
+    LockedNode(const nlohmann::json & json);
+
+    StorePath computeStorePath(Store & store) const;
+};
+
+struct LockFile
+{
+    ref<Node> root = make_ref<Node>();
+
+    LockFile() {};
+    LockFile(std::string_view contents, std::string_view path);
+
+    typedef std::map<ref<const Node>, std::string> KeyMap;
+
+    std::pair<nlohmann::json, KeyMap> toJSON() const;
+
+    std::pair<std::string, KeyMap> to_string() const;
+
+    /**
+     * Check whether this lock file has any unlocked inputs. If so,
+     * return one.
+     */
+    std::optional<FlakeRef> isUnlocked() const;
+
+    bool operator ==(const LockFile & other) const;
+    // Needed for old gcc versions that don't synthesize it (like gcc 8.2.2
+    // that is still the default on aarch64-linux)
+    bool operator !=(const LockFile & other) const;
+
+    std::shared_ptr<Node> findInput(const InputPath & path);
+
+    std::map<InputPath, Node::Edge> getAllInputs() const;
+
+    static std::string diff(const LockFile & oldLocks, const LockFile & newLocks);
+
+    /**
+     * Check that every 'follows' input target exists.
+     */
+    void check();
+};
+
+std::ostream & operator <<(std::ostream & stream, const LockFile & lockFile);
+
+InputPath parseInputPath(std::string_view s);
+
+std::string printInputPath(const InputPath & path);
+
+}