Move fetchers from libstore to libfetchers

src/libfetchers/registry.hh

@@ -0,0 +1,62 @@
+#pragma once
+
+#include "types.hh"
+#include "fetchers.hh"
+
+namespace nix { class Store; }
+
+namespace nix::fetchers {
+
+struct Registry
+{
+    enum RegistryType {
+        Flag = 0,
+        User = 1,
+        Global = 2,
+    };
+
+    RegistryType type;
+
+    std::vector<
+        std::tuple<
+            std::shared_ptr<const Input>, // from
+            std::shared_ptr<const Input>, // to
+            Attrs // extra attributes
+            >
+        > entries;
+
+    Registry(RegistryType type)
+        : type(type)
+    { }
+
+    static std::shared_ptr<Registry> read(
+        const Path & path, RegistryType type);
+
+    void write(const Path & path);
+
+    void add(
+        const std::shared_ptr<const Input> & from,
+        const std::shared_ptr<const Input> & to,
+        const Attrs & extraAttrs);
+
+    void remove(const std::shared_ptr<const Input> & input);
+};
+
+typedef std::vector<std::shared_ptr<Registry>> Registries;
+
+std::shared_ptr<Registry> getUserRegistry();
+
+Path getUserRegistryPath();
+
+Registries getRegistries(ref<Store> store);
+
+void overrideRegistry(
+    const std::shared_ptr<const Input> & from,
+    const std::shared_ptr<const Input> & to,
+    const Attrs & extraAttrs);
+
+std::pair<std::shared_ptr<const Input>, Attrs> lookupInRegistries(
+    ref<Store> store,
+    std::shared_ptr<const Input> input);
+
+}