From 2b621c8a558e5120292037ca3046de2f2444e8e2 Mon Sep 17 00:00:00 2001
From: Max <max@privatevoid.net>
Date: Fri, 13 Jan 2023 01:56:32 +0100
Subject: [PATCH] libcmd: implement base for Activatables

---
 src/libcmd/activatables.cc | 46 +++++++++++++++++++++++++
 src/libcmd/activatables.hh | 70 ++++++++++++++++++++++++++++++++++++++
 src/libcmd/command.hh      | 29 ++++++++++++++++
 3 files changed, 145 insertions(+)
 create mode 100644 src/libcmd/activatables.cc
 create mode 100644 src/libcmd/activatables.hh

diff --git a/src/libcmd/activatables.cc b/src/libcmd/activatables.cc
new file mode 100644
index 000000000..490dba75d
--- /dev/null
+++ b/src/libcmd/activatables.cc
@@ -0,0 +1,46 @@
+#include "command.hh"
+#include "progress-bar.hh"
+
+using namespace nix;
+
+ActivatableCommand::ActivatableCommand(std::string activationPackageAttrPath)
+    : activationPackageAttrPath(activationPackageAttrPath)
+{ }
+
+void ActivatableCommand::prepare() {
+    InstallableCommand::prepare();
+    auto installableFlake = std::dynamic_pointer_cast<InstallableFlake>(installable);
+    if (installableFlake) {
+        auto fragment = *installableFlake->attrPaths.begin();
+        installable = std::make_shared<InstallableFlake>(
+                this,
+                getEvalState(),
+                std::move(installableFlake->flakeRef),
+                activationPackageAttrPath == "" ? fragment : fragment + "." + activationPackageAttrPath,
+                installableFlake->outputsSpec,
+                getDefaultFlakeAttrPaths(),
+                getDefaultFlakeAttrPathPrefixes(),
+                installableFlake->lockFlags
+            );
+    }
+}
+
+StorePath ActivatableCommand::buildActivatable(nix::ref<nix::Store> store, bool dryRun) {
+    auto installableFlake = std::dynamic_pointer_cast<InstallableFlake>(installable);
+    std::vector<std::shared_ptr<Installable>> installableContext;
+    installableContext.emplace_back(installable);
+    auto buildables = Installable::build(
+        getEvalStore(), store,
+        Realise::Outputs,
+        installableContext, bmNormal);
+
+    BuiltPaths buildables2;
+    for (auto & b : buildables)
+        buildables2.push_back(b.path);
+
+    auto buildable = buildables2.front();
+    if (buildables2.size() != 1 || buildable.outPaths().size() != 1) {
+        throw UsageError("this command requires that the argument produces a single store path");
+    }
+    return *buildable.outPaths().begin();
+}
diff --git a/src/libcmd/activatables.hh b/src/libcmd/activatables.hh
new file mode 100644
index 000000000..7b564a55b
--- /dev/null
+++ b/src/libcmd/activatables.hh
@@ -0,0 +1,70 @@
+#include "command.hh"
+#include "local-fs-store.hh"
+#include "progress-bar.hh"
+#include "shared.hh"
+
+using namespace nix;
+
+
+template<class ActivatableCommand>
+ActivatableBuildCommand<ActivatableCommand>::ActivatableBuildCommand()
+{
+    addFlag({
+        .longName = "out-link",
+        .shortName = 'o',
+        .description = "Use *path* as prefix for the symlinks to the build results. It defaults to `result`.",
+        .labels = {"path"},
+        .handler = {&outLink},
+        .completer = completePath
+    });
+
+    addFlag({
+        .longName = "no-link",
+        .description = "Do not create symlinks to the build results.",
+        .handler = {&outLink, Path("")},
+    });
+
+    addFlag({
+        .longName = "print-out-paths",
+        .description = "Print the resulting output paths",
+        .handler = {&printOutputPaths, true},
+    });
+};
+
+template<class ActivatableCommand>
+void ActivatableBuildCommand<ActivatableCommand>::run(nix::ref<Store> store)
+{
+    auto installableFlake = std::dynamic_pointer_cast<InstallableFlake>(ActivatableCommand::installable);
+    if (dryRun) {
+        std::vector<std::shared_ptr<Installable>> installableContext;
+        installableContext.emplace_back(ActivatableCommand::installable);
+        std::vector<DerivedPath> pathsToBuild;
+
+        for (auto & i : installableContext) {
+            auto b = i->toDerivedPaths();
+            pathsToBuild.insert(pathsToBuild.end(), b.begin(), b.end());
+        }
+        printMissing(store, pathsToBuild, lvlError);
+        return;
+    }
+
+    auto out = ActivatableCommand::buildActivatable(store);
+
+    if (outLink != "") {
+        if (auto store2 = store.dynamic_pointer_cast<LocalFSStore>()) {
+            std::string symlink = outLink;
+            store2->addPermRoot(out, absPath(symlink));
+        }
+    }
+
+    if (printOutputPaths) {
+        stopProgressBar();
+        std::cout << store->printStorePath(out) << std::endl;
+    }
+}
+
+template<class ActivatableCommand>
+ActivationCommand<ActivatableCommand>::ActivationCommand(std::string activationType, std::string selfCommandName)
+    : activationType(activationType),
+      selfCommandName(selfCommandName)
+{ }
diff --git a/src/libcmd/command.hh b/src/libcmd/command.hh
index 60c575d56..1ee855af0 100644
--- a/src/libcmd/command.hh
+++ b/src/libcmd/command.hh
@@ -1,5 +1,6 @@
 #pragma once
 
+#include "common-args.hh"
 #include "installables.hh"
 #include "args.hh"
 #include "common-eval-args.hh"
@@ -272,6 +273,34 @@ struct MixEnvironment : virtual Args {
     void setEnviron();
 };
 
+/* A command that operates on exactly one "activatable" */
+struct ActivatableCommand : public InstallableCommand
+{
+    ActivatableCommand(std::string activationPackageAttrPath);
+    std::string activationPackageAttrPath;
+    void prepare() override;
+    StorePath buildActivatable(nix::ref<Store> store, bool dryRun = false);
+};
+
+template<class ActivatableCommand>
+struct ActivatableBuildCommand : public ActivatableCommand, public MixDryRun
+{
+    ActivatableBuildCommand();
+    Path outLink = "result";
+    bool printOutputPaths = false;
+    void run(nix::ref<Store>) override;
+};
+
+/* A command that manages the activation of exactly one "activatable" */
+template<class ActivatableCommand>
+struct ActivationCommand : public ActivatableCommand
+{
+public: 
+    ActivationCommand(std::string activationType, std::string selfCommandName);
+    const std::string activationType;
+    const std::string selfCommandName;
+};
+
 void completeFlakeRef(ref<Store> store, std::string_view prefix);
 
 void completeFlakeRefWithFragment(