image: Significantly refactor how backends are registered

4 files changed, 71 insertions, 44 deletions

diff --git a/image/backends/backends.hh b/image/backends/backends.hh
deleted file mode 100644
index 3199ee0..0000000
--- a/image/backends/backends.hh
+++ /dev/null
@@ -1,33 +0,0 @@
-/*
- * backends.hh - Horizon Image Creation backend table
- * image, the image processing utilities for
- * Project Horizon
- *
- * Copyright (c) 2020 Adélie Linux and contributors.  All rights reserved.
- * This code is licensed under the AGPL 3.0 license, as noted in the
- * LICENSE-code file in the root directory of this repository.
- *
- * SPDX-License-Identifier: AGPL-3.0-only
- */
-
-#pragma once
-
-#include <functional>
-#include <string>
-#include <vector>
-
-namespace Horizon {
-namespace Image {
-
-class BasicBackend;
-
-struct BackendDescriptor {
-    std::string type_code;
-    std::string description;
-    std::function<BasicBackend *(std::string, std::string)> creation_fn;
-};
-
-extern std::vector<BackendDescriptor> known_backends;
-
-}
-}
diff --git a/image/backends/basic.cc b/image/backends/basic.cc
index 908f1d9..dbe387c 100644
--- a/image/backends/basic.cc
+++ b/image/backends/basic.cc
@@ -11,7 +11,6 @@
  */
 
 #include "basic.hh"
-#include "backends.hh"
 
 namespace Horizon {
 namespace Image {
@@ -21,6 +20,10 @@ std::vector<BackendDescriptor> known_backends = {
    {"squashfs", "Create a SquashFS image (.squashfs)", [](std::string, std::string){ return nullptr; } }
 };
 
+const std::vector<BackendDescriptor> BasicBackend::available_backends() {
+    return known_backends;
+}
+
 int BasicBackend::prepare() {
     /* The default implementation returns success immediately;
      * no preparation is required. */
diff --git a/image/backends/basic.hh b/image/backends/basic.hh
index d39c57e..3181f69 100644
--- a/image/backends/basic.hh
+++ b/image/backends/basic.hh
@@ -12,11 +12,21 @@
 
 #pragma once
 
+#include <functional>
 #include <string>
+#include <vector>
 
 namespace Horizon {
 namespace Image {
 
+class BasicBackend;
+
+struct BackendDescriptor {
+    std::string type_code;
+    std::string description;
+    std::function<BasicBackend *(std::string, std::string)> creation_fn;
+};
+
 class BasicBackend {
 public:
     /*! Create the backend object.
@@ -43,6 +53,9 @@ public:
      */
     virtual int finalise();
 
+    /*! Returns a list of available backends. */
+    static const std::vector<BackendDescriptor> available_backends();
+
     /*! The intermediate directory which contains the sysroot the image
      *  should contain. */
     const std::string &ir_dir;
diff --git a/image/creator.cc b/image/creator.cc
index ce688fa..70571fa 100644
--- a/image/creator.cc
+++ b/image/creator.cc
@@ -13,7 +13,7 @@
 #include <boost/program_options.hpp>
 #include <cstdlib>              /* EXIT_* */
 #include <string>
-#include "backends/backends.hh"
+#include "backends/basic.hh"
 #include "hscript/script.hh"
 #include "util/output.hh"
 
@@ -28,9 +28,13 @@ bool pretty = true;     /*! Controls ASCII colour output */
 /*! Entry-point for the image creation utility. */
 int main(int argc, char *argv[]) {
     using namespace boost::program_options;
+    using namespace Horizon::Image;
+
     bool needs_help{}, disable_pretty{};
     int exit_code = EXIT_SUCCESS;
-    std::string if_path{"/etc/horizon/installfile"}, ir_dir{"/target"}, type_code{"tar"};
+    std::string if_path{"/etc/horizon/installfile"}, ir_dir{"/target"},
+                output_path{"image.tar"}, type_code{"tar"};
+    BasicBackend *backend = nullptr;
     Horizon::ScriptOptions opts;
     Horizon::Script *my_script;
 
@@ -89,9 +93,9 @@ int main(int argc, char *argv[]) {
     if(type_code == "list") {
         std::cout << "Type codes known by this build of Image Creation:"
                   << std::endl << std::endl;
-        for(auto &backend : Horizon::Image::known_backends) {
-            std::cout << std::setw(10) << std::left << backend.type_code
-                      << backend.description << std::endl;
+        for(const auto &candidate : BasicBackend::available_backends()) {
+            std::cout << std::setw(10) << std::left << candidate.type_code
+                      << candidate.description << std::endl;
         }
         return EXIT_SUCCESS;
     }
@@ -100,6 +104,27 @@ int main(int argc, char *argv[]) {
         if_path = vm["installfile"].as<std::string>();
     }
 
+    if(!vm["ir-dir"].empty()) {
+        ir_dir = vm["ir-dir"].as<std::string>();
+    }
+
+    if(!vm["output"].empty()) {
+        output_path = vm["output"].as<std::string>();
+    }
+
+    /* Load the proper backend. */
+    for(const auto &candidate : BasicBackend::available_backends()) {
+        if(candidate.type_code == type_code) {
+            backend = candidate.creation_fn(ir_dir, output_path);
+            break;
+        }
+    }
+    if(backend == nullptr) {
+        output_error("command-line", "unsupported backend or internal error",
+                     type_code);
+        return EXIT_FAILURE;
+    }
+
     opts.set(Horizon::InstallEnvironment);
     opts.set(Horizon::ImageOnly);
 
@@ -112,15 +137,34 @@ int main(int argc, char *argv[]) {
 
     /* if an error occurred during parsing, bail out now */
     if(!my_script) {
-        return EXIT_FAILURE;
-    }
+        exit_code = EXIT_FAILURE;
+        goto early_trouble;
+    } else {
+        int ret;
 
-    if(!vm["ir-dir"].empty()) {
-        my_script->setTargetDirectory(vm["ir-dir"].as<std::string>());
+        if(!my_script->execute()) {
+            exit_code = EXIT_FAILURE;
+            goto trouble;
+        }
+
+#define RUN_PHASE_OR_TROUBLE(_PHASE, _FRIENDLY) \
+    ret = backend->_PHASE();\
+    if(ret != 0) {\
+        output_error("internal", "error during output " _FRIENDLY,\
+                     std::to_string(ret));\
+        exit_code = EXIT_FAILURE;\
+        goto trouble;\
     }
 
-    my_script->execute();
+        RUN_PHASE_OR_TROUBLE(prepare, "preparation");
+        RUN_PHASE_OR_TROUBLE(create, "creation");
+        RUN_PHASE_OR_TROUBLE(finalise, "finalisation");
+    }
 
+trouble:        /* delete the Script and exit */
     delete my_script;
+early_trouble:  /* no script yet */
+    delete backend;
+
     return exit_code;
 }