Add Amber::AreAllRequirementsSupported (#321)

It determines if the engine satisfies all requirements declared
in the recipe.

2 files changed, 46 insertions, 10 deletions

diff --git a/src/amber.cc b/src/amber.cc
index 3ad7e9a..592277a 100644
--- a/src/amber.cc
+++ b/src/amber.cc
@@ -51,16 +51,18 @@ amber::Result Amber::Parse(const std::string& input, amber::Recipe* recipe) {
   return {};
 }
 
-amber::Result Amber::Execute(const amber::Recipe* recipe, Options* opts) {
-  ShaderMap map;
-  return ExecuteWithShaderData(recipe, opts, map);
-}
-
-amber::Result Amber::ExecuteWithShaderData(const amber::Recipe* recipe,
-                                           Options* opts,
-                                           const ShaderMap& shader_data) {
+namespace {
+
+// Create an engine initialize it, and check the recipe's requirements.
+// Returns a failing result if anything fails.  Otherwise pass the created
+// engine out through |engine_ptr| and the script via |script|.  The |script|
+// pointer is borrowed, and should not be freed.
+Result CreateEngineAndCheckRequirements(const Recipe* recipe,
+                                        Options* opts,
+                                        std::unique_ptr<Engine>* engine_ptr,
+                                        Script** script_ptr) {
   if (!recipe)
-    return Result("Attempting to execute and invalid recipe");
+    return Result("Attempting to check an invalid recipe");
 
   Script* script = static_cast<Script*>(recipe->GetImpl());
   if (!script)
@@ -69,15 +71,48 @@ amber::Result Amber::ExecuteWithShaderData(const amber::Recipe* recipe,
   script->SetSpvTargetEnv(opts->spv_env);
 
   auto engine = Engine::Create(opts->engine);
-  if (!engine)
+  if (!engine) {
     return Result("Failed to create engine");
+  }
 
+  // Engine initialization checks requirements.  Current backends don't do
+  // much else.  Refactor this if they end up doing to much here.
   Result r = engine->Initialize(opts->config, script->GetRequiredFeatures(),
                                 script->GetRequiredInstanceExtensions(),
                                 script->GetRequiredDeviceExtensions());
   if (!r.IsSuccess())
     return r;
 
+  *engine_ptr = std::move(engine);
+  *script_ptr = script;
+
+  return r;
+}
+}  // namespace
+
+amber::Result Amber::AreAllRequirementsSupported(const amber::Recipe* recipe,
+                                                 Options* opts) {
+  std::unique_ptr<Engine> engine;
+  Script* script = nullptr;
+
+  return CreateEngineAndCheckRequirements(recipe, opts, &engine, &script);
+}
+
+amber::Result Amber::Execute(const amber::Recipe* recipe, Options* opts) {
+  ShaderMap map;
+  return ExecuteWithShaderData(recipe, opts, map);
+}
+
+amber::Result Amber::ExecuteWithShaderData(const amber::Recipe* recipe,
+                                           Options* opts,
+                                           const ShaderMap& shader_data) {
+  std::unique_ptr<Engine> engine;
+  Script* script = nullptr;
+  Result r = CreateEngineAndCheckRequirements(recipe, opts, &engine, &script);
+  if (!r.IsSuccess())
+    return r;
+  script->SetSpvTargetEnv(opts->spv_env);
+
   Executor executor;
   Result executor_result = executor.Execute(
       engine.get(), script, shader_data,
diff --git a/src/tests b/src/tests
new file mode 100644
index 0000000..5e30749
--- /dev/null
+++ b/src/tests
@@ -0,0 +1 @@
+2 probes in a row : no actual commands in between