[core] Modularize FileSource codebase (#15768)

* [core] Introduce FileSourceManager and use it for default platform impl

  - Add `FileSourceManager` interface that provides access to `FileSource`
    instances and means of registering / unregistering `FileSource` factories
  - Split `DefaultFileSource` into smaller parts
  - Add `DatabaseFileSource` interface and it's default implementation
  - Remove inter-dependencies between concrete `FileSource` classes

* [build] Add files to next build system

* [core] Add generic property setters / getters

* [core] Remove setOnlineStatus from OnlineFileSource interface

* [core] Hide threading implementation details from DatabaseFileSource interface

* [core] Make DB file source methods virtual

* [core] Add documentation for DatabaseFileSource and rename one method

* [core] Use simple callback instead of ActorRef

* [core] Remove ActorRef from OnlineFileSource public header

* [core] Add callback to FileSource::forward async API

* [core] Pass OfflineRegionDefinition by value

* [core] Update tests to use modular file sources

* [core] Update unit tests

* [core] Update unit tests after rebase

* [core] Backport low prio fix for cached requests

* [core] Backport pack database

* [core] Return removed factory from unRegisterFileSourceFactory

* [core] Rename shadowed args in onlinefilesource

* [core] Remove simple std::function callback aliases

* [core] Expose online file source property keys in public header file

* [test-runner] Add proxy file source test runner

* [cache] Update mbgl-cache utility to use new file source

* [metrics] Rebaseline binary size metrics

* [offline] Update offline utility

* [core] Update changelog

5 files changed, 48 insertions, 22 deletions

diff --git a/render-test/file_source.cpp b/render-test/file_source.cpp
index 4d6a800d1c..f72bc08e37 100644
--- a/render-test/file_source.cpp
+++ b/render-test/file_source.cpp
@@ -1,6 +1,11 @@
+#include <mbgl/storage/file_source_manager.hpp>
+#include <mbgl/storage/resource.hpp>
 #include <mbgl/storage/resource_options.hpp>
+#include <mbgl/util/async_request.hpp>
 #include <mbgl/util/logging.hpp>
 
+#include <atomic>
+
 #include "file_source.hpp"
 
 namespace mbgl {
@@ -10,8 +15,14 @@ std::atomic_size_t transferredSize{0};
 std::atomic_bool active{false};
 std::atomic_bool offline{true};
 
-ProxyFileSource::ProxyFileSource(const std::string& cachePath, const std::string& assetPath)
-    : DefaultFileSource(cachePath, assetPath, false) {}
+ProxyFileSource::ProxyFileSource(std::shared_ptr<FileSource> defaultResourceLoader_, const ResourceOptions& options)
+    : defaultResourceLoader(std::move(defaultResourceLoader_)) {
+    assert(defaultResourceLoader);
+    if (offline) {
+        auto dbfs = FileSourceManager::get()->getFileSource(FileSourceType::Database, options);
+        dbfs->setProperty("read-only-mode", true);
+    }
+}
 
 ProxyFileSource::~ProxyFileSource() = default;
 
@@ -43,7 +54,7 @@ std::unique_ptr<AsyncRequest> ProxyFileSource::request(const Resource& resource,
         }
     }
 
-    return DefaultFileSource::request(transformed, [=](Response response) {
+    return defaultResourceLoader->request(transformed, [=](Response response) {
         if (transformed.loadingMethod == Resource::LoadingMethod::CacheOnly && response.noContent) {
             if (transformed.kind == Resource::Kind::Tile && transformed.tileData) {
                 mbgl::Log::Info(mbgl::Event::Database,
@@ -64,19 +75,6 @@ std::unique_ptr<AsyncRequest> ProxyFileSource::request(const Resource& resource,
     });
 }
 
-std::shared_ptr<FileSource> FileSource::createPlatformFileSource(const ResourceOptions& options) {
-    auto fileSource = std::make_shared<ProxyFileSource>(options.cachePath(), options.assetPath());
-
-    fileSource->setAccessToken(options.accessToken());
-    fileSource->setAPIBaseURL(options.baseURL());
-
-    if (offline) {
-        fileSource->reopenDatabaseReadOnlyForTesting();
-    }
-
-    return fileSource;
-}
-
 // static
 void ProxyFileSource::setOffline(bool status) {
     offline = status;
diff --git a/render-test/file_source.hpp b/render-test/file_source.hpp
index 34ba739a22..d0496ab8f6 100644
--- a/render-test/file_source.hpp
+++ b/render-test/file_source.hpp
@@ -1,15 +1,18 @@
 #pragma once
 
-#include <mbgl/storage/default_file_source.hpp>
+#include <mbgl/storage/file_source.hpp>
 
 namespace mbgl {
 
-class ProxyFileSource : public DefaultFileSource {
+class ResourceOptions;
+
+class ProxyFileSource : public FileSource {
 public:
-    ProxyFileSource(const std::string& cachePath, const std::string& assetPath);
+    ProxyFileSource(std::shared_ptr<FileSource>, const ResourceOptions&);
     ~ProxyFileSource();
 
-    std::unique_ptr<AsyncRequest> request(const Resource&, Callback);
+    std::unique_ptr<AsyncRequest> request(const Resource&, Callback) override;
+    bool canRequest(const Resource&) const override { return true; }
 
     /**
      * @brief Flag to change the networking mode of the file source.
@@ -39,6 +42,9 @@ public:
      * @return size_t
      */
     static size_t getTransferredSize();
+
+private:
+    std::shared_ptr<FileSource> defaultResourceLoader;
 };
 
 } // namespace mbgl
diff --git a/render-test/parser.cpp b/render-test/parser.cpp
index 484428976e..8147852c4f 100644
--- a/render-test/parser.cpp
+++ b/render-test/parser.cpp
@@ -8,6 +8,7 @@
 
 #include <mbgl/map/map.hpp>
 #include <mbgl/renderer/renderer.hpp>
+#include <mbgl/storage/resource.hpp>
 #include <mbgl/style/conversion/filter.hpp>
 #include <mbgl/style/conversion/json.hpp>
 #include <mbgl/style/conversion/layer.hpp>
diff --git a/render-test/runner.cpp b/render-test/runner.cpp
index 0492868051..cbfb0c34be 100644
--- a/render-test/runner.cpp
+++ b/render-test/runner.cpp
@@ -2,6 +2,7 @@
 #include <mbgl/map/map_observer.hpp>
 #include <mbgl/renderer/renderer.hpp>
 #include <mbgl/renderer/renderer_observer.hpp>
+#include <mbgl/storage/file_source_manager.hpp>
 #include <mbgl/style/image.hpp>
 #include <mbgl/style/layer.hpp>
 #include <mbgl/style/light.hpp>
@@ -86,7 +87,26 @@ std::string simpleDiff(const Value& result, const Value& expected) {
 }
 
 TestRunner::TestRunner(Manifest manifest_, UpdateResults updateResults_)
-    : manifest(std::move(manifest_)), updateResults(updateResults_) {}
+    : manifest(std::move(manifest_)), updateResults(updateResults_) {
+    registerProxyFileSource();
+}
+
+void TestRunner::registerProxyFileSource() {
+    static std::once_flag registerProxyFlag;
+    std::call_once(registerProxyFlag, [] {
+        auto* fileSourceManager = mbgl::FileSourceManager::get();
+
+        auto resourceLoaderFactory =
+            fileSourceManager->unRegisterFileSourceFactory(mbgl::FileSourceType::ResourceLoader);
+        auto factory = [defaultFactory = std::move(resourceLoaderFactory)](const mbgl::ResourceOptions& options) {
+            assert(defaultFactory);
+            std::shared_ptr<FileSource> fileSource = defaultFactory(options);
+            return std::make_unique<ProxyFileSource>(std::move(fileSource), options);
+        };
+
+        fileSourceManager->registerFileSourceFactory(mbgl::FileSourceType::ResourceLoader, std::move(factory));
+    });
+}
 
 const Manifest& TestRunner::getManifest() const {
     return manifest;
@@ -654,7 +674,7 @@ uint32_t getImageTileOffset(const std::set<uint32_t>& dims, uint32_t dim) {
 TestRunner::Impl::Impl(const TestMetadata& metadata, const mbgl::ResourceOptions& resourceOptions)
     : observer(std::make_unique<TestRunnerMapObserver>()),
       frontend(metadata.size, metadata.pixelRatio, swapBehavior(metadata.mapMode)),
-      fileSource(mbgl::FileSource::getSharedFileSource(resourceOptions)),
+      fileSource(mbgl::FileSourceManager::get()->getFileSource(mbgl::FileSourceType::ResourceLoader, resourceOptions)),
       map(frontend,
           *observer.get(),
           mbgl::MapOptions()
diff --git a/render-test/runner.hpp b/render-test/runner.hpp
index e6027e335c..72320dd34f 100644
--- a/render-test/runner.hpp
+++ b/render-test/runner.hpp
@@ -53,6 +53,7 @@ private:
                                TestMetadata&);
     void checkRenderTestResults(mbgl::PremultipliedImage&& image, TestMetadata&);
     void checkProbingResults(TestMetadata&);
+    void registerProxyFileSource();
 
     struct Impl {
         Impl(const TestMetadata&, const mbgl::ResourceOptions&);