From f900a81e7ad282dbad5c7fcfd1be58f081a04826 Mon Sep 17 00:00:00 2001
From: sabrina-shanman <sabrina@highfidelity.io>
Date: Wed, 14 Nov 2018 15:33:40 -0800
Subject: [PATCH] Add ModelLoader

---
 .../src/model-networking/ModelLoader.cpp      | 52 +++++++++++
 .../src/model-networking/ModelLoader.h        | 87 +++++++++++++++++++
 2 files changed, 139 insertions(+)
 create mode 100644 libraries/model-networking/src/model-networking/ModelLoader.cpp
 create mode 100644 libraries/model-networking/src/model-networking/ModelLoader.h

diff --git a/libraries/model-networking/src/model-networking/ModelLoader.cpp b/libraries/model-networking/src/model-networking/ModelLoader.cpp
new file mode 100644
index 0000000000..3eb1bec9f0
--- /dev/null
+++ b/libraries/model-networking/src/model-networking/ModelLoader.cpp
@@ -0,0 +1,52 @@
+//
+//  ModelLoader.cpp
+//  libraries/model-networking/src/model-networking
+//
+//  Created by Sabrina Shanman on 2018/11/14.
+//  Copyright 2018 High Fidelity, Inc.
+//
+//  Distributed under the Apache License, Version 2.0.
+//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
+//
+
+#include "ModelLoader.h"
+
+hfm::Model::Pointer ModelLoader::load(const hifi::ByteArray& data, const hifi::VariantHash& mapping, const hifi::URL& url, const std::string& webMediaType) const {
+    // Check file contents
+    for (auto& supportedFormat : supportedFormats) {
+        for (auto& fileSignature : supportedFormat.mimeType.fileSignatures) {
+            auto testBytes = data.mid(fileSignature.byteOffset, (int)fileSignature.bytes.size()).toStdString();
+            if (testBytes == fileSignature.bytes) {
+                return supportedFormat.loader(data, mapping, url);
+            }
+        }
+    }
+
+    // Check file extension
+    std::string urlString = url.path().toStdString();
+    std::size_t extensionSeparator = urlString.rfind('.');
+    if (extensionSeparator != std::string::npos) {
+        std::string detectedExtension = urlString.substr(extensionSeparator + 1);
+        for (auto& supportedFormat : supportedFormats) {
+            for (auto& extension : supportedFormat.mimeType.extensions) {
+                if (extension == detectedExtension) {
+                    return supportedFormat.loader(data, mapping, url);
+                }
+            }
+        }
+    }
+
+    // Check web media type
+    if (webMediaType != "") {
+        for (auto& supportedFormat : supportedFormats) {
+            for (auto& candidateWebMediaType : supportedFormat.mimeType.webMediaTypes) {
+                if (candidateWebMediaType == webMediaType) {
+                    return supportedFormat.loader(data, mapping, url);
+                }
+            }
+        }
+    }
+
+    // Supported file type not found. Abort loading.
+    return hfm::Model::Pointer();
+}
diff --git a/libraries/model-networking/src/model-networking/ModelLoader.h b/libraries/model-networking/src/model-networking/ModelLoader.h
new file mode 100644
index 0000000000..1a8901e8da
--- /dev/null
+++ b/libraries/model-networking/src/model-networking/ModelLoader.h
@@ -0,0 +1,87 @@
+//
+//  ModelLoader.h
+//  libraries/model-networking/src/model-networking
+//
+//  Created by Sabrina Shanman on 2018/11/13.
+//  Copyright 2018 High Fidelity, Inc.
+//
+//  Distributed under the Apache License, Version 2.0.
+//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
+//
+
+#ifndef hifi_ModelLoader_h
+#define hifi_ModelLoader_h
+
+#include <vector>
+#include <string>
+#include <functional>
+
+#include <shared/Hifitypes.h>
+#include <hfm/HFM.h>
+
+class ModelLoader {
+public:
+
+    // A short sequence of bytes, typically at the beginning of the file, which identifies the file format
+    class FileSignature {
+    public:
+        FileSignature(const std::string& bytes, int byteOffset) :
+            bytes(bytes),
+            byteOffset(byteOffset) {
+        }
+
+        std::string bytes;
+        int byteOffset;
+    };
+
+    // A named file extension with a list of known ways to positively identify the file type
+    class MIMEType {
+    public:
+        MIMEType(const std::string& name) :
+            name(name) {
+        }
+
+        std::string name;
+        std::vector<std::string> extensions;
+        std::vector<std::string> webMediaTypes;
+        std::vector<FileSignature> fileSignatures;
+    };
+
+    // T is a subclass of hfm::Serializer
+    template <typename T>
+    void addSupportedFormat(const MIMEType& mimeType) {
+        supportedFormats.push_back(SupportedFormat(mimeType, SupportedFormat::getLoader<T>()));
+    }
+
+    // Given the currently stored list of supported file formats, determine how to load a model from the given parameters.
+    // If successful, return an owned reference to the newly loaded model.
+    // If failed, return an empty reference.
+    hfm::Model::Pointer load(const hifi::ByteArray& data, const hifi::VariantHash& mapping, const hifi::URL& url, const std::string& webMediaType) const;
+    
+protected:
+    using Loader = std::function<hfm::Model::Pointer(const hifi::ByteArray&, const hifi::VariantHash&, const hifi::URL&)>;
+
+    class SupportedFormat {
+    public:
+        SupportedFormat(const MIMEType& mimeType, const Loader& loader) :
+            mimeType(mimeType),
+            loader(loader) {
+        }
+
+        MIMEType mimeType;
+        Loader loader;
+
+        template <typename T>
+        static Loader getLoader() {
+            assert(dynamic_cast<hfm::Serializer*>(&T()));
+
+            return [](const hifi::ByteArray& bytes, const hifi::VariantHash& mapping, const hifi::URL& url) -> hfm::Model::Pointer {
+                return T().read(bytes, mapping, url);
+            };
+        }
+    };
+
+    std::vector<SupportedFormat> supportedFormats;
+};
+
+#endif // hifi_ModelLoader_h