[WIP] Prototype a URI Template router

Signed-off-by: Juan Cruz Viotti <jv@jviotti.com>

Author: jviotti

config.cmake.in

@@ -54,6 +54,7 @@ foreach(component ${SOURCEMETA_CORE_COMPONENTS})
   elseif(component STREQUAL "uri")
     include("${CMAKE_CURRENT_LIST_DIR}/sourcemeta_core_uri.cmake")
   elseif(component STREQUAL "uritemplate")
+    include("${CMAKE_CURRENT_LIST_DIR}/sourcemeta_core_io.cmake")
     include("${CMAKE_CURRENT_LIST_DIR}/sourcemeta_core_uritemplate.cmake")
   elseif(component STREQUAL "json")
     find_dependency(mpdecimal CONFIG)

src/core/uritemplate/CMakeLists.txt

@@ -1,7 +1,9 @@
 sourcemeta_library(NAMESPACE sourcemeta PROJECT core NAME uritemplate
-  PRIVATE_HEADERS error.h token.h
-  SOURCES helpers.h uritemplate.cc)
+  PRIVATE_HEADERS error.h token.h router.h
+  SOURCES helpers.h uritemplate.cc uritemplate_router.cc uritemplate_router_view.cc)
 
 if(SOURCEMETA_CORE_INSTALL)
   sourcemeta_library_install(NAMESPACE sourcemeta PROJECT core NAME uritemplate)
 endif()
+
+target_link_libraries(sourcemeta_core_uritemplate PUBLIC sourcemeta::core::io)

src/core/uritemplate/include/sourcemeta/core/uritemplate.h

@@ -7,6 +7,7 @@
 
 // NOLINTBEGIN(misc-include-cleaner)
 #include <sourcemeta/core/uritemplate_error.h>
+#include <sourcemeta/core/uritemplate_router.h>
 #include <sourcemeta/core/uritemplate_token.h>
 // NOLINTEND(misc-include-cleaner)
 

src/core/uritemplate/include/sourcemeta/core/uritemplate_router.h

@@ -0,0 +1,122 @@
+#ifndef SOURCEMETA_CORE_URITEMPLATE_ROUTER_H_
+#define SOURCEMETA_CORE_URITEMPLATE_ROUTER_H_
+
+#ifndef SOURCEMETA_CORE_URITEMPLATE_EXPORT
+#include <sourcemeta/core/uritemplate_export.h>
+#endif
+
+#include <sourcemeta/core/io.h>
+
+// NOLINTBEGIN(misc-include-cleaner)
+#include <sourcemeta/core/uritemplate_token.h>
+// NOLINTEND(misc-include-cleaner)
+
+#include <cstdint>     // std::uint16_t, std::uint32_t, std::uint8_t
+#include <filesystem>  // std::filesystem::path
+#include <functional>  // std::function
+#include <memory>      // std::unique_ptr
+#include <optional>    // std::optional
+#include <string_view> // std::string_view
+#include <vector>      // std::vector
+
+namespace sourcemeta::core {
+
+#if defined(_MSC_VER)
+#pragma warning(push)
+#pragma warning(disable : 4251)
+#endif
+
+/// @ingroup uritemplate
+/// A URI Template path router
+class SOURCEMETA_CORE_URITEMPLATE_EXPORT URITemplateRouter {
+public:
+  /// A handler identifier 0 means "no handler"
+  using Identifier = std::uint16_t;
+
+  /// The match callback
+  using Callback = std::function<void(std::string_view, std::string_view)>;
+
+  /// A node in the router trie
+  template <typename T> struct Node {
+    Identifier identifier{0};
+
+    // This children distinction enforces that there can only be one non-literal
+    // child at the type level. Also allows us to more efficiently search on
+    // literals
+    std::vector<std::unique_ptr<T>> literals;
+    std::unique_ptr<T> variable;
+  };
+
+  /// A token in the router trie
+  struct Token {
+    URITemplateToken value;
+    Node<Token> data;
+  };
+
+  /// Construct an empty router
+  URITemplateRouter() = default;
+
+  // To avoid mistakes
+  URITemplateRouter(const URITemplateRouter &) = delete;
+  URITemplateRouter(URITemplateRouter &&) = delete;
+  auto operator=(const URITemplateRouter &) -> URITemplateRouter & = delete;
+  auto operator=(URITemplateRouter &&) -> URITemplateRouter & = delete;
+
+  /// Add a route to the router
+  auto add(const std::string_view uri_template, const Identifier identifier)
+      -> void;
+
+  /// Save the router to a binary file
+  auto save(const std::filesystem::path &path) const -> void;
+
+  /// Match a path against the router
+  [[nodiscard]] auto match(const std::string_view path,
+                           const Callback &callback) const -> Identifier;
+
+private:
+  Node<Token> root_;
+};
+
+/// @ingroup uritemplate
+/// A read-only memory-mapped view of a serialized URI Template router
+class SOURCEMETA_CORE_URITEMPLATE_EXPORT URITemplateRouterView {
+public:
+  /// A serialized node in the binary format
+  struct alignas(8) Node {
+    std::uint32_t string_offset;
+    std::uint32_t string_length;
+    std::uint32_t first_literal_child;
+    std::uint32_t literal_child_count;
+    std::uint32_t variable_child;
+    std::uint8_t type;
+    std::uint8_t padding;
+    URITemplateRouter::Identifier identifier;
+    std::uint32_t reserved;
+  };
+
+  URITemplateRouterView(const std::filesystem::path &path);
+  ~URITemplateRouterView();
+
+  // To avoid mistakes
+  URITemplateRouterView(const URITemplateRouterView &) = delete;
+  URITemplateRouterView(URITemplateRouterView &&) = delete;
+  auto operator=(const URITemplateRouterView &)
+      -> URITemplateRouterView & = delete;
+  auto operator=(URITemplateRouterView &&) -> URITemplateRouterView & = delete;
+
+  /// Match a path against the router
+  [[nodiscard]] auto match(const std::string_view path,
+                           const URITemplateRouter::Callback &callback) const
+      -> URITemplateRouter::Identifier;
+
+private:
+  FileView file_view_;
+};
+
+#if defined(_MSC_VER)
+#pragma warning(pop)
+#endif
+
+} // namespace sourcemeta::core
+
+#endif