feat: Add context type, value type, and associated builders.

libs/common/CMakeLists.txt

@@ -21,12 +21,15 @@ if (CMAKE_PROJECT_NAME STREQUAL PROJECT_NAME)
     set_property(GLOBAL PROPERTY USE_FOLDERS ON)
 endif ()
 
-#set(CMAKE_FILES "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
-#set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} ${CMAKE_FILES})
-
 # Needed to fetch external dependencies. 
 include(FetchContent)
 
+set(Boost_USE_STATIC_LIBS OFF)
+set(Boost_USE_MULTITHREADED ON)
+set(Boost_USE_STATIC_RUNTIME OFF)
+find_package(Boost 1.80 REQUIRED)
+message(STATUS "LaunchDarkly: using Boost v${Boost_VERSION}")
+
 # Add main SDK sources.
 add_subdirectory(src)
 

libs/common/include/attribute_reference.hpp

@@ -1,9 +1,13 @@
 #pragma once
 
+#include <cstddef>
 #include <ostream>
 #include <string>
+#include <unordered_set>
 #include <vector>
 
+#include <boost/container_hash/hash.hpp>
+
 namespace launchdarkly {
 
 /**
@@ -28,6 +32,19 @@ namespace launchdarkly {
  */
 class AttributeReference {
    public:
+    /**
+     * Provides a hashing function for use with unordered sets.
+     */
+    struct HashFunction {
+        std::size_t operator()(AttributeReference const& ref) const {
+            return boost::hash_range(ref.components_.begin(),
+                                     ref.components_.end());
+        }
+    };
+
+    using SetType = std::unordered_set<AttributeReference,
+                                       AttributeReference::HashFunction>;
+
     /**
      * Get the component of the attribute reference at the specified depth.
      *
@@ -38,15 +55,15 @@ class AttributeReference {
      * @return The component at the specified depth or an empty string if the
      * depth is out of bounds.
      */
-    std::string const& component(size_t depth) const;
+    std::string const& component(std::size_t depth) const;
 
     /**
      * Get the total depth of the reference.
      *
      * For example, depth() on the reference `/a/b/c` would return 3.
      * @return
      */
-    size_t depth() const;
+    std::size_t depth() const;
 
     /**
      * Check if the reference is a "kind" reference. Either `/kind` or `kind`.
@@ -94,10 +111,34 @@ class AttributeReference {
         return os;
     }
 
+    /**
+     * Construct an attribute reference from a string.
+     * @param ref_str The string to make an attribute reference from.
+     */
+    AttributeReference(std::string ref_str);
+
+    /**
+     * Construct an attribute reference from a constant string.
+     * @param ref_str The string to make an attribute reference from.
+     */
+    AttributeReference(char const* ref_str);
+
+    bool operator==(AttributeReference const& other) const {
+        return components_ == other.components_;
+    }
+
+    bool operator!=(AttributeReference const& other) const {
+        return !(*this == other);
+    }
+
+    bool operator<(AttributeReference const& rhs) const {
+        return components_ < rhs.components_;
+    }
+
    private:
     AttributeReference(std::string str, bool is_literal);
 
-    bool valid_;
+    bool valid_ = false;
 
     std::string redaction_name_;
     std::vector<std::string> components_;

libs/common/include/attributes.hpp

@@ -0,0 +1,151 @@
+#pragma once
+
+#include <string>
+#include <unordered_set>
+
+#include "attribute_reference.hpp"
+#include "value.hpp"
+
+namespace launchdarkly {
+
+/**
+ * A collection of attributes that can be present within a context.
+ * A multi-context has multiple sets of attributes keyed by their "kind".
+ */
+class Attributes {
+   public:
+    /**
+     * Get the key for the context.
+     * @return A reference to the context key.
+     */
+    std::string const& key() const;
+
+    /**
+     * Get the name for the context.
+     *
+     * @return A reference to the context name, or an empty string if no name
+     * is set.
+     */
+    std::string const& name() const;
+
+    /**
+     * Is the context anonymous or not. Defaults to false.
+     * @return True if the context is anonymous.
+     */
+    bool anonymous() const;
+
+    /**
+     * Get a set of the private attributes for the context.
+     * @return The set of private attributes for the context.
+     */
+    AttributeReference::SetType const& private_attributes() const {
+        return private_attributes_;
+    }
+
+    /**
+     * Gets the item by the specified attribute reference, or returns a null
+     * Value.
+     * @param ref The reference to get an attribute by.
+     * @return A Value containing the requested field, or a Value representing
+     * null.
+     */
+    launchdarkly::Value const& get(
+        launchdarkly::AttributeReference const& ref) const {
+        if (!ref.valid()) {
+            // Cannot index by invalid references.
+            return launchdarkly::Value::null();
+        }
+        if (ref.is_kind()) {
+            // Cannot access kind.
+            return launchdarkly::Value::null();
+        }
+
+        if (ref.depth() == 1) {
+            // Handle built-in attributes.
+            if (ref.component(0) == "key") {
+                return key_;
+            }
+            if (ref.component(0) == "name") {
+                return name_;
+            }
+            if (ref.component(0) == "anonymous") {
+                return anonymous_;
+            }
+        }
+
+        launchdarkly::Value const* node = &custom_attributes_;
+        bool found = true;
+        for (size_t index = 0; index < ref.depth(); index++) {
+            auto const& component = ref.component(index);
+            if (node->is_object()) {
+                auto const& map = node->as_object();
+                if (auto search = map.find(component); search != map.end()) {
+                    node = &search->second;
+                } else {
+                    found = false;
+                    break;
+                }
+            } else {
+                found = false;
+            }
+        }
+        if (!found) {
+            return launchdarkly::Value::null();
+        }
+        return *node;
+    }
+
+    /**
+     * Construct a set of attributes. This is used internally by the SDK
+     * but is not intended to used by consumers of the SDK.
+     *
+     * @param key The key for the context.
+     * @param name The name of the context.
+     * @param anonymous If the context is anonymous.
+     * @param attributes Additional attributes for the context.
+     * @param private_attributes A list of attributes that should be private.
+     */
+    Attributes(std::string key,
+               std::optional<std::string> name,
+               bool anonymous,
+               launchdarkly::Value attributes,
+               AttributeReference::SetType private_attributes =
+                   AttributeReference::SetType())
+        : key_(std::move(key)),
+          name_(std::move(name)),
+          anonymous_(anonymous),
+          custom_attributes_(std::move(attributes)),
+          private_attributes_(std::move(private_attributes)) {}
+
+    friend std::ostream& operator<<(std::ostream& out,
+                                    Attributes const& attrs) {
+        out << "{key: " << attrs.key_ << ", "
+            << " name: " << attrs.name_ << " anonymous: " << attrs.anonymous_
+            << " private: [";
+        bool first = true;
+        for (auto const& private_attribute : attrs.private_attributes_) {
+            if (first) {
+                first = false;
+            } else {
+                out << ", ";
+            }
+            out << private_attribute;
+        }
+        out << "] "
+            << " custom: " << attrs.custom_attributes_ << "}";
+
+        return out;
+    }
+
+   private:
+    // Built-in attributes.
+    launchdarkly::Value key_;
+    launchdarkly::Value name_;
+    launchdarkly::Value anonymous_;
+    AttributeReference::SetType private_attributes_;
+
+    launchdarkly::Value custom_attributes_;
+
+    // Kinds are contained at the context level, not inside attributes.
+};
+}  // namespace launchdarkly