vjson.h

/////////////////////////////////////////////////////////////////////////////
//
// Yes, it's yet another C++ JSON parser/printer and DOM. Please see the
// README for some of the goals of this code, and why I wasn't happy with
// the other JSON DOMs/parsers I found and decided to reinvent this wheel.
//
/////////////////////////////////////////////////////////////////////////////

#ifndef VJSON_H_INCLUDED
#define VJSON_H_INCLUDED

#include <string.h>
#include <stdint.h>
#include <stddef.h>
#include <inttypes.h>
#include <string>
#include <vector>
#include <map>

// @VALVE Memory validation, etc
#include <tier0/dbg.h>
#ifdef DBGFLAG_VALIDATE
	#include <tier0/validator.h>
#endif
#include <tier0/memdbgoff.h>
#define VJSON_ASSERT Assert

// #define VJSON_ASSERT to something else if you want to customize
// assertion behaviour. Assertions during parsing are only for bugs, not for
// malformed input. Some functions may assert if used incorrectly, and so
// if you write code that is totally intolerant of a document that doesn't
// match your expectations, you might assert. (There's always an easy way to
// avoid such assertions, though.)
#ifndef VJSON_ASSERT
	#include <assert.h>
	#define VJSON_ASSERT assert
#endif

// Default printing options.
#ifndef VJSON_DEFAULT_INDENT
	#define VJSON_DEFAULT_INDENT "\t"
#endif

namespace vjson {

// The different type of JSON values
enum EValueType
{
	kNull,
	kObject, // E.g. { "key1": "value1, "key2": 456 } Aka "dictionary" or "map". In JSON, they are usually called "objects"
	kArray, // E.g. [ "value1", 456, { } ]
	kString,
	kDouble,
	kNumber = kDouble, // Add a type alias - numbers are always doubles in JSON
	kBool,
	kDeleted, // used for debugging only
};

// Different things that can happen if you try to fetch a value. You'll interact with
// this type when you want to have robust error handling against malformed documents.
// Note that using accessors that return defaults on if anything goes wrong is another
// approach. Also, not all result values are appropriate in all situations
enum EResult
{
	kOK,
	kWrongType, // You asked for a value of type X, but we are type Y
	kNotArray, // You tried to access at item by array index from a value that is not an array
	kBadIndex, // Index was out of range
	kNotObject, // You tried to access at item by object key from a value that is not an object
	kBadKey, // Key not found in object
};

// Internal implementation details. Nothing to see here, move along...
class Value; class Object; class Array;
struct PrintOptions; struct ParseContext;
struct ObjectKeyLess
{
	bool operator()( const std::string &l, const std::string &r ) const { return strcmp( l.c_str(), r.c_str() ) < 0; }

	// With C++14, we don't need to make a copy of the key to do lookup,
	// so long as the comparator can compare the types.
	bool operator()( const std::string &l, const char *r ) const { return strcmp( l.c_str(), r ) < 0; }
	bool operator()( const char *l, const std::string &r ) const { return strcmp( l, r.c_str() ) < 0; }

	// FIXME string_view?
};
using RawObject = std::map<std::string, Value, ObjectKeyLess>; // Internal storage for for objects.
using RawArray = std::vector<Value>; // Internal storage for arrays
using ObjectItem = RawObject::value_type; // A.k.a. std::pair<const std::string,Value>. You'll get a reference to this when you iterate an Object
template<typename T> struct TypeTraits {};
template<> struct TypeTraits<std::nullptr_t> { static constexpr EValueType kType = kNull; using AsReturnType = void; using AsReturnTypeConst = void; };
template<> struct TypeTraits<bool> { static constexpr EValueType kType = kBool; using AsReturnType = bool&; using AsReturnTypeConst = const bool&; };
template<> struct TypeTraits<double> { static constexpr EValueType kType = kDouble; using AsReturnType = double&; using AsReturnTypeConst = const double&; };
template<> struct TypeTraits<int> { static constexpr EValueType kType = kNumber; using AsReturnType = int; using AsReturnTypeConst = int; };
template<> struct TypeTraits<const char *> { static constexpr EValueType kType = kString; using AsReturnType = const char *; using AsReturnTypeConst = const char *; };
template<> struct TypeTraits<std::string> { static constexpr EValueType kType = kString; using AsReturnType = std::string &; using AsReturnTypeConst = const std::string &; };
template<> struct TypeTraits<Object> { static constexpr EValueType kType = kObject; using AsReturnType = Object &; using AsReturnTypeConst = const Object &; };
template<> struct TypeTraits<Array> { static constexpr EValueType kType = kArray; using AsReturnType = Array &; using AsReturnTypeConst = const Array &; };
template<typename T, typename V, typename A, typename R> struct ArrayIter;
template<typename T> using ConstArrayIter = ArrayIter<T, const Value, const RawArray, typename TypeTraits<T>::AsReturnTypeConst >;
template<typename T> using MutableArrayIter = ArrayIter<T, Value, RawArray, typename TypeTraits<T>::AsReturnType >;
template<typename T, typename A, typename I> struct ArrayRange;
template<typename T> using ConstArrayRange = ArrayRange< T, const RawArray, ConstArrayIter<T> >;
template<typename T> using MutableArrayRange = ArrayRange< T, RawArray, MutableArrayIter<T> >;

/////////////////////////////////////////////////////////////////////////////
//
// Options for printing and parsing
//
/////////////////////////////////////////////////////////////////////////////

// Specify options for how you want your JSON formatted.
struct PrintOptions
{
	// How to indent. If empty, we use "minified" json with absolutely
	// no extra whitespace. Otherwise, we assume you want to
	// pretty-print, with the specified indentation repeated for each
	// indentation level. You can use tabs or spaces, as your preference.
	const char *indent = VJSON_DEFAULT_INDENT;
};

// Struct used to pass parsing options, and receive the error message
struct ParseContext
{
	// Options
	bool allow_trailing_comma = false;
	bool allow_cpp_comments = false;

	// If there's an error, it will be returned here
	std::string error_message;

	// Line where error occurred. 1-based
	int error_line = 0;

	// Byte offset where the error occurred. 0-based.
	int error_byte_offset = 0;
};


/////////////////////////////////////////////////////////////////////////////
//
// DOM classes
//
/////////////////////////////////////////////////////////////////////////////

// Return a reference to a Null value, empty array, or empty object.
// Do not modify this object!
extern const Value &GetStaticNullValue();
extern const Array &GetStaticEmptyArray();
extern const Object &GetStaticEmptyObject();

// A Value is a "node" in the DOM, either a primitive type (null, string,
// bool, or number) or an aggregate type (object or array).
class Value
{
public:

	//
	// Construction and assignment
	//

	// Default constructor sets us to a null value
	Value() : _type( kNull ) {}

	// Construct value with the given kind and default value for that kind (0 or empty)
	explicit Value( EValueType type );

	// Basic C++ object lifetime stuff
	Value( const Value &x ) { InternalConstruct( x ); }
	Value( Value &&x ) { InternalConstruct( std::forward<Value>( x ) ); }
	~Value() { InternalDestruct(); }

	// Construct directly from primitive values.
	Value( bool x ) : _type( kBool ) { _bool = x; }
	Value( double x ) : _type( kDouble ) { _double = x; }
	Value( int x ) : _type( kDouble ) { _double = (double)x; }
	Value( const char * x );
	Value( const std::string &x );
	Value( std::string && x );
	Value( std::nullptr_t ) = delete; // To avoid confusion. Use default constructor or kNull

	// Construct from internal object/array storage
	Value( const RawObject & x );
	Value( RawObject && x );
	Value( const RawArray & x );
	Value( RawArray && x );

	// Assignment
	Value &operator=( const Value & x );
	Value &operator=( Value && x );
	Value &operator=( bool x ) { InternalDestruct(); _type = kBool; _bool = x; return *this; }
	Value &operator=( double x ) { InternalDestruct(); _type = kDouble; _double = x; return *this; }
	Value &operator=( int x ) { InternalDestruct(); _type = kDouble; _double = (double)x; return *this; }
	Value &operator=( const char * x );
	Value &operator=( const std::string &x );
	Value &operator=( std::string && x );
	Value &operator=( std::nullptr_t ) { SetNull(); return *this; }
	Value &operator=( const RawArray & x );
	Value &operator=( RawArray && x );
	Value &operator=( const RawObject & x );
	Value &operator=( RawObject && x );
	void SetNull() { InternalDestruct(); _type = kNull; }
	void SetEmptyObject();
	void SetEmptyArray();
	void SetUint64AsString( uint64_t x );

	// Assign array from list of T's, where T is anything we can construct a Value from
	// See also class Array constructors
	template <typename T> void SetArray( const T *begin, const T *end );
	template <typename T> void SetArray( size_t n, const T *begin ) { SetArray( begin, begin+n ); }
	template <typename T> void SetArray( std::initializer_list<T> x ) { SetArray( x.begin(), x.end() ); }; // E.g. SetArray( { "one", "two", "three" } ); Note that they must all be the same type. (If not, wrap all with Value constructors.)

	//
	// Read this Value as a specific data type.
	// There are several different options depending on what checking/conversions
	// you want to do.
	//

	// Get this value as the specified type. If the value is not the exact
	// JSON type, returns a default.  No "conversions" are attempted.
	const char *  AsCString      ( const char *       defaultVal ) const { return _type == kString ? _string.c_str() : defaultVal; }
	std::string   AsString       ( const char *       defaultVal ) const { return _type == kString ? _string : std::string( defaultVal ); } // NOTE: always returns a copy
	std::string   AsString       ( const std::string &defaultVal ) const { return _type == kString ? _string : defaultVal; } // NOTE: always returns a copy, because defaultVal could be a temp!
	std::string   AsString       ( std::string &&     defaultVal ) const { return _type == kString ? _string : std::forward<std::string>(defaultVal); } // Avoids copy if defaultVal is rvalue
	bool          AsBool         ( bool               defaultVal ) const { return _type == kBool   ? _bool : defaultVal; } // NOTE: requires exact bool type!
	double        AsDouble       ( double             defaultVal ) const { return _type == kDouble ? _double : defaultVal; }
	int           AsInt          ( int                defaultVal ) const { return _type == kDouble ? (int)_double : defaultVal; }
	const Object *AsObjectPtr    (                               ) const { return _type == kObject ? (const Object *)this : nullptr; } // Returns null if this is not object
	Object       *AsObjectPtr    (                               )       { return _type == kObject ? (      Object *)this : nullptr; }
	const Array  *AsArrayPtr     (                               ) const { return _type == kArray  ? (const Array  *)this : nullptr; } // Returns null if this is not array
	Array        *AsArrayPtr     (                               )       { return _type == kArray  ? (      Array  *)this : nullptr; }
	const Object &AsObjectOrEmpty(                               ) const { return _type == kObject ? *(const Object *)this : GetStaticEmptyObject(); } // Returns empty object if this is not an object
	const Array  &AsArrayOrEmpty (                               ) const { return _type == kArray  ? *(const Array  *)this : GetStaticEmptyArray(); } // Returns empty array if this is not an array

	// Get the value as the specified type, performing the following
	// conversions if the type is not already the correct type:
	//
	// - Interpreting as std::string:
	//     - numbers as printed
	//     - bools are converted to "true" / "false"
	//     - null is mapped to the empty string
	// - Interpreting as bool:
	//     - input strings "false", "true", "0", and "1" are supported
	//       (case insensitive).  All other strings fail.
	//     - null is mapped to false
	//     - the number 0 (exactly) is mapped false, all other numbers are
	//       mapped to true.  (Inf and nan fail to convert)
	// - Interpreting as double, int, and uint64_t:
	//     - strings are parsed if possible.  A string that contains a floating point value
	//       will fail to convert to int of uint64_t.  (If you want to allow this, then convert
	//       to double first and then do the cast yourself.)
	//     - bools map to 0 / 1
	//     - doubles are cast/truncated when converted to int
	//       If the double value is converted to uint64 and exceeds the range that
	//       can be represented exactly in a double, an assert is triggered as this
	//       is almost always an indication of a problem.  (If you don't need the precision,
	//       just convert to double and then cast yourself!)
	// 
	// Arrays and objects always fail to convert to any destination type.
	// Returns kOK on success, kWrongType on failure.
	// Usually you will call one of the InterpretAsXxx functions below
	EResult TryInterpret( std::string &outVal ) const;
	EResult TryInterpret( bool        &outVal ) const;
	EResult TryInterpret( double      &outVal ) const;
	EResult TryInterpret( int         &outVal ) const;
	EResult TryInterpret( uint64_t    &outVal ) const;

	// Same as TryInterpret(), but returns your supplied default value if conversion fails
	std::string InterpretAsString( const char *       defaultVal ) const { std::string result; if ( TryInterpret( result ) != kOK ) result = defaultVal; return result; }
	std::string InterpretAsString( const std::string &defaultVal ) const { std::string result; if ( TryInterpret( result ) != kOK ) result = defaultVal; return result; }
	std::string InterpretAsString( std::string &&     defaultVal ) const { std::string result( std::forward<std::string>( defaultVal ) ); TryInterpret( result ); return result; }
	bool        InterpretAsBool  ( bool               defaultVal ) const { TryInterpret( defaultVal ); return defaultVal; }
	double      InterpretAsDouble( double             defaultVal ) const { TryInterpret( defaultVal ); return defaultVal; }
	int         InterpretAsInt   ( int                defaultVal ) const { TryInterpret( defaultVal ); return defaultVal; }
	uint64      InterpretAsUint64( uint64_t           defaultVal ) const { TryInterpret( defaultVal ); return defaultVal; }

	// Perform a blind "static cast" of the value to the specified type. The value must
	// be the exact type; no conversions or type checks are attempted; these will assert
	// and do other undefined behaviour if called on the wrong type.  You can use these
	// if you have already done a type check.
	const char *       GetCString() const { VJSON_ASSERT( _type == kString ); return _string.c_str(); }
	const std::string &GetString () const { VJSON_ASSERT( _type == kString ); return _string; }
	std::string &      GetString ()       { VJSON_ASSERT( _type == kString ); return _string; }
	const bool &       GetBool   () const { VJSON_ASSERT( _type == kBool   ); return _bool; }
	bool &             GetBool   ()       { VJSON_ASSERT( _type == kBool   ); return _bool; }
	const double &     GetDouble () const { VJSON_ASSERT( _type == kDouble ); return _double; }
	double &           GetDouble ()       { VJSON_ASSERT( _type == kDouble ); return _double; }
	int                GetInt    () const { VJSON_ASSERT( _type == kDouble ); return (int)_double; }
	const Object &     GetObject () const { VJSON_ASSERT( _type == kObject ); return *(const Object*)this; }
	Object &           GetObject ()       { VJSON_ASSERT( _type == kObject ); return *(Object*)this; }
	const Array &      GetArray  () const { VJSON_ASSERT( _type == kArray  ); return *(const Array*)(this); }
	Array &            GetArray  ()       { VJSON_ASSERT( _type == kArray  ); return *(Array*)this; }

	// Template-style Get<T> for the GetXxxxx static-cast methods above.
	// (See full list of specializations at the bottom of this file.)
	template<typename T> typename TypeTraits<T>::AsReturnTypeConst Get() const;
	template<typename T> typename TypeTraits<T>::AsReturnType Get();

	//
	// Explicit type checking
	//
	// NOTE: One of the goals of this library is to reduce the amount of
	// tedious type checking that must be done when traversing the DOM. If you
	// just wish to ignore missing or wrongly typed data, there's usually
	// a way to avoid an explicit type check!
	//

	// Return true if we are the specified type
	bool IsNull() const { return _type == kNull; }
	bool IsObject() const { return _type == kObject; }
	bool IsArray() const { return _type == kArray; }
	bool IsString() const { return _type == kString; }
	bool IsNumber() const { return _type == kDouble; }
	bool IsDouble() const { return _type == kDouble; }
	bool IsBool() const { return _type == kBool; }

	// Template-style access, e.g. if ( val.Is<bool>() ).
	// See the full list of specializations below.
	template<typename T> bool Is() const;

	// Return the type of thing we are
	EValueType Type() const { return _type; }

	//
	// Object access
	//
	// This base Value class can do a bunch of things on objects. All functions
	// do checking and will return a sensible "failure" result if called on
	// non-object, or if key is not found. The derived Object class is available,
	// and has range-based for and operator[], for a more idiomatic access.
	// Note that to iterate the key/value pairs, you can use something like
	//
	// for ( auto it: val.AsObjectOrEmpty() ) {} // See Object::begin for more info
	//
	// NOTE: Many lookup functions below accept the key argument as a
	// template argument K&&.  This was done primarily to keep the code small.
	// You really can only pass the key as a std::string or const char *.
	//

	// Set the value at the given key. If the key is not present, it is added.
	// If the key is present, the value is changed. Returns kNotObject if this
	// is not an object. See also Object::operator[]. T can be anything
	// that a Value can be constructed from.
	template <typename T, typename K> EResult SetAtKey( K&& key, T&& value );

	// Delete the specified key. Returns kOK, kNotObject, or kBadKey
	template <typename K> EResult EraseAtKey( K&& key );

	// Return true if this is an object, and the key is present
	bool HasKey( const std::string &key ) const { return ValuePtrAtKey( key ) != nullptr; }
	bool HasKey( const char        *key ) const { return ValuePtrAtKey( key ) != nullptr; }

	// Return number of key/values pairs in object as int or size_t, according to your
	// predilection for pedantic bullcrap related size_t and the C type system.
	// Returns 0 if this value is not an object.
	int    ObjectLen () const { return _type == kObject ? (int)_object.size() : 0; }
	size_t ObjectSize() const { return _type == kObject ? _object.size() : 0; }

	// Lookup by key for generic Values (does not check the type of the child).
	// Get pointer to Value at the specified key. If called on a Value that
	// isn't an Object, or if the key is not found, returns nullptr
	Value       *ValuePtrAtKey( const std::string &key );
	const Value *ValuePtrAtKey( const std::string &key ) const { return const_cast<Value*>(this)->ValuePtrAtKey( key ); }
	Value       *ValuePtrAtKey( const char *       key );
	const Value *ValuePtrAtKey( const char *       key ) const { return const_cast<Value*>(this)->ValuePtrAtKey( key ); }

	// Return reference to the value at the specified key. If this is not an object,
	// or the key is not found, returns a reference to a statically-allocated JSON null
	// value.
	//
	// Note that there is no non-const version of this function!
	// - To mutate the child if it exists, use ValuePtrAtKey() (and check for null)
	// - To add or replace a key, use SetKey() or Object::operator[]
	// - To get a mutable reference to the value, adding a new value if one does
	//   not exist, use Object::operator[]
	// - Access the underlying RawObject (which is just a std::map) directly.
	template <typename K> const Value &AtKey( K&& key ) const { const Value *t = ValuePtrAtKey( key ); return t ? *t : GetStaticNullValue(); }

	// Get the value at the specified key as the specified type. If this is not an object,
	// or the key is not found, or the item is not the correct JSON type, returns a default
	template <typename K> const char *  CStringAtKey      ( K&& key, const char *       defaultVal ) const { const Value *t = InternalAtKey( key, kString ); return t ? t->_string.c_str() : defaultVal; }
	template <typename K> std::string   StringAtKey       ( K&& key, const char *       defaultVal ) const { const Value *t = InternalAtKey( key, kString ); return t ? t->_string : std::string( defaultVal ); } // NOTE: always returns a copy
	template <typename K> std::string   StringAtKey       ( K&& key, const std::string &defaultVal ) const { const Value *t = InternalAtKey( key, kString ); return t ? t->_string : defaultVal; } // NOTE: always returns a copy
	template <typename K> std::string   StringAtKey       ( K&& key, std::string &&     defaultVal ) const { const Value *t = InternalAtKey( key, kString ); return t ? t->_string : std::forward<std::string>( defaultVal ); } // Avoids copy
	template <typename K> bool          BoolAtKey         ( K&& key, bool               defaultVal ) const { const Value *t = InternalAtKey( key, kBool   ); return t ? t->_bool : defaultVal; } // Requires strict bool type!
	template <typename K> double        DoubleAtKey       ( K&& key, double             defaultVal ) const { const Value *t = InternalAtKey( key, kDouble ); return t ? t->_double : defaultVal; }
	template <typename K> int           IntAtKey          ( K&& key, int                defaultVal ) const { const Value *t = InternalAtKey( key, kDouble ); return t ? (int)t->_double : defaultVal; }
	template <typename K> const Object *ObjectPtrAtKey    ( K&& key                                ) const { return (const Object *)InternalAtKey( key, kObject ); }
	template <typename K> Object *      ObjectPtrAtKey    ( K&& key                                )       { return (      Object *)InternalAtKey( key, kObject ); }
	template <typename K> const Array * ArrayPtrAtKey     ( K&& key                                ) const { return (const Array  *)InternalAtKey( key, kArray  ); }
	template <typename K> Array *       ArrayPtrAtKey     ( K&& key                                )       { return (      Array  *)InternalAtKey( key, kArray  ); }
	template <typename K> const Array  &ArrayAtKeyOrEmpty ( K&& key                                ) const { const Array  *t = (const Array  *)InternalAtKey( key, kArray  ); return t ? *t : GetStaticEmptyArray(); }
	template <typename K> const Object &ObjectAtKeyOrEmpty( K&& key                                ) const { const Object *t = (const Object *)InternalAtKey( key, kObject ); return t ? *t : GetStaticEmptyObject(); }

	// Locate the value by key and attempt conversion to the specified type.
	template <typename K, typename T> EResult TryInterpretAtKey( K&& key, T &outResult ) const;

	// Similar to TryInterpretAtKey(), but returns a default if this is
	// not an object, the key is not found, or conversion fails
	template <typename K> std::string InterpretAsStringAtKey( K&& key, const char *       defaultVal ) const { std::string result; if ( TryInterpretAtKey( std::forward<K>(key), result ) != kOK ) return defaultVal; return result; }
	template <typename K> std::string InterpretAsStringAtKey( K&& key, const std::string &defaultVal ) const { std::string result; if ( TryInterpretAtKey( std::forward<K>(key), result ) != kOK ) return defaultVal; return result; }
	template <typename K> std::string InterpretAsStringAtKey( K&& key, std::string &&     defaultVal ) const { std::string result( std::forward<std::string>( defaultVal ) ); TryInterpretAtKey( std::forward<K>(key), result ); return result; }
	template <typename K> bool        InterpretAsBoolAtKey  ( K&& key, bool               defaultVal ) const { TryInterpretAtKey( std::forward<K>(key), defaultVal ); return defaultVal; }
	template <typename K> double      InterpretAsDoubleAtKey( K&& key, double             defaultVal ) const { TryInterpretAtKey( std::forward<K>(key), defaultVal ); return defaultVal; }
	template <typename K> int         InterpretAsIntAtKey   ( K&& key, int                defaultVal ) const { TryInterpretAtKey( std::forward<K>(key), defaultVal ); return defaultVal; }
	template <typename K> uint64      InterpretAsUint64AtKey( K&& key, uint64_t           defaultVal ) const { TryInterpretAtKey( std::forward<K>(key), defaultVal ); return defaultVal; }

	//
	// Array access
	//
	// This base Value class can do a bunch of things on array. All functions
	// do checking and will return a sensible "failure" result if called on
	// non-array, or if the index is invalid. The derived Array class is available,
	// and has range-based for and operator[], for a more idiomatic access.
	// Note that to iterate the items in an array, you can use something like
	//
	// for ( auto it: val.AsArrayOrEmpty() ) {}
	//

	// Get the length of the array as an int or size_t, according to your
	// predilection for pedantic bullcrap related to size_t and the C type system.
	// Returns 0 if this value is not an array.
	int    ArrayLen () const { return _type == kArray ? (int)_array.size() : 0; }
	size_t ArraySize() const { return _type == kArray ? _array.size() : 0; }

	// Return reference to the value at the specified index. If this is not an array,
	// or the index is out of bounds, returns a reference to a statically-allocated null
	// value.
	//
	// Note that there is no non-const version of this function! To modify an at
	// a given index, either use ValuePtrAtIndex() or Array::operator[]
	const Value &AtIndex( size_t idx ) const { return ( _type == kArray && idx < _array.size() ) ? _array[idx] : GetStaticNullValue(); }

	// Get pointer to Value at the specified index. If you call this on a Value
	// that isn't an Array, or the index is invalid, returns nullptr
	const Value *ValuePtrAtIndex( size_t idx ) const { return ( _type == kArray && idx < _array.size() ) ? &_array[idx] : nullptr; }
	Value *      ValuePtrAtIndex( size_t idx )       { return ( _type == kArray && idx < _array.size() ) ? &_array[idx] : nullptr; }

	// Get the value at the specified index as the specified type. If this is not an array,
	// or the index is invalid, or the item is the wrong type, returns an appropriate default
	const char *  CStringAtIndex      ( size_t idx, const char *       defaultVal ) const { const Value *t = InternalAtIndex( idx, kString ); return t ? t->_string.c_str() : defaultVal; }
	std::string   StringAtIndex       ( size_t idx, const char *       defaultVal ) const { const Value *t = InternalAtIndex( idx, kString ); return t ? t->_string : std::string( defaultVal ); } // NOTE: always returns a copy
	std::string   StringAtIndex       ( size_t idx, const std::string &defaultVal ) const { const Value *t = InternalAtIndex( idx, kString ); return t ? t->_string : defaultVal; } // NOTE: always returns a copy
	std::string   StringAtIndex       ( size_t idx, std::string &&     defaultVal ) const { const Value *t = InternalAtIndex( idx, kString ); return t ? t->_string : std::forward<std::string>( defaultVal ); } // Avoids the copy
	bool          BoolAtIndex         ( size_t idx, bool               defaultVal ) const { const Value *t = InternalAtIndex( idx, kBool   ); return t ? t->_bool : defaultVal; } // Requires strict bool type
	double        DoubleAtIndex       ( size_t idx, double             defaultVal ) const { const Value *t = InternalAtIndex( idx, kDouble ); return t ? t->_bool : defaultVal; }
	int           IntAtIndex          ( size_t idx, int                defaultVal ) const { const Value *t = InternalAtIndex( idx, kDouble ); return t ? (int)t->_double : defaultVal; }
	const Object *ObjectPtrAtIndex    ( size_t idx                                ) const { return (const Object *)InternalAtIndex( idx, kObject ); }
	Object *      ObjectPtrAtIndex    ( size_t idx                                )       { return (      Object *)InternalAtIndex( idx, kObject ); }
	const Array * ArrayPtrAtIndex     ( size_t idx                                ) const { return (const Array  *)InternalAtIndex( idx, kArray  ); }
	Array *       ArrayPtrAtIndex     ( size_t idx                                )       { return (      Array  *)InternalAtIndex( idx, kArray  ); }
	const Array  &ArrayAtIndexOrEmpty ( size_t idx                                ) const { const Array  *t = (const Array  *)InternalAtIndex( idx, kArray  ); return t ? *t : GetStaticEmptyArray(); }
	const Object &ObjectAtIndexOrEmpty( size_t idx                                ) const { const Object *t = (const Object *)InternalAtIndex( idx, kObject ); return t ? *t : GetStaticEmptyObject(); }

	// Locate the value by index and attempt conversion to the specified type.
	template <typename T> EResult TryInterpretAtIndex( size_t idx, T &outResult ) const;

	// Similar to TryInterpretAtIndex(), but returns a default if this is
	// not an array, the index is invalid, or conversion fails
	std::string InterpretAsStringAtIndex( size_t idx, const char *       defaultVal ) const { std::string result; if ( TryInterpretAtIndex( idx, result ) != kOK ) result = defaultVal; return result; }
	std::string InterpretAsStringAtIndex( size_t idx, const std::string &defaultVal ) const { std::string result; if ( TryInterpretAtIndex( idx, result ) != kOK ) result = defaultVal; return result; }
	std::string InterpretAsStringAtIndex( size_t idx, std::string &&     defaultVal ) const { std::string result( std::forward<std::string>( defaultVal ) ); TryInterpretAtIndex( idx, result ); return result; }
	bool        InterpretAsBoolAtIndex  ( size_t idx, bool               defaultVal ) const { TryInterpretAtIndex( idx, defaultVal ); return defaultVal; }
	double      InterpretAsDoubleAtIndex( size_t idx, double             defaultVal ) const { TryInterpretAtIndex( idx, defaultVal ); return defaultVal; }
	int         InterpretAsIntAtIndex   ( size_t idx, int                defaultVal ) const { TryInterpretAtIndex( idx, defaultVal ); return defaultVal; }
	uint64      InterpretAsUint64AtIndex( size_t idx, uint64_t           defaultVal ) const { TryInterpretAtIndex( idx, defaultVal ); return defaultVal; }

	//
	// Parsing/print JSON text
	//

	// Parse any legitimate JSON entity. If you are OK with the default parsing
	// options and don't care about good error handling, you don't need to provide
	// the ParseContext.
	// See also Object::ParseJSON
	inline bool ParseJSON( const char *c_str, ParseContext *ctx = nullptr ) { return ParseJSON( c_str, c_str + strlen(c_str), ctx ); }
	inline bool ParseJSON( const std::string &s, ParseContext *ctx = nullptr ) { return ParseJSON( s.c_str(), s.c_str() + s.length(), ctx ); }
	bool ParseJSON( const char *begin, const char *end, ParseContext *ctx = nullptr );

	// Print the value to JSON text.
	std::string PrintJSON( const PrintOptions &opt = PrintOptions{} ) const;

	// @VALVE Memory validation
	#ifdef DBGFLAG_VALIDATE
		void Validate( CValidator &validator, const char *pchName ) const;
	#endif

protected:

	EValueType _type;
	union
	{
		double _double;
		bool _bool;
		RawObject _object;
		RawArray _array;
		std::string _string;
		struct { char x[8]; } _dummy;
	};

	void InternalDestruct();
	void InternalConstruct( const Value &x );
	void InternalConstruct( Value &&x );
	Value *InternalAtIndex( size_t idx, EValueType t ) const;
	Value *InternalAtKey( const std::string &key, EValueType t ) const;
	Value *InternalAtKey( const char *key, EValueType t ) const;
};

// An Object is a Value that is known (or at least assumed) to be of type
// kObject. Since it is assumed to be an object, we can provide a more
// idiomatic object interface, and we can optimize a few function calls.
// 
// NOTE: This is not a real, typesafe derived class!  It is just an
// interface for when you assume the Value is an Object.  It's relatively
// easy to willfully abuse this with dumb stuff like
//
//   Object foo; foo.SetDouble( 1.0 ); // Don't do this
//
// If you stuff like this, you will probably hit asserts.  If that scares
// you, then just don't use this class!
class Object : public Value
{
public:
	Object() : Value( kObject ) {}
	Object( const Object &x ) : Value( x ) {}
	Object( Object &&x ) : Value( std::forward<Object>(x) ) {}
	Object &operator=( const Object & x ) { VJSON_ASSERT( x._type == kObject ); Value::operator=(x); return *this; }
	Object &operator=( Object && x ) { VJSON_ASSERT( x._type == kObject ); Value::operator=(std::forward<Object>(x)); return *this; }
	Object &operator=( const RawObject & x ) { Value::operator=(x); return *this; }
	Object &operator=( RawObject && x ) { Value::operator=(std::forward<RawObject>(x)); return *this; }

	// Same as Value::ParseJSON, but fails if the result isn't a single Object
	inline bool ParseJSON( const char *c_str, ParseContext *ctx = nullptr ) { return ParseJSON( c_str, c_str + strlen(c_str), ctx ); }
	inline bool ParseJSON( const std::string &s, ParseContext *ctx = nullptr ) { return ParseJSON( s.c_str(), s.c_str() + s.length(), ctx ); }
	bool ParseJSON( const char *begin, const char *end, ParseContext *ctx = nullptr );

	// Override ObjectLen(), we know we are an Object
	int    ObjectLen()  const { VJSON_ASSERT( _type == kObject ); return (int)_object.size(); }
	size_t ObjectSize() const { VJSON_ASSERT( _type == kObject ); return _object.size(); }
	int    Len()        const { VJSON_ASSERT( _type == kObject ); return (int)_object.size(); }
	size_t size()       const { VJSON_ASSERT( _type == kObject ); return _object.size(); }

	// Standard array access notation Operator[]. This works just like the std::map
	// version. It inserts the default argument if not found, and cannot be invoked
	// on a const Object. (Use Value::AtKey() for read-only access that won't
	// add a new key if the key is not already present. )
	template <typename K> Value &operator[]( K &&key ) { VJSON_ASSERT( _type == kObject ); return _object[ std::forward<K>( key ) ]; }

	// Return true if the object is empty
	bool empty() const { VJSON_ASSERT( _type == kObject ); return _object.empty(); }

	// Remove all the items from the object
	void clear() { VJSON_ASSERT( _type == kObject ); _object.clear(); }

	// Access the underlying storage
	inline RawObject       &Raw()       { VJSON_ASSERT( _type == kObject ); return _object; }
	inline RawObject const &Raw() const { VJSON_ASSERT( _type == kObject ); return _object; }

	// Range-based for. Example:
	//
	// Object obj;
	// for ( auto &item: obj )
	// {
	//   const std::string & key = item.first;
	//   Value &val = item.second;
	// }

	// Iterate all values.
	RawObject::iterator       begin()       { VJSON_ASSERT( _type == kObject ); return _object.begin(); }
	RawObject::iterator       end()         { VJSON_ASSERT( _type == kObject ); return _object.end(); }
	RawObject::const_iterator begin() const { VJSON_ASSERT( _type == kObject ); return _object.begin(); }
	RawObject::const_iterator end()   const { VJSON_ASSERT( _type == kObject ); return _object.end(); }

	// TODO - add type-specific iterators, so you can easily iterate, e.g. all the ints
};

// An Array is a Value that is known (or at least assumed) to be of type
// kArray.  See comments above the Object class for more info
class Array : public Value
{
public:
	Array() : Value( kArray ) {}
	Array( const Array &x ) : Value( x ) {}
	Array( Array &&x ) : Value( std::forward<Array>(x) ) {}
	Array( const RawArray &x ) : Value( x ) {}
	Array( RawArray && x ) : Value( std::forward<RawArray>( x ) ) {}
	Array &operator=( const Array & x ) { VJSON_ASSERT( x._type == kArray ); Value::operator=(x); return *this; }
	Array &operator=( Array && x ) { VJSON_ASSERT( x._type == kArray ); Value::operator=(std::forward<Array>(x)); return *this; }
	Array &operator=( const RawArray & x ) { Value::operator=(x); return *this; }
	Array &operator=( RawArray && x ) { Value::operator=(std::forward<Array>(x)); return *this; }

	// Construct Array from initializer list.
	// E.g. Value( { "one", 5.0, false } )
	//Value( std::initializer_list<Value> x ); FIXME

	// Override ArrayLen(), we know we are an array. Also provide shorter versions
	int    ArrayLen()  const { VJSON_ASSERT( _type == kArray ); return (int)_array.size(); }
	size_t ArraySize() const { VJSON_ASSERT( _type == kArray ); return _array.size(); }
	int    Len()       const { VJSON_ASSERT( _type == kArray ); return (int)_array.size(); }
	size_t size()      const { VJSON_ASSERT( _type == kArray ); return _array.size(); } // not capitalized because we want to be as similar to std::vector as possible

	// Standard array access notation Operator[]
	Value       &operator[]( size_t idx )       { VJSON_ASSERT( _type == kArray ); return _array[idx]; }
	const Value &operator[]( size_t idx ) const { VJSON_ASSERT( _type == kArray ); return _array[idx]; }

	// Return true if the array is empty
	bool empty() const { VJSON_ASSERT( _type == kArray ); return _array.empty(); }

	// Remove all the items from the array
	void clear() { VJSON_ASSERT( _type == kArray ); _array.clear(); }

	// Add a null value to the end of the the array, and return a reference
	Value &push_back() { VJSON_ASSERT( _type == kArray ); _array.push_back( Value{} ); return _array[ _array.size()-1 ]; }

	// Push something to the end of the array, and return a reference to the newly created
	// thing. Any argument from which you can construct a Value will work.
	template< typename Arg > Value &push_back( Arg &&a ) { VJSON_ASSERT( _type == kArray ); _array.push_back( std::forward<Arg>( a ) ); return _array[ _array.size()-1 ]; }

	// Get direct access to the underlying vector
	const RawArray &Raw() const { VJSON_ASSERT( _type == kArray ); return _array; }
	RawArray       &Raw()       { VJSON_ASSERT( _type == kArray ); return _array; }

	// Iterate all the values int he array (range-based for).  Example:
	//
	// Array arr;
	// for ( Value &val: arr ) {}
	Value *      begin()       { VJSON_ASSERT( _type == kArray ); return _array.data(); }
	Value *      end()         { VJSON_ASSERT( _type == kArray ); return _array.data() + _array.size(); }
	const Value *begin() const { VJSON_ASSERT( _type == kArray ); return _array.data(); }
	const Value *end()   const { VJSON_ASSERT( _type == kArray ); return _array.data() + _array.size(); }

	// Iterate only the elements of the arrayu that are of the specified
	// type. (Elements Values of other types.)  Any T for which you can
	// do Value::Is<T> and Get<T> will work.
	//
	// Examples:
	//
	// Array arr;
	// for ( const char *s: arr.Iter<const char *>() ) {}
	// for ( Object &x: arr.Iter<Object>() ) {}
	template <typename T> ConstArrayRange<T> Iter() const;
	template <typename T> MutableArrayRange<T> Iter();
};

/////////////////////////////////////////////////////////////////////////////
//
// Internal stuff
//
// Why are you still reading this?
//
/////////////////////////////////////////////////////////////////////////////

template<> inline bool Value::Is<std::nullptr_t>() const { return _type == kNull; }
template<> inline bool Value::Is<Object>() const { return _type == kObject; }
template<> inline bool Value::Is<Array>() const { return _type == kArray; }
template<> inline bool Value::Is<const char *>() const { return _type == kString; }
template<> inline bool Value::Is<std::string>() const { return _type == kString; }
template<> inline bool Value::Is<double>() const { return _type == kDouble; }
template<> inline bool Value::Is<bool>() const { return _type == kBool; }
template<> inline const char * Value::Get<const char *>() const { VJSON_ASSERT( _type == kString ); return _string.c_str(); }
template<> inline const char * Value::Get<const char *>() { VJSON_ASSERT( _type == kString ); return _string.c_str(); }
template<> inline const std::string &Value::Get<std::string>() const { VJSON_ASSERT( _type == kString ); return _string; }
template<> inline std::string & Value::Get<std::string>() { VJSON_ASSERT( _type == kString ); return _string; }
template<> inline const bool & Value::Get<bool>() const { VJSON_ASSERT( _type == kBool ); return _bool; } // NOTE: requires exact bool type!
template<> inline bool & Value::Get<bool>() { VJSON_ASSERT( _type == kBool ); return _bool; } // NOTE: requires exact bool type!
template<> inline const double & Value::Get<double>() const { VJSON_ASSERT( _type == kDouble ); return _double; }
template<> inline double & Value::Get<double>() { VJSON_ASSERT( _type == kDouble ); return _double; }
template<> inline int Value::Get<int>() const { VJSON_ASSERT( _type == kDouble ); return (int)_double; }
template<> inline int Value::Get<int>() { VJSON_ASSERT( _type == kDouble ); return (int)_double; }
template<> inline const Object & Value::Get<Object>() const { VJSON_ASSERT( _type == kObject ); return *(const Object*)this; }
template<> inline Object & Value::Get<Object>() { VJSON_ASSERT( _type == kObject ); return *(Object*)this; }
template<> inline const Array & Value::Get<Array>() const { VJSON_ASSERT( _type == kArray ); return *(const Array*)(this); }
template<> inline Array & Value::Get<Array>() { VJSON_ASSERT( _type == kArray ); return *(Array*)this; }

template <typename T, typename K>
inline EResult Value::SetAtKey( K&& key, T&& value )
{
	if ( _type != kObject ) return kNotObject;
	_object[ std::forward<K>( key ) ] = std::forward<T>( value );
	return kOK;
}

template <typename K>
EResult Value::EraseAtKey( K&& key )
{
	if ( _type != kObject ) return kNotObject;
	if ( _object.erase( std::forward<K>( key ) ) == 0 ) return kBadKey;
	return kOK;
}

template <typename K, typename T>
EResult Value::TryInterpretAtKey( K&& key, T &outResult ) const
{
	if ( _type != kObject ) return kNotObject;
	auto it = _object.find( key );
	if ( it == _object.end() ) return kBadKey;
	return it->second.TryInterpret( outResult );
}

template <typename T>
EResult Value::TryInterpretAtIndex( size_t idx, T &outResult ) const
{
	if ( _type != kArray ) return kNotArray;
	if ( idx >= _array.size() ) return kBadIndex;
	return _array[ idx ].TryInterpret( outResult );
}

template <typename T>
void Value::SetArray( const T *begin, const T *end )
{
	VJSON_ASSERT( begin <= end );
	InternalDestruct();
	_type = kArray;
	new (&_array) RawArray( begin, end );
}

template<typename T, typename V, typename A, typename R>
struct ArrayIter {
	A &array_ref;
	V *cur_ptr;
	R operator*() const { return this->cur_ptr->template Get<T>(); }
	void operator++() {
		VJSON_ASSERT( this->cur_ptr < this->end() ); // going past the end, or array was modified during iteration
		++this->cur_ptr; this->Next();
	}

	template<typename XV, typename XA, typename XR>
	bool operator!=(const ArrayIter<T,XV,XA,XR> &x ) const {
		VJSON_ASSERT( &this->array_ref == &x.array_ref ); // Should only compare two iterators created from the same array
		VJSON_ASSERT( this->cur_ptr <= this->end() && x.cur_ptr <= this->end() ); // Should not delete from array during iteration
		return this->cur_ptr != x.cur_ptr;
	}
	void Next() {
		auto e = this->end();
		while ( this->cur_ptr < e && this->cur_ptr->Type() != TypeTraits<T>::kType )
			++this->cur_ptr; 
	}
	V *end() const { return this->array_ref.data() + this->array_ref.size(); }
};
template<typename T, typename A, typename I> struct ArrayRange
{
	A &array_ref;
	I begin() const { I beg{array_ref,array_ref.data()}; beg.Next(); return beg; }
	I end() const { return I{array_ref,array_ref.data()+array_ref.size()}; }
};

template <typename T> ConstArrayRange<T> Array::Iter() const { return ConstArrayRange<T>{this->_array}; }
template <typename T> MutableArrayRange<T> Array::Iter() { return MutableArrayRange<T>{this->_array}; }

} // namespace vjson

// @VALVE
#include <tier0/memdbgon.h>

#endif // _H