mlisp/clib/json11.h

#pragma once

#include "../ml.h"

#include <string>
#include <vector>
#include <map>
#include <memory>
#include <initializer_list>

namespace json11 {

    enum JsonParse {
	STANDARD, COMMENTS
    };

    class JsonValue;

    class Json final {
    public:
	// Types
	enum Type {
	    NUL, NUMBER, BOOL, STRING, ARRAY, OBJECT
	};

	// Array and object typedefs
	typedef std::vector<Json> array;
	typedef std::map<std::string, Json> object;

	// Constructors for the various types of JSON value.
	Json() noexcept;                // NUL
	Json(std::nullptr_t) noexcept;  // NUL
	Json(double value);             // NUMBER
	Json(int value);                // NUMBER
	Json(bool value);               // BOOL
	Json(const std::string &value); // STRING
	Json(std::string &&value);      // STRING
	Json(const char *value);       // STRING
	Json(const array &values);      // ARRAY
	Json(array &&values);           // ARRAY
	Json(const object &values);     // OBJECT
	Json(object &&values);          // OBJECT

	// Implicit constructor: anything with a to_json() function.
	template<class T, class = decltype(&T::to_json)>
	Json(const T &t) : Json(t.to_json()) {}

	// Implicit constructor: map-like objects (std::map, std::unordered_map, etc)
	template<class M, typename std::enable_if<
		std::is_constructible<std::string, decltype(std::declval<M>().begin()->first)>::value
		&& std::is_constructible<Json, decltype(std::declval<M>().begin()->second)>::value,
		int>::type = 0>
	Json(const M &m) : Json(object(m.begin(), m.end())) {}

	// Implicit constructor: vector-like objects (std::list, std::vector, std::set, etc)
	template<class V, typename std::enable_if<
		std::is_constructible<Json, decltype(*std::declval<V>().begin())>::value,
		int>::type = 0>
	Json(const V &v) : Json(array(v.begin(), v.end())) {}

	// This prevents Json(some_pointer) from accidentally producing a bool. Use
	// Json(bool(some_pointer)) if that behavior is desired.
	Json(void *) = delete;

	// Accessors
	Type type() const;

	bool is_null() const { return type() == NUL; }

	bool is_number() const { return type() == NUMBER; }

	bool is_bool() const { return type() == BOOL; }

	bool is_string() const { return type() == STRING; }

	bool is_array() const { return type() == ARRAY; }

	bool is_object() const { return type() == OBJECT; }

	// Return the enclosed value if this is a number, 0 otherwise. Note that json11 does not
	// distinguish between integer and non-integer numbers - number_value() and int_value()
	// can both be applied to a NUMBER-typed object.
	double number_value() const;

	int int_value() const;

	// Return the enclosed value if this is a boolean, false otherwise.
	bool bool_value() const;

	// Return the enclosed string if this is a string, "" otherwise.
	const std::string &string_value() const;

	// Return the enclosed std::vector if this is an array, or an empty vector otherwise.
	const array &array_items() const;

	// Return the enclosed std::map if this is an object, or an empty map otherwise.
	const object &object_items() const;

	// Return a reference to arr[i] if this is an array, Json() otherwise.
	const Json &operator[](size_t i) const;

	// Return a reference to obj[key] if this is an object, Json() otherwise.
	const Json &operator[](const std::string &key) const;

	// Serialize.
	void dump(std::string &out) const;

	std::string dump() const {
		std::string out;
		dump(out);
		return out;
	}

	MlValue ivalualize() const;

	// Parse. If parse fails, return Json() and assign an error message to err.
	static Json parse(const std::string &in,
			  std::string &err,
			  JsonParse strategy = JsonParse::STANDARD);

	static Json parse(const char *in,
			  std::string &err,
			  JsonParse strategy = JsonParse::STANDARD) {
		if (in) {
			return parse(std::string(in), err, strategy);
		} else {
			err = "null input";
			return nullptr;
		}
	}

	// Parse multiple objects, concatenated or separated by whitespace
	static std::vector<Json> parse_multi(
		const std::string &in,
		std::string::size_type &parser_stop_pos,
		std::string &err,
		JsonParse strategy = JsonParse::STANDARD);

	static inline std::vector<Json> parse_multi(
		const std::string &in,
		std::string &err,
		JsonParse strategy = JsonParse::STANDARD) {
		std::string::size_type parser_stop_pos;
		return parse_multi(in, parser_stop_pos, err, strategy);
	}

	bool operator==(const Json &rhs) const;

	bool operator<(const Json &rhs) const;

	bool operator!=(const Json &rhs) const { return !(*this == rhs); }

	bool operator<=(const Json &rhs) const { return !(rhs < *this); }

	bool operator>(const Json &rhs) const { return (rhs < *this); }

	bool operator>=(const Json &rhs) const { return !(*this < rhs); }

	/* has_shape(types, err)
	 *
	 * Return true if this is a JSON object and, for each item in types, has a field of
	 * the given type. If not, return false and set err to a descriptive message.
	 */
	typedef std::initializer_list<std::pair<std::string, Type>> shape;

	bool has_shape(const shape &types, std::string &err) const;

    private:
	std::shared_ptr<JsonValue> m_ptr;
    };

// Internal class hierarchy - JsonValue objects are not exposed to users of this API.
    class JsonValue {
    protected:
	friend class Json;

	friend class JsonInt;

	friend class JsonDouble;

	virtual Json::Type type() const = 0;

	virtual bool equals(const JsonValue *other) const = 0;

	virtual bool less(const JsonValue *other) const = 0;

	virtual void dump(std::string &out) const = 0;

	virtual MlValue ivalualize() const = 0;

	virtual double number_value() const;

	virtual int int_value() const;

	virtual bool bool_value() const;

	virtual const std::string &string_value() const;

	virtual const Json::array &array_items() const;

	virtual const Json &operator[](size_t i) const;

	virtual const Json::object &object_items() const;

	virtual const Json &operator[](const std::string &key) const;

	virtual ~JsonValue() {}
    };

} // namespace json11