CoreUtils/JString.h

#ifndef __JString_h__
#define __JString_h__

#include "MString.h"
#include <iostream>
#include <sstream>

namespace coreutils {

   ///
   /// Use the JString object when you need a JSON interface to C++. JString uses
   /// an MString to store a JSON string representing the object(s) contained.
   /// The [] operator is overriden from the ZString and provides a method to
   /// access the objects elements using a named path as the index to the items.
   ///
   /// JString default constructor will create an empty JString object pointing
   /// to an empty object ("{}").
   ///
   /// Use a constructor or assignment operator to initialize a JString to an
   /// initial JSON string.
   ///
   /// Several constructors are available including a handle to a std::FILE
   /// object to initialize the JSON string. On destruction the file is saved back.
   ///
   /// The [] operator can be used to access elements within the JSON string.
   /// Assigning a value dispatches on the C++ type of the right-hand side, so the
   /// resulting JSON is correctly typed rather than always being a quoted string:
   ///
   ///       jstring["name"]   = "value";   // JSON string, escaped correctly
   ///       jstring["count"]  = 42;        // JSON number (integer)
   ///       jstring["price"]  = 19.95;     // JSON number
   ///       jstring["active"] = true;      // JSON boolean
   ///       jstring["notes"].setNull();    // JSON null
   ///
   ///       std::cout << jstring["name"];
   ///
   /// Typed read access is available directly on the path (no need to go through
   /// operator[] first):
   ///
   ///       std::string name = jstring.getString("name");
   ///       double price     = jstring.getNumber("price");
   ///       bool active      = jstring.getBool("active");
   ///       bool missing     = !jstring.exists("notfound");
   ///       JSONType t       = jstring.getType("count");   // JSONType::NUMBER
   ///

   enum class JSONType {
      STRING, NUMBER, BOOLEAN, JNULL, ARRAY, OBJECT, NOT_FOUND
   };

   class JString : virtual public MString {

    public:

      JString();

      void set(ZString &path, ZString &value);

      ///
      /// Use the find method to look through an object for member specified by
      /// the key in parameter 1. The cursor must be pointing to the { character
      /// that begins the object's list. Returns the raw (still-escaped, for
      /// strings) span of the value - use getString()/getNumber()/getBool()/
      /// isNull() for decoded, typed access instead.
      ///

      ZString find(ZString path);

      bool locate(ZString path);
      bool notfirst;
      ZString path;

      ///
      /// Type-aware access. All of these call locate() internally, so path uses
      /// the same dotted/bracketed syntax as find()/set() (e.g. "a.b[2].c").
      ///

      JSONType getType(ZString path);
      bool exists(ZString path);
      bool isNull(ZString path);

      std::string getString(ZString path);   ///< Escape-decoded string content.
      double getNumber(ZString path);
      long getInt(ZString path);
      bool getBool(ZString path);

      void setString(ZString path, std::string value);  ///< Escapes value automatically.
      void setNumber(ZString path, double value);
      void setInt(ZString path, long value);
      void setBool(ZString path, bool value);
      void setNull(ZString path);

      ///
      /// JSON string escape/unescape helpers (exposed as static utilities since
      /// they operate on plain text, not on this object's own JSON document).
      ///

      static std::string jsonEscape(ZString value);
      static std::string jsonUnescape(ZString raw);

      class Proxy {

       public:
	 Proxy(JString &jstring, ZString key) : jstring(jstring), key(key) {}

	 friend std::ostream &operator<<(std::ostream &os, const Proxy &proxy);

	 ///
	 /// Proxy offers several implicit conversion operators below (to
	 /// ZString, MString, std::string, double, bool) so a single $[...]-
	 /// style access can be used wherever any of those types is expected.
	 /// That flexibility makes "MString << Proxy" genuinely ambiguous on
	 /// its own - operator ZString() and operator MString() (via its own
	 /// implicit upcast to ZString) both satisfy MString::operator<<(ZString),
	 /// and operator double()/operator bool() both satisfy
	 /// MString::operator<<(int) via a standard numeric conversion - so
	 /// the compiler has no way to prefer one path over another. This
	 /// exact-match overload (mirroring the ostream one above, which
	 /// solves the same problem for std::cout << proxy) resolves it by
	 /// giving MString a candidate that needs no conversion at all.
	 ///

	 friend MString &operator<<(MString &ms, const Proxy &proxy);

	 operator coreutils::ZString () {
	    return jstring.find(key);
	 }

	 operator coreutils::MString () {
	    return jstring.find(key);
	 }

	 operator std::string () {
	    return jstring.getString(key);
	 }

	 operator double () {
	    return jstring.getNumber(key);
	 }

	 operator bool () {
	    return jstring.getBool(key);
	 }

	 Proxy& operator=(coreutils::MString value) {
	    jstring.setString(key, value.str());
	    jstring.changed(key, value);
	    return *this;
	 }

	 Proxy& operator=(const char *value) {
	    jstring.setString(key, std::string(value));
	    jstring.changed(key, ZString(value));
	    return *this;
	 }

	 Proxy& operator=(double value) {
	    jstring.setNumber(key, value);
	    return *this;
	 }

	 Proxy& operator=(int value) {
	    jstring.setInt(key, value);
	    return *this;
	 }

	 Proxy& operator=(long value) {
	    jstring.setInt(key, value);
	    return *this;
	 }

	 Proxy& operator=(bool value) {
	    jstring.setBool(key, value);
	    return *this;
	 }

	 void setNull() {
	    jstring.setNull(key);
	 }

       private:
   	 JString &jstring;
	 ZString key;
      };

      Proxy operator[](coreutils::ZString key) {
	 return Proxy(*this, key);
      }

      JString & operator=(coreutils:: ZString value);

      MString pretty();

      virtual void changed(ZString key, ZString value);

    private:
      void removeWhitespace();

      ///
      /// Structural helpers used internally by locate()/set() to correctly skip
      /// past a value of any JSON type without being confused by JSON-structural
      /// characters (quotes, braces, brackets) appearing inside string literals.
      ///

      ZString findRelative(ZString path);
      JSONType typeAtCursor();
      void skipValue();
      void skipString();
      void skipContainer();
      void skipNumber();
      ZString captureString();
      ZString captureContainer();
      bool isLiteralValue(ZString value);

   };

}

#endif