ITS_OP/CctvCamViewer - ffmpeg - ini/CDS/McJSON.pas

(*****************************************************************************

The MIT License (MIT)

Copyright (c) 2021 HydroByte Software

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*****************************************************************************)

unit McJSON;

interface

uses
  Classes, SysUtils;

type
  EMcJsonException = class(Exception);

  TJItemType  = (jitUnset, jitValue, jitObject, jitArray);
  TJValueType = (jvtString, jvtNumber, jvtBoolean, jvtNull);

  TMcJsonItemEnumerator = class;

  TMcJsonItem = class
  private
    fType   : TJItemType;  // item type (value/object/array)
    fKey    : string;      // item name
    fValue  : string;      // value (if item type is value)
    fValType: TJValueType; // value type (text/number/boolean)
    fChild  : TList;       // child nodes (if item type is object/array)
    fSpeedUp: Boolean;     // flag to speed up the parse task

    // property getters
    function fGetCount: Integer;
    function fGetKey(aIdx: Integer): string;
    function fGetType: TJItemType;
    function fGetItemByKey(const aKey: string): TMcJsonItem;
    function fGetItemByIdx(aIdx: Integer): TMcJsonItem;
    function fHasChild: Boolean;
    function fIsNull  : Boolean;
    // AsSomething getters
    function fGetAsJSON   : string     ;
    function fGetAsObject : TMcJsonItem;
    function fGetAsArray  : TMcJsonItem;
    function fGetAsInteger: Integer    ;
    function fGetAsDouble : Double     ;
    function fGetAsString : string     ;
    function fGetAsBoolean: Boolean    ;
    function fGetAsNull   : string     ;

    // property setters
    procedure fSetType(aType: TJItemType);
    // AsSomething setters.
    procedure fSetAsJSON   (aValue: string     );
    procedure fSetAsObject (aValue: TMcJsonItem);
    procedure fSetAsArray  (aValue: TMcJsonItem);
    procedure fSetAsInteger(aValue: Integer    );
    procedure fSetAsDouble (aValue: Double     );
    procedure fSetAsString (aValue: string     );
    procedure fSetAsBoolean(aValue: Boolean    );
    procedure fSetAsNull   (aValue: string     );

    // string single-pass parser
    function parse(const aCode: string; aPos, aLen: Integer): Integer;
    // read methods used by parse
    function readString (const aCode: string; out aStr:string; aPos, aLen: Integer): Integer;
    function readChar   (const aCode: string; aChar: Char; aPos, aLen: Integer): Integer;
    function readKeyword(const aCode, aKeyword: string; aPos, aLen: Integer): Integer;
    function readValue  (const aCode: string; aPos, aLen: Integer): Integer;
    function readObject (const aCode: string; aPos, aLen: Integer): Integer;
    function readArray  (const aCode: string; aPos, aLen: Integer): Integer;
    function readNumber (const aCode: string; aPos, aLen: Integer): Integer;
    function readBoolean(const aCode: string; aPos, aLen: Integer): Integer;
    function readNull   (const aCode: string; aPos, aLen: Integer): Integer;

    // aux functions used in ToString
    function sFormat(aHuman: Boolean): string;
    function sFormatItem(aStrS: TStringStream; const aIn, aNL, aSp: string): string;
    function isIndexValid(aIdx: Integer): Boolean;

  public
    property Count   : Integer    read fGetCount;
    property Key     : string     read fKey;
    property Value   : string     read fValue;
    property ItemType: TJItemType read fGetType write fSetType;

    property Keys  [aIdx      : Integer]: string      read fGetKey;
    property Items [aIdx      : Integer]: TMcJsonItem read fGetItemByIdx;
    property Values[const aKey: string ]: TMcJsonItem read fGetItemByKey; default;

    property HasChild: Boolean read fHasChild;
    property IsNull  : Boolean read fIsNull;
    property SpeedUp : Boolean read fSpeedUp write fSpeedUp;

    // AsSomething properties
    property AsJSON   : string      read fGetAsJSON    write fSetAsJSON   ;
    property AsObject : TMcJsonItem read fGetAsObject  write fSetAsObject ;
    property AsArray  : TMcJsonItem read fGetAsArray   write fSetAsArray  ;
    property AsInteger: Integer     read fGetAsInteger write fSetAsInteger;
    property AsNumber : Double      read fGetAsDouble  write fSetAsDouble ;
    property AsString : string      read fGetAsString  write fSetAsString ;
    property AsBoolean: Boolean     read fGetAsBoolean write fSetAsBoolean;
    property AsNull   : string      read fGetAsNull    write fSetAsNull   ;

    constructor Create; overload;
    constructor Create(aJItemType: TJItemType); overload;
    constructor Create(const aItem: TMcJsonItem); overload;
    constructor Create(const aCode: string); overload;
    destructor  Destroy; override;

    procedure Clear;
    function IndexOf(const aKey: string): Integer; overload;
    function Path(const aPath: string): TMcJsonItem; overload;
    function Add(const aKey: string = ''): TMcJsonItem; overload;
    function Add(const aKey: string; aItemType: TJItemType): TMcJsonItem; overload;
    function Add(aItemType: TJItemType): TMcJsonItem; overload;
    function Add(const aItem: TMcJsonItem): TMcJsonItem; overload;
    function Copy(const aItem: TMcJsonItem): TMcJsonItem; overload;
    function Clone: TMcJsonItem; overload;
    function Insert(const aKey: string; aIdx: Integer): TMcJsonItem; overload;
    function Insert(const aItem: TMcJsonItem; aIdx: Integer): TMcJsonItem; overload;
    function Delete(aIdx: Integer): Boolean; overload;
    function Delete(const aKey: string): Boolean; overload;
    function HasKey(const aKey: string): Boolean;
    function IsEqual(const aItem: TMcJsonItem): Boolean;
    function Check(const aStr: string; aSpeedUp: Boolean = False): Boolean;
    function CountItems: Integer;

    // array shortener
    function At(aIdx: Integer; const aKey: string = ''): TMcJsonItem; overload;
    function At(const aKey: string; aIdx: Integer = -1): TMcJsonItem; overload;

    function ToString: string; overload;
    function ToString(aHuman: Boolean = False): string; overload;
    function Minify(const aCode: string): string;

    procedure LoadFromStream(Stream: TStream; aUTF8: Boolean = True);
    procedure SaveToStream(Stream: TStream; aHuman: Boolean = True);
    procedure LoadFromFile(const aFileName: string; aUTF8: Boolean = True);
    procedure SaveToFile(const aFileName: string; aHuman: Boolean = True);

    function GetEnumerator: TMcJsonItemEnumerator;

    // helpers
    function  GetTypeStr: string;
    function  GetValueStr: string;
    function  Qot(const aMsg: string): string;
    function  QotKey(const aKey: string): string;
    procedure Error(const Msg: string; const S1: string = '';
                                       const S2: string = '';
                                       const S3: string = '');
  end;

  // TMcJsonItemEnumerator
  TMcJsonItemEnumerator = class
  strict private
    fItem : TMcJsonItem;
    fIndex: Integer;
  public
    constructor Create(aItem: TMcJsonItem);
    function GetCurrent: TMcJsonItem;
    function MoveNext: Boolean;
    property Current: TMcJsonItem read GetCurrent;
  end;

  // Auxiliary functions
  function GetItemTypeStr(aType: TJItemType): string;
  function GetValueTypeStr(aType: TJValueType): string;
  function UnEscapeUnicode(const aStr: string): string;
  function CheckIsUtf8(const aStr: AnsiString; out aAux: AnsiString): Boolean;

implementation

const C_MCJSON_VERSION = '1.0.1';
const C_EMPTY_KEY      = '__a3mptyStr__';

resourcestring
  SItemNil           = 'Object reference is nil: %s';
  SItemTypeInvalid   = 'Invalid item type: expected "%s" got "%s"';
  SItemTypeConvValue = 'Can''t convert item "%s" with value "%s" to "%s"';
  SItemTypeConv      = 'Can''t convert item "%s" to "%s"';
  SParsingError      = 'Error while parsing text: "%s" at pos "%s"';
  SIndexInvalid      = 'Invalid index: %s';

const
  WHITESPACE: set of char = [#9, #10, #13, #32]; // \t(ab), \r(CR), \n(LF), spc
  LINEBREAK:  set of char = [#10, #13];
  ESCAPES:    set of char = ['b', 't', 'n', 'f', 'r', 'u', '"', '\', '/'];
  DIGITS:     set of char = ['0'..'9'];
  SIGNS:      set of char = ['+', '-'];
  CLOSES:     set of char = ['}', ']'];
  HEXA:       set of char = ['0'..'9', 'A'..'F', 'a'..'f'];
  PATHSEPS:   set of char = ['\', '/', '.'];

{ ---------------------------------------------------------------------------- }
{ Auxiliary private functions }
{ ---------------------------------------------------------------------------- }

function escapeChar(const aStr: string; aPos, aLen: Integer; out aUnk: Boolean): Integer;
var
  n: Integer;
begin
  aUnk := False;
  n    := 1;
  if (aStr[aPos] = '\') then
  begin
    // check next char is escapable
    if (aPos < aLen) and
       (aStr[aPos+1] in ESCAPES) then
    begin
      // one char escapes
      if (aStr[aPos+1] <> 'u') then
        n := 2
      else
      //  u+(4 hexa) escape
      begin
        if (aLen-aPos-1  >  4   ) and
           (aStr[aPos+2] in HEXA) and
           (aStr[aPos+3] in HEXA) and
           (aStr[aPos+4] in HEXA) and
           (aStr[aPos+5] in HEXA)
          then n := 6        // \u1234 (6 chars)
          else aUnk := True; // bad \u escape
      end
    // if not escapable
    end
    else aUnk := True;
  end;
  // return the gap escaped
  Result := n;
end;

function escapeWS(const aStr: string; aPos, aLen: Integer): Integer;
var
  n,c: Integer;
begin
  c := aPos;
  n := 0;
  while (c <= aLen) and (aStr[c] in WHITESPACE) do
  begin
    Inc(c);
    Inc(n);
  end;
  // return the gap escaped
  Result := n;
end;

// removes all the whitespaces from the begining of the line
function trimWS(const aStr: string): string;
var
  i, j, k, n, len: Integer;
  sRes: string;
  opn, unk: Boolean;
begin
  i := 1;
  j := 1;
  len := Length(aStr);
  SetLength(sRes, len);
  opn := false;

  while ( i <= len ) do
  begin
    // check escapes
    n := escapeChar(aStr, i, len, unk);
    // control '"' for keys and string values.
    // if not escaped, toggle opn status
    if (n = 1) and (aStr[i] = '"') then
      opn := not opn;
    // ignore whitespaces chars
    if not (opn) and (aStr[i] in WHITESPACE) then
      Inc(i)
    else
    // copy n chars from aStr to sRes and move on
    begin
      for k := 1 to n do
      begin
        sRes[j] := aStr[i];
        Inc(i);
        Inc(j);
      end;
    end;
  end;
  if (j > 1) then
    SetLength(sRes, j-1);
  // result
  Result := sRes;
end;

{ ---------------------------------------------------------------------------- }
{ TMcJsonItem }
{ ---------------------------------------------------------------------------- }

function TMcJsonItem.fGetCount: Integer;
begin
  if (Self = nil) then Error(SItemNil, 'get count');
  Result := fChild.Count;
end;

function TMcJsonItem.fGetKey(aIdx: Integer): string;
var
  aItem: TMcJsonItem;
begin
  if (Self = nil) then Error(SItemNil, 'get key');
  // return the key of the idx-th child
  Result := '';
  aItem := fGetItemByIdx(aIdx);
  Result := aItem.fKey;
end;

function TMcJsonItem.fGetType(): TJItemType;
begin
  if (Self = nil) then Error(SItemNil, 'get type');
  Result := fType;
end;

function TMcJsonItem.fGetItemByKey(const aKey: string): TMcJsonItem;
var
  idx: Integer;
begin
  Result := nil;
  // check
  if (Self = nil) then Error(SItemNil, 'get item by key ' + Qot(aKey));
  // find index of item with aKey
  idx := Self.IndexOf(aKey);
  if (idx >= 0)
    then Result := TMcJsonItem(fChild[idx])
    else Error(SItemNil, 'get item by key ' + Qot(aKey));
end;

function TMcJsonItem.fGetItemByIdx(aIdx: Integer): TMcJsonItem;
begin
  // check
  if (Self = nil) then Error(SItemNil, 'get item by index ' + IntToStr(aIdx));
  // type compatibility check
  if (fType <> jitObject) and
     (fType <> jitArray ) then
    Error(SItemNil, 'get item by index ' + IntToStr(aIdx));
  // range check
  if (not isIndexValid(aIdx)) then
    Error(SIndexInvalid, 'get item by index ' + IntToStr(aIdx));
  // return valid child at index aIdx
  Result := TMcJsonItem(fChild[aIdx]);
end;

function TMcJsonItem.fHasChild: Boolean;
begin
  if (Self = nil) then Error(SItemNil, 'has child');
  Result := ( fChild.Count > 0 );
end;

function TMcJsonItem.fIsNull: Boolean;
begin
  if (Self = nil) then Error(SItemNil, 'is null');
  Result := ( fValType = jvtNull );
end;

function TMcJsonItem.fGetAsJSON(): string;
begin
  if (Self = nil) then Error(SItemNil, 'get as JSON');
  Result := ToString(False);
end;

function TMcJsonItem.fGetAsObject: TMcJsonItem;
begin
  if      (Self = nil        ) then Error(SItemNil, 'get as object')
  else if (fType <> jitObject) then Error(SItemTypeInvalid, 'object', GetTypeStr);
  // return a compatible value type
  Result := Self;
end;

function TMcJsonItem.fGetAsArray: TMcJsonItem;
begin
  if      (Self = nil       ) then Error(SItemNil, 'get as array')
  else if (fType <> jitArray) then Error(SItemTypeInvalid, 'array', GetTypeStr);
  // return a compatible value type
  Result := Self;
end;

function TMcJsonItem.fGetAsInteger: Integer;
var
  Ans: Integer;
  Aux: Integer;
begin
  Ans := 0;
  Aux := 0;
  if      (Self = nil       ) then Error(SItemNil, 'get as integer')
  else if (fType <> jitValue) then Error(SItemTypeInvalid, 'value', GetTypeStr);
  // return a compatible value type
  // try to convert
  try
    case fValType of
      jvtNumber : Ans := StrToInt(fValue);         // expected
      jvtString : Ans := StrToInt(fValue);         // convertion
      jvtBoolean: Ans := Integer(fValue = 'true'); // convertion
      else        Aux := -1;
    end;
  except
    Error(SItemTypeConvValue, GetValueStr, fValue, 'integer');
  end;
  // can´t convert, value type does not permit it
  if (Aux = -1) then
    Error(SItemTypeConv, GetValueStr, 'integer');
  Result := Ans;
end;

function TMcJsonItem.fGetAsDouble: Double;
var
  Ans: Double;
  Aux: Integer;
begin
  Ans := 0.0;
  Aux := 0;
  if      (Self = nil       ) then Error(SItemNil, 'get as double')
  else if (fType <> jitValue) then Error(SItemTypeInvalid, 'value', GetTypeStr);
  // return a compatible value type
  // try to convert
  try
    case fValType of
      jvtNumber : Ans := StrToFloat(fValue);       // expected
      jvtString : Ans := StrToFloat(fValue);       // convertion
      jvtBoolean: Ans := Integer(fValue = 'true'); // convertion
      else        Aux := -1;
    end;
  except
    Error(SItemTypeConvValue, GetValueStr, fValue, 'double');
  end;
  // can´t convert, value type does not permit it
  if (Aux = -1) then
    Error(SItemTypeConv, GetValueStr, 'double');
  Result := Ans;
end;

function TMcJsonItem.fGetAsString: string;
begin
  if      (Self = nil       ) then Error(SItemNil, 'get as string')
  else if (fType <> jitValue) then Error(SItemTypeInvalid, 'value', GetTypeStr);
  // return fValue that is string already
  // no need to convert
  Result := fValue;
end;

function TMcJsonItem.fGetAsBoolean: Boolean;
var
  Ans: Boolean;
  Aux: Integer;
begin
  Ans := False;
  Aux := 0;
  if      (Self = nil       ) then Error(SItemNil, 'get as boolean')
  else if (fType <> jitValue) then Error(SItemTypeInvalid, 'value', GetTypeStr);
  // return a compatible value type
  // try to convert
  try
    case fValType of
      jvtBoolean: Ans := Boolean(fValue = 'true') ; // expected
      jvtString : Ans := Boolean(StrToInt(fValue)); // convertion
      jvtNumber : Ans := Boolean(StrToInt(fValue)); // convertion
      else        Aux := -1;
    end;
  except
    Error(SItemTypeConvValue, GetValueStr, fValue, 'boolean');
  end;
  // can´t convert, value type does not permit it
  if (Aux = -1) then
    Error(SItemTypeConv, GetValueStr, 'boolean');
  Result := Ans;
end;

function TMcJsonItem.fGetAsNull: string;
begin
  if      (Self = nil       ) then Error(SItemNil, 'get as null')
  else if (fType <> jitValue) then Error(SItemTypeInvalid, 'value', GetTypeStr);
  // return fValue that is string already
  // no need to convert (null does not convet to anything, not presume zero)
  Result := fValue;
end;

procedure TMcJsonItem.fSetType(aType: TJItemType);
var
  i: Integer;
begin
  if (Self = nil) then Error(SItemNil, 'set type');
  // if an array or object is converted to a number, clear all descendants
  if (aType = jitValue) and (fType <> jitValue) then
  begin
    Clear;
    // the default value type is text
    fValType := jvtString;
  end
  // if a number is converted to an object or array, then take away the value from it
  else if (aType <> jitValue) and (fType = jitValue) then
  begin
    fValue := '';
  end
  // if the array is converted into an object, then assign keys to all its elements
  else if (aType = jitObject) and (fType = jitArray) then
  begin
    for i := 0 to (fChild.Count - 1) do
      TMcJsonItem(fChild[i]).fKey := IntToStr(i);
  end
  // if an object is converted into an array, then remove the keys from its descendants
  else if (aType = jitArray) and (fType = jitObject) then
  begin
    for i := 0 to (fChild.Count - 1) do
      TMcJsonItem(fChild[i]).fKey := '';
  end;
  // return aked type
  fType := aType;
end;

procedure TMcJsonItem.fSetAsJSON(aValue: string);
var
  c, len: Integer;
begin
  if (Self = nil) then Error(SItemNil, 'set as JSON');
  Clear;
  len := Length(aValue);
  c   := 1;
  try
    c := Self.parse(aValue, 1, len);
  except
    on EOutOfMemory do
      Error(SItemNil, 'out of memory with ' + IntToStr(CountItems) + ' items');
  end;
  // valid-JSON
  if (c < len) then
    Error(SParsingError, 'bad json', IntToStr(len));
end;

procedure TMcJsonItem.fSetAsObject(aValue: TMcJsonItem);
begin
  if (Self  = nil) then Error(SItemNil, 'set as object');
  // if unset, set as value
  if (fType <> jitObject) then fSetType(jitObject);
  // make a copy (parsing)
  Self.AsJSON := aValue.AsJSON;
end;

procedure TMcJsonItem.fSetAsArray(aValue: TMcJsonItem);
begin
  if (Self  = nil) then Error(SItemNil, 'set as array');
  // if unset, set as value
  if (fType <> jitArray) then fSetType(jitArray);
  // make a copy (parsing)
  Self.AsJSON := aValue.AsJSON;
end;

procedure TMcJsonItem.fSetAsInteger(aValue: Integer);
var
  i: Integer;
begin
  if (Self  = nil     ) then Error(SItemNil, 'set as integer');
  // if unset, set as value
  if (fType = jitUnset) then fSetType(jitValue);
  // if container, set aValue for each child
  if (fType = jitArray) or (fType = jitObject) then
  begin
     for i := 0 to (fChild.Count - 1) do
       TMcJsonItem(fChild[i]).AsInteger := aValue;
  end
  else
  begin
    if (fValType <> jvtNumber) then fValType := jvtNumber;
    // set aValue as string
    fValue := IntToStr(aValue);
  end;
end;

procedure TMcJsonItem.fSetAsDouble(aValue: Double);
var
  i: Integer;
begin
  if (Self  = nil     ) then Error(SItemNil, 'set as double');
  // if unset, set as value
  if (fType = jitUnset) then fSetType(jitValue);
  // if container, set aValue for each child
  if (fType = jitArray) or (fType = jitObject) then
  begin
     for i := 0 to (fChild.Count - 1) do
       TMcJsonItem(fChild[i]).AsNumber := aValue;
  end
  else
  begin
    if (fValType <> jvtNumber) then fValType := jvtNumber;
    // set aValue as string
    fValue := FloatToStr(aValue);
  end;
end;

procedure TMcJsonItem.fSetAsString(aValue: string);
var
  i: Integer;
begin
  if (Self  = nil     ) then Error(SItemNil, 'set as string');
  // if unset, set as value
  if (fType = jitUnset) then fSetType(jitValue);
  // if container, set aValue for each child
  if (fType = jitArray) or (fType = jitObject) then
  begin
     for i := 0 to (fChild.Count - 1) do
       TMcJsonItem(fChild[i]).AsString := aValue;
  end
  else
  begin
    if (fValType <> jvtString) then fValType := jvtString;
    // set aValue as string
    fValue := aValue;
  end;
end;

procedure TMcJsonItem.fSetAsBoolean(aValue: Boolean);
var
  i: Integer;
begin
  if (Self  = nil     ) then Error(SItemNil, 'set as boolean');
  // if unset, set as value
  if (fType = jitUnset) then fSetType(jitValue);
  // if container, set aValue for each child
  if (fType = jitArray) or (fType = jitObject) then
  begin
     for i := 0 to (fChild.Count - 1) do
       TMcJsonItem(fChild[i]).AsBoolean := aValue;
  end
  else
  begin
    if (fValType <> jvtBoolean) then fValType := jvtBoolean;
    // set aValue as string
    if aValue
      then fValue := 'true'
      else fValue := 'false';
  end;
end;

procedure TMcJsonItem.fSetAsNull(aValue: string);
var
  i: Integer;
begin
  if (Self  = nil     ) then Error(SItemNil, 'set as null');
  // if unset, set as value
  if (fType = jitUnset) then fSetType(jitValue);
  // if container, set aValue for each child
  if (fType = jitArray) or (fType = jitObject) then
  begin
     for i := 0 to (fChild.Count - 1) do
       TMcJsonItem(fChild[i]).AsNull := 'null'; // ignore aValue
  end
  else
  begin
    if (fValType <> jvtNull) then fValType := jvtNull;
    // set aValue as string
    fValue := 'null'; // ignore aValue
  end;
end;

function TMcJsonItem.parse(const aCode: string; aPos, aLen: Integer): Integer;
begin
  Result := aPos;
  // check position
  if (aPos > aLen) then
    Exit;
  // escape white spaces
  Inc(aPos, escapeWS(aCode, aPos, aLen));
  // now in the first character our open parenthesis
  case aCode[aPos] of
    '{':                aPos := readObject (aCode, aPos, aLen); // recursive
    '[':                aPos := readArray  (aCode, aPos, aLen); // recursive
    '"':                aPos := readValue  (aCode, aPos, aLen);
    '0'..'9', '+', '-': aPos := readNumber (aCode, aPos, aLen);
    't', 'T', 'f', 'F': aPos := readBoolean(aCode, aPos, aLen);
    'n', 'N':           aPos := readNull   (aCode, aPos, aLen);
    else
    begin
      // valid-JSON
      Error(SParsingError, 'invalid char', IntToStr(aPos));
    end;
  end;
  // escape white spaces
  Inc(aPos, escapeWS(aCode, aPos, aLen));
  // move on
  Result := aPos;
end;

function TMcJsonItem.readObject(const aCode: string; aPos, aLen: Integer): Integer;
var
  c: Integer;
  aItem: TMcJsonItem;
  sKey : string;
  first: Boolean;
begin
  // we got here because current symbol was '{'
  c  := aPos+1; 
  // escape white spaces
  Inc(c, escapeWS(aCode, c, aLen));
  // set item type
  Self.fSetType(jitObject);
  first := True;
  // reading values until we reach a '}'
  while ( (c <= aLen) and (aCode[c] <> '}') ) do
  begin
    // parse ','
    if (not first) then
      c := readChar(aCode, ',', c, aLen);
    first := False;
    // escape white spaces
    Inc(c, escapeWS(aCode, c, aLen));
    // parsing a "key", stop next to '"'
    c := readString(aCode, sKey, c, aLen);
    // check empty key like {"":"value"}
    if (sKey = '') then
      sKey := C_EMPTY_KEY;
    // create a new item with parsed key
    // check duplicate (subject to speed up flag)
    aItem := nil;
    if (fSpeedUp) then
      aItem := Self.Add(sKey)
    else
    begin
      // valid-JSON
      if (Self.IndexOf(sKey) < 0)
        then aItem := Self.Add(sKey)
        else Error(SParsingError, 'duplicated key ' + sKey, IntToStr(c));
    end;
    // escape white spaces
    Inc(c, escapeWS(aCode, c, aLen));
    // parse ':'
    c := readChar(aCode, ':', c, aLen);
    // escape white spaces
    Inc(c, escapeWS(aCode, c, aLen));
    // parsing a value (recursive)
    if (aItem <> nil) then
      c := aItem.parse(aCode, c, aLen);
    // move on
    Inc(c, escapeWS(aCode, c, aLen));
  end;
  // valid-JSON
  if (c > aLen) then
    Error(SParsingError, 'bad object', IntToStr(aLen))
  else if (aCode[c] <> '}') then
    Error(SParsingError, 'bad object', IntToStr(c)   );
  // stop next to '}'
  Result := c+1;
end;

function TMcJsonItem.readArray(const aCode: string; aPos, aLen: Integer): Integer;
var
  c: Integer;
  aItem: TMcJsonItem;
  first: Boolean;
begin
  // we got here because current symbol was '['
  c := aPos+1;
  // escape white spaces
  Inc(c, escapeWS(aCode, c, aLen));
  // set item type
  Self.fSetType(jitArray);
  first := True;
  // reading values until we reach a ']'
  while ( (c <= aLen) and (aCode[c] <> ']') ) do
  begin
    // parse ','
    if (not first) then
      c := readChar(aCode, ',', c, aLen);
    first := False;
    // escape white spaces
    Inc(c, escapeWS(aCode, c, aLen));
    // Creating a new value (here explicity whith no key)
    aItem := Self.Add();
    // parsing values (recursive)
    c := aItem.parse(aCode, c, aLen); // 1,2,3 or {...},{...}
    if (c > aLen) then
      Error(SParsingError, 'bad array', IntToStr(aLen));
    // move on
    Inc(c, escapeWS(aCode, c, aLen));
  end;
  // valid-JSON
  if (c > aLen) then
    Error(SParsingError, 'bad object', IntToStr(aLen))
  else if (aCode[c] <> ']') then
    Error(SParsingError, 'bad array', IntToStr(c)   );
  // stop next to ']'
  Result := c+1;
end;

function TMcJsonItem.readString(const aCode: string; out aStr:string; aPos, aLen: Integer): Integer;
var
  c: Integer;
  unk: Boolean;
begin
  aStr := '';
  c    := aPos;
  if (aCode[aPos] = '"') then
  begin
    Inc(c);
    while ( (c <= aLen) and (aCode[c] <> '"') ) do
    begin
      // do escapes
      Inc(c, escapeChar(aCode, c, aLen, unk));
      // Valid-JSON: break lines
      if (c > aLen) or (aCode[c] in LINEBREAK) then
        Error(SParsingError, 'line break', IntToStr(c));
      // Valid-JSON: unknown escape
      if (unk) then
        Error(SParsingError, 'unknown escape', IntToStr(c));
    end;
    // copy between '"'
    if (aCode[c] = '"') then
      aStr := System.Copy(aCode, aPos+1, c-aPos-1); // "string" -> string
  end;
  // stop next to '"'
  if (c < aLen) then Inc(c);
  Result := c;
end;

function TMcJsonItem.readChar(const aCode: string; aChar: Char; aPos, aLen: Integer): Integer;
begin
  if ( aCode[aPos] <> aChar ) then
    Error(SParsingError, 'expected ' + aChar + ' got ' + aCode[aPos], IntToStr(aPos));
  // stop next to aChar
  Result := aPos+1;
end;

function TMcJsonItem.readKeyword(const aCode, aKeyword: string; aPos, aLen: Integer): Integer;
var
  len: Integer;
  sAux: string;
begin
  len  := Length(aKeyword);
  sAux := System.Copy(aCode, aPos, len);
  // valid-JSON
  if (Lowercase(sAux) <> aKeyword) then
    Error(SParsingError, 'invalid keyword ' + sAux, IntToStr(aPos));
  // stop next to keyword last char
  Result := aPos + len;
end;

function TMcJsonItem.readValue(const aCode: string; aPos, aLen: Integer): Integer;
var
  c: Integer;
  sVal: string;
begin
  // we got here because current symbol is '"'
  c := aPos;
  // parse a "value" -> value
  c := readString(aCode, sVal, c, aLen);
  // valid-JSON
  if (c > aLen) then
    Error(SParsingError, 'bad value', IntToStr(aLen));
  // set item and value types
  Self.fSetType(jitValue);
  Self.fValType := jvtString;
  Self.fValue   := sVal;
  // stop next to '"'
  Result := c;
end;

function TMcJsonItem.readNumber(const aCode: string; aPos, aLen: Integer): Integer;
var
  c, ePos: Integer;
begin
  // we got here because current symbol was '+/-' or Digit
  c := aPos;
  // 1. sign (optional)
  if aCode[c] in SIGNS
    then Inc(c);
  // 2. some digits but not leading zeros
  while (aCode[c] in DIGITS) do
    Inc(c);
  // 3. decimal dot (optional)
  if aCode[c] = '.'
    then Inc(c);
  // 4. fractional digits (optional)
  while (aCode[c] in DIGITS) do
    Inc(c);
  // 5. scientific notation ...E-01
  if LowerCase(aCode[c]) = 'e' then
  begin
    ePos := c;
    Inc(c);
    if aCode[c] in SIGNS
      then Inc(c);
    while (aCode[c] in DIGITS) do
      Inc(c);
    // valid-JSON: bad scientific number
    if (ePos+1 = c) then
      Error(SParsingError, 'bad scientific number', IntToStr(c));
  end;
  // Result
  Self.fSetType(jitValue);
  Self.fValType := jvtNumber;
  Self.fValue   := System.Copy(aCode, aPos, c-aPos);
  // escape white spaces
  Inc(c, escapeWS(aCode, c, aLen));
  // valid-JSON: not a number
  if not ((aCode[c] = ','    ) or
          (aCode[c] in CLOSES)) then
    Error(SParsingError, 'not a number', IntToStr(c));
  // valid-JSON: leading zero
  if (aCode[aPos]   =  '0') and (aPos < aLen) and (c-aPos > 1) and
     (aCode[aPos+1] <> '.') then
    Error(SParsingError, 'bad number, leading zero', IntToStr(c));
  // stop next to number last char
  Result := c;
end;

function TMcJsonItem.readBoolean(const aCode: string; aPos, aLen: Integer): Integer;
var
  c: Integer;
  sAux: string;
begin
  // we got here because current symbol was 't/T' or 'f/F'
  c    := aPos;
  sAux := '';
  // check boolean value 'true'
  if (aCode[aPos] = 't') or
     (aCode[aPos] = 'T') then
  begin
    c := readKeyword(aCode, 'true', c, aLen);
    Self.fValue := 'true';
  end
  // check boolean value 'false'
  else if (aCode[aPos] = 'f') or
          (aCode[aPos] = 'F') then
  begin
    c := readKeyword(aCode, 'false', c, aLen);
    Self.fValue := 'false';
  end;
  // set item and value types
  Self.fSetType(jitValue);
  Self.fValType := jvtBoolean;
  // stop next to keyword last char
  Result := c;
end;

function TMcJsonItem.readNull(const aCode: string; aPos, aLen: Integer): Integer;
var
  c: Integer;
  sAux: string;
begin
  // we got here because current symbol was 'n/N'
  c    := aPos;
  sAux := '';
  // check if null
  if (aCode[aPos] = 'n') or
     (aCode[aPos] = 'N') then
  begin
    c := readKeyword(aCode, 'null', c, aLen);
    Self.fValue := 'null';
  end;
  // set item and value types
  Self.fSetType(jitValue);
  Self.fValType := jvtNull;
  // stop next to keyword last char
  Result := c;
end;

function TMcJsonItem.sFormat(aHuman: Boolean): string;
var
  strS: TStringStream;
  sNL, sSp: string;
begin
  strS := TStringStream.Create('');
  try
    // new line
    if aHuman
      then sNL := #13#10
      else sNL := '';
    // key value separator
    if (aHuman)
      then sSp := ': '
      else sSp := ':';
    // call format item recursively
    SFormatItem(strS, '', sNL, sSp);
    // final result;
    Result := strS.DataString;
  finally
    strS.Free;
  end;
end;

function TMcJsonItem.sFormatItem(aStrS: TStringStream; const aIn, aNL, aSp: string): string;
var
  i, len: Integer;
  sGoIn: string;
begin
  Result := '';
  sGoIn  := '';

  if (Self = nil) then
    Exit;

  case Self.fType of
    // format JSON object
    jitObject:
    begin
      if (fKey <> '') then
        aStrS.WriteString(QotKey(fKey) + aSp);
      aStrS.WriteString('{' + aNL);
      len := Self.Count - 1;
      // use aSp to define if aHuman is true.
      if (aSp <> ':') then sGoIn := aIn + '  ';
      // mount recursively
      for i := 0 to len do
      begin
        aStrS.WriteString(sGoIn);
        aStrS.WriteString(TMcJsonItem(fChild[i]).sFormatItem(aStrS, sGoIn, aNL, aSP) );
        if ( i < len ) then
          aStrS.WriteString(',' + aNL);
      end;
      aStrS.WriteString(aNL + aIn + '}');
    end;
    // format JSON array
    jitArray:
    begin
      if (fKey <> '') then
        aStrS.WriteString(QotKey(fKey) + aSp);
      aStrS.WriteString('[' + aNL);
      len := Self.Count - 1;
      // use aSp to define if aHuman is true.
      if (aSp <> ':') then sGoIn := aIn + '  ';
      // mount recursively
      for i := 0 to len do
      begin
        aStrS.WriteString(sGoIn);
        aStrS.WriteString(TMcJsonItem(fChild[i]).SFormatItem(aStrS, sGoIn, aNL, aSP) );
        if ( i < len ) then
          aStrS.WriteString(','+ aNL);
      end;
      aStrS.WriteString(aNL + aIn + ']');
    end;
    // format JSON key:value pair
    jitValue:
    begin
      if (fKey <> '') then
        aStrS.WriteString(QotKey(fKey) + aSp);
      if (fValType = jvtString)
        then aStrS.WriteString(Qot(fValue))
        else aStrS.WriteString(    fValue );
    end;
  end;
end;

function TMcJsonItem.isIndexValid(aIdx: Integer): Boolean;
var
  Ans: Boolean;
begin
  if (fChild.Count <= 0)
    then Ans := (AIdx  = 0)
    else Ans := (AIdx >= 0) and (AIdx < fChild.Count);
  Result := Ans;
end;

{ ---------------------------------------------------------------------------- }
{ TMcJsonItem - Public methods }
{ ---------------------------------------------------------------------------- }

constructor TMcJsonItem.Create;
begin
  fChild   := TList.Create;
  fType    := jitUnset;
  fSpeedUp := True;
end;

constructor TMcJsonItem.Create(aJItemType: TJItemType);
begin
  inherited Create;
  Create;
  Self.ItemType := aJItemType;
end;

constructor TMcJsonItem.Create(const aItem: TMcJsonItem);
begin
  inherited Create;
  Create;
  Self.AsJSON := aItem.AsJSON;
end;

constructor TMcJsonItem.Create(const aCode: string);
begin
  inherited Create;
  Create;
  try
    Self.AsJSON := aCode;
  except
    Self.AsJSON := '';
  end;
end;

destructor TMcJsonItem.Destroy;
begin
  Clear;
  fChild.Free;
  inherited Destroy;
end;

procedure TMcJsonItem.Clear;
var
  i: Integer;
begin
  if (Self = nil) then Error(SItemNil, 'clear');
  // free memory of all children (will be recursive)
  for i := 0 to (fChild.Count - 1) do
    TMcJsonItem(fChild[i]).Free;
  // clear list
  fChild.Clear;
end;

function TMcJsonItem.IndexOf(const aKey: string): Integer;
var
  i, idx: Integer;
begin
  idx    := -1;
  Result := idx;
  // check
  if  (Self = nil) then Error(SItemNil, 'index of');
  // looking for an element
  for i := 0 to (fChild.Count - 1) do
  begin
    if (TMcJsonItem(fChild[i]).fKey = aKey) then
    begin
      idx := i;
      Break;
    end;
  end;
  // return the Result
  if (idx >= 0           ) and
     (idx <  fChild.Count) then
    Result := idx;
end;

function TMcJsonItem.Path(const aPath: string): TMcJsonItem;

  function GetKeyByPath(const aPath: string; out aPos, aLen: Integer): string;
  var
    c: Integer;
  begin
    Result := '';
    // check start with sep
    if (aPath[aPos] in PATHSEPS) then
      Inc(aPos);
    c := aPos;
    while (c <= aLen) and not (aPath[c] in PATHSEPS) do
    begin
      Inc(c);
    end;
    // copy between seps
    if (c-aPos >= 0) then
      Result := System.Copy(aPath, aPos, c-aPos);
    // move on  
    aPos := c;
  end;

var
  aItem: TMcJsonItem;
  c, len: Integer;
  sKey: string;
begin
  if (Self = nil) then Error(SItemNil, 'get by path ' + Qot(aPath));
  aItem  := Self;
  // parse path of keys using seps
  c   := 1;
  len := Length(aPath);
  while (c < len) do
  begin
    // get by key
    sKey := GetKeyByPath(aPath, c, len);
    if (sKey <> '') then
      aItem := aItem.fGetItemByKey(sKey);
  end;
  // result aItem to permit chain
  Result := aItem;
end;

function TMcJsonItem.Add(const aKey: string): TMcJsonItem;
var
  aItem: TMcJsonItem;
begin
  if (Self = nil) then Error(SItemNil, 'add using key ' + Qot(aKey));
  // check unset item
  if (fType = jitUnset) then
    fSetType(jitObject);
  // create a new item with aKey and add it.
  aItem := TMcJsonItem.Create;
  aItem.fKey := aKey;
  fChild.Add(aItem);
  // result aItem to permit chain
  Result := aItem;
end;

function TMcJsonItem.Add(const aKey: string; aItemType: TJItemType): TMcJsonItem;
var
  aItem: TMcJsonItem;
begin
  aItem := Self.Add(aKey);
  aItem.ItemType := aItemType;
  // result aItem to permit chain
  Result := aItem;
end;

function TMcJsonItem.Add(aItemType: TJItemType): TMcJsonItem;
var
  aItem: TMcJsonItem;
begin
  aItem := Self.Add();
  aItem.ItemType := aItemType;
  // result aItem to permit chain
  Result := aItem;
end;

function TMcJsonItem.Add(const aItem: TMcJsonItem): TMcJsonItem;
var
  aNewItem: TMcJsonItem;
begin
  if (Self = nil) then Error(SItemNil, 'add using item');
  // check unset item
  if (fType = jitUnset) then
    fSetType(jitObject);
  // check if self is an array
  if (fType <> jitArray) then
    Error(SItemTypeInvalid, 'array', GetTypeStr);
  // create a new item copy of aItem and add it.
  aNewItem := TMcJsonItem.Create(aItem);
  // add item.
  fChild.Add(aNewItem);
  // result aNewItem to permit chain
  Result := aNewItem;
end;

function TMcJsonItem.Copy(const aItem: TMcJsonItem): TMcJsonItem;
begin
  if (Self = nil) then Error(SItemNil, 'copy');
  // clear self and copy JSON from aItem
  Self.Clear;
  Self.AsJSON := aItem.AsJSON;
  // result self to permit chain
  Result := Self;
end;

function TMcJsonItem.Clone: TMcJsonItem;
var
  aItem: TMcJsonItem;
begin
  if (Self = nil) then Error(SItemNil, 'clone');
  // create a new item using self
  aItem := TMcJsonItem.Create(Self);
  // result aItem to permit chain
  Result := aItem;
end;

function TMcJsonItem.Insert(const aKey: string; aIdx: Integer): TMcJsonItem;
var
  aItem: TMcJsonItem;
begin
  if (Self = nil            ) then Error(SItemNil, 'insert using key ' + Qot(aKey));
  if (not isIndexValid(aIdx)) then Error(SIndexInvalid, 'insert index ' + IntToStr(aIdx));
  // check unset item
  if (fType = jitUnset) then
    fSetType(jitObject);
  // create a new item with aKey and insert it.
  aItem := TMcJsonItem.Create;
  aItem.fKey := aKey;
  fChild.Insert(aIdx, aItem);
  // result aItem to permit chain
  Result := aItem;
end;

function TMcJsonItem.Insert(const aItem: TMcJsonItem; aIdx: Integer): TMcJsonItem;
var
  aNewItem: TMcJsonItem;
begin
  if (Self = nil            ) then Error(SItemNil, 'insert using item');
  if (not isIndexValid(aIdx)) then Error(SIndexInvalid, 'insert index ' + IntToStr(aIdx));
  // check unset item
  if (fType = jitUnset) then
    fSetType(jitObject);
  // check if self is an array
  if (fType <> jitArray) then
    Error(SItemTypeInvalid, 'array', GetTypeStr);
  // create a new item copy of aItem and insert it.
  aNewItem := TMcJsonItem.Create(aItem);
  // insert item.
  fChild.Insert(aIdx, aNewItem);
  // result aNewItem to permit chain
  Result := aNewItem;
end;

function TMcJsonItem.Delete(aIdx: Integer): Boolean;
var
  Size: Integer;
  aItemDel: TMcJsonItem;
  Ans: Boolean;
begin
  Ans := False;
  if (Self = nil) then Error(SItemNil, 'delete index ' + IntToStr(aIdx));
  // check idx and size
  Size := fChild.Count;
  if (not isIndexValid(aIdx)) or (Size <= 0) then
    Ans := False
  else
  begin
    // item to delete
    aItemDel := TMcJsonItem(fChild[aIdx]);
    // delete position and free memory.
    if (aItemDel <> nil) then
    begin
      fChild.Delete(aIdx);
      aItemDel.Free;
      Ans := True;
    end;
  end;
  Result := Ans;
end;

function TMcJsonItem.Delete(const aKey: string): Boolean;
var
  Ans: Boolean;
  idx: Integer;
begin
  Ans := False;
  if (Self = nil) then Error(SItemNil, 'delete key ' + Qot(aKey));
  // find index of item with aKey
  idx := Self.IndexOf(aKey);
  if (idx >= 0) then
    Ans := Self.Delete(idx);
  Result := Ans;
end;

function TMcJsonItem.HasKey(const aKey: string): Boolean;
begin
  if (Self = nil) then Error(SItemNil, 'has key ' + Qot(aKey));
  try
    fGetItemByKey(aKey);
    Result := True;
  except
    Result := False;
  end;
end;

function TMcJsonItem.IsEqual(const aItem: TMcJsonItem): Boolean;
begin
  Result := False;
  if (Self  =  nil) then Error(SItemNil, 'is equal item');
  if (aItem <> nil) then
    Result := (Self.AsJSON = aItem.AsJSON);
end;

function TMcJsonItem.Check(const aStr: string; aSpeedUp: Boolean): Boolean;
var
  aItem: TMcJsonItem;
begin
  aItem := TMcJsonItem.Create;
  try
    aItem.fSpeedUp := aSpeedUp;
    aItem.AsJSON   := aStr;
//    Result := True;
    Result := (aItem.AsJSON = trimWS(aStr));
  except
    Result := False;
  end;
  aItem.Free;
end;

function TMcJsonItem.CountItems: Integer;

  function CountItemsRec(const aItem: TMcJsonItem): Integer;
  var
    i, sum: Integer;
  begin
    sum := aItem.Count;
    for i := 0 to aItem.Count-1 do
      sum := sum + CountItemsRec( TMcJsonItem(aItem.fChild[i]) );
    Result := sum;
  end;

begin
  Result := CountItemsRec(Self);
end;

function TMcJsonItem.At(aIdx: Integer; const aKey: string): TMcJsonItem;
var
  aItem: TMcJsonItem;
begin
  // get by index
  aItem := fGetItemByIdx(aIdx);
  // get by key
  if ((aKey <> '') and (aItem <> nil)) then
    aItem := aItem.fGetItemByKey(aKey);
  Result := aItem;
end;

function TMcJsonItem.At(const aKey: string; aIdx: Integer): TMcJsonItem;
var
  aItem: TMcJsonItem;
begin
  // get by key
  aItem := fGetItemByKey(aKey);
  // get by index
  if ((aIdx >= 0) and (aItem <> nil)) then
    aItem := aItem.fGetItemByIdx(aIdx);
  Result := aItem;
end;

function TMcJsonItem.ToString: string;
begin
  Result := sFormat(False);
end;

function TMcJsonItem.ToString(aHuman: Boolean): string;
begin
  Result := sFormat(aHuman);
end;

function TMcJsonItem.Minify(const aCode: string): string;
begin
  Result := trimWS(aCode);
end;

procedure TMcJsonItem.LoadFromStream(Stream: TStream; aUTF8: Boolean);
var
  sCode, sAux: AnsiString;
  len  : Int64;
begin
  len   := Stream.Size - Stream.Position;
  sCode := '';
  SetLength(sCode, len);
  Stream.Read(Pointer(sCode)^, len);
  if (aUTF8 and CheckIsUtf8(sCode, sAux))
    then Self.AsJSON := sAux
    else Self.AsJSON := sCode;
end;

procedure TMcJsonItem.SaveToStream(Stream: TStream; aHuman: Boolean);
var
  sCode: AnsiString;
  len  : Int64;
begin
  sCode := AnsiToUtf8(Self.ToString(aHuman));
  len   := Length(sCode);
  Stream.Write(Pointer(sCode)^, len);
end;

procedure TMcJsonItem.LoadFromFile(const aFileName: string; aUTF8: Boolean);
var
  fileStream: TFileStream;
begin
  fileStream := nil;
  try
    fileStream := TFileStream.Create(aFileName, fmOpenRead or fmShareDenyWrite);
    Clear;
    LoadFromStream(fileStream, aUTF8);
  finally
    fileStream.Free;
  end;
end;

procedure TMcJsonItem.SaveToFile(const aFileName: string; aHuman: Boolean);
var
  fileStream: TFileStream;
begin
  fileStream := nil;
  try
    fileStream := TFileStream.Create(aFileName, fmCreate or fmShareDenyWrite);
    SaveToStream(fileStream, aHuman);
  finally
    fileStream.Free;
  end;
end;

function TMcJsonItem.GetEnumerator: TMcJsonItemEnumerator;
var
  enum: TMcJsonItemEnumerator;
begin
  enum := TMcJsonItemEnumerator.Create(Self);
  Result := enum;
end;

function TMcJsonItem.GetTypeStr: string;
begin
  if (Self = nil) then Error(SItemNil, 'get type description');
  Result := GetItemTypeStr(Self.fType);
end;

function TMcJsonItem.GetValueStr: string;
begin
  if (Self = nil) then Error(SItemNil, 'get value type description');
  Result := GetValueTypeStr(Self.fValType);
end;

function TMcJsonItem.Qot(const aMsg: string): string;
begin
  Result := '"' + aMsg + '"';
end;

function TMcJsonItem.QotKey(const aKey: string): string;
begin
  Result := '';
  if (aKey = C_EMPTY_KEY)
    then Result := Qot('')
    else Result := Qot(aKey);
end;

procedure TMcJsonItem.Error(const Msg: string; const S1: string;
                                               const S2: string;
                                               const S3: string);
var
  aStr: string;
begin
  aStr := Format(Msg, [S1, S2, S3]);
  raise EMcJsonException.Create(aStr);
end;

{ ---------------------------------------------------------------------------- }
{ TMcJsonItemEnumerator }
{ ---------------------------------------------------------------------------- }

constructor TMcJsonItemEnumerator.Create(aItem: TMcJsonItem);
begin
  fItem  := aItem;
  FIndex := -1;
end;

function TMcJsonItemEnumerator.GetCurrent: TMcJsonItem;
begin
  if      (fItem.fChild = nil         ) then Result := nil
  else if (fIndex < 0                 ) then Result := nil
  else if (fIndex < fItem.fChild.Count) then Result := TMcJsonItem(fItem.fChild[fIndex])
  else                                  Result := nil;
end;

function TMcJsonItemEnumerator.MoveNext: Boolean;
begin
  Inc(fIndex);
  if (fItem.fChild = nil)
    then Result := False
    else Result := (fIndex < fItem.fChild.Count);
end;

{ ---------------------------------------------------------------------------- }
{ Auxiliary public functions }
{ ---------------------------------------------------------------------------- }
function GetItemTypeStr(aType: TJItemType): string;
begin
  Result := 'unknown';
  case aType of
    jitValue : Result := 'value' ;
    jitObject: Result := 'object';
    jitArray : Result := 'array' ;
    jitUnset : Result := 'unset' ;
  end;
end;

function GetValueTypeStr(aType: TJValueType): string;
begin
  Result := 'unknown';
  case aType of
    jvtString : Result := 'string' ;
    jvtNumber : Result := 'number' ;
    jvtBoolean: Result := 'boolean';
    jvtNull   : Result := 'null'   ;
  end;
end;

function UnEscapeUnicode(const aStr: string): string;
var
  cs, cd, len: Integer;
  ans: string;
begin
  cs  := 1; // char in source
  cd  := 1; // char in destiny
  len := Length(aStr);
  SetLength(ans, len);
  while (cs <= len) do
  begin
    // no escape, copy and move on
    if (aStr[cs] <> '\') then
    begin
      ans[cd] := aStr[cs];
      Inc(cs);
      Inc(cd);
    end
    else
    begin
      // u+(4 hexa) escape
      if (cs < len) and (aStr[cs+1] = 'u') then
      begin
        if (len-cs-1   >  4   ) and
           (aStr[cs+2] in HEXA) and (aStr[cs+3] in HEXA) and
           (aStr[cs+4] in HEXA) and (aStr[cs+5] in HEXA) then
        begin
          try
            try
              ans[cd] := Chr( StrToInt('$' + Copy(aStr, cs+2, 4)) );
              Inc(cd);
            except
              ; // invalid hexa, ignore and move on
            end;
          finally
            Inc(cs, 6); // \uXXXX
          end;
        end;
      end
      // ignore other escapes
      else
        Inc(cs, 2);
    end;
  end;
  // trim extra size
  cd := Pos(#0, ans);
  SetLength(ans, cd-1);
  // return the string unescaped
  Result := ans;
end;

function CheckIsUtf8(const aStr: AnsiString; out aAux: AnsiString): Boolean;
var
  len : Integer;
begin
  len := Length(aStr);
  // convert to Ansi (if Utf8, will lead to length zero)
  try
    aAux := Utf8ToAnsi(aStr);
  except
    ; // ignore
  end;
  Result := (len > 0) and (Length(aAux) <> 0);
end;

end.