JSON returned by TIdHTTP cannot be decoded - json

Question

I have the following code:
var
MemoryStream1: TMemoryStream;
IdHTTP1: TIdHTTP;
Bytes1: TBytes;
s1: string;
begin
IdHTTP1 := TIdHTTP.Create(nil);
MemoryStream1 := TMemoryStream.Create;
IdHTTP1.Get('https://restcountries.eu/rest/v2/all', MemoryStream1);
MemoryStream1.Position := 0;
MemoryStream1.SaveToFile('C:\Temp\MemoryStream1.txt');
MemoryStream1.Position := 0;
SetLength(Bytes1, MemoryStream1.Size);
MemoryStream1.Read(Bytes1[0], MemoryStream1.Size);
s1 := TEncoding.UTF8.GetString(Bytes1);
It fails at the last line with the message "no mapping for the unicode character in the target multi-byte code page exists"
However, I can see the returned JSON clearly in HttpAnalyzer.
The file 'C:\Temp\MemoryStream1.txt' starts with the hex '1F8B0800000000000003DC9BED6F1BB7' when I am expecting something corresponding to { - a left brace - as the first character
when I try
s1 := TEncoding.Unicode.GetString(Bytes1);
String s1 contains "Chinese" characters.

Answer 1

I worked it out. Apparently, the gzip is not decompressed. One must do it oneself. Here goes:
var
IdHTTP1: TIdHTTP;
a1: AnsiString;
s1: string;
MemoryStream1, MemoryStream2: TMemoryStream;
begin
Screen.Cursor := crHourGlass;
IdHTTP1 := TIdHTTP.Create(nil);
MemoryStream1 := TMemoryStream.Create;
MemoryStream2 := TMemoryStream.Create;
IdHTTP1.Get('https://restcountries.eu/rest/v2/all', MemoryStream1);
MemoryStream1.Position := 0;
IdCompressorZLib1.DecompressGZipStream(MemoryStream1, MemoryStream2);
FreeAndNil(MemoryStream1);
MemoryStream2.Position := 0;
SetLength(a1, MemoryStream2.Size);
MemoryStream2.Read(a1[1], MemoryStream2.Size);
// AnsiString a1 now contains the decompressed data