Delphi DLL GMail: Get a specific message (format="metadata")

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Gets a specific message using format=metadata.

Documentation: https://developers.google.com/gmail/api/v1/reference/users/messages/get

var
rest: HCkRest;
success: Boolean;
oauth2: HCkOAuth2;
sbJson: HCkStringBuilder;
json: HCkJsonObject;
id: PWideChar;
threadId: PWideChar;
snippet: PWideChar;
historyId: PWideChar;
internalDate: PWideChar;
payloadMimeType: PWideChar;
sizeEstimate: Integer;
i: Integer;
count_i: Integer;
strVal: PWideChar;
name: PWideChar;
value: PWideChar;

begin
rest := CkRest_Create();

//   Provide a previously obtained OAuth2 access token.
oauth2 := CkOAuth2_Create();
CkOAuth2_putAccessToken(oauth2,'OAUTH2_ACCESS_TOKEN');
CkRest_SetAuthOAuth2(rest,oauth2);

success := CkRest_Connect(rest,'www.googleapis.com',443,True,True);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    Exit;
  end;

CkRest_AddPathParam(rest,'messageId','15fc23688c553739');

CkRest_AddQueryParam(rest,'format','metadata');

sbJson := CkStringBuilder_Create();
success := CkRest_FullRequestNoBodySb(rest,'GET','/gmail/v1/users/me/messages/messageId',sbJson);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    Exit;
  end;

if (CkRest_getResponseStatusCode(rest) <> 200) then
  begin
    Memo1.Lines.Add('Received error response code: ' + IntToStr(CkRest_getResponseStatusCode(rest)));
    Memo1.Lines.Add('Response body:');
    Memo1.Lines.Add(CkStringBuilder__getAsString(sbJson));
    Exit;
  end;

json := CkJsonObject_Create();
CkJsonObject_LoadSb(json,sbJson);

//  The following code parses the JSON response.
//  A sample JSON response is shown below the sample code.

id := CkJsonObject__stringOf(json,'id');
threadId := CkJsonObject__stringOf(json,'threadId');
snippet := CkJsonObject__stringOf(json,'snippet');
historyId := CkJsonObject__stringOf(json,'historyId');
internalDate := CkJsonObject__stringOf(json,'internalDate');
payloadMimeType := CkJsonObject__stringOf(json,'payload.mimeType');
sizeEstimate := CkJsonObject_IntOf(json,'sizeEstimate');
i := 0;
count_i := CkJsonObject_SizeOfArray(json,'labelIds');
while i < count_i do
  begin
CkJsonObject_putI(json,i);
    strVal := CkJsonObject__stringOf(json,'labelIds[i]');
    i := i + 1;
  end;

i := 0;
count_i := CkJsonObject_SizeOfArray(json,'payload.headers');
while i < count_i do
  begin
CkJsonObject_putI(json,i);
    name := CkJsonObject__stringOf(json,'payload.headers[i].name');
    value := CkJsonObject__stringOf(json,'payload.headers[i].value');
    i := i + 1;
  end;

Memo1.Lines.Add('Example Completed.');

CkRest_Dispose(rest);
CkOAuth2_Dispose(oauth2);
CkStringBuilder_Dispose(sbJson);
CkJsonObject_Dispose(json);

Sample JSON Response Body

{
  "id": "15fc23688c553739",
  "threadId": "15fc23688c553739",
  "labelIds": [
    "IMPORTANT",
    "SENT",
    "INBOX"
  ],
  "snippet": "This is a test. \u200b",
  "historyId": "1438",
  "internalDate": "1510791874000",
  "payload": {
    "mimeType": "multipart/mixed",
    "headers": [
      {
        "name": "MIME-Version",
        "value": "1.0"
      },
      {
        "name": "Received",
        "value": "by 10.25.23.105 with HTTP; Wed, 15 Nov 2017 16:24:34 -0800 (PST)"
      },
      {
        "name": "X-Originating-IP",
        "value": "[2601:249:e00:9093:e894:b27f:e5d6:d01d]"
      },
      {
        "name": "Date",
        "value": "Wed, 15 Nov 2017 18:24:34 -0600"
      },
      {
        "name": "Delivered-To",
        "value": "matt@chilkat.io"
      },
      {
        "name": "Message-ID",
        "value": "\u003cCAPhjyBM1qqXS6NVB65W8Zt5-McF03qWSRDjW5am66wTMuard=w@mail.gmail.com\u003e"
      },
      {
        "name": "Subject",
        "value": "Test HTML email with image and attachment."
      },
      {
        "name": "From",
        "value": "Matt Fausey \u003cmatt@chilkat.io\u003e"
      },
      {
        "name": "To",
        "value": "Matt Fausey \u003cmatt@chilkat.io\u003e"
      },
      {
        "name": "Content-Type",
        "value": "multipart/mixed; boundary=\"001a11401a6c097887055e0ea572\""
      }
    ]
  },
  "sizeEstimate": 11716
}