# 1. Authorization Request (User Initiates Login)

A user clicks on the **Login with Google** button on the the app `xorismesiti.gr`.

The app request permission to access certain Google APIs (like the user's email, profile, etc.).

```sh
GET https://accounts.google.com/o/oauth2/v2/auth?
    response_type=code&
    client_id=YOUR_GOOGLE_CLIENT_ID&
    redirect_uri=https://xorismesiti.gr/callback&
    scope=email%20profile&
    state=xyz123
```

- `response_type=code`: This indicates you're using the "authorization code" flow.
- `client_id`: Your Google API client ID.
- `redirect_uri`: The URI Google will redirect to after the user consents.
- `scope`: The permissions you're requesting (e.g., email, profile).
- `state`: A random string to protect against CSRF attacks.

# 2. User Login and Consent

- The user is redirected to Google's login page.

- If they're not already logged in, they will be prompted to enter their Google credentials.

- After successful login, the user will be shown a consent screen where they can grant or deny permission for your app to access their Google account (e.g., email and profile information).

**User Action**: The user clicks "Allow" to grant access.

# 3. Authorization Code Response (Google Redirects to Your Platform)

Google redirects the user back to your platform's redirect_uri `https://xorismesiti.gr/callback` with an authorization_code in the query parameters.

```sh
GET https://xorismesiti.gr/callback?
    code=4/0AX4XfWgNmGZVbV7Kdr8Q9yVyzIYBnbbBdLfX39ZaE8m0w8zT8jKRLl7w-uT8k7WiyLg0Q&
    state=xyz123
```

- `HTTP` Method: GET
- `URL`: https://xorismesiti.gr/callback
- `Parameters`:
    - `code`: The authorization code sent by Google.
    - `state`: The same state value sent in the original request (for CSRF protection).


# 4. Access Token Request (Exchange Authorization Code for Token)

Now that your platform has the authorization code, 

it sends a POST request to Google's token endpoint 

to exchange the authorization code for an access token and refresh token.

- `HTTP` Method: POST
- `URL`: https://oauth2.googleapis.com/token
- `Headers`:
    - `Content`-Type: application/x-www-form-urlencoded
- `Body` Parameters:
    - `grant_type`=authorization_code: This specifies the grant type.
    - `code`: The authorization code you received in the previous step.
    - `redirect_uri`: The same redirect URI used in the authorization request.
    - `client_id`: Your Google API client ID.
    - `client_secret`: Your Google API client secret (which should be kept secure).


```sh
POST https://oauth2.googleapis.com/token
Content-Type: application/x-www-form-urlencoded

grant_type=authorization_code&
code=4/0AX4XfWgNmGZVbV7Kdr8Q9yVyzIYBnbbBdLfX39ZaE8m0w8zT8jKRLl7w-uT8k7WiyLg0Q&
redirect_uri=https://xorismesiti.gr/callback&
client_id=YOUR_GOOGLE_CLIENT_ID&
client_secret=YOUR_GOOGLE_CLIENT_SECRET
```

# 5. Access Token Response (Google Returns Tokens)

Google validates the request 

and returns a response with the access token (which can be used to access the user's Google resources) 

and optionally, a refresh token (which can be used to refresh the access token when it expires).

```json
{
    "access_token": "ya29.a0AfH6SMC8Op6zXZkHi2XITkDoOVzYXt3hTY6sny54UlWlxrnKlX5Xv78is7BEHekVX-VoA",
    "token_type": "Bearer",
    "expires_in": 3600,
    "refresh_token": "1//04d5XHqmn6Hdy3wTf5OYDP1SyBa74zEFURjddQ2A1cFw78PY13pQyWhlD2A6XhDQtKlrjAqU4kS3vGdMvckw",
    "scope": "email profile"
}
```

- HTTP Method: 200 OK
- Response Body:
    - access_token: The access token used for accessing the user's resources (e.g., profile, email).
    - token_type: Usually Bearer, indicating the type of token.
    - expires_in: The lifetime of the access token in seconds (e.g., 3600 seconds = 1 hour).
    - refresh_token: (Optional) The refresh token used to obtain a new access token when the current one expires.
    - scope: The scope of access granted (e.g., email, profile).