OAuth 2.0 Implementation

class OAuth2Client:
    """OAuth 2.0 client implementation."""
    
    def __init__(self, client_id: str, client_secret: str = None, token_endpoint_auth_method: str = 'client_secret_basic', revocation_endpoint_auth_method: str = None, scope: str = None, redirect_uri: str = None, token: dict = None, token_placement: str = 'header', update_token: callable = None, **kwargs) -> None:
        """
        Initialize OAuth 2.0 client.
        
        Args:
            client_id: Client identifier
            client_secret: Client secret
            token_endpoint_auth_method: Token endpoint authentication method
            revocation_endpoint_auth_method: Revocation endpoint authentication method
            scope: Default scope
            redirect_uri: Default redirect URI
            token: Access token dictionary
            token_placement: Where to place token (header, body, uri)
            update_token: Callback for token updates
        """

    def create_authorization_url(self, authorization_endpoint: str, state: str = None, code_challenge: str = None, code_challenge_method: str = None, **kwargs) -> tuple:
        """
        Create authorization URL for authorization code flow.
        
        Args:
            authorization_endpoint: Authorization server's authorization endpoint
            state: CSRF protection state parameter
            code_challenge: PKCE code challenge
            code_challenge_method: PKCE code challenge method
            **kwargs: Additional authorization parameters
            
        Returns:
            Tuple of (authorization_url, state)
        """

    def fetch_token(self, token_endpoint: str, code: str = None, authorization_response: str = None, body: str = '', auth: tuple = None, username: str = None, password: str = None, **kwargs) -> dict:
        """
        Fetch access token from authorization server.
        
        Args:
            token_endpoint: Token endpoint URL
            code: Authorization code
            authorization_response: Full authorization response URL
            body: Additional request body
            auth: HTTP basic auth tuple
            username: Username for password grant
            password: Password for password grant
            **kwargs: Additional token parameters
            
        Returns:
            Token dictionary with access_token, token_type, etc.
        """

    def refresh_token(self, token_endpoint: str, refresh_token: str = None, body: str = '', auth: tuple = None, **kwargs) -> dict:
        """
        Refresh access token using refresh token.
        
        Args:
            token_endpoint: Token endpoint URL
            refresh_token: Refresh token (uses stored token if None)
            body: Additional request body
            auth: HTTP basic auth tuple
            **kwargs: Additional parameters
            
        Returns:
            New token dictionary
        """

    def revoke_token(self, revocation_endpoint: str, token: str = None, token_type_hint: str = None, body: str = '', auth: tuple = None, **kwargs) -> dict:
        """
        Revoke access or refresh token.
        
        Args:
            revocation_endpoint: Revocation endpoint URL
            token: Token to revoke (uses stored token if None)
            token_type_hint: Hint about token type
            body: Additional request body
            auth: HTTP basic auth tuple
            **kwargs: Additional parameters
            
        Returns:
            Response dictionary
        """

    def introspect_token(self, introspection_endpoint: str, token: str = None, token_type_hint: str = None, **kwargs) -> dict:
        """
        Introspect token at authorization server.
        
        Args:
            introspection_endpoint: Introspection endpoint URL
            token: Token to introspect
            token_type_hint: Hint about token type
            **kwargs: Additional parameters
            
        Returns:
            Introspection response dictionary
        """

    def register_client(self, registration_endpoint: str, **kwargs) -> dict:
        """
        Register client dynamically.
        
        Args:
            registration_endpoint: Registration endpoint URL
            **kwargs: Client metadata
            
        Returns:
            Registration response with client credentials
        """

    @property
    def access_token(self) -> str:
        """Get current access token."""

    @property
    def token_type(self) -> str:
        """Get current token type."""

class AuthorizationServer:
    """OAuth 2.0 authorization server."""
    
    def __init__(self, query_client: callable, save_token: callable = None) -> None:
        """
        Initialize authorization server.
        
        Args:
            query_client: Function to query client by client_id
            save_token: Function to save issued tokens
        """

    def register_grant(self, grant_cls: type, extensions: list = None) -> None:
        """
        Register a grant type.
        
        Args:
            grant_cls: Grant class to register
            extensions: List of grant extensions
        """

    def register_endpoint(self, endpoint: object) -> None:
        """
        Register an endpoint.
        
        Args:
            endpoint: Endpoint instance
        """

    def validate_consent_request(self, request: OAuth2Request, end_user: object = None) -> None:
        """
        Validate consent request at authorization endpoint.
        
        Args:
            request: OAuth2Request object
            end_user: End user object
        """

    def create_authorization_response(self, request: OAuth2Request, grant_user: callable) -> tuple:
        """
        Create authorization response.
        
        Args:
            request: OAuth2Request object
            grant_user: Function to grant authorization to user
            
        Returns:
            Tuple of (status_code, body, headers)
        """

    def create_token_response(self, request: OAuth2Request) -> tuple:
        """
        Create token response.
        
        Args:
            request: OAuth2Request object
            
        Returns:
            Tuple of (status_code, body, headers)
        """

    def create_revocation_response(self, request: OAuth2Request) -> tuple:
        """
        Create revocation response.
        
        Args:
            request: OAuth2Request object
            
        Returns:
            Tuple of (status_code, body, headers)
        """

class ResourceProtector:
    """OAuth 2.0 resource server protection."""
    
    def __init__(self) -> None:
        """Initialize resource protector."""

    def register_token_validator(self, validator: 'TokenValidator') -> None:
        """
        Register token validator.
        
        Args:
            validator: Token validator instance
        """

    def validate_request(self, scopes: list, request: OAuth2Request) -> 'OAuth2Token':
        """
        Validate OAuth 2.0 request.
        
        Args:
            scopes: Required scopes
            request: OAuth2Request object
            
        Returns:
            OAuth2Token object if valid
        """

    def acquire_token(self, scopes: list = None, request: OAuth2Request = None) -> 'OAuth2Token':
        """
        Acquire token from request.
        
        Args:
            scopes: Required scopes
            request: OAuth2Request object
            
        Returns:
            OAuth2Token object
        """

class OAuth2Request:
    """OAuth 2.0 request wrapper."""
    
    def __init__(self, method: str, uri: str, body: str = None, headers: dict = None) -> None:
        """
        Initialize OAuth 2.0 request.
        
        Args:
            method: HTTP method
            uri: Request URI
            body: Request body
            headers: Request headers
        """

    @property
    def client_id(self) -> str:
        """Get client ID from request."""

    @property
    def client_secret(self) -> str:
        """Get client secret from request."""

    @property
    def redirect_uri(self) -> str:
        """Get redirect URI from request."""

    @property
    def scope(self) -> str:
        """Get scope from request."""

    @property
    def state(self) -> str:
        """Get state from request."""

    @property
    def response_type(self) -> str:
        """Get response type from request."""

    @property
    def grant_type(self) -> str:
        """Get grant type from request."""

class OAuth2Token:
    """OAuth 2.0 token representation."""
    
    def __init__(self, params: dict = None) -> None:
        """
        Initialize OAuth 2.0 token.
        
        Args:
            params: Token parameters dictionary
        """

    @property
    def access_token(self) -> str:
        """Get access token."""

    @property
    def token_type(self) -> str:
        """Get token type."""

    @property
    def refresh_token(self) -> str:
        """Get refresh token."""

    @property
    def expires_in(self) -> int:
        """Get token expiration time."""

    @property
    def scope(self) -> str:
        """Get token scope."""

    def is_expired(self) -> bool:
        """Check if token is expired."""

    def get_expires_at(self) -> int:
        """Get expiration timestamp."""

class BaseGrant:
    """Base class for OAuth 2.0 grants."""
    
    def __init__(self, request: OAuth2Request, server: AuthorizationServer) -> None:
        """
        Initialize grant.
        
        Args:
            request: OAuth2Request object
            server: AuthorizationServer instance
        """

    def validate_request(self) -> None:
        """Validate the grant request."""

    def create_authorization_response(self, redirect_uri: str, grant_user: callable) -> dict:
        """Create authorization response."""

    def create_token_response(self) -> dict:
        """Create token response."""

class AuthorizationCodeGrant(BaseGrant):
    """Authorization code grant implementation."""
    
    GRANT_TYPE: str = 'authorization_code'
    RESPONSE_TYPES: list = ['code']
    
    def create_authorization_code(self, client: object, grant_user: callable, request: OAuth2Request) -> str:
        """
        Create authorization code.
        
        Args:
            client: Client object
            grant_user: Grant user function
            request: OAuth2Request object
            
        Returns:
            Authorization code string
        """

    def parse_authorization_code(self, code: str, client: object) -> object:
        """
        Parse and validate authorization code.
        
        Args:
            code: Authorization code
            client: Client object
            
        Returns:
            Authorization code object
        """

    def delete_authorization_code(self, authorization_code: object) -> None:
        """
        Delete authorization code after use.
        
        Args:
            authorization_code: Authorization code object
        """

    def authenticate_user(self, authorization_code: object) -> object:
        """
        Authenticate user from authorization code.
        
        Args:
            authorization_code: Authorization code object
            
        Returns:
            User object
        """

class ImplicitGrant(BaseGrant):
    """Implicit grant implementation."""
    
    GRANT_TYPE: str = None
    RESPONSE_TYPES: list = ['token']

class ResourceOwnerPasswordCredentialsGrant(BaseGrant):
    """Resource owner password credentials grant implementation."""
    
    GRANT_TYPE: str = 'password'
    
    def authenticate_user(self, username: str, password: str, client: object, request: OAuth2Request) -> object:
        """
        Authenticate user with username and password.
        
        Args:
            username: Username
            password: Password
            client: Client object
            request: OAuth2Request object
            
        Returns:
            User object if authenticated
        """

class ClientCredentialsGrant(BaseGrant):
    """Client credentials grant implementation."""
    
    GRANT_TYPE: str = 'client_credentials'

class RefreshTokenGrant(BaseGrant):
    """Refresh token grant implementation."""
    
    GRANT_TYPE: str = 'refresh_token'
    
    def authenticate_refresh_token(self, refresh_token: str, client: object, request: OAuth2Request) -> object:
        """
        Authenticate refresh token.
        
        Args:
            refresh_token: Refresh token string
            client: Client object
            request: OAuth2Request object
            
        Returns:
            Token object if valid
        """

    def authenticate_user(self, credential: object) -> object:
        """
        Authenticate user from refresh token credential.
        
        Args:
            credential: Token credential object
            
        Returns:
            User object
        """

    def revoke_old_credential(self, credential: object) -> None:
        """
        Revoke old refresh token.
        
        Args:
            credential: Token credential to revoke
        """

class BearerTokenGenerator:
    """Generate bearer tokens."""
    
    def __init__(self, access_token_generator: callable = None, refresh_token_generator: callable = None, expires_generator: callable = None) -> None:
        """
        Initialize bearer token generator.
        
        Args:
            access_token_generator: Function to generate access tokens
            refresh_token_generator: Function to generate refresh tokens
            expires_generator: Function to generate expiration times
        """

    def generate(self, client: object, grant_type: str, user: object = None, scope: str = None, expires_in: int = None, include_refresh_token: bool = True) -> dict:
        """
        Generate bearer token.
        
        Args:
            client: Client object
            grant_type: Grant type used
            user: User object
            scope: Token scope
            expires_in: Token lifetime in seconds
            include_refresh_token: Whether to include refresh token
            
        Returns:
            Token dictionary
        """

class BearerTokenValidator:
    """Validate bearer tokens."""
    
    def authenticate_token(self, token_string: str) -> object:
        """
        Authenticate bearer token.
        
        Args:
            token_string: Bearer token string
            
        Returns:
            Token object if valid
        """

    def request_invalid(self, request: OAuth2Request) -> bool:
        """
        Check if request is invalid.
        
        Args:
            request: OAuth2Request object
            
        Returns:
            True if request is invalid
        """

    def token_revoked(self, token: object) -> bool:
        """
        Check if token is revoked.
        
        Args:
            token: Token object
            
        Returns:
            True if token is revoked
        """

def add_bearer_token(uri: str, http_method: str, body: str, headers: dict, token: dict) -> tuple:
    """
    Add bearer token to request.
    
    Args:
        uri: Request URI
        http_method: HTTP method
        body: Request body
        headers: Request headers
        token: Token dictionary
        
    Returns:
        Tuple of (uri, headers, body)
    """

class CodeChallenge:
    """PKCE code challenge implementation."""
    
    def __init__(self, code_verifier: str, code_challenge_method: str = 'S256') -> None:
        """
        Initialize code challenge.
        
        Args:
            code_verifier: Code verifier string
            code_challenge_method: Challenge method (plain or S256)
        """

    def get_code_challenge(self) -> str:
        """Get code challenge string."""

    def get_code_challenge_method(self) -> str:
        """Get code challenge method."""

    def verify_code_verifier(self, code_verifier: str) -> bool:
        """
        Verify code verifier against challenge.
        
        Args:
            code_verifier: Code verifier to verify
            
        Returns:
            True if verifier is valid
        """

def create_s256_code_challenge(code_verifier: str) -> str:
    """
    Create S256 code challenge from verifier.
    
    Args:
        code_verifier: Code verifier string
        
    Returns:
        S256 code challenge string
    """

class DeviceAuthorizationEndpoint:
    """Device authorization endpoint."""
    
    def __init__(self, server: AuthorizationServer) -> None:
        """
        Initialize device authorization endpoint.
        
        Args:
            server: AuthorizationServer instance
        """

    def create_endpoint_response(self, request: OAuth2Request) -> tuple:
        """
        Create device authorization response.
        
        Args:
            request: OAuth2Request object
            
        Returns:
            Tuple of (status_code, body, headers)
        """

class DeviceCodeGrant(BaseGrant):
    """Device code grant implementation."""
    
    GRANT_TYPE: str = 'urn:ietf:params:oauth:grant-type:device_code'
    
    def query_device_credential(self, device_code: str, client: object) -> object:
        """
        Query device credential by device code.
        
        Args:
            device_code: Device code
            client: Client object
            
        Returns:
            Device credential object
        """

    def should_slow_down(self, credential: object, now: int) -> bool:
        """
        Check if client should slow down polling.
        
        Args:
            credential: Device credential object
            now: Current timestamp
            
        Returns:
            True if client should slow down
        """

# Device flow constants
DEVICE_CODE_GRANT_TYPE: str = 'urn:ietf:params:oauth:grant-type:device_code'

# Device flow errors
class AuthorizationPendingError(OAuth2Error):
    """Authorization is pending user action."""
    error: str = 'authorization_pending'

class SlowDownError(OAuth2Error):
    """Client is polling too frequently."""
    error: str = 'slow_down'

class ClientMixin:
    """Mixin for OAuth 2.0 client model."""
    
    client_id: str  # Client identifier
    client_secret: str  # Client secret (may be None for public clients)
    client_id_issued_at: int  # Client ID issued timestamp
    client_secret_expires_at: int  # Client secret expiration timestamp
    
    def get_client_id(self) -> str:
        """Get client ID."""
    
    def get_default_redirect_uri(self) -> str:
        """Get default redirect URI."""
    
    def get_allowed_scope(self, scope: str) -> str:
        """Get allowed scope for client."""
    
    def check_redirect_uri(self, redirect_uri: str) -> bool:
        """Check if redirect URI is allowed."""
    
    def has_client_secret(self) -> bool:
        """Check if client has a secret."""
    
    def check_client_secret(self, client_secret: str) -> bool:
        """Verify client secret."""
    
    def check_token_endpoint_auth_method(self, method: str) -> bool:
        """Check if token endpoint auth method is supported."""
    
    def check_response_type(self, response_type: str) -> bool:
        """Check if response type is supported."""
    
    def check_grant_type(self, grant_type: str) -> bool:
        """Check if grant type is supported."""

class AuthorizationCodeMixin:
    """Mixin for authorization code model."""
    
    code: str  # Authorization code
    client_id: str  # Client identifier
    redirect_uri: str  # Redirect URI
    scope: str  # Authorized scope
    user_id: str  # User identifier
    code_challenge: str  # PKCE code challenge
    code_challenge_method: str  # PKCE challenge method
    
    def is_expired(self) -> bool:
        """Check if authorization code is expired."""
    
    def get_redirect_uri(self) -> str:
        """Get redirect URI."""
    
    def get_scope(self) -> str:
        """Get authorized scope."""
    
    def get_user_id(self) -> str:
        """Get user ID."""
    
    def get_code_challenge(self) -> str:
        """Get PKCE code challenge."""
    
    def get_code_challenge_method(self) -> str:
        """Get PKCE challenge method."""

class TokenMixin:
    """Mixin for access token model."""
    
    access_token: str  # Access token
    client_id: str  # Client identifier
    token_type: str  # Token type (usually 'Bearer')
    refresh_token: str  # Refresh token
    scope: str  # Token scope
    user_id: str  # User identifier
    issued_at: int  # Token issued timestamp
    expires_in: int  # Token lifetime in seconds
    
    def get_scope(self) -> str:
        """Get token scope."""
    
    def get_user_id(self) -> str:
        """Get user ID."""
    
    def is_expired(self) -> bool:
        """Check if token is expired."""
    
    def is_revoked(self) -> bool:
        """Check if token is revoked."""

def scope_to_list(scope: str) -> list:
    """
    Convert scope string to list.
    
    Args:
        scope: Space-separated scope string
        
    Returns:
        List of scope values
    """

def list_to_scope(scopes: list) -> str:
    """
    Convert scope list to string.
    
    Args:
        scopes: List of scope values
        
    Returns:
        Space-separated scope string
    """

from authlib.oauth2 import OAuth2Client

# Initialize client
client = OAuth2Client(
    client_id='your-client-id',
    client_secret='your-client-secret',
    scope='read write'
)

# Step 1: Generate authorization URL
authorization_url, state = client.create_authorization_url(
    'https://provider.com/authorize',
    state='random-state-string'
)
print(f"Visit: {authorization_url}")

# Step 2: Exchange code for token
token = client.fetch_token(
    'https://provider.com/token',
    code='authorization-code-from-callback'
)
print(f"Access token: {token['access_token']}")

# Step 3: Refresh token when needed
if 'refresh_token' in token:
    new_token = client.refresh_token(
        'https://provider.com/token',
        refresh_token=token['refresh_token']
    )

from authlib.oauth2 import OAuth2Client, create_s256_code_challenge
from authlib.common.security import generate_token

# Generate PKCE parameters
code_verifier = generate_token(128)
code_challenge = create_s256_code_challenge(code_verifier)

# Create authorization URL with PKCE
client = OAuth2Client(client_id='public-client-id')
auth_url, state = client.create_authorization_url(
    'https://provider.com/authorize',
    code_challenge=code_challenge,
    code_challenge_method='S256'
)

# Exchange code with verifier
token = client.fetch_token(
    'https://provider.com/token',
    code='authorization-code',
    code_verifier=code_verifier
)

from authlib.oauth2 import AuthorizationServer, ResourceProtector
from authlib.oauth2.rfc6749.grants import AuthorizationCodeGrant

# Define query functions
def query_client(client_id):
    return get_client_by_id(client_id)

def save_token(token, request, *args, **kwargs):
    store_access_token(token)

# Create authorization server
authorization_server = AuthorizationServer(
    query_client=query_client,
    save_token=save_token
)

# Register authorization code grant
authorization_server.register_grant(AuthorizationCodeGrant)

# Handle authorization endpoint
@app.route('/authorize', methods=['GET', 'POST'])
def authorize():
    request = OAuth2Request(request.method, request.url, request.form, request.headers)
    
    if request.method == 'GET':
        # Show authorization form
        try:
            authorization_server.validate_consent_request(request, current_user)
            return render_template('authorize.html')
        except OAuth2Error as error:
            return {'error': error.error}, 400
    
    # Handle authorization
    def grant_user():
        return current_user
    
    status_code, body, headers = authorization_server.create_authorization_response(
        request, grant_user
    )
    return Response(body, status=status_code, headers=headers)

# Handle token endpoint
@app.route('/token', methods=['POST'])
def issue_token():
    request = OAuth2Request(request.method, request.url, request.form, request.headers)
    status_code, body, headers = authorization_server.create_token_response(request)
    return Response(body, status=status_code, headers=headers)