from collections.abc import Awaitable, Callable
from typing import Any
from urllib.parse import urlparse

from pydantic import AnyHttpUrl
from starlette.middleware.cors import CORSMiddleware
from starlette.requests import Request
from starlette.responses import Response
from starlette.routing import Route, request_response  # type: ignore
from starlette.types import ASGIApp

from mcp.server.auth.handlers.authorize import AuthorizationHandler
from mcp.server.auth.handlers.metadata import MetadataHandler, ProtectedResourceMetadataHandler
from mcp.server.auth.handlers.register import RegistrationHandler
from mcp.server.auth.handlers.revoke import RevocationHandler
from mcp.server.auth.handlers.token import TokenHandler
from mcp.server.auth.middleware.client_auth import ClientAuthenticator
from mcp.server.auth.provider import OAuthAuthorizationServerProvider
from mcp.server.auth.settings import ClientRegistrationOptions, RevocationOptions
from mcp.server.transport_security import DEFAULT_MAX_REQUEST_BODY_SIZE, RequestBodyLimitMiddleware
from mcp.shared.auth import JWT_BEARER_GRANT_TYPE, OAuthMetadata, ProtectedResourceMetadata
from mcp.shared.inbound import MCP_PROTOCOL_VERSION_HEADER


def validate_issuer_url(url: AnyHttpUrl):
    """Validate that the issuer URL meets OAuth 2.0 requirements.

    Args:
        url: The issuer URL to validate.

    Raises:
        ValueError: If the issuer URL is invalid.
    """

    # RFC 8414 requires HTTPS, but we allow loopback/localhost HTTP for testing
    if url.scheme != "https" and url.host not in ("localhost", "127.0.0.1", "[::1]"):
        raise ValueError("Issuer URL must be HTTPS")

    # No fragments or query parameters allowed
    if url.fragment:
        raise ValueError("Issuer URL must not have a fragment")
    if url.query:
        raise ValueError("Issuer URL must not have a query string")


AUTHORIZATION_PATH = "/authorize"
TOKEN_PATH = "/token"
REGISTRATION_PATH = "/register"
REVOCATION_PATH = "/revoke"

# SEP-990: leg 2 uses the RFC 7523 jwt-bearer grant; support is advertised as the ID-JAG profile.
ID_JAG_GRANT_PROFILE = "urn:ietf:params:oauth:grant-profile:id-jag"


def _cors(app: ASGIApp, allow_methods: list[str]) -> ASGIApp:
    return CORSMiddleware(
        app=app,
        allow_origins="*",
        allow_methods=allow_methods,
        allow_headers=[MCP_PROTOCOL_VERSION_HEADER],
    )


def _body_limited(app: ASGIApp) -> ASGIApp:
    return RequestBodyLimitMiddleware(app, DEFAULT_MAX_REQUEST_BODY_SIZE)


def cors_middleware(
    handler: Callable[[Request], Response | Awaitable[Response]],
    allow_methods: list[str],
) -> ASGIApp:
    return _cors(request_response(handler), allow_methods)


def create_auth_routes(
    provider: OAuthAuthorizationServerProvider[Any, Any, Any],
    issuer_url: AnyHttpUrl,
    service_documentation_url: AnyHttpUrl | None = None,
    client_registration_options: ClientRegistrationOptions | None = None,
    revocation_options: RevocationOptions | None = None,
    identity_assertion_enabled: bool = False,
) -> list[Route]:
    validate_issuer_url(issuer_url)

    client_registration_options = client_registration_options or ClientRegistrationOptions()
    revocation_options = revocation_options or RevocationOptions()
    metadata = build_metadata(
        issuer_url,
        service_documentation_url,
        client_registration_options,
        revocation_options,
        supports_identity_assertion=identity_assertion_enabled,
    )
    client_authenticator = ClientAuthenticator(provider)
    token_handler = TokenHandler(provider, client_authenticator, identity_assertion_enabled=identity_assertion_enabled)

    # Create routes
    # Allow CORS requests for endpoints meant to be hit by the OAuth client
    # (with the client secret). This is intended to support things like MCP Inspector,
    # where the client runs in a web browser. CORS is the outermost wrapper so that
    # responses produced by inner layers (such as a 413) still carry CORS headers.
    routes = [
        Route(
            "/.well-known/oauth-authorization-server",
            endpoint=cors_middleware(
                MetadataHandler(metadata).handle,
                ["GET", "OPTIONS"],
            ),
            methods=["GET", "OPTIONS"],
        ),
        Route(
            AUTHORIZATION_PATH,
            # do not allow CORS for authorization endpoint;
            # clients should just redirect to this
            endpoint=_body_limited(request_response(AuthorizationHandler(provider).handle)),
            methods=["GET", "POST"],
        ),
        Route(
            TOKEN_PATH,
            endpoint=_cors(_body_limited(request_response(token_handler.handle)), ["POST", "OPTIONS"]),
            methods=["POST", "OPTIONS"],
        ),
    ]

    if client_registration_options.enabled:  # pragma: no branch
        registration_handler = RegistrationHandler(
            provider,
            options=client_registration_options,
        )
        routes.append(
            Route(
                REGISTRATION_PATH,
                endpoint=_cors(_body_limited(request_response(registration_handler.handle)), ["POST", "OPTIONS"]),
                methods=["POST", "OPTIONS"],
            )
        )

    if revocation_options.enabled:  # pragma: no branch
        revocation_handler = RevocationHandler(provider, client_authenticator)
        routes.append(
            Route(
                REVOCATION_PATH,
                endpoint=_cors(_body_limited(request_response(revocation_handler.handle)), ["POST", "OPTIONS"]),
                methods=["POST", "OPTIONS"],
            )
        )

    return routes


def build_metadata(
    issuer_url: AnyHttpUrl,
    service_documentation_url: AnyHttpUrl | None,
    client_registration_options: ClientRegistrationOptions,
    revocation_options: RevocationOptions,
    supports_identity_assertion: bool = False,
) -> OAuthMetadata:
    authorization_url = AnyHttpUrl(str(issuer_url).rstrip("/") + AUTHORIZATION_PATH)
    token_url = AnyHttpUrl(str(issuer_url).rstrip("/") + TOKEN_PATH)

    grant_types_supported = ["authorization_code", "refresh_token"]
    # SEP-990 / ext-auth §6: support for the ID-JAG flow is advertised as a grant PROFILE, not as
    # the jwt-bearer grant type (which an AS might support for other purposes).
    authorization_grant_profiles_supported: list[str] | None = None
    if supports_identity_assertion:
        grant_types_supported.append(JWT_BEARER_GRANT_TYPE)
        authorization_grant_profiles_supported = [ID_JAG_GRANT_PROFILE]

    # Create metadata
    metadata = OAuthMetadata(
        issuer=issuer_url,
        authorization_endpoint=authorization_url,
        token_endpoint=token_url,
        scopes_supported=client_registration_options.valid_scopes,
        response_types_supported=["code"],
        response_modes_supported=None,
        grant_types_supported=grant_types_supported,
        token_endpoint_auth_methods_supported=["client_secret_post", "client_secret_basic"],
        token_endpoint_auth_signing_alg_values_supported=None,
        service_documentation=service_documentation_url,
        ui_locales_supported=None,
        op_policy_uri=None,
        op_tos_uri=None,
        introspection_endpoint=None,
        code_challenge_methods_supported=["S256"],
        authorization_grant_profiles_supported=authorization_grant_profiles_supported,
    )

    # Add registration endpoint if supported
    if client_registration_options.enabled:  # pragma: no branch
        metadata.registration_endpoint = AnyHttpUrl(str(issuer_url).rstrip("/") + REGISTRATION_PATH)

    # Add revocation endpoint if supported
    if revocation_options.enabled:  # pragma: no branch
        metadata.revocation_endpoint = AnyHttpUrl(str(issuer_url).rstrip("/") + REVOCATION_PATH)
        metadata.revocation_endpoint_auth_methods_supported = ["client_secret_post", "client_secret_basic"]

    return metadata


def build_resource_metadata_url(resource_server_url: AnyHttpUrl) -> AnyHttpUrl:
    """Build RFC 9728 compliant protected resource metadata URL.

    Inserts /.well-known/oauth-protected-resource between host and resource path
    as specified in RFC 9728 §3.1.

    Args:
        resource_server_url: The resource server URL (e.g., https://example.com/mcp)

    Returns:
        The metadata URL (e.g., https://example.com/.well-known/oauth-protected-resource/mcp)
    """
    parsed = urlparse(str(resource_server_url))
    # Handle trailing slash: if path is just "/", treat as empty
    resource_path = parsed.path if parsed.path != "/" else ""
    return AnyHttpUrl(f"{parsed.scheme}://{parsed.netloc}/.well-known/oauth-protected-resource{resource_path}")


def create_protected_resource_routes(
    resource_url: AnyHttpUrl,
    authorization_servers: list[AnyHttpUrl],
    scopes_supported: list[str] | None = None,
    resource_name: str | None = None,
    resource_documentation: AnyHttpUrl | None = None,
) -> list[Route]:
    """Create routes for OAuth 2.0 Protected Resource Metadata (RFC 9728).

    Args:
        resource_url: The URL of this resource server
        authorization_servers: List of authorization servers that can issue tokens
        scopes_supported: Optional list of scopes supported by this resource
        resource_name: Optional human-readable name for this resource
        resource_documentation: Optional URL to documentation for this resource

    Returns:
        List of Starlette routes for protected resource metadata
    """
    metadata = ProtectedResourceMetadata(
        resource=resource_url,
        authorization_servers=authorization_servers,
        scopes_supported=scopes_supported,
        resource_name=resource_name,
        resource_documentation=resource_documentation,
        # bearer_methods_supported defaults to ["header"] in the model
    )

    handler = ProtectedResourceMetadataHandler(metadata)

    # RFC 9728 §3.1: Register route at /.well-known/oauth-protected-resource + resource path
    metadata_url = build_resource_metadata_url(resource_url)
    # Extract just the path part for route registration
    parsed = urlparse(str(metadata_url))
    well_known_path = parsed.path

    return [
        Route(
            well_known_path,
            endpoint=cors_middleware(handler.handle, ["GET", "OPTIONS"]),
            methods=["GET", "OPTIONS"],
        )
    ]