"""HTTP nodes: an inbound webhook trigger and an outbound request sender."""

from __future__ import annotations

import hmac
import logging
import threading
from collections.abc import Iterable
from enum import Enum
from typing import TYPE_CHECKING, Any, Literal
from urllib.parse import urlsplit, urlunsplit

import httpx
from pydantic import BaseModel, ConfigDict, Field

from fluksio.flow.messages import MessageSpec
from fluksio.flow.nodes.base import Node

if TYPE_CHECKING:
    from fastapi import FastAPI

logger = logging.getLogger(__name__)

# One pooled client for every sender node: connections are the expensive part
# of an HTTP request, and a node that fires every second should keep its own.
_client: httpx.Client | None = None
_client_lock = threading.Lock()


def shared_client() -> httpx.Client:
    """The process-wide HTTP client, built on first use."""
    global _client
    with _client_lock:
        if _client is None:
            _client = httpx.Client()
        return _client


def close_shared_client() -> None:
    """Release pooled connections at shutdown. Safe to call more than once."""
    global _client
    with _client_lock:
        if _client is not None:
            _client.close()
            _client = None


def _first_catch_all(app: FastAPI) -> int:
    """Where a webhook has to go in to be reachable.

    A mount at the root answers for every path, so anything registered after
    it is dead. Returns that mount's index, or the end of the table.
    """
    from starlette.routing import Mount

    for index, route in enumerate(app.routes):
        if isinstance(route, Mount) and route.path in ("", "/"):
            return index
    return len(app.routes)


class HttpNode(Node):
    """
    HTTP node that can act as a trigger (receiver) or sender based on configuration.

    This node integrates with FastAPI to either:

    - **Trigger mode**: Receive incoming HTTP requests (GET/POST) and inject data
      into the pipeline. Used when ``provides`` is specified but ``requires`` is empty.
    - **Sender mode**: Make outgoing HTTP requests with pipeline data. Used when
      ``requires`` is specified.

    :param url: The URL endpoint. For trigger mode, this is the route path
        (e.g., "/sensors/temperature"). For sender mode, this is the full URL
        to send requests to.
    :type url: str
    :param method: HTTP method - "GET" or "POST".
    :type method: Literal["GET", "POST"]
    :param requires: Messages required by this node (makes it a sender node).
    :type requires: MessageSpec | list[MessageSpec] | None
    :param provides: Messages provided by this node (makes it a trigger node).
    :type provides: MessageSpec | list[MessageSpec] | None
    :param params: Additional parameters for the node.
    :type params: dict
    :param name: Optional name for the node.
    :type name: str | None
    :param timeout: Request timeout in seconds (for sender mode).
    :type timeout: float
    :param headers: Additional HTTP headers.
    :type headers: dict[str, str] | None
    :param secret: Shared secret callers append to the webhook URL (trigger mode).
    :type secret: str

    :raises ValueError: If both ``requires`` and ``provides`` are empty, or if
        the configuration is invalid.

    :example:
        Trigger node (receives POST requests):

        >>> trigger = HttpNode(
        ...     url="/api/sensors/temperature",
        ...     method="POST",
        ...     provides=[MessageSpec(name="temperature", dtype=DType.FLOAT)],
        ...     params={},
        ... )

        Sender node (makes POST requests):

        >>> sender = HttpNode(
        ...     url="https://api.example.com/data",
        ...     method="POST",
        ...     requires=[MessageSpec(name="temperature", dtype=DType.FLOAT)],
        ...     params={},
        ... )
    """

    class Mode(Enum):
        """Operating mode of the HTTP node."""

        TRIGGER = "trigger"  # Receives HTTP requests
        SENDER = "sender"  # Sends HTTP requests

    # A repeated request is a repeated request, whatever the endpoint does
    # with it.
    idempotent = False

    __slots__ = (
        "url",
        "method",
        "mode",
        "timeout",
        "headers",
        "query",
        "send_inputs",
        "secret",
        "_route_registered",
    )

    class Params(BaseModel):
        model_config = ConfigDict(extra="allow")

        url: str
        method: Literal["GET", "POST"] = "POST"
        timeout: float = 30.0
        headers: dict[str, str] = {}
        query: dict[str, Any] = Field(
            default_factory=dict,
            description=(
                "Fixed query parameters, sender mode. A value may be a secret "
                "reference, which is how an API key stays out of the flow file."
            ),
        )
        send_inputs: bool = Field(
            default=True,
            description=(
                "Send the node's inputs as the request body or query. Off when "
                "the inputs are only a trigger and the request is fully "
                "described by 'url' and 'query'."
            ),
        )
        secret: str = Field(
            default="",
            description=(
                "Shared secret for a webhook, appended to its URL: "
                "/hooks/<flow>/<url>/<secret>. Empty leaves the webhook open "
                "to anyone."
            ),
            json_schema_extra={"x-secret": True},
        )

    @classmethod
    def instance_key(cls, params: dict[str, Any]) -> str | None:
        # ponytail: a webhook's stored url is the path before the flow name is
        # prefixed onto it, so two flows both receiving on "/tick" merge into
        # one neuron. Key on mode as well if that ever misleads.
        url = params.get("url")
        if not url:
            return None
        # A URL may legally carry credentials, and this key becomes a group id
        # in the brain graph — rendered into the response and into the DOM.
        parts = urlsplit(str(url))
        if parts.username or parts.password:
            host = parts.netloc.rsplit("@", 1)[-1]
            return urlunsplit(parts._replace(netloc=host))
        return str(url)

    def __init__(
        self,
        url: str | None = None,
        method: Literal["GET", "POST"] | None = None,
        requires: MessageSpec | Iterable[MessageSpec] = (),
        provides: MessageSpec | Iterable[MessageSpec] = (),
        params: dict[str, Any] | None = None,
        name: str | None = None,
    ):
        params = dict(params) if params else {}
        if url is not None:
            params["url"] = url
        if method is not None:
            params["method"] = method
        cfg = self.Params.model_validate(params)

        requires = Node._normalize_ports(requires)
        provides = Node._normalize_ports(provides)
        if not requires and not provides:
            raise ValueError(
                "An HTTP node needs either inputs (to send) or outputs (to receive)"
            )

        # Inputs mean this node sends data out; outputs mean it receives.
        self.mode = HttpNode.Mode.SENDER if requires else HttpNode.Mode.TRIGGER

        self.url = cfg.url
        self.method = cfg.method.upper()
        self.timeout = cfg.timeout
        self.headers = cfg.headers
        self.query = cfg.query
        self.send_inputs = cfg.send_inputs
        self.secret = cfg.secret
        self._route_registered = False

        # Set default name based on mode and URL
        if name is None:
            safe_url = self.url.replace("/", "_").replace(":", "").strip("_")
            name = f"http_{self.mode.value}_{safe_url}"

        # Initialize parent with appropriate function
        # For trigger mode, f is a no-op since data is injected via inject()
        # For sender mode, f handles the outgoing HTTP request
        super().__init__(
            f=(
                self._noop_trigger
                if self.mode == HttpNode.Mode.TRIGGER
                else self._sender_handler
            ),
            requires=requires,
            provides=provides,
            params=params,
            name=name,
        )

    @staticmethod
    def _noop_trigger(params: dict[str, Any], **kwargs: Any) -> dict[str, Any] | None:
        """
        No-op function for trigger mode nodes.

        Trigger mode nodes inject data via :meth:`inject`, not :meth:`__call__`.
        This function exists only to satisfy the Node interface.
        """
        return None

    def _sender_handler(
        self, params: dict[str, Any], **kwargs: Any
    ) -> dict[str, Any] | None:
        """
        Send HTTP request with pipeline data (sender mode).

        This method is called when upstream dependencies are satisfied.
        It sends the required data via HTTP request.

        Node functions already run on a worker thread, so the request is sent
        synchronously over the shared pooled client: a node publishing every
        second should reuse its connection, not open one per message.

        :param params: Node parameters.
        :type params: dict
        :param kwargs: Pipeline data to send (from required messages).
        :type kwargs: Any
        :returns: Response data if the endpoint returns JSON, None otherwise.
        :rtype: dict | None
        """
        client = shared_client()
        payload = dict(kwargs) if self.send_inputs else {}
        try:
            if self.method == "GET":
                response = client.get(
                    self.url,
                    params={**self.query, **payload},
                    headers=self.headers,
                    timeout=self.timeout,
                )
            else:  # POST
                response = client.post(
                    self.url,
                    params=self.query or None,
                    json=payload,
                    headers=self.headers,
                    timeout=self.timeout,
                )

            response.raise_for_status()

            try:
                body = response.json()
            except Exception:
                return None
            # Outputs are keyed by port, so only an object can be one. A bare
            # scalar or list is a valid reply, just not something to publish.
            return body if isinstance(body, dict) else None

        except httpx.HTTPStatusError as e:
            logger.error(
                "HTTP error in node '%s': status=%s, url=%s",
                self.name,
                e.response.status_code,
                self.url,
            )
            raise
        except httpx.RequestError as e:
            logger.error("Request error in node '%s': %s", self.name, e)
            raise

    async def start(self, app: FastAPI | None = None) -> None:
        """A webhook needs a route; a sender reaches out on its own."""
        if self.mode is HttpNode.Mode.TRIGGER and app is not None:
            self.register_route(app)

    async def stop(self, app: FastAPI | None = None) -> None:
        if self.mode is HttpNode.Mode.TRIGGER and app is not None:
            self.unregister_route(app)

    def register_route(self, app: FastAPI) -> None:
        """
        Register this node's HTTP endpoint with a FastAPI application.

        This method should only be called for trigger mode nodes. It creates
        a route that, when called, triggers the node in the pipeline.

        :param app: The FastAPI application instance.
        :type app: FastAPI
        :raises RuntimeError: If called on a sender mode node.

        :example:
            >>> from fastapi import FastAPI
            >>> app = FastAPI()
            >>> trigger_node = HttpNode(
            ...     url="/sensors/data",
            ...     method="POST",
            ...     provides=[MessageSpec(name="value", dtype=DType.FLOAT)],
            ...     params={},
            ... )
            >>> trigger_node.register_route(app)
        """
        if self.mode != HttpNode.Mode.TRIGGER:
            raise RuntimeError("Can only register routes for trigger mode nodes")

        if self._route_registered:
            return

        from starlette.requests import Request
        from starlette.responses import JSONResponse
        from starlette.routing import Route

        async def handle_request(request: Request) -> JSONResponse:
            """
            Handle incoming HTTP request and trigger the pipeline.

            :param request: The incoming Starlette request.
            :type request: Request
            :returns: JSON response with trigger result.
            :rtype: JSONResponse
            """
            if self.secret and not hmac.compare_digest(
                str(request.path_params.get("secret", "")).encode(),
                self.secret.encode(),
            ):
                # A wrong secret must look like no such hook at all.
                return JSONResponse(content={"detail": "Not Found"}, status_code=404)

            try:
                # Parse request data
                data: dict[str, Any]
                if self.method == "GET":
                    data = dict(request.query_params)
                else:  # POST
                    content_type = request.headers.get("content-type", "")
                    if "application/json" in content_type:
                        data = await request.json()
                    elif "application/x-www-form-urlencoded" in content_type:
                        form = await request.form()
                        data = dict(form)
                    else:
                        data = await request.json()  # Default to JSON

                # Payload keys are port names; values arrive as text.
                typed_data = {}
                for spec in self.output_ports:
                    if spec.port in data:
                        typed_data[spec.port] = spec.coerce(data[spec.port])

                # Inject data into the pipeline (trigger mode nodes inject via provides)
                result = self.inject(typed_data)

                return JSONResponse(
                    content={
                        "status": "triggered",
                        "node": self.name,
                        "data": typed_data,
                        "result": result if isinstance(result, dict) else None,
                    }
                )

            except ValueError as e:
                return JSONResponse(
                    content={"error": str(e)},
                    status_code=400,
                )
            except Exception as e:
                return JSONResponse(
                    content={"error": str(e)},
                    status_code=500,
                )

        # The secret is a path parameter, not part of the registered path, so
        # neither the route table nor the logs below carry its value.
        path = f"{self.url}/{{secret}}" if self.secret else self.url

        # Create a Starlette Route and add it directly to the app's routes
        route = Route(
            path,
            handle_request,
            methods=[self.method],
            name=self.id,
        )
        # Ahead of any catch-all mount. Starlette takes the first route that
        # matches, and the MCP app is mounted at "/", so appending would put
        # every webhook behind something that answers for every path.
        app.routes.insert(_first_catch_all(app), route)

        self._route_registered = True
        logger.info(
            "Registered %s route for node '%s': %s",
            self.method,
            self.name,
            path,
        )

    def unregister_route(self, app: FastAPI) -> None:
        """
        Unregister this node's HTTP endpoint from a FastAPI application.

        :param app: The FastAPI application instance.
        :type app: FastAPI

        .. note::
            FastAPI doesn't natively support route removal. This method
            removes the route from the internal routes list, but the change
            may not take effect until the application is restarted or
            the OpenAPI schema is regenerated.
        """
        if not self._route_registered:
            return

        # FastAPI doesn't have a clean way to remove routes
        # We need to filter them out from the routes list
        app.routes[:] = [
            route
            for route in app.routes
            if not (hasattr(route, "name") and route.name == self.id)
        ]

        self._route_registered = False
        logger.info("Unregistered route for node '%s': %s", self.name, self.url)