from collections.abc import Generator
from typing import Annotated, Any

import jwt
from fastapi import Depends, HTTPException, Request, status
from fastapi.security import OAuth2PasswordBearer
from jwt.exceptions import InvalidTokenError
from pydantic import ValidationError
from sqlmodel import Session, select

from fluksio.cloud import config as cloud_config
from fluksio.core import security
from fluksio.core.config import settings
from fluksio.core.db import engine
from fluksio.flow import panels
from fluksio.flow.controller import FlowController
from fluksio.flow.dashboards import DashboardStore
from fluksio.flow.workers import PythonWorkerPool
from fluksio.models import TokenPayload, User

reusable_oauth2 = OAuth2PasswordBearer(
    tokenUrl=f"{settings.API_V1_STR}/login/access-token"
)


def get_db() -> Generator[Session, None, None]:
    with Session(engine) as session:
        yield session


SessionDep = Annotated[Session, Depends(get_db)]
TokenDep = Annotated[str, Depends(reusable_oauth2)]


#: What a `draft` query parameter has to say to mean "no". Pydantic's own false
#: literals; anything else is refused rather than guessed at.
_NOT_DRAFT = {"false", "0", "off", "f", "n", "no", ""}


def _panel_may(payload: dict[str, Any], request: Request) -> None:
    """Refuse anything a wall panel has no business asking for.

    A panel credential names the account that approved the pairing, so without
    this it would be that person's session hanging on a wall. What a panel
    genuinely needs is small and worth writing out: the dashboards it was
    assigned, its own definition, and the message endpoints its widgets speak.

    Publishing a message is in the list because a panel cannot be strictly
    read-only — a querying chart asks for its window by publishing the request
    — and a control on a panel is the point of putting one there.
    """
    panel = panels.find(str(payload.get("panel", "")))
    if panel is None:
        # Deleting a panel is how its credential is revoked, so a token naming
        # one that is gone is a token to stop trusting.
        raise InvalidTokenError("This panel no longer exists")

    api = settings.API_V1_STR
    path = request.url.path
    method = request.method

    allowed = False
    if method == "GET" and path.startswith(f"{api}/dashboards/"):
        name = path[len(f"{api}/dashboards/") :]
        # One segment only: a dashboard it shows, published — never a draft,
        # and never a sibling route like `/publish`. The flag is read the way
        # the endpoint reads it rather than by presence, because the generated
        # client spells the default out as `?draft=false` — and it is read
        # fail-closed, so a spelling neither side recognises is a draft.
        draft = request.query_params.get("draft")
        published = draft is None or draft.lower() in _NOT_DRAFT
        allowed = "/" not in name and name in panel.dashboards and published
    elif method == "GET" and path == f"{api}/panels/{panel.id}":
        allowed = True
    elif method in ("GET", "POST") and path.startswith(f"{api}/messages/"):
        allowed = True

    if not allowed:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="A panel credential cannot do that",
        )


def decode_token(token: str, request: Request | None = None) -> dict[str, Any]:
    """Read a bearer token, whichever channel issued it.

    A browser session is signed with the app's own secret; an agent's token is
    signed with the OAuth keypair, so that set can be revoked on its own and
    the public half published. Both name a user, and both grant that user's
    rights — the difference is only in who is holding it, which the MCP
    endpoint checks separately.

    A paired wall panel's token is signed with the app's secret too, and is
    told apart from a session by its audience: the session decode above
    refuses it outright, so the only door it fits is the one ``_panel_may``
    guards.

    The last branch is the seam a hosted deployment widens: a portal this
    installation was enrolled with signs tokens with a key pinned at
    enrolment, and they name the portal account holding them, which resolves
    to whichever local account was mapped to it — the superuser who enrolled,
    or a remote user one of them admitted since. With no enrolment the branch
    raises immediately, so an offline installation pays nothing for the
    possibility. A screen that paired through that portal
    arrives there too, naming a panel — which is why the gate below is applied
    to whichever branch produced the claims rather than to one of them: where a
    panel credential was minted is not what decides what it may read.
    """
    try:
        session: dict[str, Any] = jwt.decode(
            token, settings.SECRET_KEY, algorithms=[security.ALGORITHM]
        )
        return session
    except InvalidTokenError:
        pass
    try:
        panel_token = security.decode_panel_token(token)
    except InvalidTokenError:
        pass
    else:
        if not panel_token.get("panel"):
            raise InvalidTokenError("a panel token must name its panel")
        return _gate_panel(panel_token, request)
    try:
        return security.decode_oauth_token(token)
    except InvalidTokenError:
        return _gate_panel(cloud_config.decode_portal_token(token), request)


def _gate_panel(payload: dict[str, Any], request: Request | None) -> dict[str, Any]:
    """Scope a payload that names a panel; pass anything else through.

    Without a request — from the websocket, which has no route to scope — the
    check is only that the panel still exists, which is what makes deleting one
    revoke its credential.
    """
    if not payload.get("panel"):
        return payload
    if request is not None:
        _panel_may(payload, request)
    elif panels.find(str(payload["panel"])) is None:
        raise InvalidTokenError("This panel no longer exists")
    return payload


def _user_for(session: Session, token_data: TokenPayload) -> User | None:
    """The local account a payload names, by id or by portal identity.

    A token the portal minted names a person on the portal, not a user here, so
    the mapping a superuser made when they admitted them is what turns one into
    the other. No mapping, no user — the caller answers that the same way it
    answers a token naming a deleted account, which is what makes deleting the
    local user the whole of the revocation.
    """
    if token_data.portal_sub:
        return session.exec(
            select(User).where(User.portal_sub == token_data.portal_sub)
        ).first()
    return session.get(User, token_data.sub) if token_data.sub else None


def user_from_token(
    session: Session, token: str, request: Request | None = None
) -> User | None:
    """Resolve a bearer token to its user, or None if it does not hold up.

    Shared with the websocket, which cannot use the HTTP security scheme, and
    with the artifact endpoint, which accepts a worker's credential as well as
    a person's. Pass the request wherever there is one: a panel's credential is
    scoped by route, and without it the scope check cannot run.
    """
    try:
        token_data = TokenPayload(**decode_token(token, request))
    except (InvalidTokenError, ValidationError):
        return None
    user = _user_for(session, token_data)
    if user is None or not user.is_active:
        return None
    return user


def get_current_user(request: Request, session: SessionDep, token: TokenDep) -> User:
    """Resolve the bearer token to its user.

    Every failure here is an authentication failure, so all of them answer 401:
    a token naming a user who no longer exists is a session to log in again,
    not a missing resource to report. A panel credential reaching past what it
    is allowed is the one exception — that is a 403 raised inside
    ``decode_token``, and it travels through here untouched.
    """
    try:
        token_data = TokenPayload(**decode_token(token, request))
    except (InvalidTokenError, ValidationError):
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Could not validate credentials",
        )
    user = _user_for(session, token_data)
    if user is None or not user.is_active:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="This session is no longer valid — please log in again",
        )
    return user


CurrentUser = Annotated[User, Depends(get_current_user)]


def get_flow_controller(request: Request) -> FlowController:
    controller: FlowController | None = getattr(
        request.app.state, "flow_controller", None
    )
    if controller is None:
        raise HTTPException(status_code=503, detail="The flow engine is not running")
    return controller


FlowControllerDep = Annotated[FlowController, Depends(get_flow_controller)]


def get_dashboard_store(request: Request) -> DashboardStore:
    store: DashboardStore | None = getattr(request.app.state, "dashboard_store", None)
    if store is None:
        raise HTTPException(status_code=503, detail="The flow engine is not running")
    return store


DashboardStoreDep = Annotated[DashboardStore, Depends(get_dashboard_store)]


def get_worker_pool(request: Request) -> PythonWorkerPool:
    pool: PythonWorkerPool | None = getattr(request.app.state, "worker_pool", None)
    if pool is None:
        raise HTTPException(status_code=503, detail="The flow engine is not running")
    return pool


WorkerPoolDep = Annotated[PythonWorkerPool, Depends(get_worker_pool)]


def get_current_active_superuser(current_user: CurrentUser) -> User:
    if not current_user.is_superuser:
        raise HTTPException(
            status_code=403, detail="The user doesn't have enough privileges"
        )
    return current_user