import uuid
from collections.abc import Generator
from typing import Annotated, Any
from urllib.parse import unquote

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.cloud import enroll
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.artifacts import is_reference
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", ""}

#: The one route under a message name a panel reads.
_HISTORY = "/history"


def _panel_for(payload: dict[str, Any]) -> panels.PanelDef:
    """The panel a credential names, if that credential still stands.

    Two ways it stops standing. The panel was deleted, which revokes every
    credential ever minted for it — read from disk on each call, so it takes
    effect at once. Or the panel's nonce moved on, which revokes exactly one
    screen's and leaves the panel, its dashboards and their arrangement alone.

    The nonce is only held against a credential this instance signed. One
    the portal minted for a remote screen carries none — the portal names the
    panel and nothing else — and is revoked at the hub instead.
    """
    panel = panels.find(str(payload.get("panel", "")))
    if panel is None:
        raise InvalidTokenError("This panel no longer exists")
    if (
        payload.get("aud") == security.PANEL_AUDIENCE
        and int(payload.get("pnc") or 0) != panel.nonce
    ):
        raise InvalidTokenError("This panel was paired with another device")
    return panel


def _panel_messages(panel_id: str, request: Request) -> set[str]:
    """Every message this panel's widgets read or write.

    The same walk that bounds its socket, so the two surfaces a screen has
    agree on what it is entitled to. No store means nothing resolves, which is
    the answer to give when the answer cannot be worked out.
    """
    store: DashboardStore | None = getattr(request.app.state, "dashboard_store", None)
    if store is None:
        return set()
    return panels.messages_for(panel_id, store)


def _panel_digests(panel_id: str, request: Request) -> set[str]:
    """The artifacts this panel's messages are pointing at right now.

    A media tile fetches the bytes its message names, so the messages already
    bounding the panel bound this too — one step further along, through
    whatever those messages currently hold.
    """
    controller: FlowController | None = getattr(
        request.app.state, "flow_controller", None
    )
    if controller is None:
        return set()
    names = _panel_messages(panel_id, request)
    if not names:
        return set()
    found: set[str] = set()
    for value in controller.state.get_present(sorted(names)).values():
        if is_reference(value):
            found.add(str(value["digest"]))
    return found


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, the messages its own widgets bind to, and the
    bytes those messages currently point at, for a tile drawing a camera frame.

    Publishing is in the list because a panel cannot be strictly read-only — a
    control on a panel is the point of putting one there, and a querying chart
    asks for its window by publishing a request, which is why that request
    counts as one of its widget's messages. Bounded to those, though: a screen
    on a wall has no business reaching a message no tile on it draws, and the
    catalogue behind ``GET /messages/`` is the whole namespace at once.

    # ponytail: the panel file and the published dashboards are re-read per
    # request. Cache them behind the store's version if this shows up in a
    # profile.
    """
    panel = _panel_for(payload)

    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 path.startswith(f"{api}/messages/"):
        # The two a widget speaks: a chart reads a series, a control puts a
        # value in. Percent-decoded, because a message name is a path segment
        # here and the client encodes it as one.
        rest = unquote(path[len(f"{api}/messages/") :])
        if method == "GET" and rest.endswith(_HISTORY):
            name = rest[: -len(_HISTORY)]
        elif method == "POST":
            name = rest
        else:
            name = ""
        allowed = bool(name) and name in _panel_messages(panel.id, request)
    elif method == "GET" and path.startswith(f"{api}/artifacts/"):
        # The bytes behind a media message a tile on this panel is drawing.
        # Scoped to what those messages hold *now*, which is exactly what a
        # live widget asks for — a screen has no business reading an artifact
        # off an old run because it happens to know the digest.
        digest = unquote(path[len(f"{api}/artifacts/") :])
        allowed = "/" not in digest and digest in _panel_digests(panel.id, request)

    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
    instance 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 instance 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 credential still stands, which is what makes
    deleting a panel, or bumping its nonce, revoke one.
    """
    if not payload.get("panel"):
        return payload
    if request is not None:
        _panel_may(payload, request)
    else:
        _panel_for(payload)
    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
    a mapping is what turns one into the other. There are two ways one comes to
    exist: a superuser typed their code in, which makes the account up front,
    or the owner shared a link from the portal, which admits them there and
    leaves this instance to find out when they first arrive. So an unmapped
    identity is checked once against the portal's own list of who may reach
    this instance, and adopted only if the portal vouches for it.

    Deleting the local user stays the whole of the revocation: the portal is
    asked rather than the token believed, so a still-valid token cannot rebuild
    the account it named, and a person dropped at the portal is not adopted
    again.
    """
    if token_data.portal_sub:
        user = session.exec(
            select(User).where(User.portal_sub == token_data.portal_sub)
        ).first()
        if user is None:
            return enroll.adopt_member(session, token_data.portal_sub)
        return user
    if not token_data.sub:
        return None
    try:
        # The subject is a string on the wire. Postgres cast it on the way in;
        # nothing else does, so parse it here rather than hand a driver a
        # string where it wants a UUID.
        user_id = uuid.UUID(token_data.sub)
    except ValueError:
        return None
    return session.get(User, user_id)


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