"""
FastAPI shared dependencies — injected via Depends().

JWT scope enforcement:
  - "user" scope (browser login): full access to all endpoints
  - "node" scope (Ed25519 daemon auth): read-only group access + node operations
  Node-scoped tokens CANNOT create/delete groups or manage membership.
"""

import logging

from fastapi import Depends, Header, HTTPException, status
from sqlalchemy import select
from sqlalchemy.exc import IntegrityError
from sqlalchemy.ext.asyncio import AsyncSession

from meshbay_hub.auth import decode_access_token
from meshbay_hub.db.engine import get_db
from meshbay_hub.db.models import AdminPin, User

log = logging.getLogger(__name__)

# `hub.toml`'s `admin_usernames`, and the account each of those names was pinned
# to (`AdminPin`). The names only say which accounts to pin; what grants the
# role is the pinned id, so a listed name released by an account deletion and
# registered again by somebody else grants nothing.
_admin_usernames: set[str] = set()
_admin_pins: dict[str, str] = {}


def set_admin_usernames(usernames: list[str]) -> None:
    global _admin_usernames, _admin_pins
    _admin_usernames = set(usernames)
    _admin_pins = {}


def set_admin_pins(pins: dict[str, str]) -> None:
    global _admin_pins
    _admin_pins = {name: uid for name, uid in pins.items() if name in _admin_usernames}


def _is_pinned_admin(user: User) -> bool:
    return user.id in _admin_pins.values()


async def _pin_if_listed(db: AsyncSession, user: User) -> None:
    """Pin an allow-listed name to the first active account seen holding it.

    Startup pins every listed name that already has an account; this covers a
    name registered while the hub runs, so the operator's own first sign-in is
    an admin one without a restart, as it was before pins existed.
    """
    name = user.username
    if name not in _admin_usernames or name in _admin_pins:
        return
    pin = await db.get(AdminPin, name)
    if pin is None:
        db.add(AdminPin(username=name, user_id=user.id))
        user.role = "admin"
        try:
            await db.commit()
        except IntegrityError:
            # Another worker pinned it first; its answer stands.
            await db.rollback()
            await db.refresh(user)
            pin = await db.get(AdminPin, name)
            if pin is None:
                return
        else:
            log.info("Admin allow-list: %s pinned to account %s", name, user.id[:8])
            _admin_pins[name] = user.id
            return
    _admin_pins[name] = pin.user_id


async def _decode_token(authorization: str = Header(...)) -> dict:
    """Decode and verify JWT bearer token. Returns full payload."""
    try:
        scheme, token = authorization.split(None, 1)
        if scheme.lower() != "bearer":
            raise ValueError
        return decode_access_token(token)
    except Exception:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid or expired token",
            headers={"WWW-Authenticate": "Bearer"},
        )


async def get_current_user(
    payload: dict = Depends(_decode_token),
    db: AsyncSession = Depends(get_db),
) -> User:
    """
    Verify the JWT bearer token and return the User from the database.
    Accepts both user-scoped and node-scoped tokens.
    """
    result = await db.execute(
        select(User).where(User.id == payload["sub"]))
    user = result.scalar_one_or_none()

    if user is None:
        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED,
                            detail="User not found")
    if user.status != "active":
        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN,
                            detail=f"Account {user.status}")
    await _pin_if_listed(db, user)
    return user


def _reject_node_scope(payload: dict) -> None:
    """Refuse a node-scoped daemon token on a route meant for a person.

    A node's authority and a hub role are **different notions**. What a node may
    do is decided by its operator's roster pin on the node itself (NS4) and by
    the node scope's deliberately narrow reach; being an admin or a moderator is
    a hub role attached to a person's account. A node daemon authenticates with
    the node key and receives a `scope:"node"` token so that the machine can
    register, signal and host — never so that it can act as its operator on the
    hub. When the operator's account happens to also hold a hub role, that role
    is the *person's*, exercised from a browser with a user-scoped token, and
    must not be reachable by a token the daemon holds in memory. So the scope
    gate lives in one place and fronts every privileged dependency, not only
    group mutation.
    """
    if payload.get("scope") == "node":
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Node-scoped token cannot perform this operation — use browser",
        )


async def require_user_scope(
    payload: dict = Depends(_decode_token),
    current_user: User = Depends(get_current_user),
) -> User:
    """Reject node-scoped tokens — only browser (user-scope) can mutate groups."""
    _reject_node_scope(payload)
    return current_user


async def require_node_scope(
    payload: dict = Depends(_decode_token),
    current_user: User = Depends(get_current_user),
) -> User:
    """Only a node daemon's own token — for what a node fetches on its own behalf."""
    if payload.get("scope") != "node":
        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN,
                            detail="Node token required")
    return current_user


def user_is_admin(user: User) -> bool:
    """Admin by DB role or as the account a config allow-listed name is pinned
    to. Use inside a handler that already depends on `require_moderator` but has
    to draw the admin line for one field (see `admin_patch_user`)."""
    return user.role == "admin" or _is_pinned_admin(user)


def user_is_moderator(user: User) -> bool:
    return user.role in ("moderator", "admin") or _is_pinned_admin(user)


async def require_moderator(
    payload: dict = Depends(_decode_token),
    current_user: User = Depends(get_current_user),
) -> User:
    # A node-scoped daemon token is refused here even for a moderator's own
    # account: the hub moderation surface (suspending accounts, reading the IP
    # audit log, listing nodes) is the person's, not the machine's.
    _reject_node_scope(payload)
    if not user_is_moderator(current_user):
        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN,
                            detail="Moderator access required")
    return current_user


async def require_admin(
    payload: dict = Depends(_decode_token),
    current_user: User = Depends(get_current_user),
) -> User:
    # Likewise: revoking accounts and groups (signed, broadcast to every node)
    # and changing instance policy are administrative acts a person performs
    # from a browser, never something a node token may reach.
    _reject_node_scope(payload)
    if not user_is_admin(current_user):
        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN,
                            detail="Admin access required")
    return current_user