"""Admin-only onboarding: review access requests (Invites), approve/deny, manual add.
Also the demo-account admin surface: the demo email whitelist + a manual state reset."""

from collections.abc import Iterable
from datetime import datetime, timezone

from fastapi import APIRouter, BackgroundTasks, Depends, HTTPException
from pydantic import BaseModel
from sqlalchemy import or_, select
from sqlalchemy.orm import Session

from app import audit
from app import email as email_mod
from app import mailtext
from app.audit import AuditAction
from app.auth import (
    admin_user,
    can_activate,
    count_admins,
    env_allowed_canonicals,
    find_user_by_email,
    get_or_create_demo_user,
    is_allowed,
    operator_contact,
    purge_user,
)
from app.db import get_db
from app.demo import reset_demo_state
from app.models import (
    DemoWhitelist,
    Invite,
    User,
)
from app.routes._common import get_or_404
from app.routes.auth import (
    APPROVAL_VERIFY_TTL,
    issue_set_password_link,
    issue_verification_link,
    send_verification_link,
)
from app.utils import canonical_email, iso, valid_email
from app.refusal import refused

router = APIRouter(prefix="/api/admin", tags=["admin"])


def _accounts_for(db: Session, emails: Iterable[str]) -> set[str]:
    """Which of these addresses already have an account, as a set of CANONICAL forms. Batched, so
    listing the invites costs one extra query. An invite whose address has an account must not be
    deletable: `is_allowed` reads this row, so removing it would silently revoke a live user's access.

    Canonical on both sides, because `is_allowed` matches that way: an invite for `x.y@gmail.com`
    whose account registered as `xy@gmail.com` would otherwise look account-less, offer the admin a
    delete button, and take away a live user's access — precisely the accident this guard exists to
    prevent."""
    wanted = {canonical_email(e) for e in emails if e}
    if not wanted:
        return set()
    rows = db.execute(
        select(User.email_canonical).where(User.email_canonical.in_(wanted))
    ).scalars()
    return {e for e in rows if e}


def _env_allowed(email: str) -> bool:
    """Whether the env bootstrap lists still let this address in. `is_allowed` consults them only
    when no Invite row exists, so this is exactly what deleting the row would fall back to — and the
    admin has to know that BEFORE they confirm, not from a toast afterwards.

    Canonical, because `is_allowed` is: a warning that disagrees with the gate it is warning about is
    worse than no warning."""
    return canonical_email(email or "") in env_allowed_canonicals()


def _serialize(inv: Invite, *, has_account: bool = False) -> dict:
    return {
        "id": inv.id,
        "email": inv.email,
        "status": inv.status,
        "note": inv.note,
        "requested_at": iso(inv.requested_at),
        "decided_at": iso(inv.decided_at),
        "decided_by": inv.decided_by,
        # When (if ever) the admin sent this person an invitation. Adding an address is silent, so
        # without this the admin has no way to answer "did I already write to them?" — and the only
        # failure mode is writing to a real person twice.
        "invited_at": iso(inv.invited_at),
        # Drives the delete affordance: an entry backed by an account is not removable here.
        "has_account": has_account,
        # …and whether removing it would actually take access away, or leave the env allow-list
        # granting it anyway (for an ADMIN_EMAILS address, as an admin).
        "still_allowed_by_env": _env_allowed(inv.email),
        # The language this person asked us in, or null when nobody ever told us (a hand-added
        # whitelist row). The invitation dialog preselects it, and falls back to the admin's own UI
        # language — a guess, but a visible one the admin can correct before sending.
        "lang": inv.lang,
    }


@router.get("/invites")
def list_invites(
    status: str | None = None,
    _: User = Depends(admin_user),
    db: Session = Depends(get_db),
) -> list[dict]:
    stmt = select(Invite)
    if status:
        stmt = stmt.where(Invite.status == status)
    # Pending first, then most-recently requested.
    rows = db.execute(stmt.order_by(Invite.requested_at.desc())).scalars().all()
    order = {"pending": 0, "approved": 1, "denied": 2}
    rows.sort(key=lambda i: order.get(i.status, 9))
    accounts = _accounts_for(db, (i.email for i in rows))
    return [_serialize(i, has_account=canonical_email(i.email) in accounts) for i in rows]


def _welcome_mail_parts(db: Session, email: str) -> tuple[str | None, bool, int]:
    """What a welcome or invitation mail should tell this address to do next: a confirmation link (if
    there is an unconfirmed account behind it), whether an account exists at all, and how long the
    link lasts.

    This is the C option's whole mechanic. In the common ordering — the address is approved and the
    person signs up either side of that — they would otherwise have to find and open TWO messages:
    one saying they are in, another asking them to confirm. Carrying the link inside the mail that is
    already going out makes it one mail and one click.

    Resolved through `find_user_by_email`, so an account registered under another spelling of the
    same Gmail mailbox is still recognised — and, deliberately, so several candidates resolve to
    "no single answer" rather than a guess: an invitation that carried the wrong account's link would
    be worse than one that simply pointed at the sign-up page.
    """
    hours = int(APPROVAL_VERIFY_TTL.total_seconds() // 3600)
    user = find_user_by_email(db, email)
    if user is None or user.is_demo:
        return None, False, hours
    if user.email_verified or not email_mod.email_enabled(db):
        return None, True, hours
    return issue_verification_link(db, user, APPROVAL_VERIFY_TTL), True, hours


def _activate_user_by_email(db: Session, email: str) -> None:
    """Approving access activates a matching (e.g. pending password-registration) account so
    it can sign in. No-op if no such user exists yet (a Google user is created at first login).

    E9.5 S1: this path deliberately does NOT revoke a preset password. Revoking here destroyed the
    password a legitimate registrant had just chosen and made "your password was cleared for
    security" the DEFAULT experience, because approve-before-verify is the normal ordering.

    S1 justified that by saying `password_login` refuses an unverified account BEFORE it looks at
    `is_active`, so a pre-emptor could not sign in "approved or not". A review of the finished epic
    showed that argument only holds while the address stays unverified — and S6's approval mail
    hands the real owner a confirmation link precisely so they will end that state. Nothing replaced
    the revoke, and that is deliberate: round 2 of the same review tried "the newest registration
    owns an unverified account" and reverted it, because the rule is symmetric — an attacker can
    always register last — and it handed anonymous callers a write onto a real account's credential.
    The owner's recourse is password-reset, which proves the mailbox, rewrites the hash and bumps
    the session epoch. The residual is logged as SEC-16. The revoke also stays on the Google-adoption path
    (auth.revoke_preset_password_if_unverified), where ownership is actually attested."""
    # Canonical, with the literal spelling preferred when both exist: approving
    # `npeter83.temu@gmail.com` must activate the account that registered as `npeter83temu@gmail.com`,
    # since Gmail delivers both to one mailbox and the admin decided about the mailbox.
    email = email.lower()
    candidates = (
        db.execute(
            select(User).where(User.email_canonical == canonical_email(email)).order_by(User.id)
        )
        .scalars()
        .all()
    )
    user = next((u for u in candidates if u.email == email), None) or next(iter(candidates), None)
    if user is not None and not user.is_active:
        user.is_active = True
        db.flush()  # the handler commits (CLAUDE.md: helpers flush)


def _decide(db: Session, invite_id: int, admin: User, approved: bool) -> Invite:
    inv = get_or_404(db, Invite, invite_id, what="invite")
    # Idempotency guard: only a still-pending invite can be decided. Without this a repeat/stale
    # approve or deny re-runs its side effects — re-activating a user, or (now that deny emails)
    # sending a duplicate decision mail, even flipping an already-approved invite to "denied" and
    # mailing a rejection to an already-active account.
    if inv.status != "pending":
        raise refused(409, "invite_decided")
    inv.status = "approved" if approved else "denied"
    inv.decided_at = datetime.now(timezone.utc)
    inv.decided_by = admin.email
    audit.record(
        db,
        admin.id,
        AuditAction.INVITE_APPROVE if approved else AuditAction.INVITE_DENY,
        target_type="invite",
        target_id=inv.id,
        summary=inv.email,
    )
    db.flush()  # the handler commits, with the activation that goes with it
    return inv


@router.post("/invites/{invite_id}/approve")
def approve_invite(
    invite_id: int,
    background: BackgroundTasks,
    admin: User = Depends(admin_user),
    db: Session = Depends(get_db),
) -> dict:
    inv = _decide(db, invite_id, admin, approved=True)
    _activate_user_by_email(db, inv.email)
    # Computed here, not in the background task: issuing the token needs this request's session, and
    # the task must not outlive it. Approval answers a request the person MADE, so unlike the
    # invitation below it is sent automatically — a reply is owed, not a nudge.
    link, has_account, hours = _welcome_mail_parts(db, inv.email)
    lang = mailtext.lang_for_email(db, inv.email)
    background.add_task(email_mod.send_access_approved, inv.email, lang, link, has_account, hours)
    # Before the response, so the mail (a background task, after it) never describes a decision
    # the database does not hold yet.
    db.commit()
    return _serialize(inv, has_account=bool(_accounts_for(db, [inv.email])))


@router.post("/invites/{invite_id}/deny")
def deny_invite(
    invite_id: int,
    background: BackgroundTasks,
    admin: User = Depends(admin_user),
    db: Session = Depends(get_db),
) -> dict:
    # Symmetry with approve: the requester hears back either way, instead of a silent limbo. No
    # account is activated, so this is an email only (the requester has no in-app inbox yet).
    inv = _decide(db, invite_id, admin, approved=False)
    background.add_task(
        email_mod.send_access_denied, inv.email, mailtext.lang_for_email(db, inv.email)
    )
    db.commit()
    return _serialize(inv, has_account=bool(_accounts_for(db, [inv.email])))


class AddInviteIn(BaseModel):
    email: str = ""


@router.post("/invites")
def add_invite(
    body: AddInviteIn,
    admin: User = Depends(admin_user),
    db: Session = Depends(get_db),
) -> dict:
    """Manually whitelist an email (approved straight away). Convenience for the admin."""
    email = body.email.strip().lower()
    if not valid_email(email):
        raise refused(400, "invalid_email")
    # Reuse a canonically-equal row instead of adding a second one for the same mailbox. Prod carries
    # exactly that pair for one person from 2026-06-16 (hartmann.peter1986@ / hartmannpeter1986@),
    # which is how an admin ends up approving the same human twice and still seeing them bounce.
    canon = canonical_email(email)
    rows = (
        db.execute(select(Invite).where(Invite.email_canonical == canon).order_by(Invite.id))
        .scalars()
        .all()
    )
    inv = next((r for r in rows if r.email == email), None) or next(iter(rows), None)
    if inv is None:
        inv = Invite(email=email)
        db.add(inv)
    inv.status = "approved"
    inv.decided_at = datetime.now(timezone.utc)
    inv.decided_by = admin.email
    db.flush()  # a new invite's id, for the audit row — before it, the row named no target
    audit.record(
        db, admin.id, AuditAction.INVITE_ADD, target_type="invite", target_id=inv.id, summary=email
    )
    # One transaction: the whitelisting and the activation it implies land together or not at all.
    _activate_user_by_email(db, email)
    db.commit()
    return _serialize(inv, has_account=bool(_accounts_for(db, [email])))


class InviteSendIn(BaseModel):
    # Which language to write this person in. Optional so an existing caller (and a test) can post
    # an empty body, but the admin UI always sends it: this is the one recipient the app has no
    # signal about, because the admin typed the address in themselves.
    lang: str | None = None


@router.post("/invites/{invite_id}/invite")
def send_invitation(
    invite_id: int,
    body: InviteSendIn | None = None,
    admin: User = Depends(admin_user),
    db: Session = Depends(get_db),
) -> dict:
    """Tell someone their address is whitelisted — only when the admin asks for it.

    Whitelisting stays SILENT on purpose. The operator opens a door as a possibility, usually having
    already agreed it with the person, and an address can sit approved for weeks with nobody
    registering; a mail fired automatically would be nudging someone who never asked to be nudged.
    So the send is its own act, on its own button, and `invited_at` records it so the admin can see
    they have already written rather than writing twice.

    Only an APPROVED row can be invited: there is nothing to invite someone to while their request is
    undecided, and inviting a denied address would contradict the decision."""
    inv = get_or_404(db, Invite, invite_id, what="invite")
    if inv.status != "approved":
        raise HTTPException(
            status_code=409,
            detail={"code": "invite_send", "reason": "not_approved", "email": inv.email},
        )
    if not email_mod.email_enabled(db):
        # Same reasoning as the admin-side verification resend: mail is fail-soft everywhere else,
        # but a button the admin pressed must not answer with a success toast for a mail that was
        # never sent.
        raise HTTPException(status_code=409, detail={"code": "invite_send", "reason": "email_off"})
    link, has_account, hours = _welcome_mail_parts(db, inv.email)
    # An explicit pick from the dialog is recorded, so a later mail to this address matches the one
    # the admin already sent. Only the explicit pick — writing the fallback back would turn a column
    # that means "what this person told us" into "what we last guessed".
    picked = body.lang if body else None
    if picked in mailtext.SUPPORTED:
        lang = inv.lang = picked
    else:
        lang = mailtext.lang_for_email(db, inv.email)
    # Sent INLINE, so `invited_at` records the send rather than the intent. Every other mail here is
    # fail-soft in the background, which is right when nobody is waiting on it — but this column
    # exists to answer "did I already write to them?", and the UI dims the button and warns about a
    # second mail on the strength of it. Stamping it before a send that then failed makes the one
    # question it answers a lie, and talks the admin out of the retry that would fix it.
    #
    # One thing a failed send does leave behind: the confirmation token `_welcome_mail_parts` minted
    # to render the link, which commits inside `_issue_token`. Accepted rather than chased — the
    # token is single-use, expires on its own, and was mailed nowhere; deferring it would mean
    # rewriting a helper three callers share so the handler owns its commit.
    if not email_mod.send_access_invitation(inv.email, lang, link, has_account, hours):
        raise HTTPException(
            status_code=422, detail={"code": "invite_send", "reason": "send_failed"}
        )
    # Only after the mail is actually out. Same as the other two paths that decide for an address
    # (`approve_invite`, `add_invite`): an approved row means this mailbox may come in, so finish it,
    # or the mail can promise "your account is ready — just sign in" to someone `password_login` will
    # refuse for `is_active`. Doing it BEFORE the send would mean a request the UI reports as failed
    # had quietly activated an account behind the admin's back.
    _activate_user_by_email(db, inv.email)
    inv.invited_at = datetime.now(timezone.utc)
    audit.record(
        db,
        admin.id,
        AuditAction.INVITE_SEND,
        target_type="invite",
        target_id=inv.id,
        summary=inv.email,
    )
    db.commit()
    return _serialize(inv, has_account=has_account)


@router.delete("/invites/{invite_id}")
def delete_invite(
    invite_id: int,
    admin: User = Depends(admin_user),
    db: Session = Depends(get_db),
) -> dict:
    """Remove a whitelist/request entry outright — the counterpart to add_invite, for an address that
    never became an account (an approval added by mistake, or one that is no longer wanted). Deny
    records a decision and keeps the row for the audit trail; delete forgets the address. Neither
    stops the person asking again: `upsert_pending_invite` reopens a denied row, and a deleted one
    simply comes back as a fresh pending request.

    Refused once an account exists for the address, whatever its state: this row is the account's
    approval gate, and orphaning the account from it would leave a person who can neither sign in nor
    be approved. Delete the USER instead — purge_user removes the invite along with it.

    Reports `still_allowed_by_env`, because deleting the row is NOT always a revoke: `is_allowed`
    falls back to the env ALLOWED_EMAILS / ADMIN_EMAILS bootstrap lists once no invite exists, so for
    an address on those the deletion leaves access intact (and an ADMIN_EMAILS address is still
    promoted to admin on its next Google sign-in). The admin has to hear that, not guess it."""
    inv = get_or_404(db, Invite, invite_id, what="invite")
    if _accounts_for(db, [inv.email]):
        raise refused(409, "address_has_account")
    still_allowed_by_env = _env_allowed(inv.email)
    audit.record(
        db,
        admin.id,
        AuditAction.INVITE_DELETE,
        target_type="invite",
        target_id=inv.id,
        summary=inv.email,
    )
    db.delete(inv)
    db.commit()
    return {"deleted": invite_id, "still_allowed_by_env": still_allowed_by_env}


# --- Users & roles --------------------------------------------------------------------


def _serialize_user(u: User) -> dict:
    return {
        "id": u.id,
        "email": u.email,
        "display_name": u.display_name,
        "role": u.role,
        "is_active": u.is_active,
        "is_suspended": u.is_suspended,
        "email_verified": u.email_verified,
        "is_demo": u.is_demo,
        "has_password": u.password_hash is not None,
        # Distinguishes "this account never had a password" (Google-only) from "SEC-10 cleared it" —
        # the same distinction _send_reset_if_eligible needs, and the one an admin has to see before
        # deciding what kind of help someone needs.
        "password_revoked_at": iso(u.password_revoked_at),
        "has_google": u.google_sub is not None,
        # Only when it DIFFERS from the account address (E9.5 S3): "connected" is not the same
        # statement as "connected as someone else", and the second one is the one that explains a
        # confusing sign-in.
        "google_email": u.google_email if u.google_email != u.email else None,
        "created_at": iso(u.created_at),
        # NULL = no sign-in since the column existed (0085), or the shared demo account.
        "last_login_at": iso(u.last_login_at),
    }


@router.get("/users")
def list_users(_: User = Depends(admin_user), db: Session = Depends(get_db)) -> list[dict]:
    rows = db.execute(select(User).order_by(User.created_at.desc())).scalars().all()
    return [_serialize_user(u) for u in rows]


class SetRoleIn(BaseModel):
    role: str


@router.patch("/users/{user_id}/role")
def set_user_role(
    user_id: int,
    body: SetRoleIn,
    background: BackgroundTasks,
    admin: User = Depends(admin_user),
    db: Session = Depends(get_db),
) -> dict:
    """Promote/demote a user. Guards: can't change your own role, can't touch the demo
    account, and can't remove the last remaining admin. Emails the user when it actually changes."""
    role = body.role
    if role not in ("user", "admin"):
        raise refused(400, "invalid_role")
    target = get_or_404(db, User, user_id, what="user")
    if target.is_demo:
        raise refused(400, "demo_role")
    if target.id == admin.id:
        raise refused(400, "own_role")
    if (
        target.role == "admin"
        and role == "user"
        and not target.is_suspended
        and count_admins(db, active_only=True) <= 1
    ):
        raise refused(400, "last_admin")
    changed = target.role != role
    if changed:
        audit.record(
            db,
            admin.id,
            AuditAction.USER_ROLE_CHANGE,
            target_type="user",
            target_id=target.id,
            summary=target.email,
            before={"role": target.role},
            after={"role": role},
        )
    target.role = role
    db.commit()
    if changed:
        background.add_task(
            email_mod.send_role_changed,
            target.email,
            mailtext.lang_for_user(target),
            role,
            operator_contact(),
        )
    return _serialize_user(target)


class SetSuspendedIn(BaseModel):
    suspended: bool = False


@router.patch("/users/{user_id}/suspend")
def set_user_suspended(
    user_id: int,
    body: SetSuspendedIn,
    background: BackgroundTasks,
    admin: User = Depends(admin_user),
    db: Session = Depends(get_db),
) -> dict:
    """Suspend or un-suspend an account. A suspended user can't sign in by any method and any
    live session is dropped on its next request. Guards: can't suspend the demo account, can't
    suspend yourself, and can't suspend the last active admin (that would lock admin out). On
    un-suspend the user is emailed they can return (suspend is announced reactively, on a blocked
    sign-in)."""
    suspended = body.suspended
    target = get_or_404(db, User, user_id, what="user")
    if target.is_demo:
        raise refused(400, "demo_suspend")
    if target.id == admin.id:
        raise refused(400, "own_suspend")
    if (
        suspended
        and target.role == "admin"
        and not target.is_suspended
        and count_admins(db, active_only=True) <= 1
    ):
        raise refused(400, "last_active_admin")
    was_suspended = target.is_suspended
    if was_suspended != suspended:
        audit.record(
            db,
            admin.id,
            AuditAction.USER_SUSPEND if suspended else AuditAction.USER_UNSUSPEND,
            target_type="user",
            target_id=target.id,
            summary=target.email,
        )
    target.is_suspended = suspended
    db.commit()
    if was_suspended and not suspended:
        background.add_task(
            email_mod.send_account_unsuspended,
            target.email,
            mailtext.lang_for_user(target),
            operator_contact(),
        )
    return _serialize_user(target)


@router.delete("/users/{user_id}")
def admin_delete_user(
    user_id: int,
    background: BackgroundTasks,
    admin: User = Depends(admin_user),
    db: Session = Depends(get_db),
) -> dict:
    """Admin-triggered account deletion — the same full erasure a user can perform on themselves
    (cascade delete of all personal data + access-request cleanup + Google-grant revoke). Guards:
    not the demo account, not yourself (use Settings → Account), and not the last admin."""
    target = get_or_404(db, User, user_id, what="user")
    if target.is_demo:
        raise refused(400, "demo_delete")
    if target.id == admin.id:
        raise refused(400, "own_delete")
    if (
        target.role == "admin"
        and not target.is_suspended
        and count_admins(db, active_only=True) <= 1
    ):
        raise refused(400, "last_admin")
    # Record BEFORE the purge — the target row (and its email) is gone afterwards.
    audit.record(
        db,
        admin.id,
        AuditAction.USER_DELETE,
        target_type="user",
        target_id=target.id,
        summary=target.email,
    )
    purge_user(db, target, background)
    return {"deleted": user_id}


# --- Demo account: email whitelist + state reset -------------------------------------


# --- Stuck sign-ups: the admin lifeline (E9.5 S5, roadmap UX-25) ---------------------------------


def _pending_access_rows(db: Session) -> list[User]:
    """Accounts that have signed up but still cannot sign in, newest first.

    Two different dead ends share this list, because from the admin's chair they look the same — a
    person who registered and is still outside:
      · `is_active=False` — approved BEFORE they signed up, so nothing ever landed in the
        Access-requests queue and its Approve button doesn't apply (`_decide` only takes a pending
        row). This is roadmap UX-25, and it is why the list exists.
      · `email_verified=False` — the confirmation mail hasn't been acted on. Not the admin's to
        decide, but theirs to help with: on 2026-09-03 the first mail to a fresh Gmail landed in
        Spam, so "send it again" is a real move.
    A suspended account is deliberately excluded: it cannot sign in either, but that is a decision
    already made, not a person stuck waiting on one.
    """
    return list(
        db.execute(
            select(User)
            .where(
                User.is_demo.is_(False),
                User.is_suspended.is_(False),
                or_(User.is_active.is_(False), User.email_verified.is_(False)),
            )
            .order_by(User.created_at.desc())
        )
        .scalars()
        .all()
    )


@router.get("/pending-access")
def list_pending_access(_: User = Depends(admin_user), db: Session = Depends(get_db)) -> list[dict]:
    """The sign-ups that are still outside, with which gate is shut for each. `can_activate` cannot
    be derived on the client — it needs the invite/allow-list lookup — so it is answered here.

    One `is_allowed` query per row rather than a batched re-implementation of it: the row count is
    the admin's own backlog of stuck sign-ups (single digits on any real instance), and a second,
    subtly different copy of the "may this address sign in" rule is exactly the drift this codebase
    keeps getting bitten by."""
    out = []
    for u in _pending_access_rows(db):
        # The whole rule in one line: this address MAY sign in, and this account still can't. An
        # undecided request fails it (nothing is allowed yet) and so does a denied one — both belong
        # to the queue above, which owns that decision. Without this, every fresh registration
        # appeared in both lists at once, which UAT caught on 2026-09-05.
        if not is_allowed(db, u.email):
            continue
        out.append(_serialize_user(u) | {"can_activate": can_activate(db, u)})
    return out


@router.get("/users/{user_id}/access")
def user_access(
    user_id: int,
    _: User = Depends(admin_user),
    db: Session = Depends(get_db),
) -> dict:
    """Everything the account panel shows about why this person can or cannot get in (E12 S5).

    Its own endpoint rather than extra columns on /users: `is_allowed` and `can_activate` each run a
    query, and the panel opens for ONE user at a time — folding them into the list would pay that cost
    per row on every load to answer a question nobody asked yet."""
    target = get_or_404(db, User, user_id, what="user")
    return _serialize_user(target) | {
        "is_allowed": is_allowed(db, target.email),
        "can_activate": can_activate(db, target),
        "email_configured": email_mod.email_enabled(db),
    }


@router.post("/users/{user_id}/set-password-link")
def create_set_password_link(
    user_id: int,
    admin: User = Depends(admin_user),
    db: Session = Depends(get_db),
) -> dict:
    """Mint a one-time link that lets this account set a password, with no email involved (E12 S5).

    The answer to SEC-15, SEC-16 and "no SMTP and someone forgot their password" at once. The admin
    hands the link over by whatever channel they trust; opening it sets a password and signs out
    whoever held the old one.

    Deliberately NOT gated on the account's state. It is useful for a pre-empted address, for a
    revoked password, for a Google-only account that wants one, and for a plain forgotten password on
    an instance with no mail — narrowing it to one of those would only make the admin's real case the
    one it refuses. The demo account is the single exception: it is shared, so handing anyone a way to
    change its password is handing them everyone else's session."""
    target = get_or_404(db, User, user_id, what="user")
    if target.is_demo:
        raise HTTPException(
            status_code=400, detail={"code": "setpw", "reason": "demo", "email": target.email}
        )
    url, expires_at = issue_set_password_link(db, target)
    # The URL itself is NOT recorded: the audit log is read by humans and kept long, and a live
    # credential-setting link is the last thing that belongs in it. That the link was issued, by whom,
    # for whom, is the auditable fact.
    audit.record(
        db,
        admin.id,
        AuditAction.USER_SETPW_LINK,
        target_type="user",
        target_id=target.id,
        summary=target.email,
    )
    db.commit()
    return {"ok": True, "url": url, "expires_at": iso(expires_at), "email": target.email}


@router.post("/users/{user_id}/activate")
def activate_user(
    user_id: int,
    admin: User = Depends(admin_user),
    db: Session = Depends(get_db),
) -> dict:
    """Let in a registrant whose address was approved before they signed up (roadmap UX-25).

    Admin-side ONLY, and that is the whole design. Two earlier attempts at this were reverted after
    review, and both moved authority rather than visibility: auto-activating on registration turns a
    standing whitelist entry into a bearer grant for whoever registers the address first, and
    reopening the approved invite to `pending` lets an anonymous sign-up REVOKE a standing approval.
    This endpoint changes nothing about what an unauthenticated caller can cause — the admin could
    already do exactly this by re-entering the address in the whitelist box (`add_invite` →
    `_activate_user_by_email`). What was missing was any way to know they had to."""
    target = get_or_404(db, User, user_id, what="user")
    if target.is_demo:
        raise refused(400, "demo_activate")
    if target.is_active:
        return _serialize_user(target)  # idempotent: a double click is not an error
    if not is_allowed(db, target.email):
        raise HTTPException(
            status_code=409,
            detail={"code": "activate", "reason": "not_allowed", "email": target.email},
        )
    audit.record(
        db,
        admin.id,
        AuditAction.USER_ACTIVATE,
        target_type="user",
        target_id=target.id,
        summary=target.email,
        before={"is_active": False},
        after={"is_active": True},
    )
    target.is_active = True
    db.commit()
    return _serialize_user(target)


@router.post("/users/{user_id}/resend-verification")
def resend_user_verification(
    user_id: int,
    admin: User = Depends(admin_user),
    db: Session = Depends(get_db),
) -> dict:
    """Re-send an account's confirmation link from the admin side.

    The public /auth/verify/resend answers uniformly and reveals nothing, which is right for an
    anonymous caller but leaves the admin unable to tell a delivered mail from a dropped one. Here
    the caller is already authenticated as an admin, so this one says plainly what happened.

    Not rate-limited: an admin is not a threat model to enumerate against, and the deliberate silence
    of the public endpoint is exactly what this exists to escape."""
    target = get_or_404(db, User, user_id, what="user")
    if target.is_demo or target.email_verified:
        raise HTTPException(
            status_code=409,
            detail={"code": "resend", "reason": "not_applicable", "email": target.email},
        )
    if not email_mod.email_enabled(db):
        # Mail is fail-soft everywhere else, which is what left the 0.78.5 sign-ups with nothing to
        # fall back on. An admin pressing a button deserves the failure, not a success toast.
        raise HTTPException(status_code=409, detail={"code": "resend", "reason": "email_off"})
    if not send_verification_link(db, target):
        # Same rule as the invitation above: a button an admin pressed must not answer with a
        # success for a mail that was dropped. Mail is fail-soft everywhere else because nobody is
        # waiting on the answer; here somebody is.
        raise HTTPException(status_code=422, detail={"code": "resend", "reason": "send_failed"})
    audit.record(
        db,
        admin.id,
        AuditAction.USER_VERIFY_RESEND,
        target_type="user",
        target_id=target.id,
        summary=target.email,
    )
    db.commit()
    return {"ok": True, "email": target.email}


def _serialize_demo(row: DemoWhitelist) -> dict:
    return {
        "id": row.id,
        "email": row.email,
        "note": row.note,
        "added_by": row.added_by,
        "created_at": iso(row.created_at),
    }


@router.get("/demo/whitelist")
def list_demo_whitelist(_: User = Depends(admin_user), db: Session = Depends(get_db)) -> list[dict]:
    rows = (
        db.execute(select(DemoWhitelist).order_by(DemoWhitelist.created_at.desc())).scalars().all()
    )
    return [_serialize_demo(r) for r in rows]


class AddDemoWhitelistIn(BaseModel):
    email: str = ""
    note: str | None = None


@router.post("/demo/whitelist")
def add_demo_whitelist(
    body: AddDemoWhitelistIn,
    admin: User = Depends(admin_user),
    db: Session = Depends(get_db),
) -> dict:
    """Add an email that may enter the shared demo account from the login page (no Google
    sign-in). Idempotent — re-adding an existing email just returns it."""
    email = body.email.strip().lower()
    if not valid_email(email):
        raise refused(400, "invalid_email")
    row = db.execute(select(DemoWhitelist).where(DemoWhitelist.email == email)).scalar_one_or_none()
    if row is None:
        row = DemoWhitelist(
            email=email,
            note=(body.note or "").strip() or None,
            added_by=admin.email,
        )
        db.add(row)
        audit.record(
            db, admin.id, AuditAction.DEMO_ADD, target_type="demo", target_id=email, summary=email
        )
        db.commit()
    return _serialize_demo(row)


@router.delete("/demo/whitelist/{entry_id}")
def remove_demo_whitelist(
    entry_id: int,
    admin: User = Depends(admin_user),
    db: Session = Depends(get_db),
) -> dict:
    row = db.get(DemoWhitelist, entry_id)
    if row is not None:
        audit.record(
            db,
            admin.id,
            AuditAction.DEMO_REMOVE,
            target_type="demo",
            target_id=row.email,
            summary=row.email,
        )
        db.delete(row)
        db.commit()
    return {"deleted": entry_id}


@router.post("/demo/reset")
def reset_demo(admin: User = Depends(admin_user), db: Session = Depends(get_db)) -> dict:
    """Manually clean up the shared demo sandbox back to a baseline. A scheduled job does the
    same automatically (admin-tunable interval); this is the admin's on-demand button."""
    demo = get_or_create_demo_user(db)
    seeded = reset_demo_state(db, demo)
    audit.record(
        db,
        admin.id,
        AuditAction.DEMO_RESET,
        summary=f"{seeded} sample playlists re-seeded",
        after={"playlists_seeded": seeded},  # the count as data: named in the reader's language
    )
    db.commit()
    return {"ok": True, "reset": True, "playlists_seeded": seeded}


@router.post("/purge-discovery")
def purge_discovery(admin: User = Depends(admin_user), db: Session = Depends(get_db)) -> dict:
    """Reclaim all un-kept discovery content NOW (ignoring the grace period): live-search result
    videos nobody watched/saved/subscribed to, plus explored-but-unsubscribed channels. The
    scheduled discovery-cleanup job does the same on its interval; this is the on-demand button."""
    from app.sync.explore import purge_unkept_explored, purge_unkept_search

    result = {**purge_unkept_search(db, grace_days=0), **purge_unkept_explored(db)}
    audit.record(
        db,
        admin.id,
        AuditAction.DISCOVERY_PURGE,
        summary=", ".join(f"{k}: {v}" for k, v in result.items()) or None,
        after=result,
    )
    db.commit()
    return {"ok": True, **result}