"""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 select
from sqlalchemy.orm import Session

from app import audit
from app import email as email_mod
from app.audit import AuditAction
from app.auth import (
    admin_user,
    count_admins,
    get_or_create_demo_user,
    operator_contact,
    purge_user,
)
from app.config import settings
from app.db import get_db
from app.demo import reset_demo_state
from app.models import (
    DemoWhitelist,
    Invite,
    User,
)
from app.utils import canonical_email, iso, valid_email

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."""
    email = (email or "").lower()
    return email in settings.allowed_email_set or email in settings.admin_email_set


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,
        # 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),
    }


@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 _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. Approval is not an ownership
    attestation, and it does not need to be one — `password_login` refuses an unverified account
    BEFORE it looks at `is_active`, so a pre-emptor who set a password on someone else's address
    still cannot sign in with it, approved or not. Revoking here only ever 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. The revoke stays on
    the Google-adoption path (auth.revoke_preset_password_if_unverified), where the real owner does
    attest ownership and the preset password must not survive."""
    # 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.commit()


def _decide(db: Session, invite_id: int, admin: User, approved: bool) -> Invite:
    inv = db.get(Invite, invite_id)
    if inv is None:
        raise HTTPException(status_code=404, detail="No such 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 HTTPException(status_code=409, detail="Invite already 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.commit()
    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)
    background.add_task(email_mod.send_access_approved, inv.email)
    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)
    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 HTTPException(status_code=400, detail="Enter a valid email address.")
    # 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)).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
    audit.record(
        db, admin.id, AuditAction.INVITE_ADD, target_type="invite", target_id=inv.id, summary=email
    )
    db.commit()
    _activate_user_by_email(db, email)
    return _serialize(inv, has_account=bool(_accounts_for(db, [email])))


@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 = db.get(Invite, invite_id)
    if inv is None:
        raise HTTPException(status_code=404, detail="No such invite")
    if _accounts_for(db, [inv.email]):
        raise HTTPException(
            status_code=409,
            detail="That address already has an account — delete the account instead.",
        )
    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,
        "has_google": u.google_sub is not None,
        "created_at": iso(u.created_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 HTTPException(status_code=400, detail="role must be 'user' or 'admin'")
    target = db.get(User, user_id)
    if target is None:
        raise HTTPException(status_code=404, detail="No such user")
    if target.is_demo:
        raise HTTPException(status_code=400, detail="The demo account's role can't be changed.")
    if target.id == admin.id:
        raise HTTPException(status_code=400, detail="You can't change your own role.")
    if (
        target.role == "admin"
        and role == "user"
        and not target.is_suspended
        and count_admins(db, active_only=True) <= 1
    ):
        raise HTTPException(status_code=400, detail="Can't remove the 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, 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 = db.get(User, user_id)
    if target is None:
        raise HTTPException(status_code=404, detail="No such user")
    if target.is_demo:
        raise HTTPException(status_code=400, detail="The demo account can't be suspended.")
    if target.id == admin.id:
        raise HTTPException(status_code=400, detail="You can't suspend your own account.")
    if (
        suspended
        and target.role == "admin"
        and not target.is_suspended
        and count_admins(db, active_only=True) <= 1
    ):
        raise HTTPException(status_code=400, detail="Can't suspend the 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, 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 = db.get(User, user_id)
    if target is None:
        raise HTTPException(status_code=404, detail="No such user")
    if target.is_demo:
        raise HTTPException(status_code=400, detail="The demo account can't be deleted.")
    if target.id == admin.id:
        raise HTTPException(
            status_code=400, detail="Delete your own account from Settings → Account."
        )
    if (
        target.role == "admin"
        and not target.is_suspended
        and count_admins(db, active_only=True) <= 1
    ):
        raise HTTPException(status_code=400, detail="Can't delete the 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 -------------------------------------


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 HTTPException(status_code=400, detail="Enter a valid email address.")
    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"
    )
    db.commit()
    return {"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 result