"""HTML page routes: first-run setup, login/logout, user settings, and
the admin panel. The per-frame pages (Photos/Configuration/Stats) live in
routers/frame_pages.py.

All POSTs here are plain HTML forms, so CSRF rides a hidden form field
(checked explicitly) rather than the X-CSRF-Token header the JSON API
uses."""

from __future__ import annotations

import hmac
import logging
import time

from fastapi import APIRouter, Depends, Form, HTTPException, Request
from fastapi.responses import FileResponse, HTMLResponse, RedirectResponse
from fastapi.templating import Jinja2Templates
from sqlalchemy import select
from sqlalchemy.orm import Session

from .. import caldav_client, mail
from ..auth import (
    SESSION_COOKIE,
    SESSION_LIFETIME_S,
    consume_password_reset_token,
    create_password_reset_token,
    create_session,
    current_session,
    current_user,
    destroy_session,
    get_server_settings,
    hash_password,
    require_user_api,
    users_exist,
    verify_password,
)
from ..db import get_db
from ..logging_setup import LOG_PATH, read_log_tail
from ..models import Frame, PasswordResetToken, PendingClaim, User, UserFrame
from .common import valid_http_url

logger = logging.getLogger(__name__)

router = APIRouter()
templates = Jinja2Templates(directory="app/templates")

USERNAME_MAX_LEN = 64
PASSWORD_MIN_LEN = 8
PENDING_CLAIM_TTL_S = 24 * 3600


def _set_session_cookie(response, cookie_value: str) -> None:
    # No Secure flag: the server itself is plain HTTP by design (TLS is a
    # reverse proxy's job, see README) and a LAN deployment without HTTPS
    # must still be able to log in.
    response.set_cookie(
        SESSION_COOKIE,
        cookie_value,
        max_age=SESSION_LIFETIME_S,
        httponly=True,
        samesite="lax",
    )


def _check_form_csrf(request: Request, db: Session, csrf_token: str) -> None:
    session = current_session(request, db)
    if session is None or not hmac.compare_digest(csrf_token, session.csrf_token):
        raise HTTPException(403, "Missing or invalid CSRF token")


def _normalize_username(username: str) -> str:
    return username.strip().lower()


def _validate_credentials(username: str, password: str) -> str:
    username = _normalize_username(username)
    if not username or len(username) > USERNAME_MAX_LEN:
        raise HTTPException(400, "Invalid username")
    if len(password) < PASSWORD_MIN_LEN:
        raise HTTPException(400, f"Password must be at least {PASSWORD_MIN_LEN} characters")
    return username


@router.get("/setup", response_class=HTMLResponse)
def setup_page(request: Request, db: Session = Depends(get_db)):
    if users_exist(db):
        return RedirectResponse("/login", status_code=303)
    return templates.TemplateResponse("setup.html", {"request": request, "error": None})


@router.post("/setup")
def setup_submit(
    request: Request,
    username: str = Form(...),
    display_name: str = Form(""),
    password: str = Form(...),
    db: Session = Depends(get_db),
):
    """Creates admin #1 -- only ever available while no users exist, so it
    needs no CSRF/session (there is nothing to ride). Links every
    existing frame (i.e. the migrated frame #1) to the new admin, makes
    them its owner + controller, and inherits the migrated Immich creds
    onto their account (that's how env/config.json creds become per-user
    state)."""
    if users_exist(db):
        raise HTTPException(403, "Setup has already been completed")
    username = _validate_credentials(username, password)

    admin = User(
        username=username,
        display_name=display_name.strip() or username,
        password_hash=hash_password(password),
        is_admin=True,
        created_at=time.time(),
    )
    db.add(admin)
    db.flush()

    for frame in db.scalars(select(Frame)):
        db.add(UserFrame(user_id=admin.id, frame_id=frame.id))
        if frame.owner_user_id is None:
            frame.owner_user_id = admin.id
            frame.claimed_at = time.time()
        if frame.controlled_by_user_id is None:
            frame.controlled_by_user_id = admin.id
        if not admin.immich_url and frame.immich_url and frame.immich_api_key:
            admin.immich_url = frame.immich_url
            admin.immich_api_key = frame.immich_api_key

    db.commit()
    logger.info("First-run setup: created admin '%s' and linked %s", username,
                ", ".join(f"frame #{f.id}" for f in db.scalars(select(Frame))) or "no frames")

    cookie_value, _ = create_session(db, admin)
    response = RedirectResponse("/", status_code=303)
    _set_session_cookie(response, cookie_value)
    return response


def _safe_next(next_url: str) -> str:
    """Same-site relative paths only -- a login redirect target from a
    query param must never become an open redirect."""
    if next_url.startswith("/") and not next_url.startswith("//"):
        return next_url
    return "/"


@router.get("/login", response_class=HTMLResponse)
def login_page(request: Request, next: str = "", db: Session = Depends(get_db)):
    if not users_exist(db):
        return RedirectResponse("/setup", status_code=303)
    if current_user(request, db) is not None:
        return RedirectResponse(_safe_next(next), status_code=303)
    return templates.TemplateResponse(
        "login.html", {"request": request, "error": None, "next": next}
    )


@router.post("/login")
def login_submit(
    request: Request,
    username: str = Form(...),
    password: str = Form(...),
    next: str = Form(""),
    db: Session = Depends(get_db),
):
    user = db.scalars(
        select(User).where(User.username == _normalize_username(username))
    ).first()
    if user is None or not user.password_hash or not verify_password(password, user.password_hash):
        return templates.TemplateResponse(
            "login.html",
            {"request": request, "error": "Wrong username or password.", "next": next},
            status_code=401,
        )
    cookie_value, _ = create_session(db, user)
    response = RedirectResponse(_safe_next(next), status_code=303)
    _set_session_cookie(response, cookie_value)
    return response


@router.post("/logout")
def logout(request: Request, csrf_token: str = Form(""), db: Session = Depends(get_db)):
    _check_form_csrf(request, db, csrf_token)
    destroy_session(db, request)
    response = RedirectResponse("/login", status_code=303)
    response.delete_cookie(SESSION_COOKIE)
    return response


@router.get("/forgot-password", response_class=HTMLResponse)
def forgot_password_page(request: Request):
    return templates.TemplateResponse(
        "forgot_password.html", {"request": request, "sent": False, "error": None}
    )


@router.post("/forgot-password", response_class=HTMLResponse)
def forgot_password_submit(
    request: Request, email: str = Form(...), db: Session = Depends(get_db)
):
    """Always shows the same "check your email" result regardless of
    whether the address matches an account -- otherwise this endpoint
    would let anyone enumerate registered emails. Silently no-ops (same
    response) if SMTP isn't configured or the user has no email set."""
    email = email.strip().lower()
    user = db.scalars(select(User).where(User.email != "").where(User.email == email)).first()
    if user is not None:
        token = create_password_reset_token(db, user)
        reset_url = str(request.base_url).rstrip("/") + f"/reset-password/{token}"
        settings = get_server_settings(db)
        mail.send_email(
            settings, user.email, "Reset your ESPresso Frame password",
            f"Someone (hopefully you) asked to reset the password for '{user.username}'.\n\n"
            f"Reset it here (valid for 1 hour): {reset_url}\n\n"
            "If you didn't request this, ignore this email.",
        )
    return templates.TemplateResponse(
        "forgot_password.html", {"request": request, "sent": True, "error": None}
    )


@router.get("/reset-password/{token}", response_class=HTMLResponse)
def reset_password_page(token: str, request: Request, db: Session = Depends(get_db)):
    row = db.get(PasswordResetToken, token)
    valid = row is not None and row.expires_at > time.time()
    return templates.TemplateResponse(
        "reset_password.html", {"request": request, "token": token, "valid": valid, "error": None}
    )


@router.post("/reset-password/{token}", response_class=HTMLResponse)
def reset_password_submit(
    token: str, request: Request, password: str = Form(...), db: Session = Depends(get_db)
):
    if len(password) < PASSWORD_MIN_LEN:
        return templates.TemplateResponse(
            "reset_password.html",
            {"request": request, "token": token, "valid": True,
             "error": f"Password must be at least {PASSWORD_MIN_LEN} characters."},
        )
    user = consume_password_reset_token(db, token)
    if user is None:
        return templates.TemplateResponse(
            "reset_password.html",
            {"request": request, "token": token, "valid": False, "error": None},
        )
    user.password_hash = hash_password(password)
    db.commit()
    logger.info("Password reset via email link for user '%s'", user.username)
    cookie_value, _ = create_session(db, user)
    response = RedirectResponse("/", status_code=303)
    _set_session_cookie(response, cookie_value)
    return response


def _normalize_device_id(device_id: str) -> str:
    device_id = device_id.strip().lower()
    if len(device_id) != 12 or any(c not in "0123456789abcdef" for c in device_id):
        raise HTTPException(400, "Invalid device id")
    return device_id


def _attempt_claim(db: Session, user: User, device_id: str) -> str:
    """Claims the frame for `user` if it has registered, else records a
    pending claim the frame's first check-in will attach (see
    auth._register_frame). Returns "claimed" or "pending"."""
    frame = db.scalars(select(Frame).where(Frame.device_id == device_id)).first()
    now = time.time()
    if frame is not None:
        if frame.owner_user_id is not None:
            raise HTTPException(409, "That frame is already claimed")
        frame.owner_user_id = user.id
        frame.claimed_at = now
        if frame.controlled_by_user_id is None:
            frame.controlled_by_user_id = user.id
        if db.get(UserFrame, (user.id, frame.id)) is None:
            db.add(UserFrame(user_id=user.id, frame_id=frame.id))
        pending = db.get(PendingClaim, device_id)
        if pending is not None:
            db.delete(pending)
        db.commit()
        logger.info("User '%s' claimed frame #%d (%s)", user.username, frame.id, device_id)
        return "claimed"

    pending = db.get(PendingClaim, device_id)
    if pending is None:
        pending = PendingClaim(device_id=device_id, user_id=user.id, created_at=now,
                               expires_at=now + PENDING_CLAIM_TTL_S)
        db.add(pending)
    else:
        pending.user_id = user.id
        pending.expires_at = now + PENDING_CLAIM_TTL_S
    db.commit()
    logger.info("User '%s' filed a pending claim for device %s", user.username, device_id)
    return "pending"


def _render_claim(request: Request, db: Session, device_id: str, error: str | None = None):
    user = current_user(request, db)
    session = current_session(request, db) if user else None
    frame = db.scalars(select(Frame).where(Frame.device_id == device_id)).first()
    if frame is None:
        status = "unregistered"
        pending = db.get(PendingClaim, device_id)
        pending_yours = bool(pending and user and pending.user_id == user.id
                             and pending.expires_at > time.time())
    elif frame.owner_user_id is None:
        status, pending_yours = "unclaimed", False
    elif user is not None and (
        frame.owner_user_id == user.id or db.get(UserFrame, (user.id, frame.id)) is not None
    ):
        status, pending_yours = "claimed_yours", False
        if frame.device_token_ack:
            # The device's captive portal redirects here on EVERY
            # (re)provisioning cycle (see wifi_provisioning.c) -- if the
            # physical frame was reset/reprovisioned, it no longer has
            # the access token this frame row already acknowledged, and
            # auth.require_device permanently locks out an id-only
            # request once device_token_ack is set (device_id alone,
            # unlike the token, isn't secret -- it's shown on the
            # frame's own screen/QR). Reopening that handshake window
            # here is what "give it a minute to connect" below actually
            # depends on: it's safe because landing on this branch
            # already requires knowing the device_id (physical/local
            # access to the frame) AND being logged in as an owner/
            # linked user of it.
            frame.device_token_ack = False
            db.commit()
            logger.info("Frame #%d's device token handshake reopened (re-provisioned)", frame.id)
    else:
        status, pending_yours = "claimed", False
    return templates.TemplateResponse(
        "claim.html",
        {
            "request": request,
            "device_id": device_id,
            "status": status,
            "pending_yours": pending_yours,
            "user": user,
            "csrf_token": session.csrf_token if session else None,
            "error": error,
        },
    )


@router.get("/claim", response_class=HTMLResponse)
def claim_page(request: Request, device_id: str = "", db: Session = Depends(get_db)):
    """Where the captive portal's post-provisioning redirect lands. Also
    the enrollment gate: a valid device id is what entitles a stranger to
    create an account (signup form on this page); everyone else gets
    enrolled by the admin."""
    device_id = _normalize_device_id(device_id)
    return _render_claim(request, db, device_id)


@router.post("/claim")
def claim_submit(
    request: Request,
    device_id: str = Form(...),
    csrf_token: str = Form(""),
    db: Session = Depends(get_db),
):
    device_id = _normalize_device_id(device_id)
    user = current_user(request, db)
    if user is None:
        return RedirectResponse(f"/login?next=/claim%3Fdevice_id%3D{device_id}", status_code=303)
    _check_form_csrf(request, db, csrf_token)
    try:
        _attempt_claim(db, user, device_id)
    except HTTPException as e:
        if e.status_code == 409:
            return _render_claim(request, db, device_id, error=e.detail)
        raise
    return RedirectResponse(f"/claim?device_id={device_id}", status_code=303)


@router.post("/claim/signup")
def claim_signup(
    request: Request,
    device_id: str = Form(...),
    username: str = Form(...),
    password: str = Form(...),
    db: Session = Depends(get_db),
):
    """Account creation, gated on a plausible frame claim: the device id
    must belong to a frame that is unclaimed (or not yet registered --
    the user beat the device here after provisioning). A fabricated id
    can create an orphan account whose pending claim expires in 24h --
    accepted at household scale, and visible in /admin."""
    device_id = _normalize_device_id(device_id)
    frame = db.scalars(select(Frame).where(Frame.device_id == device_id)).first()
    if frame is not None and frame.owner_user_id is not None:
        return _render_claim(request, db, device_id,
                             error="That frame is already claimed -- log in instead.")
    username = _validate_credentials(username, password)
    if db.scalars(select(User).where(User.username == username)).first() is not None:
        return _render_claim(request, db, device_id,
                             error=f"Username '{username}' is taken -- log in instead?")

    user = User(
        username=username,
        display_name=username,
        password_hash=hash_password(password),
        is_admin=False,
        created_at=time.time(),
    )
    db.add(user)
    db.commit()
    logger.info("User '%s' signed up via claim gate for device %s", username, device_id)

    _attempt_claim(db, user, device_id)
    cookie_value, _ = create_session(db, user)
    response = RedirectResponse(f"/claim?device_id={device_id}", status_code=303)
    _set_session_cookie(response, cookie_value)
    return response


def _settings_context(request: Request, db: Session, user, saved: bool, error: str | None) -> dict:
    from .common import shell_context

    ctx = shell_context(request, db, user, active_nav="settings")
    ctx.update({"saved": saved, "error": error})
    return ctx


@router.get("/settings", response_class=HTMLResponse)
def settings_page(request: Request, db: Session = Depends(get_db)):
    user = current_user(request, db)
    if user is None:
        return RedirectResponse("/login", status_code=303)
    return templates.TemplateResponse(
        "settings.html", _settings_context(request, db, user, saved=False, error=None)
    )


@router.post("/settings", response_class=HTMLResponse)
def settings_submit(
    request: Request,
    csrf_token: str = Form(""),
    display_name: str = Form(""),
    email: str = Form(""),
    immich_url: str = Form(""),
    immich_api_key: str = Form(""),
    calendar_ics_url: str = Form(""),
    calendar_caldav_url: str = Form(""),
    calendar_caldav_username: str = Form(""),
    calendar_caldav_password: str = Form(""),
    webdav_username: str = Form(""),
    webdav_password: str = Form(""),
    webdav_reuse_caldav_creds: bool = Form(False),
    webdav_base_url: str = Form(""),
    current_password: str = Form(""),
    new_password: str = Form(""),
    db: Session = Depends(get_db),
):
    user = current_user(request, db)
    if user is None:
        return RedirectResponse("/login", status_code=303)
    _check_form_csrf(request, db, csrf_token)

    error = None
    user.display_name = display_name.strip() or user.username
    user.email = email.strip().lower()
    user.immich_url = immich_url.strip()
    # Blank API key field = keep the existing one (it's never echoed back
    # into the form -- a secret that round-trips through HTML is a secret
    # in every browser's autofill store).
    if immich_api_key.strip():
        user.immich_api_key = immich_api_key.strip()

    # Unlike the API key, this isn't a secret -- it round-trips visibly in
    # the form, so blank means an explicit clear (there needs to be some
    # way to actually remove a linked calendar), not "keep existing".
    stripped_ics = calendar_ics_url.strip()
    if stripped_ics and not valid_http_url(stripped_ics):
        error = "Calendar URL must be a plain http:// or https:// URL."
    else:
        user.calendar_ics_url = stripped_ics

    stripped_caldav_url = calendar_caldav_url.strip()
    if stripped_caldav_url and not valid_http_url(stripped_caldav_url):
        error = "CalDAV URL must be a plain http:// or https:// URL."
    else:
        if stripped_caldav_url != user.calendar_caldav_url:
            # Server (and likely account) changed -- last discovery no
            # longer describes what's actually there.
            user.calendar_caldav_calendars = None
            user.calendar_caldav_checked_at = 0.0
        user.calendar_caldav_url = stripped_caldav_url
    user.calendar_caldav_username = calendar_caldav_username.strip()
    # Blank password field = keep the existing one, same idiom as the
    # Immich API key -- a secret that round-trips through HTML is a
    # secret in every browser's autofill store.
    if calendar_caldav_password.strip():
        user.calendar_caldav_password = calendar_caldav_password.strip()

    user.webdav_reuse_caldav_creds = webdav_reuse_caldav_creds
    user.webdav_username = webdav_username.strip()
    if webdav_password.strip():
        user.webdav_password = webdav_password.strip()

    # Not a secret -- round-trips visibly, so blank is an explicit clear,
    # same convention as calendar_ics_url above.
    stripped_webdav_base = webdav_base_url.strip()
    if stripped_webdav_base and not valid_http_url(stripped_webdav_base):
        error = "WebDAV browse root must be a plain http:// or https:// URL."
    else:
        user.webdav_base_url = stripped_webdav_base

    if new_password:
        if not user.password_hash or not verify_password(current_password, user.password_hash):
            error = "Current password is wrong -- password not changed."
        elif len(new_password) < PASSWORD_MIN_LEN:
            error = f"New password must be at least {PASSWORD_MIN_LEN} characters."
        else:
            user.password_hash = hash_password(new_password)

    db.commit()
    return templates.TemplateResponse(
        "settings.html", _settings_context(request, db, user, saved=error is None, error=error)
    )


@router.post("/api/settings/caldav-discover")
def api_caldav_discover(request: Request, db: Session = Depends(get_db)):
    """Lists the calendars in the CalDAV account already saved on this
    user's Settings (not whatever's currently typed in the form but not
    yet saved -- same idiom as /api/frames/{id}/albums using the frame's
    already-saved Immich creds). Caches the result on the user row so
    every frame's Calendar tab can offer it without a live round-trip."""
    user = require_user_api(request, db)
    if not user.calendar_caldav_url or not user.calendar_caldav_username:
        raise HTTPException(400, "Save a CalDAV URL and username first")
    try:
        calendars = caldav_client.discover_calendars(
            user.calendar_caldav_url, user.calendar_caldav_username, user.calendar_caldav_password
        )
    except caldav_client.CalDavError as e:
        raise HTTPException(502, f"Could not discover calendars: {e}") from e
    user.calendar_caldav_calendars = calendars
    user.calendar_caldav_checked_at = time.time()
    db.commit()
    return calendars


def _require_admin_page(request: Request, db: Session) -> User:
    user = current_user(request, db)
    if user is None or not user.is_admin:
        raise HTTPException(403, "Admin only")
    return user


def _render_admin(request: Request, db: Session, admin: User, notice: str | None = None,
                  error: str | None = None) -> HTMLResponse:
    from .common import shell_context

    users = list(db.scalars(select(User).order_by(User.id)))
    frames = list(db.scalars(select(Frame).order_by(Frame.id)))
    links = list(db.scalars(select(UserFrame)))
    links_by_frame: dict[int, list[User]] = {}
    users_by_id = {u.id: u for u in users}
    for link in links:
        links_by_frame.setdefault(link.frame_id, []).append(users_by_id[link.user_id])
    from ..image_pipeline import PANEL_LABELS

    ctx = shell_context(request, db, admin, active_nav="admin")
    ctx.update({
        "users": users,
        "frames": frames,
        "links_by_frame": links_by_frame,
        "smtp": get_server_settings(db),
        "notice": notice,
        "error": error,
        "active_admin_tab": "main",
        "panel_labels": PANEL_LABELS,
    })
    return templates.TemplateResponse("admin.html", ctx)


@router.get("/admin", response_class=HTMLResponse)
def admin_page(request: Request, db: Session = Depends(get_db)):
    user = current_user(request, db)
    if user is None:
        return RedirectResponse("/login", status_code=303)
    if not user.is_admin:
        raise HTTPException(403, "Admin only")
    return _render_admin(request, db, user)


@router.get("/admin/logs", response_class=HTMLResponse)
def admin_logs_page(request: Request, lines: int = 500, db: Session = Depends(get_db)):
    user = current_user(request, db)
    if user is None:
        return RedirectResponse("/login", status_code=303)
    if not user.is_admin:
        raise HTTPException(403, "Admin only")
    from .common import shell_context

    lines = max(50, min(lines, 5000))
    ctx = shell_context(request, db, user, active_nav="admin")
    ctx.update({
        "active_admin_tab": "logs",
        "log_exists": LOG_PATH.exists(),
        "log_path": str(LOG_PATH),
        "log_lines": lines,
        "log_text": read_log_tail(lines),
    })
    return templates.TemplateResponse("admin_logs.html", ctx)


@router.get("/admin/logs/download")
def admin_logs_download(request: Request, db: Session = Depends(get_db)):
    _require_admin_page(request, db)
    if not LOG_PATH.exists():
        raise HTTPException(404, "No log file yet")
    return FileResponse(LOG_PATH, filename="server.log", media_type="text/plain")


@router.post("/admin/users", response_class=HTMLResponse)
def admin_create_user(
    request: Request,
    csrf_token: str = Form(""),
    username: str = Form(...),
    password: str = Form(...),
    is_admin: bool = Form(False),
    db: Session = Depends(get_db),
):
    admin = _require_admin_page(request, db)
    _check_form_csrf(request, db, csrf_token)
    username = _validate_credentials(username, password)
    if db.scalars(select(User).where(User.username == username)).first() is not None:
        return _render_admin(request, db, admin, error=f"Username '{username}' already exists.")
    db.add(User(
        username=username,
        display_name=username,
        password_hash=hash_password(password),
        is_admin=is_admin,
        created_at=time.time(),
    ))
    db.commit()
    return _render_admin(request, db, admin, notice=f"User '{username}' created.")


@router.post("/admin/users/{user_id}/reset-password", response_class=HTMLResponse)
def admin_reset_password(
    user_id: int,
    request: Request,
    csrf_token: str = Form(""),
    password: str = Form(...),
    db: Session = Depends(get_db),
):
    admin = _require_admin_page(request, db)
    _check_form_csrf(request, db, csrf_token)
    target = db.get(User, user_id)
    if target is None:
        return _render_admin(request, db, admin, error="No such user.")
    if len(password) < PASSWORD_MIN_LEN:
        return _render_admin(request, db, admin,
                             error=f"Password must be at least {PASSWORD_MIN_LEN} characters.")
    target.password_hash = hash_password(password)
    db.commit()
    return _render_admin(request, db, admin, notice=f"Password reset for '{target.username}'.")


@router.post("/admin/users/{user_id}/delete", response_class=HTMLResponse)
def admin_delete_user(
    user_id: int,
    request: Request,
    csrf_token: str = Form(""),
    db: Session = Depends(get_db),
):
    admin = _require_admin_page(request, db)
    _check_form_csrf(request, db, csrf_token)
    if user_id == admin.id:
        return _render_admin(request, db, admin, error="You can't delete your own account.")
    target = db.get(User, user_id)
    if target is None:
        return _render_admin(request, db, admin, error="No such user.")
    name = target.username
    db.delete(target)  # sessions/links cascade; frames.owner goes NULL
    db.commit()
    return _render_admin(request, db, admin, notice=f"User '{name}' deleted.")


@router.post("/admin/frames/{frame_id}/link-user", response_class=HTMLResponse)
def admin_link_user(
    frame_id: int,
    request: Request,
    csrf_token: str = Form(""),
    username: str = Form(...),
    db: Session = Depends(get_db),
):
    admin = _require_admin_page(request, db)
    _check_form_csrf(request, db, csrf_token)
    frame = db.get(Frame, frame_id)
    target = db.scalars(select(User).where(User.username == _normalize_username(username))).first()
    if frame is None or target is None:
        return _render_admin(request, db, admin, error="No such frame or user.")
    if db.get(UserFrame, (target.id, frame_id)) is not None:
        return _render_admin(request, db, admin, error=f"'{target.username}' is already linked.")
    db.add(UserFrame(user_id=target.id, frame_id=frame_id))
    if frame.owner_user_id is None:
        # Linking to an unclaimed frame claims it -- the admin flow for
        # adopting a frame that self-registered without a pending claim.
        frame.owner_user_id = target.id
        frame.claimed_at = time.time()
    db.commit()
    return _render_admin(request, db, admin,
                         notice=f"Linked '{target.username}' to frame #{frame_id}.")


@router.post("/admin/smtp", response_class=HTMLResponse)
def admin_smtp_save(
    request: Request,
    csrf_token: str = Form(""),
    smtp_host: str = Form(""),
    smtp_port: int = Form(587),
    smtp_username: str = Form(""),
    smtp_password: str = Form(""),
    smtp_from_address: str = Form(""),
    smtp_encryption: str = Form("starttls"),
    db: Session = Depends(get_db),
):
    """Saves the SMTP config used for password-reset emails and battery-
    threshold alerts. Blank password = keep the existing one, same
    round-trip-avoidance as the Immich API key field in /settings."""
    admin = _require_admin_page(request, db)
    _check_form_csrf(request, db, csrf_token)
    settings = get_server_settings(db)
    settings.smtp_host = smtp_host.strip()
    settings.smtp_port = max(1, min(65535, smtp_port))
    settings.smtp_username = smtp_username.strip()
    if smtp_password.strip():
        settings.smtp_password = smtp_password.strip()
    settings.smtp_from_address = smtp_from_address.strip()
    settings.smtp_encryption = smtp_encryption if smtp_encryption in ("none", "starttls", "ssl") else "starttls"
    db.commit()
    return _render_admin(request, db, admin, notice="SMTP settings saved.")


@router.post("/admin/smtp/test", response_class=HTMLResponse)
def admin_smtp_test(request: Request, csrf_token: str = Form(""), db: Session = Depends(get_db)):
    admin = _require_admin_page(request, db)
    _check_form_csrf(request, db, csrf_token)
    if not admin.email:
        return _render_admin(request, db, admin, error="Set an email on your own account (Settings) to test SMTP.")
    settings = get_server_settings(db)
    ok = mail.send_email(
        settings, admin.email, "ESPresso Frame test email",
        "If you're reading this, SMTP is configured correctly.",
    )
    if ok:
        return _render_admin(request, db, admin, notice=f"Test email sent to {admin.email}.")
    return _render_admin(request, db, admin, error="Failed to send -- check the SMTP settings and server logs.")


@router.post("/admin/frames/{frame_id}/delete", response_class=HTMLResponse)
def admin_delete_frame(
    frame_id: int,
    request: Request,
    csrf_token: str = Form(""),
    db: Session = Depends(get_db),
):
    admin = _require_admin_page(request, db)
    _check_form_csrf(request, db, csrf_token)
    frame = db.get(Frame, frame_id)
    if frame is None:
        return _render_admin(request, db, admin, error="No such frame.")
    db.delete(frame)  # links/battery log cascade
    db.commit()
    return _render_admin(request, db, admin, notice=f"Frame #{frame_id} deleted.")