"""Small cross-cutting helpers shared across modules (kept dependency-light on purpose)."""

import re
from datetime import date, datetime, timezone


def iso(dt: date | None) -> str | None:
    """Serialize a date/datetime for a JSON response: ISO-8601, or None when the column is
    NULL. Single source of truth for the `x.isoformat() if x else None` idiom the routes had
    hand-rolled ~17 times — so a future tz/format tweak lands in one place. Accepts `date`
    too (datetime is a subclass) — e.g. MediaAsset.upload_date is a plain `date`."""
    return dt.isoformat() if dt is not None else None


# Single source of truth for "looks like an email" — used by every endpoint that accepts an
# address (auth register/reset/demo, admin invites + demo whitelist, the setup wizard). Keep
# the strictness in one place so routes don't drift between this and a looser "@"-in check.
_EMAIL_RE = re.compile(r"^[^@\s]+@[^@\s]+\.[^@\s]+$")


def valid_email(value: str | None) -> bool:
    return bool(value and _EMAIL_RE.match(value))


# Gmail (and its googlemail.com alias) delivers to one mailbox regardless of dots in the local part
# and of any `+tag`; nobody else is guaranteed to. So the canonical form below strips those for
# Gmail only, and merely lowercases everything else.
_GMAIL_DOMAINS = {"gmail.com", "googlemail.com"}


def canonical_email(value: str | None) -> str:
    """The form used to decide whether two addresses are the SAME MAILBOX. Never used for sending —
    mail always goes to the address as the user typed it.

    Why this exists (observed on prod, 2026-09-03): someone registered as `npeter83.temu@gmail.com`
    and was approved, but Google's OAuth `email` claim came back as the account's stored primary,
    `npeter83temu@gmail.com`. The invite gate only lowercased, found no approved row for that literal
    string, and turned an approved user's sign-in into a silent SECOND access request — plus a second
    User row. The `+tag` case is worse and fails every time: a Google account cannot contain `+`, so
    OAuth can only ever return the base address, meaning anyone who registers with
    `user+siftlode@gmail.com` (a common throwaway habit) is guaranteed to be denied after approval.

    Scope is deliberately narrow. The dot rule does NOT hold for Google Workspace custom domains
    unless the admin turned it on, and dots are significant on most providers, so anything outside
    gmail.com/googlemail.com is only lowercased. Approving one Gmail spelling always did mean
    approving that mailbox, so collapsing them is the honest reading of an invite, not a widening
    of it.
    """
    email = (value or "").strip().lower()
    local, sep, domain = email.partition("@")
    if not sep or domain not in _GMAIL_DOMAINS:
        return email
    local = local.partition("+")[0].replace(".", "")
    # Normalise the alias domain too, so googlemail and gmail spellings meet.
    return f"{local}@gmail.com" if local else email


def now_utc() -> datetime:
    """Current time as a timezone-aware UTC datetime."""
    return datetime.now(timezone.utc)


# The shortest last word that is prefix-matched. A 1–2 letter prefix matches a large share of the
# library and ts_rank then scores every match: "m" took ~5–8 s on prod against ~100 ms for a whole
# word (E31 S4e). A shorter last word is matched whole instead ("tv", "4k" still find themselves).
MIN_PREFIX_LEN = 3


def to_tsquery_str(q: str) -> str | None:
    """Turn free-text into a to_tsquery() string: word runs ANDed together, the LAST word
    prefix-matched (`:*`) for as-you-type search — e.g. "ti amo magyar" → "ti & amo & magyar:*" —
    once it has MIN_PREFIX_LEN characters ("ti amo m" → "ti & amo & m").
    Only `\\w` runs containing an alphanumeric are kept, so no tsquery operators can leak in
    (the string is built from sanitised tokens, never the raw query). Shared by the YouTube feed
    search and the Plex library search, hence this neutral home rather than either domain module."""
    tokens = [t for t in re.findall(r"\w+", q, flags=re.UNICODE) if any(c.isalnum() for c in t)]
    if not tokens:
        return None
    if len(tokens[-1]) >= MIN_PREFIX_LEN:
        tokens[-1] = tokens[-1] + ":*"
    return " & ".join(tokens)


def like_escape(s: str) -> str:
    """`s` as a LITERAL inside a LIKE/ILIKE pattern: `%` and `_` are wildcards there, and `\\` is
    Postgres's default escape character, so all three are escaped. Every pattern built from text a
    person typed goes through this — unescaped, a search for `100%` or `my_channel` matches rows it
    should not."""
    return s.replace("\\", "\\\\").replace("%", "\\%").replace("_", "\\_")


def normalize_description(text: str | None) -> str | None:
    """Strip whitespace-only lines from a CHANNEL description before storing. YouTube channel
    descriptions pad their contact/link blocks with runs of blank lines; keeping them wastes storage,
    bloats the About popover, and adds nothing to the search document. Drops purely-empty lines and
    right-strips each kept line; `str.splitlines()` also folds CR / CRLF and Unicode line separators
    to "\\n" (a benign line-ending normalization). None stays None; all-blank collapses to "".

    Deliberately CHANNEL-only — video descriptions are left with their original formatting: they are
    user-facing prose where paragraph breaks carry meaning, unlike a channel's metadata block."""
    if text is None:
        return None
    kept = [line.rstrip() for line in text.splitlines() if line.strip()]
    return "\n".join(kept)