from datetime import datetime, timezone
from bson import ObjectId

from app.services.message_ids import build_references_header, normalize_message_id, parse_message_id_list
from app.services.subject_normalize import normalize_subject
from app.services.thread_resolver import KnownMessage, resolve_thread_from_known


def _known(
    internet_id: str,
    thread_id: ObjectId,
    account_id: str = "acct-1",
    participants: frozenset[str] | None = None,
) -> KnownMessage:
    now = datetime.now(timezone.utc)
    return KnownMessage(
        id=ObjectId(),
        thread_id=thread_id,
        internet_message_id=normalize_message_id(internet_id) or "",
        account_id=account_id,
        sent_at=now,
        received_at=now,
        created_at=now,
        participants=participants or frozenset({"sender@example.com"}),
        normalized_subject=normalize_subject("Project update"),
    )


def test_new_message_creates_new_thread():
    resolution = resolve_thread_from_known(
        account_id="acct-1",
        in_reply_to=None,
        references=[],
        subject="Project update",
        participants={"sender@example.com"},
        known_by_internet_id={},
    )
    assert resolution.thread_id is None
    assert resolution.thread_resolution_method == "new_thread"
    assert resolution.thread_relation == "new_thread"


def test_direct_reply_matches_in_reply_to():
    thread_id = ObjectId()
    parent = _known("<a@gentic.email>", thread_id)
    known = {parent.internet_message_id: parent}
    resolution = resolve_thread_from_known(
        account_id="acct-1",
        in_reply_to="<a@gentic.email>",
        references=["<a@gentic.email>"],
        subject="Re: Project update",
        participants={"rahul@example.com"},
        known_by_internet_id=known,
    )
    assert resolution.thread_id == thread_id
    assert resolution.thread_resolution_method == "in_reply_to"
    assert resolution.parent_message_id == parent.id


def test_references_fallback_when_parent_missing():
    thread_id = ObjectId()
    parent = _known("<a@gentic.email>", thread_id)
    known = {parent.internet_message_id: parent}
    resolution = resolve_thread_from_known(
        account_id="acct-1",
        in_reply_to="<b@example.com>",
        references=["<a@gentic.email>", "<b@example.com>"],
        subject="Re: Project update",
        participants={"rahul@example.com"},
        known_by_internet_id=known,
    )
    assert resolution.thread_id == thread_id
    assert resolution.thread_resolution_method == "references"


def test_fake_re_subject_does_not_thread():
    thread_id = ObjectId()
    parent = _known("<a@gentic.email>", thread_id)
    known = {parent.internet_message_id: parent}
    resolution = resolve_thread_from_known(
        account_id="acct-1",
        in_reply_to=None,
        references=[],
        subject="Re: Project update",
        participants={"rahul@example.com"},
        known_by_internet_id=known,
    )
    assert resolution.thread_id is None
    assert resolution.thread_resolution_method == "new_thread"


def test_changed_subject_with_valid_reply_headers():
    thread_id = ObjectId()
    parent = _known("<a@gentic.email>", thread_id)
    known = {parent.internet_message_id: parent}
    resolution = resolve_thread_from_known(
        account_id="acct-1",
        in_reply_to="<a@gentic.email>",
        references=[],
        subject="Completely changed subject",
        participants={"rahul@example.com"},
        known_by_internet_id=known,
    )
    assert resolution.thread_id == thread_id


def test_cross_tenant_message_is_ignored():
    thread_id = ObjectId()
    parent = _known("<a@gentic.email>", thread_id, account_id="other-acct")
    known = {parent.internet_message_id: parent}
    resolution = resolve_thread_from_known(
        account_id="acct-1",
        in_reply_to="<a@gentic.email>",
        references=[],
        subject="Re: Project update",
        participants={"rahul@example.com"},
        known_by_internet_id=known,
    )
    assert resolution.thread_id is None


def test_build_references_header_appends_parent():
    header = build_references_header(["<a@gentic.email>"], "<b@example.com>")
    assert header == "<a@gentic.email> <b@example.com>"


def test_parse_message_id_list_handles_folded_references():
    values = parse_message_id_list("<a@gentic.email>\r\n <b@example.com>")
    assert values == ["<a@gentic.email>", "<b@example.com>"]