"""Invite redemption endpoints.

Deliberately *not* nested under ``/organizations/{org_id}``: the person
accepting an invite is by definition not yet a member, so ``get_org_context``
would (correctly) refuse them. Here the invite token itself is the
authorization. It is stored only as a hash and is single-use.

Because signup is closed (accounts come from the owner or from an invite), the
token doubles as an account-creation capability: a brand-new invitee redeems
it **with a password**, which creates their account bound to the invited email
and joins the organization in one step. The token can never reset the password
of an *existing* account — those must authenticate first, which keeps a leaked
link from taking over an account that already exists.
"""

from __future__ import annotations

from datetime import UTC, datetime

from fastapi import APIRouter, Depends, Request, status
from pydantic import BaseModel, Field
from sqlalchemy.ext.asyncio import AsyncSession

from app.application.services.audit_service import record_audit
from app.core.database import get_session
from app.core.errors import (
    ConflictError,
    NotFoundError,
    PermissionDeniedError,
    ValidationError,
)
from app.core.security import hash_password, hash_token
from app.domain.audit.models import AuditAction
from app.domain.identity.models import (
    Invite,
    Membership,
    MembershipStatus,
    Organization,
    PlatformRole,
    User,
)
from app.infrastructure.repositories.identity import (
    InviteRepository,
    MembershipRepository,
    OrganizationRepository,
    UserRepository,
)
from app.interfaces.http.deps import client_meta, get_optional_user

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


class InvitePreview(BaseModel):
    organization_id: str
    organization_name: str
    email: str
    role: str
    expires_at: datetime
    #: True when the caller is already a member, so the UI can say "open it"
    #: instead of "join".
    already_member: bool
    #: True when an account exists for the invited email. The invitee then logs
    #: in first; anonymous redemption with a password is only for brand-new
    #: accounts (a token must never be able to reset an existing password).
    has_account: bool


class AcceptInviteRequest(BaseModel):
    token: str
    #: Required only when redeeming anonymously — it becomes the password of
    #: the account the invite creates. Ignored for a signed-in user, who has
    #: already proven ownership of the email.
    password: str | None = Field(default=None, min_length=8, max_length=128)


class AcceptInviteResult(BaseModel):
    organization_id: str
    organization_name: str
    role: str


async def _load_pending_invite(
    token: str, user: User | None, session: AsyncSession
) -> tuple[Invite, Organization]:
    """Resolve a raw token into a redeemable invite, or raise.

    Every rejection is a distinct, user-actionable error rather than a generic
    "invalid link": the real failure modes (already used, expired, wrong
    account) each need a different response from the person holding the link.

    The email binding is only enforced when a user is signed in: an anonymous
    holder of the token sees the preview but must create an account for exactly
    the invited email, which the accept path checks.
    """
    invite = await InviteRepository(session).get_by_token_hash(hash_token(token))
    if invite is None:
        raise NotFoundError("این لینک دعوت معتبر نیست.")
    if invite.accepted_at is not None:
        raise ConflictError("این دعوت‌نامه قبلاً پذیرافته شده است.")
    if invite.is_expired():
        raise ValidationError("این دعوت‌نامه منقضی شده است؛ از مدیر بخواهید دوباره دعوت کند.")
    if user is not None and invite.email.strip().lower() != user.email.strip().lower():
        raise PermissionDeniedError(
            "این دعوت‌نامه برای ایمیل دیگری صادر شده است؛ با همان ایمیل وارد شوید.",
            details={"invite_email": invite.email},
        )

    organization = await OrganizationRepository(session).get(invite.organization_id)
    if organization is None:
        raise NotFoundError("سازمان این دعوت‌نامه دیگر وجود ندارد.")
    return invite, organization


@router.get("/{token}", response_model=InvitePreview)
async def preview_invite(
    token: str,
    user: User | None = Depends(get_optional_user),
    session: AsyncSession = Depends(get_session),
) -> InvitePreview:
    """Show the invitee what they are about to join, without joining yet.

    Works without a session on purpose: a brand-new invitee must be able to
    see which organization invited them (and whether they already have an
    account) *before* deciding to sign in or create one.
    """
    invite, organization = await _load_pending_invite(token, user, session)
    existing_user = await UserRepository(session).get_by_email(invite.email)
    membership = (
        await MembershipRepository(session).get(organization.id, user.id)
        if user is not None
        else None
    )
    return InvitePreview(
        organization_id=organization.id,
        organization_name=organization.name,
        email=invite.email,
        role=invite.role.value,
        expires_at=invite.expires_at,
        already_member=membership is not None,
        has_account=existing_user is not None,
    )


@router.post("/accept", response_model=AcceptInviteResult, status_code=status.HTTP_200_OK)
async def accept_invite(
    payload: AcceptInviteRequest,
    request: Request,
    user: User | None = Depends(get_optional_user),
    session: AsyncSession = Depends(get_session),
) -> AcceptInviteResult:
    """Redeem an invite: create the account if needed, join, and burn the token.

    Two redemption paths, one outcome:

    - **Signed in** — the account already exists and has proven ownership of
      the invited email; no password is needed.
    - **Anonymous** — the invite itself is the capability: a *new* account is
      created for the invited email with the supplied password and joins the
      organization. If an account for that email already exists, the caller
      must authenticate first — a link can never become a password reset.

    Idempotent by construction — accepting twice is a no-op the second time,
    so a double-click or a retried request cannot create two memberships.
    """
    invite, organization = await _load_pending_invite(payload.token, user, session)
    users = UserRepository(session)
    memberships = MembershipRepository(session)

    created_account = False
    if user is None:
        existing = await users.get_by_email(invite.email)
        if existing is not None:
            raise PermissionDeniedError(
                "برای این ایمیل قبلاً حساب ساخته شده است؛ وارد شوید و سپس دعوت را بپذیرید."
            )
        if not payload.password:
            raise ValidationError("برای ساخت حساب جدید، تعیین رمز عبور الزامی است.")
        user = await users.create(
            User(
                email=invite.email,
                password_hash=hash_password(payload.password),
                name="",
                platform_role=PlatformRole.USER,
            )
        )
        created_account = True

    if await memberships.get(organization.id, user.id) is None:
        await memberships.add(
            Membership(
                organization_id=organization.id,
                user_id=user.id,
                role=invite.role,
                status=MembershipStatus.ACTIVE,
            )
        )
        ip, ua = client_meta(request)
        await record_audit(
            session,
            action=AuditAction.MEMBER_JOIN,
            organization_id=organization.id,
            actor_user_id=user.id,
            target_type="invite",
            target_id=invite.id,
            metadata={"email": invite.email, "role": invite.role.value},
            ip=ip,
            user_agent=ua,
        )
        if created_account:
            # Account creation is audited separately from the join: one is a
            # platform identity event, the other a tenant event.
            ip, ua = client_meta(request)
            await record_audit(
                session,
                action=AuditAction.SIGNUP,
                actor_user_id=user.id,
                target_type="user",
                target_id=user.id,
                metadata={"via": "invite", "organization_id": organization.id},
                ip=ip,
                user_agent=ua,
            )

    # Burn the token regardless: whether the membership was just created or
    # already existed, this invite must not be redeemable a second time.
    await InviteRepository(session).mark_accepted(invite.id, datetime.now(UTC))
    return AcceptInviteResult(
        organization_id=organization.id,
        organization_name=organization.name,
        role=invite.role.value,
    )