"""
Router messaggi PEC.

Fornisce:
  - GET  /messages              - lista messaggi con filtri (inbox/sent/search/...)
  - GET  /messages/{id}         - singolo messaggio
  - PATCH /messages/{id}        - aggiorna flags (is_read, is_starred, is_archived, is_trashed,
                                  is_pending_conservation, is_conserved)
  - PATCH /messages/bulk        - aggiorna in blocco piu messaggi
  - GET  /messages/{id}/attachments           - lista allegati
  - GET  /messages/{id}/attachments/{att_id}/download - scarica allegato da MinIO
  - GET  /messages/{id}/receipts              - ricevute (messaggi figlio)

Permessi:
  - Admin: accede a tutti i messaggi del proprio tenant.
  - Operator/Supervisor/Readonly: solo i messaggi delle caselle su cui
    hanno almeno il permesso can_read.
  - is_pending_conservation / is_conserved: richiedono can_conserve
    (implicito per admin, esplicito per supervisor/operator).
"""

import uuid
from datetime import datetime, timezone
from typing import Optional

from fastapi import APIRouter, Query, status
from fastapi.responses import StreamingResponse
from sqlalchemy import func, or_, select
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.orm import selectinload

from app.services.search_service import SearchService

from app.config import get_settings
from app.core.exceptions import ForbiddenError, NotFoundError
from app.database import get_db
from app.dependencies import CurrentUser, DB
from app.models.label import Label
from app.models.message import Attachment, Message
from app.schemas.message import (
    AttachmentResponse,
    MessageBulkUpdateRequest,
    MessageBulkUpdateResponse,
    MessageListResponse,
    MessageResponse,
    MessageUpdateRequest,
)

router = APIRouter(prefix="/messages", tags=["Messages"])
settings = get_settings()


# ─── Helpers ──────────────────────────────────────────────────────────────────

def _apply_vbox_rule(q, field: str, operator: str, value: str):
    """
    Applica una singola regola di Virtual Box alla query SQLAlchemy.

    field    : subject | from_address | to_address | imap_folder
    operator : contains | equals | starts_with | ends_with | regex
    """
    if field == "subject":
        col = Message.subject
    elif field == "from_address":
        col = Message.from_address
    elif field == "to_address":
        arr_text = func.array_to_string(Message.to_addresses, ",")
        if operator == "contains":
            return q.where(arr_text.ilike(f"%{value}%"))
        elif operator == "equals":
            return q.where(arr_text.ilike(value))
        elif operator == "starts_with":
            return q.where(arr_text.ilike(f"{value}%"))
        elif operator == "ends_with":
            return q.where(arr_text.ilike(f"%{value}"))
        elif operator == "regex":
            return q.where(arr_text.op("~*")(value))
        return q
    elif field == "imap_folder":
        col = Message.imap_folder
    else:
        return q

    if operator == "contains":
        return q.where(col.ilike(f"%{value}%"))
    elif operator == "equals":
        return q.where(func.lower(col) == value.lower())
    elif operator == "starts_with":
        return q.where(col.ilike(f"{value}%"))
    elif operator == "ends_with":
        return q.where(col.ilike(f"%{value}"))
    elif operator == "regex":
        return q.where(col.op("~*")(value))
    return q


async def _get_visible_mailbox_ids(
    user, db: AsyncSession
) -> Optional[list[uuid.UUID]]:
    """
    Per utenti non-admin/supervisor restituisce la lista di mailbox_id accessibili.
    Restituisce None se l'utente e' admin o supervisor (accesso illimitato al tenant).
    """
    if user.is_supervisor_or_admin:
        return None

    from app.services.permission_service import PermissionService
    perm_svc = PermissionService(db)
    return await perm_svc.get_visible_mailboxes(user)


async def _resolve_message(
    message_id: uuid.UUID,
    current_user,
    db: AsyncSession,
) -> Message:
    """Carica il messaggio e verifica i permessi di accesso."""
    result = await db.execute(
        select(Message)
        .where(
            Message.id == message_id,
            Message.tenant_id == current_user.tenant_id,
        )
        .options(selectinload(Message.labels))
    )
    message = result.scalar_one_or_none()
    if not message:
        raise NotFoundError(f"Messaggio {message_id} non trovato")

    if not current_user.is_admin:
        from app.services.permission_service import PermissionService
        perm_svc = PermissionService(db)
        has_direct_access = await perm_svc.check_can_read(current_user, message.mailbox_id)

        if not has_direct_access:
            from app.models.virtual_box import (
                VirtualBox,
                VirtualBoxAssignment,
                virtual_box_mailboxes,
            )
            vbox_result = await db.execute(
                select(VirtualBox.id)
                .join(
                    VirtualBoxAssignment,
                    VirtualBox.id == VirtualBoxAssignment.virtual_box_id,
                )
                .join(
                    virtual_box_mailboxes,
                    VirtualBox.id == virtual_box_mailboxes.c.virtual_box_id,
                )
                .where(
                    VirtualBoxAssignment.user_id == current_user.id,
                    virtual_box_mailboxes.c.mailbox_id == message.mailbox_id,
                    VirtualBox.tenant_id == current_user.tenant_id,
                    VirtualBox.is_active == True,
                )
                .limit(1)
            )
            has_vbox_access = vbox_result.scalar_one_or_none() is not None

            if not has_vbox_access:
                raise ForbiddenError("Accesso al messaggio non autorizzato")

    return message


# ─── Endpoints ───────────────────────────────────────────────────────────────

@router.get("", response_model=MessageListResponse)
async def list_messages(
    current_user: CurrentUser,
    db: DB,
    # Filtri
    vbox_id: Optional[uuid.UUID] = Query(None, description="Filtra per Virtual Box assegnata"),
    mailbox_id: Optional[uuid.UUID] = Query(None),
    direction: Optional[str] = Query(None, pattern="^(inbound|outbound)$"),
    state: Optional[str] = Query(None),
    is_read: Optional[bool] = Query(None),
    is_starred: Optional[bool] = Query(None),
    is_archived: Optional[bool] = Query(False),
    is_trashed: Optional[bool] = Query(False),
    is_pending_conservation: Optional[bool] = Query(None, description="Filtra per messaggi in attesa di conservazione"),
    is_conserved: Optional[bool] = Query(None, description="Filtra per messaggi gia' conservati"),
    search: Optional[str] = Query(None, max_length=500),
    pec_type: Optional[str] = Query(None),
    date_from: Optional[datetime] = Query(None, description="Data minima (received_at o sent_at)"),
    date_to: Optional[datetime] = Query(None, description="Data massima (received_at o sent_at)"),
    page: int = Query(1, ge=1),
    page_size: int = Query(50, ge=1, le=200),
) -> MessageListResponse:
    """
    Elenca i messaggi PEC con filtri opzionali.

    - `is_archived=False` (default) esclude i messaggi archiviati.
    - `is_trashed=False` (default) esclude i messaggi nel cestino.
    - `is_pending_conservation` filtra messaggi da conservare (cartella Da Conservare).
    - `is_conserved` filtra messaggi gia' conservati (cartella Storico).
    - `search` usa ricerca full-text (tsvector) con fallback ILIKE.
    """
    visible_mailbox_ids = await _get_visible_mailbox_ids(current_user, db)

    # ── Filtro Virtual Box ────────────────────────────────────────────────────
    vbox_rules: list = []
    if vbox_id is not None:
        from app.models.virtual_box import VirtualBox, VirtualBoxAssignment

        vbox_result = await db.execute(
            select(VirtualBox)
            .where(
                VirtualBox.id == vbox_id,
                VirtualBox.tenant_id == current_user.tenant_id,
                VirtualBox.is_active == True,
            )
            .options(
                selectinload(VirtualBox.rules),
                selectinload(VirtualBox.mailboxes),
            )
        )
        vbox = vbox_result.scalar_one_or_none()
        if not vbox:
            raise NotFoundError("Virtual Box")

        if not current_user.is_admin:
            assign_result = await db.execute(
                select(VirtualBoxAssignment).where(
                    VirtualBoxAssignment.virtual_box_id == vbox_id,
                    VirtualBoxAssignment.user_id == current_user.id,
                )
            )
            if not assign_result.scalar_one_or_none():
                raise ForbiddenError("Virtual Box non accessibile")

        if vbox.mailboxes:
            visible_mailbox_ids = [m.id for m in vbox.mailboxes]

        vbox_rules = vbox.rules or []

    # Query base
    q = select(Message).where(
        Message.tenant_id == current_user.tenant_id,
        Message.parent_message_id.is_(None),
    )

    if visible_mailbox_ids is not None:
        if not visible_mailbox_ids:
            return MessageListResponse(items=[], total=0, page=page, page_size=page_size)
        q = q.where(Message.mailbox_id.in_(visible_mailbox_ids))

    if mailbox_id is not None:
        if visible_mailbox_ids is not None and mailbox_id not in visible_mailbox_ids:
            raise ForbiddenError("Accesso alla casella non autorizzato")
        q = q.where(Message.mailbox_id == mailbox_id)

    if direction is not None:
        q = q.where(Message.direction == direction)

    if state is not None:
        q = q.where(Message.state == state)

    if pec_type is not None:
        q = q.where(Message.pec_type == pec_type)

    if is_read is not None:
        q = q.where(Message.is_read == is_read)

    if is_starred is not None:
        q = q.where(Message.is_starred == is_starred)

    if is_archived is not None:
        q = q.where(Message.is_archived == is_archived)

    if is_trashed is not None:
        q = q.where(Message.is_trashed == is_trashed)

    # ── Filtri Conservazione ──────────────────────────────────────────────────
    if is_pending_conservation is not None:
        q = q.where(Message.is_pending_conservation == is_pending_conservation)

    if is_conserved is not None:
        q = q.where(Message.is_conserved == is_conserved)

    # ── Full-text search ──────────────────────────────────────────────────────
    if search:
        from sqlalchemy import case as sa_case

        tsquery = func.websearch_to_tsquery("italian", search)
        term_like = f"%{search}%"
        q = q.where(
            or_(
                Message.search_vector.op("@@")(tsquery),
                Message.search_vector.is_(None) & or_(
                    Message.subject.ilike(term_like),
                    Message.from_address.ilike(term_like),
                    Message.body_text.ilike(term_like),
                ),
            )
        )

    # ── Filtri data ───────────────────────────────────────────────────────────
    if date_from:
        q = q.where(or_(Message.received_at >= date_from, Message.sent_at >= date_from))
    if date_to:
        q = q.where(or_(Message.received_at <= date_to, Message.sent_at <= date_to))

    for rule in vbox_rules:
        q = _apply_vbox_rule(q, rule.field, rule.operator, rule.value)

    count_q = select(func.count()).select_from(q.subquery())
    total = (await db.execute(count_q)).scalar_one()

    if search:
        from sqlalchemy import case as sa_case

        tsquery_ord = func.websearch_to_tsquery("italian", search)
        rank_expr = sa_case(
            (Message.search_vector.isnot(None), func.ts_rank(Message.search_vector, tsquery_ord)),
            else_=0.0,
        )
        order_clauses = [rank_expr.desc(), Message.received_at.desc().nullslast(), Message.created_at.desc()]
    else:
        order_clauses = [Message.received_at.desc().nullslast(), Message.created_at.desc()]

    q = (
        q.options(selectinload(Message.labels))
        .order_by(*order_clauses)
        .offset((page - 1) * page_size)
        .limit(page_size)
    )

    result = await db.execute(q)
    items = list(result.scalars().all())

    return MessageListResponse(
        items=[MessageResponse.model_validate(m) for m in items],
        total=total,
        page=page,
        page_size=page_size,
    )


@router.patch("/bulk", response_model=MessageBulkUpdateResponse)
async def bulk_update_messages(
    data: MessageBulkUpdateRequest,
    current_user: CurrentUser,
    db: DB,
) -> MessageBulkUpdateResponse:
    """
    Aggiorna in blocco i flag operativi di piu messaggi.

    Per is_pending_conservation=True o is_conserved=True richiede can_conserve.
    """
    if not data.ids:
        return MessageBulkUpdateResponse(updated=0, items=[])

    result = await db.execute(
        select(Message).where(
            Message.id.in_(data.ids),
            Message.tenant_id == current_user.tenant_id,
        )
    )
    messages = list(result.scalars().all())

    # Filtra per permessi di lettura
    if not current_user.is_admin:
        from app.services.permission_service import PermissionService
        perm_svc = PermissionService(db)
        visible = await perm_svc.get_visible_mailboxes(current_user)
        visible_set = set(visible) if visible else set()
        messages = [m for m in messages if m.mailbox_id in visible_set]

    # Se si tenta di modificare flag di conservazione, verifica can_conserve
    conservation_change = (
        data.is_pending_conservation is not None or data.is_conserved is not None
    )
    if conservation_change and messages:
        from app.services.permission_service import PermissionService
        perm_svc = PermissionService(db)
        # Verifica per ogni casella unica coinvolta
        mailbox_ids = {m.mailbox_id for m in messages}
        for mb_id in mailbox_ids:
            can = await perm_svc.check_can_conserve(current_user, mb_id)
            if not can:
                raise ForbiddenError(
                    "Permesso 'conservazione' non assegnato per questa casella"
                )

    now = datetime.now(timezone.utc)
    for message in messages:
        if data.is_read is not None:
            message.is_read = data.is_read
        if data.is_starred is not None:
            message.is_starred = data.is_starred
        if data.is_archived is not None:
            message.is_archived = data.is_archived
            if data.is_archived and not message.archived_at:
                message.archived_at = now
            elif not data.is_archived:
                message.archived_at = None
        if data.is_trashed is not None:
            message.is_trashed = data.is_trashed
            if data.is_trashed and not message.trashed_at:
                message.trashed_at = now
            elif not data.is_trashed:
                message.trashed_at = None
        if data.is_pending_conservation is not None:
            message.is_pending_conservation = data.is_pending_conservation
            if data.is_pending_conservation and not message.pending_conservation_at:
                message.pending_conservation_at = now
            elif not data.is_pending_conservation:
                message.pending_conservation_at = None
        if data.is_conserved is not None:
            message.is_conserved = data.is_conserved
            if data.is_conserved and not message.conserved_at:
                message.conserved_at = now
            elif not data.is_conserved:
                message.conserved_at = None

    await db.commit()

    if messages:
        updated_ids = [m.id for m in messages]
        refreshed_result = await db.execute(
            select(Message)
            .where(Message.id.in_(updated_ids))
            .options(selectinload(Message.labels))
        )
        messages = list(refreshed_result.scalars().all())

    return MessageBulkUpdateResponse(
        updated=len(messages),
        items=[MessageResponse.model_validate(m) for m in messages],
    )


@router.get("/{message_id}", response_model=MessageResponse)
async def get_message(
    message_id: uuid.UUID,
    current_user: CurrentUser,
    db: DB,
) -> MessageResponse:
    """Carica un messaggio per ID."""
    message = await _resolve_message(message_id, current_user, db)
    return MessageResponse.model_validate(message)


@router.patch("/{message_id}", response_model=MessageResponse)
async def update_message(
    message_id: uuid.UUID,
    data: MessageUpdateRequest,
    current_user: CurrentUser,
    db: DB,
) -> MessageResponse:
    """
    Aggiorna i flag operativi di un messaggio.

    Per is_pending_conservation=True o is_conserved=True richiede can_conserve.
    """
    message = await _resolve_message(message_id, current_user, db)

    # Verifica permesso conservazione se necessario
    if data.is_pending_conservation is not None or data.is_conserved is not None:
        from app.services.permission_service import PermissionService
        perm_svc = PermissionService(db)
        await perm_svc.require_can_conserve(current_user, message.mailbox_id)

    now = datetime.now(timezone.utc)

    if data.is_read is not None:
        message.is_read = data.is_read
    if data.is_starred is not None:
        message.is_starred = data.is_starred
    if data.is_archived is not None:
        message.is_archived = data.is_archived
        if data.is_archived and not message.archived_at:
            message.archived_at = now
        elif not data.is_archived:
            message.archived_at = None
    if data.is_trashed is not None:
        message.is_trashed = data.is_trashed
        if data.is_trashed and not message.trashed_at:
            message.trashed_at = now
        elif not data.is_trashed:
            message.trashed_at = None
    if data.is_pending_conservation is not None:
        message.is_pending_conservation = data.is_pending_conservation
        if data.is_pending_conservation and not message.pending_conservation_at:
            message.pending_conservation_at = now
        elif not data.is_pending_conservation:
            message.pending_conservation_at = None
    if data.is_conserved is not None:
        message.is_conserved = data.is_conserved
        if data.is_conserved and not message.conserved_at:
            message.conserved_at = now
        elif not data.is_conserved:
            message.conserved_at = None

    await db.commit()
    refreshed = await db.execute(
        select(Message)
        .where(Message.id == message_id)
        .options(selectinload(Message.labels))
    )
    message = refreshed.scalar_one()
    return MessageResponse.model_validate(message)


@router.get("/{message_id}/attachments", response_model=list[AttachmentResponse])
async def list_attachments(
    message_id: uuid.UUID,
    current_user: CurrentUser,
    db: DB,
) -> list[AttachmentResponse]:
    """Elenca gli allegati di un messaggio."""
    message = await _resolve_message(message_id, current_user, db)

    result = await db.execute(
        select(Attachment)
        .where(Attachment.message_id == message.id)
        .order_by(Attachment.created_at)
    )
    attachments = list(result.scalars().all())
    return [AttachmentResponse.model_validate(a) for a in attachments]


@router.get("/{message_id}/attachments/{attachment_id}/download")
async def download_attachment(
    message_id: uuid.UUID,
    attachment_id: uuid.UUID,
    current_user: CurrentUser,
    db: DB,
) -> StreamingResponse:
    """Scarica un allegato direttamente da MinIO."""
    await _resolve_message(message_id, current_user, db)

    result = await db.execute(
        select(Attachment).where(
            Attachment.id == attachment_id,
            Attachment.message_id == message_id,
        )
    )
    attachment = result.scalar_one_or_none()
    if not attachment:
        raise NotFoundError(f"Allegato {attachment_id} non trovato")

    try:
        from miniopy_async import Minio

        client = Minio(
            endpoint=settings.minio_endpoint,
            access_key=settings.minio_access_key,
            secret_key=settings.minio_secret_key,
            secure=settings.minio_use_ssl,
        )

        storage_path = attachment.storage_path
        response = await client.get_object(settings.minio_bucket, storage_path)

        content_type = attachment.content_type or "application/octet-stream"
        filename = attachment.filename.replace('"', "'")

        async def _stream():
            async for chunk in response.content.iter_chunked(65536):
                yield chunk
            response.close()

        return StreamingResponse(
            _stream(),
            media_type=content_type,
            headers={
                "Content-Disposition": f'attachment; filename="{filename}"',
                "Content-Length": str(attachment.size_bytes or ""),
            },
        )
    except Exception as e:
        from app.core.logging import get_logger
        logger = get_logger(__name__)
        logger.error(f"Errore download allegato {attachment_id}: {e}")
        raise NotFoundError("File non disponibile al momento")


@router.get("/{message_id}/download-package")
async def download_package(
    message_id: uuid.UUID,
    current_user: CurrentUser,
    db: DB,
) -> StreamingResponse:
    """Scarica un archivio ZIP con tutti i file originali della PEC."""
    import io
    import zipfile as _zipfile

    from miniopy_async import Minio

    message = await _resolve_message(message_id, current_user, db)

    client = Minio(
        endpoint=settings.minio_endpoint,
        access_key=settings.minio_access_key,
        secret_key=settings.minio_secret_key,
        secure=settings.minio_use_ssl,
    )

    buf = io.BytesIO()

    async def _read_minio(path: str) -> bytes:
        try:
            resp = await client.get_object(settings.minio_bucket, path)
            data = await resp.content.read()
            resp.close()
            return data
        except Exception:
            return b""

    with _zipfile.ZipFile(buf, mode="w", compression=_zipfile.ZIP_DEFLATED) as zf:
        att_result = await db.execute(
            select(Attachment)
            .where(Attachment.message_id == message.id)
            .order_by(Attachment.created_at)
        )
        main_attachments = list(att_result.scalars().all())

        for att in main_attachments:
            data = await _read_minio(att.storage_path)
            if data:
                zf.writestr(att.filename, data)

        if message.raw_eml_path:
            data = await _read_minio(message.raw_eml_path)
            if data:
                eml_name = message.raw_eml_path.rsplit("/", 1)[-1]
                if not eml_name.endswith(".eml"):
                    eml_name = "messaggio_originale.eml"
                existing = {info.filename for info in zf.infolist()}
                if eml_name not in existing:
                    zf.writestr(eml_name, data)

        if message.direction == "outbound":
            receipts_result = await db.execute(
                select(Message)
                .where(Message.parent_message_id == message.id)
                .order_by(Message.received_at.asc().nullslast(), Message.created_at.asc())
            )
            receipts = list(receipts_result.scalars().all())

            for receipt in receipts:
                pec_type = receipt.pec_type or "ricevuta"
                folder = f"ricevute/{pec_type}"

                r_att_result = await db.execute(
                    select(Attachment)
                    .where(Attachment.message_id == receipt.id)
                    .order_by(Attachment.created_at)
                )
                r_attachments = list(r_att_result.scalars().all())

                for att in r_attachments:
                    data = await _read_minio(att.storage_path)
                    if data:
                        zip_path = f"{folder}/{att.filename}"
                        existing = {info.filename for info in zf.infolist()}
                        final_path = zip_path
                        counter = 1
                        while final_path in existing:
                            name, _, ext = att.filename.rpartition(".")
                            final_path = f"{folder}/{name}_{counter}.{ext}" if ext else f"{folder}/{att.filename}_{counter}"
                            counter += 1
                        zf.writestr(final_path, data)

                if receipt.raw_eml_path:
                    data = await _read_minio(receipt.raw_eml_path)
                    if data:
                        eml_name = receipt.raw_eml_path.rsplit("/", 1)[-1]
                        if not eml_name.endswith(".eml"):
                            eml_name = f"{pec_type}.eml"
                        zip_path = f"{folder}/{eml_name}"
                        existing = {info.filename for info in zf.infolist()}
                        if zip_path not in existing:
                            zf.writestr(zip_path, data)

    buf.seek(0)
    zip_bytes = buf.getvalue()

    safe_subject = (message.subject or "pec").replace("/", "_").replace("\\", "_")[:50]
    zip_filename = f"pec_{safe_subject}.zip"

    return StreamingResponse(
        iter([zip_bytes]),
        media_type="application/zip",
        headers={
            "Content-Disposition": f'attachment; filename="{zip_filename}"',
            "Content-Length": str(len(zip_bytes)),
        },
    )


@router.get("/{message_id}/receipts", response_model=list[MessageResponse])
async def list_receipts(
    message_id: uuid.UUID,
    current_user: CurrentUser,
    db: DB,
) -> list[MessageResponse]:
    """Elenca le ricevute associate a un messaggio outbound."""
    await _resolve_message(message_id, current_user, db)

    result = await db.execute(
        select(Message)
        .where(Message.parent_message_id == message_id)
        .options(selectinload(Message.labels))
        .order_by(Message.received_at.asc().nullslast(), Message.created_at.asc())
    )
    receipts = list(result.scalars().all())
    return [MessageResponse.model_validate(r) for r in receipts]


# ─── Feature 3: Thread/conversazioni ─────────────────────────────────────────

@router.get("/{message_id}/thread", response_model=list[MessageResponse])
async def get_thread(
    message_id: uuid.UUID,
    current_user: CurrentUser,
    db: DB,
) -> list[MessageResponse]:
    """
    Restituisce l'intera conversazione (thread) di cui fa parte il messaggio.

    Risale alla radice della conversazione (risalendo i parent_message_id),
    poi carica tutti i messaggi del thread ordinati cronologicamente.
    Esclude le ricevute PEC (pec_type != posta_certificata).
    """
    message = await _resolve_message(message_id, current_user, db)

    # Risale alla radice del thread
    root_id = message.id
    visited: set[uuid.UUID] = {message.id}
    current = message
    while current.parent_message_id and current.parent_message_id not in visited:
        visited.add(current.parent_message_id)
        parent_result = await db.execute(
            select(Message).where(
                Message.id == current.parent_message_id,
                Message.tenant_id == current_user.tenant_id,
            )
        )
        parent = parent_result.scalar_one_or_none()
        if not parent:
            break
        current = parent
        root_id = current.id

    # Carica ricorsivamente tutti i messaggi del thread dalla radice
    # Limita a posta_certificata (esclude accettazioni, consegne, ecc.)
    thread_messages: list[Message] = []

    async def _collect(msg_id: uuid.UUID) -> None:
        result = await db.execute(
            select(Message)
            .where(
                Message.id == msg_id,
                Message.tenant_id == current_user.tenant_id,
                Message.pec_type == "posta_certificata",
            )
            .options(selectinload(Message.labels))
        )
        msg = result.scalar_one_or_none()
        if msg:
            thread_messages.append(msg)

        children_result = await db.execute(
            select(Message)
            .where(
                Message.parent_message_id == msg_id,
                Message.tenant_id == current_user.tenant_id,
                Message.pec_type == "posta_certificata",
            )
            .options(selectinload(Message.labels))
            .order_by(Message.received_at.asc().nullslast(), Message.created_at.asc())
        )
        children = list(children_result.scalars().all())
        for child in children:
            await _collect(child.id)

    await _collect(root_id)

    # Ordina cronologicamente
    thread_messages.sort(
        key=lambda m: m.received_at or m.sent_at or m.created_at
    )

    return [MessageResponse.model_validate(m) for m in thread_messages]


# ─── Feature 7: Preview allegati (presigned URL) ──────────────────────────────

@router.get("/{message_id}/attachments/{attachment_id}/preview-url")
async def get_attachment_preview_url(
    message_id: uuid.UUID,
    attachment_id: uuid.UUID,
    current_user: CurrentUser,
    db: DB,
) -> dict:
    """
    Restituisce una presigned URL MinIO per la preview inline dell'allegato.

    La URL e' valida per 5 minuti. Supporta PDF e immagini.
    Per altri tipi di file reindirizza al download normale.
    """
    await _resolve_message(message_id, current_user, db)

    result = await db.execute(
        select(Attachment).where(
            Attachment.id == attachment_id,
            Attachment.message_id == message_id,
        )
    )
    attachment = result.scalar_one_or_none()
    if not attachment:
        raise NotFoundError(f"Allegato {attachment_id} non trovato")

    content_type = attachment.content_type or "application/octet-stream"
    previewable = (
        content_type.startswith("image/") or
        content_type == "application/pdf"
    )

    if not previewable:
        return {
            "previewable": False,
            "content_type": content_type,
            "filename": attachment.filename,
        }

    try:
        from datetime import timedelta as _timedelta
        from miniopy_async import Minio

        client = Minio(
            endpoint=settings.minio_endpoint,
            access_key=settings.minio_access_key,
            secret_key=settings.minio_secret_key,
            secure=settings.minio_use_ssl,
        )
        presigned_url = await client.presigned_get_object(
            settings.minio_bucket,
            attachment.storage_path,
            expires=_timedelta(minutes=5),
        )
        return {
            "previewable": True,
            "content_type": content_type,
            "filename": attachment.filename,
            "url": presigned_url,
        }
    except Exception as e:
        from app.core.logging import get_logger
        logger = get_logger(__name__)
        logger.error(f"Errore generazione presigned URL allegato {attachment_id}: {e}")
        return {
            "previewable": False,
            "content_type": content_type,
            "filename": attachment.filename,
        }


# ─── Feature 7b: Serve allegato inline per preview ───────────────────────────

@router.get("/{message_id}/attachments/{attachment_id}/inline")
async def inline_attachment(
    message_id: uuid.UUID,
    attachment_id: uuid.UUID,
    current_user: CurrentUser,
    db: DB,
):
    """
    Serve l'allegato con Content-Disposition: inline per la preview nel browser.

    Legge il file da MinIO internamente e lo restituisce attraverso il backend,
    evitando i problemi di accessibilita' con i presigned URL di MinIO in ambienti Docker.
    Supporta PDF e immagini; per altri tipi restituisce 404.
    """
    await _resolve_message(message_id, current_user, db)

    result = await db.execute(
        select(Attachment).where(
            Attachment.id == attachment_id,
            Attachment.message_id == message_id,
        )
    )
    attachment = result.scalar_one_or_none()
    if not attachment:
        raise NotFoundError(f"Allegato {attachment_id} non trovato")

    content_type = attachment.content_type or "application/octet-stream"
    filename = attachment.filename.replace('"', "'")

    try:
        from miniopy_async import Minio

        client = Minio(
            endpoint=settings.minio_endpoint,
            access_key=settings.minio_access_key,
            secret_key=settings.minio_secret_key,
            secure=settings.minio_use_ssl,
        )
        response = await client.get_object(settings.minio_bucket, attachment.storage_path)
        data = await response.content.read()
        response.close()
        return StreamingResponse(
            iter([data]),
            media_type=content_type,
            headers={
                "Content-Disposition": f'inline; filename="{filename}"',
                "Content-Length": str(len(data)),
            },
        )
    except Exception as e:
        from app.core.logging import get_logger
        logger = get_logger(__name__)
        logger.error(f"Errore inline allegato {attachment_id}: {e}")
        raise NotFoundError("File non disponibile al momento")


# ─── Feature 8: Stampa/export HTML ────────────────────────────────────────────

@router.get("/{message_id}/print")
async def print_message(
    message_id: uuid.UUID,
    current_user: CurrentUser,
    db: DB,
) -> "HTMLResponse":
    """
    Restituisce una rappresentazione HTML ottimizzata per la stampa del messaggio.

    Include: intestazione, corpo, lista allegati, albero ricevute.
    Pronto per window.print() o salvataggio come PDF tramite browser.
    """
    from fastapi.responses import HTMLResponse

    message = await _resolve_message(message_id, current_user, db)

    att_result = await db.execute(
        select(Attachment).where(Attachment.message_id == message.id).order_by(Attachment.created_at)
    )
    attachments = list(att_result.scalars().all())

    receipts_html = ""
    if message.direction == "outbound":
        rec_result = await db.execute(
            select(Message)
            .where(Message.parent_message_id == message.id)
            .order_by(Message.received_at.asc().nullslast(), Message.created_at.asc())
        )
        receipts = list(rec_result.scalars().all())

        PEC_TYPE_LABELS = {
            "accettazione": "Accettazione",
            "avvenuta_consegna": "Avvenuta consegna",
            "non_accettazione": "Non accettazione",
            "mancata_consegna": "Mancata consegna",
            "errore_consegna": "Errore consegna",
            "presa_in_carico": "Presa in carico",
            "preavviso_mancata_consegna": "Preavviso mancata consegna",
            "rilevazione_virus": "Rilevazione virus",
        }

        receipt_rows = ""
        for r in receipts:
            label = PEC_TYPE_LABELS.get(r.pec_type, r.pec_type)
            date_str = ""
            if r.received_at:
                date_str = r.received_at.strftime("%d/%m/%Y %H:%M:%S")
            receipt_rows += f"<tr><td>{label}</td><td>{date_str}</td></tr>"

        if receipt_rows:
            receipts_html = f"""
            <section>
                <h3>Tracciamento invio</h3>
                <table>
                    <thead><tr><th>Tipo ricevuta</th><th>Data</th></tr></thead>
                    <tbody>{receipt_rows}</tbody>
                </table>
            </section>"""

    att_rows = ""
    for att in attachments:
        size_str = f"{att.size_bytes:,} byte" if att.size_bytes else ""
        att_rows += f"<li>{att.filename} ({att.content_type or ''}) {size_str}</li>"

    att_html = f"<section><h3>Allegati ({len(attachments)})</h3><ul>{att_rows}</ul></section>" if attachments else ""

    from_label = "Da" if message.direction == "inbound" else "A"
    from_val = message.from_address if message.direction == "inbound" else ", ".join(message.to_addresses or [])
    date_val = ""
    date_field = message.received_at or message.sent_at or message.created_at
    if date_field:
        date_val = date_field.strftime("%d/%m/%Y %H:%M:%S")

    body_html = ""
    if message.body_html:
        body_html = f"<div class='body'>{message.body_html}</div>"
    elif message.body_text:
        body_html = f"<pre class='body'>{message.body_text}</pre>"

    deadline_html = ""
    if message.deadline_at:
        dl_str = message.deadline_at.strftime("%d/%m/%Y %H:%M")
        deadline_html = f"<p class='deadline'><strong>Scadenza:</strong> {dl_str}</p>"
        if message.deadline_note:
            deadline_html += f"<p><em>Nota scadenza: {message.deadline_note}</em></p>"

    html = f"""<!DOCTYPE html>
<html lang="it">
<head>
<meta charset="UTF-8">
<title>PEC - {message.subject or '(nessun oggetto)'}</title>
<style>
  body {{ font-family: Arial, sans-serif; font-size: 12pt; margin: 2cm; color: #000; }}
  h1 {{ font-size: 16pt; border-bottom: 2px solid #333; padding-bottom: 8px; }}
  h3 {{ font-size: 13pt; margin-top: 20px; border-bottom: 1px solid #ccc; }}
  .meta {{ background: #f5f5f5; border: 1px solid #ddd; padding: 12px; margin-bottom: 16px; }}
  .meta p {{ margin: 4px 0; }}
  .body {{ border: 1px solid #ddd; padding: 12px; white-space: pre-wrap; word-wrap: break-word; }}
  table {{ border-collapse: collapse; width: 100%; }}
  th, td {{ border: 1px solid #ccc; padding: 6px 10px; text-align: left; }}
  th {{ background: #eee; }}
  ul {{ padding-left: 20px; }}
  .deadline {{ color: #c00; font-weight: bold; }}
  @media print {{ body {{ margin: 1cm; }} }}
</style>
</head>
<body>
<h1>{message.subject or '(nessun oggetto)'}</h1>
<div class="meta">
  <p><strong>{from_label}:</strong> {from_val}</p>
  {'<p><strong>Da:</strong> ' + message.from_address + '</p>' if message.direction == "outbound" and message.from_address else ''}
  {'<p><strong>A:</strong> ' + ', '.join(message.to_addresses or []) + '</p>' if message.direction == "inbound" and message.to_addresses else ''}
  {'<p><strong>Cc:</strong> ' + ', '.join(message.cc_addresses or []) + '</p>' if message.cc_addresses else ''}
  <p><strong>Data:</strong> {date_val}</p>
  <p><strong>Stato:</strong> {message.state}</p>
  <p><strong>Tipo:</strong> {message.pec_type}</p>
</div>
{deadline_html}
{body_html}
{att_html}
{receipts_html}
<p style="margin-top: 30px; font-size: 9pt; color: #888;">
  Documento generato da PEChub il {date_val} – ID messaggio: {message.id}
</p>
</body>
</html>"""

    return HTMLResponse(content=html, media_type="text/html; charset=utf-8")