from __future__ import annotations

import logging
from pathlib import Path
from uuid import uuid4

from django.conf import settings
from django.db import transaction
from django.utils.text import get_valid_filename

from review_agent.models import Conversation, FileAttachment

from .constants import ATTACHMENT_ROOT


logger = logging.getLogger("review_agent.file_summary.storage")


def _safe_original_name(name: str) -> str:
    clean = get_valid_filename(Path(name).name)
    return clean or f"upload-{uuid4().hex}"


def _relative_attachment_path(conversation: Conversation, filename: str, version_no: int) -> Path:
    suffix = Path(filename).suffix
    stem = Path(filename).stem
    stored_name = f"{stem}_v{version_no}_{uuid4().hex[:8]}{suffix}"
    return (
        ATTACHMENT_ROOT
        / str(conversation.user_id)
        / str(conversation.pk)
        / "attachments"
        / stored_name
    )


def _ensure_inside_media_root(path: Path) -> None:
    media_root = Path(settings.MEDIA_ROOT).resolve()
    resolved = path.resolve()
    if media_root != resolved and media_root not in resolved.parents:
        raise ValueError("上传路径必须位于 MEDIA_ROOT 内。")


@transaction.atomic
def save_uploaded_attachment(*, conversation: Conversation, user, uploaded_file) -> FileAttachment:
    """Stores an uploaded file and creates a versioned attachment record."""

    original_name = _safe_original_name(uploaded_file.name)
    logger.info(
        "Attachment upload save started",
        extra={
            "conversation_id": conversation.pk,
            "user_id": user.pk,
            "original_name": original_name,
            "file_size": uploaded_file.size,
            "content_type": getattr(uploaded_file, "content_type", "") or "",
        },
    )
    latest = (
        FileAttachment.objects.filter(conversation=conversation, original_name=original_name)
        .order_by("-version_no")
        .first()
    )
    version_no = (latest.version_no if latest else 0) + 1
    relative_path = _relative_attachment_path(conversation, original_name, version_no)
    absolute_path = Path(settings.MEDIA_ROOT) / relative_path
    _ensure_inside_media_root(absolute_path)
    absolute_path.parent.mkdir(parents=True, exist_ok=True)

    with absolute_path.open("wb") as target:
        for chunk in uploaded_file.chunks():
            target.write(chunk)

    FileAttachment.objects.filter(
        conversation=conversation,
        original_name=original_name,
        is_active=True,
    ).update(is_active=False)

    attachment = FileAttachment.objects.create(
        conversation=conversation,
        user=user,
        original_name=original_name,
        version_no=version_no,
        is_active=True,
        storage_path=relative_path.as_posix(),
        file_size=uploaded_file.size,
        content_type=getattr(uploaded_file, "content_type", "") or "",
    )
    logger.info(
        "Attachment upload save finished",
        extra={
            "conversation_id": conversation.pk,
            "attachment_id": attachment.pk,
            "version_no": attachment.version_no,
            "storage_path": attachment.storage_path,
        },
    )
    return attachment


def serialize_attachment(attachment: FileAttachment) -> dict[str, object]:
    return {
        "id": attachment.pk,
        "original_name": attachment.original_name,
        "version_no": attachment.version_no,
        "is_active": attachment.is_active,
        "file_size": attachment.file_size,
        "content_type": attachment.content_type,
        "upload_status": attachment.upload_status,
        "created_at": attachment.created_at.isoformat(),
    }