"""全能创作 · 会话与消息的写入服务(契约 §1/§2)。

只放「怎么把一条消息安全落库」这类底座能力;agent 循环、工具执行、SSE 在
后续的 creation_agent.py 里,别混进来。
"""
from __future__ import annotations

from django.db import transaction
from django.db.models import Max
from django.utils import timezone

from .models import CreationConversation, CreationMessage


@transaction.atomic
def append_message(
    conversation: CreationConversation,
    *,
    role: str,
    kind: str = CreationMessage.Kind.TEXT,
    text: str = "",
    payload: dict | None = None,
    refs: list | None = None,
    task=None,
) -> CreationMessage:
    """往会话尾部追加一条消息,并刷新 last_active_at。

    seq 在事务里 select_for_update 锁住会话行再取 max+1 —— SSE 流式期间可能有
    并发写(用户抢答 / 轮询回填),不锁会撞 uniq_creation_message_seq。
    """
    locked = CreationConversation.objects.select_for_update().get(pk=conversation.pk)
    next_seq = (locked.messages.aggregate(m=Max("seq"))["m"] or 0) + 1
    message = CreationMessage.objects.create(
        conversation=locked,
        role=role,
        kind=kind,
        text=text,
        payload=payload or {},
        refs=refs or [],
        task=task,
        seq=next_seq,
    )
    locked.last_active_at = timezone.now()
    locked.save(update_fields=["last_active_at", "updated_at"])
    conversation.last_active_at = locked.last_active_at
    return message


def _assets_from_task(task) -> list[dict]:
    """任务落库的资产 → 结果卡要用的 {id,url,cover,type}。

    URL 必须走长期直链:预签名链 1 小时过期,写进消息 payload 第二天就打不开。
    """
    from apps.ai.services import asset_stable_url
    from apps.assets.models import Asset

    items = []
    assets = Asset.objects.filter(
        origin_task=task, is_deleted=False, purged_at__isnull=True,
    ).prefetch_related("files")
    for asset in assets:
        url, cover = asset_stable_url(asset)
        if not url:
            continue
        items.append({
            "id": str(asset.id),
            "url": url,
            "cover": cover or url,
            "type": "video" if asset.asset_type == Asset.Type.VIDEO else "image",
        })
    return items


def _meta_from_task(task, message: CreationMessage) -> dict:
    payload = message.payload or {}
    req = task.request_payload or {}
    model = ""
    if task.model_config_id:
        model = task.model_config.display_name or task.model_config.name
    return {
        "model": model or payload.get("model") or req.get("model") or "",
        "ratio": req.get("ratio") or payload.get("ratio") or "",
        "prompt": payload.get("prompt") or req.get("prompt") or "",
    }


def _message_task(message: CreationMessage):
    """GENERATING 消息挂的任务:优先 FK,payload.task_id 兜底(旧数据 / 序列化往返)。"""
    if message.task_id:
        return message.task
    task_id = (message.payload or {}).get("task_id")
    if not task_id:
        return None
    from .models import AITask

    return AITask.objects.select_related("model_config").filter(id=task_id).first()


@transaction.atomic
def fail_generating_message(message: CreationMessage, error: str) -> CreationMessage:
    """生成失败:GENERATING 原地改成 ERROR,不另开一条,避免中间态刷屏。"""
    message.kind = CreationMessage.Kind.ERROR
    message.text = (error or "生成失败")[:500]
    message.save(update_fields=["kind", "text", "updated_at"])
    conversation = message.conversation
    conversation.status = CreationConversation.Status.FAILED
    conversation.last_active_at = timezone.now()
    conversation.save(update_fields=["status", "last_active_at", "updated_at"])
    return message


def sync_generating_message(message: CreationMessage) -> bool:
    """看挂着的 AITask 是否已经终态,是就把 GENERATING 改成 RESULT / ERROR。

    出图/出片在 worker 里跑,agent 只提交。前端轮询 GET 会话时靠这个回填;
    worker 结束时也会调一次,不用干等到下一次轮询。
    返回是否改了这条消息。
    """
    from .models import AITask

    if message.kind != CreationMessage.Kind.GENERATING:
        return False
    task = _message_task(message)
    if task is None:
        return False
    if task.status == AITask.Status.SUCCEEDED:
        assets = _assets_from_task(task)
        if not assets:
            return False  # 状态已成功但资产还没落(极端竞态),下轮再试
        finish_generating_message(message, assets=assets, meta=_meta_from_task(task, message))
        return True
    if task.status in (AITask.Status.FAILED, AITask.Status.CANCELLED):
        fail_generating_message(message, task.error_message or "生成失败")
        return True
    return False


def sync_generating_messages(conversation: CreationConversation) -> int:
    """把一条会话里所有已结束的 GENERATING 回填。返回改了几条。"""
    pending = list(
        conversation.messages.filter(kind=CreationMessage.Kind.GENERATING)
        .select_related("task", "task__model_config")
    )
    return sum(1 for message in pending if sync_generating_message(message))


def sync_generating_for_task(task) -> int:
    """worker / poll 终态后:只扫挂在这个任务上的 GENERATING。失败不能向外抛。"""
    try:
        pending = list(
            CreationMessage.objects.filter(
                task=task, kind=CreationMessage.Kind.GENERATING,
            ).select_related("conversation", "task", "task__model_config")
        )
        return sum(1 for message in pending if sync_generating_message(message))
    except Exception:  # noqa: BLE001 — 回填失败不能把已经成功的出图任务打成失败
        import logging

        logging.getLogger(__name__).warning(
            "omni create: sync generating for task %s failed", getattr(task, "id", "?"),
            exc_info=True,
        )
        return 0


@transaction.atomic
def finish_generating_message(message: CreationMessage, *, assets: list[dict], meta: dict) -> CreationMessage:
    """把「生成中」原地改成「结果」(契约 §2:不新增消息,避免中间态刷屏)。

    重生成是**新开一条** GENERATING → RESULT,所以对话流仍然是往下叠加;
    这里改的只是同一次生成自己的中间态。
    """
    message.kind = CreationMessage.Kind.RESULT
    message.payload = {**(message.payload or {}), **meta, "assets": assets}
    message.save(update_fields=["kind", "payload", "updated_at"])
    conversation = message.conversation
    conversation.status = CreationConversation.Status.COMPLETED
    conversation.last_active_at = timezone.now()
    conversation.save(update_fields=["status", "last_active_at", "updated_at"])
    return message


def pin_refs(conversation: CreationConversation, refs: list[dict]) -> list[dict]:
    """把本轮引用的实体并进「实体锁定」。按 (type, id) 去重,保留首次出现的顺序 ——
    每轮无条件带上它们,这是多次生成之间锁脸/锁商品的唯一手段(契约 §5)。
    """
    merged = list(conversation.pinned_refs or [])
    seen = {(item.get("type"), str(item.get("id"))) for item in merged}
    changed = False
    for ref in refs or []:
        ref_type, ref_id = ref.get("type"), ref.get("id")
        if not ref_type or not ref_id:
            continue  # 缺 type/id 的 ref 解析不出实体,直接丢
        key = (ref_type, str(ref_id))
        if key in seen:
            continue
        merged.append(ref)
        seen.add(key)
        changed = True
    if changed:
        conversation.pinned_refs = merged
        conversation.save(update_fields=["pinned_refs", "updated_at"])
    return merged