import uuid

from fastapi import APIRouter, Depends, HTTPException, status
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.deps import get_current_user, get_db_session, require_study_not_locked
from app.crud import audit as audit_crud
from app.crud import faq_category as category_crud
from app.crud import faq_item as faq_crud
from app.crud import faq_reply as reply_crud
from app.crud import member as member_crud
from app.schemas.common import PaginatedResponse
from app.schemas.faq import (
    FaqBestReplyUpdate,
    FaqCreate,
    FaqRead,
    FaqReplyCreate,
    FaqReplyQuote,
    FaqReplyRead,
    FaqStatusUpdate,
    FaqUpdate,
)
from app.utils.pagination import paginate

router = APIRouter()


def _check_write_permission(study_id: uuid.UUID, current_user, member_role: str | None):
    if current_user.role != "ADMIN" and member_role != "PM":
        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="权限不足")


def _check_create_permission(current_user, is_member: bool):
    if current_user.role != "ADMIN" and not is_member:
        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="不是该项目成员")


@router.post(
    "/",
    response_model=FaqRead,
    status_code=status.HTTP_201_CREATED,
    summary="创建 FAQ",
    description="创建全局或项目内 FAQ，项目 FAQ 需项目 PM/ADMIN 权限。",
    dependencies=[Depends(require_study_not_locked())],
)
async def create_faq(
    payload: FaqCreate,
    db: AsyncSession = Depends(get_db_session),
    current_user=Depends(get_current_user),
) -> FaqRead:
    if not payload.study_id:
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="必须提供项目 ID")
    cat = await category_crud.get_category(db, payload.category_id)
    if not cat:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="分类不存在")
    if cat.study_id != payload.study_id:
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="分类范围不匹配")
    member_role = None
    is_member = False
    member = await member_crud.get_member(db, payload.study_id, current_user.id)
    member_role = member.role_in_study if member else None
    is_member = member is not None
    _check_create_permission(current_user, is_member)
    try:
        item = await faq_crud.create_item(db, payload, created_by=current_user.id)
    except ValueError as exc:
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail=str(exc)) from exc
    if payload.answer:
        await reply_crud.create_reply(
            db,
            faq_id=item.id,
            study_id=item.study_id,
            created_by=current_user.id,
            reply_in=FaqReplyCreate(content=payload.answer),
        )
        await faq_crud.set_status(db, item.id, "PROCESSING")
    await audit_crud.log_action(
        db,
        study_id=payload.study_id,
        entity_type="faq_item",
        entity_id=item.id,
        action="CREATE_FAQ_ITEM",
        detail="FAQ 已创建",
        operator_id=current_user.id,
        operator_role=current_user.role,
    )
    return FaqRead.model_validate(item)


@router.get(
    "/",
    response_model=PaginatedResponse[FaqRead],
    summary="FAQ 列表",
    description="返回全局与项目 FAQ，可按关键词、分类过滤。",
)
async def list_faqs(
    study_id: uuid.UUID | None = None,
    category_id: uuid.UUID | None = None,
    keyword: str | None = None,
    is_active: bool | None = None,
    db: AsyncSession = Depends(get_db_session),
    current_user=Depends(get_current_user),
) -> list[FaqRead]:
    membership_cache: dict[uuid.UUID, str | None] = {}

    async def _get_member_role(sid: uuid.UUID) -> str | None:
        if sid in membership_cache:
            return membership_cache[sid]
        member = await member_crud.get_member(db, sid, current_user.id)
        role = member.role_in_study if member else None
        membership_cache[sid] = role
        return role

    if not study_id:
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="必须提供项目 ID")
    if current_user.role != "ADMIN":
        role = await _get_member_role(study_id)
        if not role:
            raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="不是该项目成员")

    if is_active is False and current_user.role != "ADMIN":
        role = await _get_member_role(study_id)
        if role != "PM":
            raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="权限不足")

    items = await faq_crud.list_items(
        db,
        study_id=study_id,
        category_id=category_id,
        keyword=keyword,
        is_active=is_active,
        study_scope="project",
    )

    visible: list[FaqRead] = []
    for it in items:
        if current_user.role != "ADMIN":
            role = await _get_member_role(it.study_id)
            if not role:
                continue
        if not it.is_active and current_user.role != "ADMIN":
            role = await _get_member_role(it.study_id)
            if role != "PM":
                continue
        visible.append(FaqRead.model_validate(it))
    return paginate(visible, total=len(visible))


@router.get(
    "/{item_id}",
    response_model=FaqRead,
    summary="FAQ 详情",
    description="获取单条 FAQ，非 PM 不能查看停用 FAQ。",
)
async def get_faq(
    item_id: uuid.UUID,
    db: AsyncSession = Depends(get_db_session),
    current_user=Depends(get_current_user),
) -> FaqRead:
    item = await faq_crud.get_item(db, item_id)
    if not item:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="FAQ 不存在")
    if not item.study_id:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="FAQ 不存在")
    if current_user.role != "ADMIN":
        member = await member_crud.get_member(db, item.study_id, current_user.id)
        if not member:
            raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="不是该项目成员")
    if not item.is_active and current_user.role not in {"ADMIN"}:
        member = await member_crud.get_member(db, item.study_id, current_user.id)
        member_role = member.role_in_study if member else None
        if member_role != "PM":
            raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="FAQ 已停用")
    return FaqRead.model_validate(item)


@router.patch(
    "/{item_id}",
    response_model=FaqRead,
    summary="更新 FAQ",
    description="更新 FAQ 内容或启停状态，项目内需 PM/ADMIN 权限。",
    dependencies=[Depends(require_study_not_locked())],
)
async def update_faq(
    item_id: uuid.UUID,
    payload: FaqUpdate,
    db: AsyncSession = Depends(get_db_session),
    current_user=Depends(get_current_user),
) -> FaqRead:
    item = await faq_crud.get_item(db, item_id)
    if not item:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="FAQ 不存在")
    if item.created_by != current_user.id:
        member_role = None
        if item.study_id:
            member = await member_crud.get_member(db, item.study_id, current_user.id)
            member_role = member.role_in_study if member else None
        _check_write_permission(item.study_id, current_user, member_role)
    old_active = item.is_active
    updated = await faq_crud.update_item(db, item, payload)
    action = "UPDATE_FAQ_ITEM"
    detail = "FAQ updated"
    if payload.is_active is not None and payload.is_active != old_active:
        action = "FAQ_STATUS_CHANGE"
        detail = "FAQ disabled" if not payload.is_active else "FAQ enabled"
    await audit_crud.log_action(
        db,
        study_id=item.study_id,
        entity_type="faq_item",
        entity_id=item_id,
        action=action,
        detail=detail,
        operator_id=current_user.id,
        operator_role=current_user.role,
    )
    return FaqRead.model_validate(updated)


@router.patch(
    "/{item_id}/status",
    response_model=FaqRead,
    summary="更新 FAQ 状态",
    description="提问者或项目 PM/ADMIN 可确认已解决。",
    dependencies=[Depends(require_study_not_locked())],
)
async def update_faq_status(
    item_id: uuid.UUID,
    payload: FaqStatusUpdate,
    db: AsyncSession = Depends(get_db_session),
    current_user=Depends(get_current_user),
) -> FaqRead:
    item = await faq_crud.get_item(db, item_id)
    if not item:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="FAQ 不存在")
    if payload.status != "RESOLVED":
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="仅允许设置为已解决")
    if item.created_by != current_user.id and current_user.role != "ADMIN":
        member_role = None
        if item.study_id:
            member = await member_crud.get_member(db, item.study_id, current_user.id)
            member_role = member.role_in_study if member else None
        if member_role != "PM":
            raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="权限不足")
    await faq_crud.set_status(db, item.id, "RESOLVED", resolved_by_confirm=True)
    updated = await faq_crud.get_item(db, item_id)
    return FaqRead.model_validate(updated)


@router.patch(
    "/{item_id}/best-reply",
    response_model=FaqRead,
    summary="设置最佳回复",
    description="项目成员可设置最佳回复，全局仅 ADMIN。",
    dependencies=[Depends(require_study_not_locked())],
)
async def set_best_reply(
    item_id: uuid.UUID,
    payload: FaqBestReplyUpdate,
    db: AsyncSession = Depends(get_db_session),
    current_user=Depends(get_current_user),
) -> FaqRead:
    item = await faq_crud.get_item(db, item_id)
    if not item:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="FAQ 不存在")
    if not item.study_id:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="FAQ 不存在")
    is_member = False
    member = await member_crud.get_member(db, item.study_id, current_user.id)
    is_member = member is not None
    _check_create_permission(current_user, is_member)
    if payload.best_reply_id:
        reply = await reply_crud.get_reply(db, payload.best_reply_id)
        if not reply or reply.faq_id != item.id:
            raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="回复无效")
        if reply.is_deleted:
            raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="回复已删除")
        await faq_crud.set_best_reply(db, item.id, reply.id)
        await faq_crud.set_status(db, item.id, "RESOLVED", resolved_by_confirm=item.resolved_by_confirm)
    else:
        await faq_crud.set_best_reply(db, item.id, None)
        if not item.resolved_by_confirm:
            remaining = await reply_crud.count_active_replies(db, item.id)
            await faq_crud.set_status(
                db,
                item.id,
                "PROCESSING" if remaining > 0 else "PENDING",
                resolved_by_confirm=False,
            )
    updated = await faq_crud.get_item(db, item_id)
    return FaqRead.model_validate(updated)


@router.get(
    "/{item_id}/replies",
    response_model=PaginatedResponse[FaqReplyRead],
    summary="FAQ 回复列表",
    description="获取 FAQ 的回复列表。",
)
async def list_replies(
    item_id: uuid.UUID,
    db: AsyncSession = Depends(get_db_session),
    current_user=Depends(get_current_user),
) -> list[FaqReplyRead]:
    item = await faq_crud.get_item(db, item_id)
    if not item:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="FAQ 不存在")
    if item.study_id and current_user.role != "ADMIN":
        member = await member_crud.get_member(db, item.study_id, current_user.id)
        if not member:
            raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="不是该项目成员")
    replies = await reply_crud.list_replies(db, item_id)
    reply_map = {r.id: r for r in replies}
    result: list[FaqReplyRead] = []
    for r in replies:
        data = FaqReplyRead.model_validate(r)
        if r.quote_reply_id and r.quote_reply_id in reply_map:
            quote = reply_map[r.quote_reply_id]
            if quote.is_deleted:
                data.quote = FaqReplyQuote(
                    id=quote.id,
                    content="回复已删除",
                    created_by=quote.created_by,
                    created_at=quote.created_at,
                )
            else:
                data.quote = FaqReplyQuote.model_validate(quote)
        result.append(data)
    return paginate(result, total=len(result))


@router.post(
    "/{item_id}/replies",
    response_model=FaqReplyRead,
    status_code=status.HTTP_201_CREATED,
    summary="创建 FAQ 回复",
    description="回复 FAQ，项目内成员可回复，全局仅 ADMIN。",
    dependencies=[Depends(require_study_not_locked())],
)
async def create_reply(
    item_id: uuid.UUID,
    payload: FaqReplyCreate,
    db: AsyncSession = Depends(get_db_session),
    current_user=Depends(get_current_user),
) -> FaqReplyRead:
    item = await faq_crud.get_item(db, item_id)
    if not item:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="FAQ 不存在")
    if not item.study_id:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="FAQ 不存在")
    if not payload.content.strip():
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="回复内容不能为空")
    is_member = False
    member = await member_crud.get_member(db, item.study_id, current_user.id)
    is_member = member is not None
    _check_create_permission(current_user, is_member)
    quote = None
    if payload.quote_reply_id:
        quote = await reply_crud.get_reply(db, payload.quote_reply_id)
        if not quote or quote.faq_id != item.id:
            raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="引用回复无效")
    reply = await reply_crud.create_reply(
        db,
        faq_id=item.id,
        study_id=item.study_id,
        created_by=current_user.id,
        reply_in=payload,
    )
    if item.status != "RESOLVED":
        await faq_crud.set_status(db, item.id, "PROCESSING")
    await faq_crud.touch_item(db, item.id)
    await audit_crud.log_action(
        db,
        study_id=item.study_id,
        entity_type="faq_reply",
        entity_id=reply.id,
        action="CREATE_FAQ_REPLY",
        detail="FAQ 已回复",
        operator_id=current_user.id,
        operator_role=current_user.role,
    )
    data = FaqReplyRead.model_validate(reply)
    if quote:
        if quote.is_deleted:
            data.quote = FaqReplyQuote(
                id=quote.id,
                content="回复已删除",
                created_by=quote.created_by,
                created_at=quote.created_at,
            )
        else:
            data.quote = FaqReplyQuote.model_validate(quote)
    return data


@router.delete(
    "/{item_id}",
    status_code=status.HTTP_204_NO_CONTENT,
    summary="删除 FAQ",
    description="删除 FAQ，项目内需 PM/ADMIN 权限，全局仅 ADMIN。",
    dependencies=[Depends(require_study_not_locked())],
)
async def delete_faq(
    item_id: uuid.UUID,
    db: AsyncSession = Depends(get_db_session),
    current_user=Depends(get_current_user),
) -> None:
    item = await faq_crud.get_item(db, item_id)
    if not item:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="FAQ 不存在")
    if item.created_by != current_user.id:
        member_role = None
        if item.study_id:
            member = await member_crud.get_member(db, item.study_id, current_user.id)
            member_role = member.role_in_study if member else None
        _check_write_permission(item.study_id, current_user, member_role)
    await reply_crud.delete_replies_by_faq_id(db, item.id)
    await db.delete(item)
    await db.commit()
    await audit_crud.log_action(
        db,
        study_id=item.study_id,
        entity_type="faq_item",
        entity_id=item_id,
        action="DELETE_FAQ_ITEM",
        detail="FAQ 已删除",
        operator_id=current_user.id,
        operator_role=current_user.role,
    )


@router.delete(
    "/{item_id}/replies/{reply_id}",
    status_code=status.HTTP_204_NO_CONTENT,
    summary="删除 FAQ 回复",
    description="删除 FAQ 回复，管理员、项目 PM 或回复者可删除。",
    dependencies=[Depends(require_study_not_locked())],
)
async def delete_reply(
    item_id: uuid.UUID,
    reply_id: uuid.UUID,
    db: AsyncSession = Depends(get_db_session),
    current_user=Depends(get_current_user),
) -> None:
    item = await faq_crud.get_item(db, item_id)
    if not item:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="FAQ 不存在")
    reply = await reply_crud.get_reply(db, reply_id)
    if not reply or reply.faq_id != item.id:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="回复不存在")
    if reply.created_by != current_user.id and current_user.role != "ADMIN":
        member_role = None
        if item.study_id:
            member = await member_crud.get_member(db, item.study_id, current_user.id)
            member_role = member.role_in_study if member else None
        if member_role != "PM":
            raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="权限不足")
    if item.best_reply_id == reply.id:
        await faq_crud.set_best_reply(db, item.id, None)
    ref_count = await reply_crud.count_quote_references(db, reply.id)
    if ref_count > 0:
        await reply_crud.soft_delete_reply(db, reply)
    else:
        await reply_crud.delete_reply(db, reply)
    if not item.resolved_by_confirm:
        if item.best_reply_id and item.best_reply_id != reply.id:
            await faq_crud.set_status(db, item.id, "RESOLVED", resolved_by_confirm=False)
        else:
            remaining = await reply_crud.count_active_replies(db, item.id)
            await faq_crud.set_status(
                db,
                item.id,
                "PROCESSING" if remaining > 0 else "PENDING",
                resolved_by_confirm=False,
            )
    await faq_crud.touch_item(db, item.id)
    await audit_crud.log_action(
        db,
        study_id=item.study_id,
        entity_type="faq_reply",
        entity_id=reply_id,
        action="DELETE_FAQ_REPLY",
        detail="FAQ 回复已删除",
        operator_id=current_user.id,
        operator_role=current_user.role,
    )