"""附件接口：上传 / 列表 / 下载 / 删除。

三条约束（都会有用例守）：
1. 只认「本工作区的条目」。拿着别的租户的 item_id 上传，返回 5001 而不是 403——
   对外不该暴露那条记录是否存在。
2. 大小上限在**读流时**卡住，不能先落盘再判断（否则等于给了别人一个写满磁盘的入口）。
3. 磁盘上的名字由服务端生成，用户文件名只进库和 Content-Disposition。
"""

from __future__ import annotations

import urllib.parse
import uuid
from typing import Annotated

from fastapi import APIRouter, File, Query, UploadFile
from fastapi.responses import FileResponse
from sqlalchemy import select
from starlette.concurrency import run_in_threadpool

from app.audit import record as audit_record
from app.config import get_settings
from app.db import bind_tenant
from app.deps import MemberDep, SessionDep
from app.errors import AppError, ErrorCode
from app.models import Member
from app.models_attachment import Attachment
from app.models_task import Item
from app.schemas import ok
from app.security import decode_token
from app.services import signing, storage

router = APIRouter(prefix="/workspaces/{ws_id}", tags=["attachments"])

ALLOWED_KINDS = ("task", "ticket", "knowledge")


def _attachment_out(row: Attachment, viewer_id=None, role=None) -> dict:
    settings = get_settings()
    return {
        "id": str(row.id),
        "item_id": str(row.item_id),
        "filename": row.filename,
        "content_type": row.content_type,
        "size": row.size_bytes,
        "sha256": row.sha256,
        "uploader_id": str(row.uploader_id),
        "created_at": row.created_at.isoformat(),
        # 图片直链：自带短期签名，浏览器 <img> 直接能用，不需要把登录令牌塞进 URL
        "raw_url": (
            f"{settings.api_prefix}/workspaces/{row.workspace_id}"
            f"/attachments/{row.id}/raw?{signing.sign(row.workspace_id, row.id)}"
        ),
        "can_delete": row.uploader_id == viewer_id or role in ("owner", "admin"),
    }


async def _load_item(session, ws_id, item_id) -> Item:
    item = await session.scalar(
        select(Item).where(
            Item.id == item_id,
            Item.workspace_id == ws_id,
            Item.deleted_at.is_(None),
            Item.kind.in_(ALLOWED_KINDS),
        )
    )
    if item is None:
        raise AppError(ErrorCode.ITEM_NOT_FOUND, "事项不存在")
    return item


def _safe_filename(name: str | None, fallback: str = "未命名文件") -> str:
    """只用于展示与下载响应头：去掉路径分隔符与控制字符，长度截断。"""
    raw = (name or "").strip().replace("\\", "/").split("/")[-1]
    cleaned = "".join(ch for ch in raw if ch.isprintable() and ch not in '\r\n"')
    cleaned = cleaned.strip() or fallback
    if len(cleaned) > 200:
        stem, dot, ext = cleaned.rpartition(".")
        cleaned = (stem[:180] + dot + ext[-16:]) if dot and ext else cleaned[:200]
    return cleaned


@router.post("/items/{item_id}/attachments", status_code=201)
async def upload_attachment(
    ctx: MemberDep,
    session: SessionDep,
    item_id: str,
    file: Annotated[UploadFile, File()],
):
    item = await _load_item(session, ctx.ws_id, item_id)
    limit = get_settings().max_upload_mb * 1024 * 1024

    # 先看声明的大小（可选，客户端不一定给），真正的限额在读流时兜底
    if file.size is not None and file.size > limit:
        raise AppError(
            ErrorCode.ATTACHMENT_TOO_LARGE,
            f"文件超过 {get_settings().max_upload_mb}MB 上限",
        )

    try:
        stored = await run_in_threadpool(
            storage.save, file.file, workspace_id=ctx.ws_id, item_id=item.id
        )
        if stored.size > limit:
            await run_in_threadpool(storage.remove, stored.key)
            raise AppError(
                ErrorCode.ATTACHMENT_TOO_LARGE,
                f"文件超过 {get_settings().max_upload_mb}MB 上限",
            )

        row = Attachment(
            workspace_id=ctx.ws_id,
            item_id=item.id,
            uploader_id=ctx.user.id,
            filename=_safe_filename(file.filename),
            content_type=(file.content_type or "application/octet-stream")[:120],
            size_bytes=stored.size,
            sha256=stored.sha256,
            storage_key=stored.key,
        )
        session.add(row)
        await session.flush()
        await audit_record(
            session,
            workspace_id=ctx.ws_id,
            actor_user_id=ctx.user.id,
            action="attachment_uploaded",
            target_type="item",
            target_id=str(item.id),
            payload={"attachment_id": str(row.id), "filename": row.filename},
        )
        await session.commit()
    finally:
        await file.close()

    return ok(_attachment_out(row, ctx.user.id, ctx.role))


@router.get("/items/{item_id}/attachments")
async def list_attachments(ctx: MemberDep, session: SessionDep, item_id: str):
    item = await _load_item(session, ctx.ws_id, item_id)
    rows = (
        await session.scalars(
            select(Attachment)
            .where(Attachment.workspace_id == ctx.ws_id, Attachment.item_id == item.id)
            .order_by(Attachment.created_at.asc())
        )
    ).all()
    return ok({"items": [_attachment_out(row, ctx.user.id, ctx.role) for row in rows]})


@router.get("/attachments/{attachment_id}/download")
async def download_attachment(ctx: MemberDep, session: SessionDep, attachment_id: str):
    row = await session.scalar(
        select(Attachment).where(
            Attachment.id == attachment_id, Attachment.workspace_id == ctx.ws_id
        )
    )
    if row is None:
        raise AppError(ErrorCode.ATTACHMENT_NOT_FOUND, "附件不存在")

    path = storage.path_of(row.storage_key)
    if not path.exists():
        # 库里有记录、盘上没文件：说明备份漏了 blob，明确报错而不是返回空文件
        raise AppError(ErrorCode.ATTACHMENT_NOT_FOUND, "附件文件已丢失，请联系管理员")

    return FileResponse(
        path,
        media_type=row.content_type,
        headers={
            # 中文文件名必须按 RFC 5987 编码，否则浏览器拿到的是乱码
            "Content-Disposition": "attachment; filename*=UTF-8''"
            + urllib.parse.quote(row.filename),
            # 附件是不可信内容：禁止浏览器嗅探类型，否则 .txt 里的 HTML 会被执行
            "X-Content-Type-Options": "nosniff",
        },
    )


@router.get("/attachments/{attachment_id}/raw")
async def raw_attachment(
    ws_id: uuid.UUID,
    session: SessionDep,
    attachment_id: uuid.UUID,
    exp: Annotated[int | None, Query(description="签名过期时间（unix 秒）")] = None,
    sig: Annotated[str | None, Query(description="短期签名，见 services/signing.py")] = None,
    token: Annotated[str | None, Query(description="兼容旧链接用的 access token")] = None,
):
    """给 Markdown 里的图片用：浏览器 `<img>` 无法附加 Authorization 头。

    优先认 `?exp=&sig=` 的短期签名（由附件列表接口签发，只为这一张图、只活 30 分钟）；
    老链接里的 `?token=` 仍能用，但那是过渡期兼容，前端已不再生成。
    """
    if exp is not None or sig is not None:
        if not signing.verify(ws_id, attachment_id, exp, sig):
            raise AppError(ErrorCode.ATTACHMENT_FORBIDDEN, "图片链接已失效，请刷新页面")
        # 这个接口不走 MemberDep，RLS 不会自动绑租户，得手动绑一次
        await bind_tenant(session, ws_id=ws_id, user_id=None)
    else:
        if not token:
            raise AppError(ErrorCode.UNAUTHORIZED, "缺少访问凭据")
        try:
            user_id = decode_token(token, "access")
        except Exception:  # noqa: BLE001 —— 任何解码失败都按未认证处理
            raise AppError(ErrorCode.UNAUTHORIZED, "登录已过期，请重新登录") from None

        await bind_tenant(session, ws_id=ws_id, user_id=user_id)

        member = await session.scalar(
            select(Member.id).where(
                Member.workspace_id == ws_id,
                Member.user_id == user_id,
                Member.status == "active",
            )
        )
        if member is None:
            # 不是成员就当作不存在：不暴露"这里有个附件但你看不到"
            raise AppError(ErrorCode.ATTACHMENT_NOT_FOUND, "附件不存在")

    row = await session.scalar(
        select(Attachment).where(Attachment.id == attachment_id, Attachment.workspace_id == ws_id)
    )
    if row is None:
        raise AppError(ErrorCode.ATTACHMENT_NOT_FOUND, "附件不存在")

    path = storage.path_of(row.storage_key)
    if not path.exists():
        raise AppError(ErrorCode.ATTACHMENT_NOT_FOUND, "附件文件已丢失，请联系管理员")

    return FileResponse(
        path,
        media_type=row.content_type,
        headers={
            "Content-Disposition": "inline",
            "X-Content-Type-Options": "nosniff",
            # 附件内容不变（key 由内容哈希决定），可以放心长缓存；换了文件就是换了 id
            "Cache-Control": "private, max-age=86400",
        },
    )


@router.delete("/attachments/{attachment_id}")
async def delete_attachment(
    ctx: MemberDep, session: SessionDep, attachment_id: str, confirm: bool = Query(False)
):
    row = await session.scalar(
        select(Attachment).where(
            Attachment.id == attachment_id, Attachment.workspace_id == ctx.ws_id
        )
    )
    if row is None:
        raise AppError(ErrorCode.ATTACHMENT_NOT_FOUND, "附件不存在")

    is_uploader = row.uploader_id == ctx.user.id
    if not is_uploader and ctx.role not in ("owner", "admin"):
        raise AppError(ErrorCode.ATTACHMENT_FORBIDDEN, "只有上传者或管理员能删除附件")
    if not confirm:
        # 删除不可逆，要求显式确认，避免误点
        raise AppError(
            ErrorCode.CONFIRM_REQUIRED, "删除附件需要二次确认", details={"confirm": True}
        )

    await run_in_threadpool(storage.remove, row.storage_key)
    await session.delete(row)
    await audit_record(
        session,
        workspace_id=ctx.ws_id,
        actor_user_id=ctx.user.id,
        action="attachment_deleted",
        target_type="item",
        target_id=str(row.item_id),
        payload={"attachment_id": str(row.id), "filename": row.filename},
    )
    await session.commit()
    return ok({"deleted": True})


async def list_for_item(session, ws_id, item_id) -> list[dict]:
    """给其他接口内联用（列表/详情里带上附件摘要）。"""
    rows = (
        await session.scalars(
            select(Attachment)
            .where(Attachment.workspace_id == ws_id, Attachment.item_id == item_id)
            .order_by(Attachment.created_at.asc())
        )
    ).all()
    return [_attachment_out(row) for row in rows]


async def count_for_items(session, ws_id, item_ids: list) -> dict[str, int]:
    """列表页只显示"几个附件"，避免每条都拉全量。"""
    if not item_ids:
        return {}
    rows = (
        await session.execute(
            select(Attachment.item_id).where(
                Attachment.workspace_id == ws_id, Attachment.item_id.in_(item_ids)
            )
        )
    ).all()
    counts: dict[str, int] = {}
    for (item_id,) in rows:
        counts[str(item_id)] = counts.get(str(item_id), 0) + 1
    return counts


__all__ = ["router", "list_for_item", "count_for_items"]