"""The Files library HTTP API — a user's files, the folders they sit in, and the file itself.

A file in the library is a user's DONE job (`DownloadJob`) over its shared `MediaAsset`: the job is
the per-user layer (name, folder, kept, expiry, shares and links all hang off it), the asset the
bytes. Folders are rows (`downloads.folders`), so a rename or a move never touches the disk.

In-flight jobs are not here: they are the download tray's (`routes.downloads`). The helpers above
the routes are shared with that module — serialization, the ownership locks, the upload spool —
because a download and a library file are one row at two moments.

A machine with an API token (`app.apitokens`) may use the routes that take `files_caller`: list the
folders and files, fetch a file and its hash, upload, delete — each only in a folder its token was
granted that right in, and never the files shared with the user. A folder or file out of its reach
answers like a missing one. Everything else here is the signed-in user's alone (`current_user`).
"""

import base64
import hashlib
import os
import tempfile
import threading
from collections.abc import AsyncIterator, Sequence
from dataclasses import dataclass
from datetime import datetime, timezone
from pathlib import Path
from typing import BinaryIO, Literal
from urllib.parse import unquote, urlparse

from fastapi import APIRouter, Depends, HTTPException, Query, Request
from fastapi.responses import FileResponse, Response
from pydantic import BaseModel, Field
from sqlalchemy import func, or_, select, update
from sqlalchemy.exc import IntegrityError
from sqlalchemy.orm import Session

from app import audit, sysconfig
from app.apitokens import FilesCaller, Right, files_caller
from app.audit import AuditAction
from app.auth import current_user
from app.collation import collated
from app.config import settings
from app.db import get_db, release_read_connection
from app.downloads import folders, preview, quota, service, storage
from app.downloads import upload as uploadmod
from app.downloads.status import JobStatus
from app.mailtext import lang_for_user
from app.models import (
    DISPLAY_TEXT_MAX,
    DownloadJob,
    DownloadLink,
    DownloadShare,
    FileFolder,
    LibraryState,
    MediaAsset,
    User,
    display_text,
)
from app.refusal import refused
from app.routes._common import capped_stream_to, not_found, owned_or_404
from app.utils import iso, like_escape

router = APIRouter(prefix="/api/files", tags=["files"])

# Cap the listing so a heavy library can't return an unbounded result set (the old Download Center's
# own cap; far beyond any real library).
MAX_LIST = 500
# The longest a folder may keep a file, in days — ten years is "forever" in all but name.
_MAX_RETENTION_DAYS = 3650
_HASH_CHUNK = 1 << 20
# How many files the hash route reads at once: each holds a threadpool thread for the whole read.
_HASHERS = 2
_HASHING = threading.BoundedSemaphore(_HASHERS)


# --- shared with routes.downloads -------------------------------------------------------


def serialize(job: DownloadJob, asset: MediaAsset | None) -> dict:
    ready = asset is not None and asset.status == "ready" and bool(asset.rel_path)
    return {
        "id": job.id,
        "status": job.status,
        "progress": job.progress,
        "speed_bps": job.speed_bps,
        "eta_s": job.eta_s,
        "phase": job.phase,
        "error": job.error,
        "error_code": job.error_code,
        "error_detail": job.error_detail,
        "queue_pos": job.queue_pos,
        "created_at": iso(job.created_at),
        "ready_at": iso(job.ready_at),
        "source_kind": job.source_kind,
        "source_ref": job.source_ref,
        "source_url": service.reference_url(job, asset),
        # A locally-generated poster to fall back to when the source had no thumbnail.
        "poster_url": f"/api/downloads/{job.id}/poster.jpg"
        if (asset is not None and asset.poster_path)
        else None,
        "profile_id": job.profile_id,
        "spec": job.profile_snapshot,
        "display_name": job.display_name,
        "display_uploader": job.display_uploader,
        "display_uploader_url": job.display_uploader_url,
        "extra_links": job.extra_links or [],
        "job_kind": job.job_kind,
        "source_job_id": job.source_job_id,
        "edit_spec": job.edit_spec,
        "can_download": ready and job.status == JobStatus.DONE,
        # The Files library: its folder, whether the user keeps it, and when it goes (NULL = never).
        "folder_id": job.folder_id,
        "kept": job.kept,
        "expires_at": iso(job.expires_at),
        "asset": None
        if asset is None
        else {
            "id": asset.id,
            "status": asset.status,
            "title": asset.title,
            "uploader": asset.uploader,
            "upload_date": iso(asset.upload_date),
            "duration_s": asset.duration_s,
            "size_bytes": asset.size_bytes,
            "width": asset.width,
            "height": asset.height,
            "container": asset.container,
            # "video" | "audio" | "file" — the library gates play/edit on this (media only); a
            # generic uploaded file is download-only. Null while still in flight (set at finalize).
            "media_kind": asset.media_kind,
            "uploader_url": asset.uploader_url,
            "thumbnail_url": asset.thumbnail_url,
            # "image" | "pdf" | "text" | null — what `/preview` shows (`downloads/preview.py`).
            "preview": preview.kind(asset.media_kind, asset.container),
        },
    }


def assets_for(db: Session, jobs: Sequence[DownloadJob]) -> dict[int, MediaAsset]:
    ids = {j.asset_id for j in jobs if j.asset_id}
    if not ids:
        return {}
    rows = db.execute(select(MediaAsset).where(MediaAsset.id.in_(ids))).scalars()
    return {a.id: a for a in rows}


def positions_for(db: Session, user: User, jobs: Sequence[DownloadJob]) -> dict[int, int]:
    """`user`'s resume point in each of `jobs` that has one (the library player's `library_states`)."""
    ids = [j.id for j in jobs]
    if not ids:
        return {}
    rows = db.execute(
        select(LibraryState.job_id, LibraryState.position_seconds).where(
            LibraryState.user_id == user.id, LibraryState.job_id.in_(ids)
        )
    ).all()
    return {job_id: pos for job_id, pos in rows}


def serialize_job(db: Session, job: DownloadJob) -> dict:
    """Resolve a job's cache asset (if any) and serialize the pair — the resolve-then-serialize step
    every single-job handler shares."""
    asset = db.get(MediaAsset, job.asset_id) if job.asset_id else None
    return serialize(job, asset)


def own_job_for_update(db: Session, user: User, job_id: int) -> DownloadJob:
    """The ownership check (`owned_or_404`) for a transition that moves its asset's ref count (resume, cancel, delete, redownload)
    or writes the status those decide on (pause). The job is re-read under a row lock, so two
    overlapping requests for one job run one after the other and the second decides on the first's
    committed result — never both releasing the same hold, and never a pause turning a job a cancel
    just released back into a holder; either can free a file another job still holds.

    The asset is locked BEFORE the job: the order a finishing worker child takes them in
    (`service.finalize_if_running`), so the two can never deadlock."""
    while True:
        asset_id = owned_or_404(db, DownloadJob, job_id, user, what="download").asset_id
        if asset_id is not None:
            db.execute(select(MediaAsset.id).where(MediaAsset.id == asset_id).with_for_update())
        job = db.execute(
            select(DownloadJob)
            .where(DownloadJob.id == job_id)
            .with_for_update()
            .execution_options(populate_existing=True)
        ).scalar_one_or_none()
        if job is None:
            raise not_found("download")
        if job.asset_id == asset_id:
            return job
        db.rollback()  # another request moved the job to another asset meanwhile: lock that one


def quota_detail(e: quota.QuotaExceeded) -> dict:
    """Structured error the trilingual client localizes (reason key + numbers), instead of a
    pre-baked English string with a dot-decimal GB value. See lib/api.ts localizeDetail()."""
    return {"code": "quota", "reason": e.reason, "limit": e.limit, "current": e.current}


# The upload's filename and display name travel as HEADERS, not as multipart parts. That is not a
# style choice: a DECLARED body parameter (`file: UploadFile = File(...)`) is read and spooled by
# FastAPI *before the first dependency runs*, so the auth dependency could not gate it and an anonymous
# caller could make the process write the whole per-file allowance to temp, per request (SEC-20
# bounded the number but could not stop the writing). Reading the body ourselves, from a dependency
# declared AFTER the auth one, is the only shape that closes it — the same one
# `POST /api/debug-sessions/{sid}/screenshots` uses, and `test_body_limit.py` now enforces it for
# every route with a raised ceiling rather than leaving it to a comment like this one.
#
# Headers are latin-1 on the wire, so both are percent-encoded by the client and unquoted here; a
# Hungarian filename would otherwise be unsendable.
UPLOAD_FILENAME_HEADER = "x-upload-filename"
UPLOAD_DISPLAY_NAME_HEADER = "x-upload-display-name"
# The folder the file goes in (its id); without it, the user's Uploads folder.
UPLOAD_FOLDER_HEADER = "x-upload-folder"


@dataclass(frozen=True)
class SpooledUpload:
    """What the body dependency hands the handler: the bytes already on disk and their hash, plus
    the names and the folder that came alongside them, and who sent them."""

    path: Path
    size: int
    sha256: str
    user_id: int
    filename: str
    display_name: str | None
    folder_id: int | None
    via: str | None = None


def _header_text(request: Request, name: str) -> str:
    """One percent-encoded header, decoded. A header that is not valid UTF-8 once unquoted is the
    caller's doing, not a server fault — it degrades to empty rather than 500ing, and the route's
    own fallback names the file."""
    raw = request.headers.get(name, "")
    try:
        return unquote(raw, errors="strict").strip()
    except (UnicodeDecodeError, ValueError):
        # silent-ok: a mis-encoded header is the caller's own malformed request, and this one is
        # cosmetic — it names the file. Refusing the upload over it would fail a 500 MiB transfer on
        # a label; logging it would hand any client a free log line per request.
        return ""


def _upload_folder(db: Session, caller: FilesCaller, raw: str) -> int | None:
    """The folder id an upload asked for (`UPLOAD_FOLDER_HEADER`), checked; None when it asked for
    none — which a token may not: it writes only where it was granted to."""
    if not raw.strip():
        if caller.grants is not None:
            raise refused(400, "api_token_folder_required")
        return None
    try:
        folder_id = int(raw)
    except ValueError as e:
        raise refused(409, "file_folder_gone") from e
    if not caller.may(folder_id, Right.WRITE):
        raise not_found("folder")
    try:
        return folders.upload_target(db, caller.user.id, folder_id, hold=False).id
    except folders.FolderError as e:
        raise refused(409, e.reason) from e


class _HashingSink:
    """The upload's file, hashing the bytes on their way in: the hash costs no second read."""

    def __init__(self, out: BinaryIO) -> None:
        self.out = out
        self.hash = hashlib.sha256()

    def write(self, data: bytes, /) -> int:
        self.hash.update(data)
        return self.out.write(data)


async def spool_upload(
    request: Request,
    caller: FilesCaller = Depends(files_caller),
    db: Session = Depends(get_db),
) -> AsyncIterator[SpooledUpload]:
    """Stream the request body to a staging temp file, enforcing the per-file cap as it arrives.

    `caller` comes first on purpose. Dependencies resolve in declaration order, so naming
    `files_caller` here makes the auth check a precondition of reading the body at all — a stranger,
    or a token without the right to write in that folder, is refused before a byte moves. The
    `yield` shape owns the temp file's life: ingest MOVES it into place on success (the unlink is
    then a no-op), and on any other exit — cap hit, empty, quota, probe or move error, a client that
    vanished mid-upload — it is removed."""
    cap = sysconfig.get_int(db, "download_upload_max_bytes")
    user_id = caller.user.id
    via = caller.via
    # A folder the file may not go in is refused before the transfer, not after it.
    folder_id = _upload_folder(db, caller, request.headers.get(UPLOAD_FOLDER_HEADER, ""))
    # Hand the pooled connection back BEFORE the transfer starts — see `db.release_read_connection`
    # for why, and for the precondition it enforces. Everything this dependency still needs is
    # already an int, a string or a header in hand: touching an ORM attribute below (`caller.user`)
    # would reload it and check a connection straight back out.
    release_read_connection(db)
    staging = Path(settings.files_root) / ".staging" / "uploads"
    staging.mkdir(parents=True, exist_ok=True)
    fd, tmp = tempfile.mkstemp(dir=str(staging))
    tmp_path = Path(tmp)
    try:
        with os.fdopen(fd, "wb") as out:
            sink = _HashingSink(out)
            size = await capped_stream_to(
                request,
                sink,
                cap,
                HTTPException(status_code=422, detail={"code": "upload_too_large", "limit": cap}),
            )
        yield SpooledUpload(
            path=tmp_path,
            size=size,
            sha256=sink.hash.hexdigest(),
            user_id=user_id,
            filename=_header_text(request, UPLOAD_FILENAME_HEADER) or "upload",
            display_name=display_text(_header_text(request, UPLOAD_DISPLAY_NAME_HEADER)),
            folder_id=folder_id,
            via=via,
        )
    finally:
        tmp_path.unlink(missing_ok=True)


def accessible_job(db: Session, user: User, job_id: int) -> DownloadJob:
    """A file the caller may read: their own, or one shared with them."""
    job = db.get(DownloadJob, job_id)
    if job is None:
        raise not_found("download")
    if job.user_id == user.id:
        return job
    shared = db.execute(
        select(DownloadShare.id).where(
            DownloadShare.job_id == job_id, DownloadShare.to_user_id == user.id
        )
    ).first()
    if shared is None:
        raise not_found("download")
    return job


def readable_job(db: Session, caller: FilesCaller, job_id: int) -> DownloadJob:
    """A file `caller` may read: as `accessible_job` for the user; for a token, one of the user's
    own in a folder it may read."""
    if caller.grants is None:
        return accessible_job(db, caller.user, job_id)
    job = db.get(DownloadJob, job_id)
    if job is None or job.user_id != caller.user.id or not caller.may(job.folder_id, Right.READ):
        raise not_found("download")
    return job


# --- folders -------------------------------------------------------------------------------


def _serialize_folder(folder: FileFolder, count: int, size: int, linked: bool = False) -> dict:
    return {
        "id": folder.id,
        "kind": folder.kind,
        # A source folder's name is the client's to render from its key, in the reader's language.
        "source_key": folder.source_key,
        "name": folder.name,
        "retention_days": folder.retention_days,
        "count": count,
        "size_bytes": size,
        "created_at": iso(folder.created_at),
        # A live public link opens it: whatever is moved in is shown to whoever holds the link.
        "has_link": linked,
    }


def _linked(db: Session, folder_ids: list[int]) -> set[int]:
    """Which of these folders a live public link opens (one not past its expiry)."""
    now = datetime.now(timezone.utc)
    rows = db.execute(
        select(DownloadLink.folder_id).where(
            DownloadLink.folder_id.in_(folder_ids),
            or_(DownloadLink.expires_at.is_(None), DownloadLink.expires_at > now),
        )
    ).scalars()
    return {folder_id for folder_id in rows if folder_id is not None}


@router.get("/folders")
def list_folders(
    caller: FilesCaller = Depends(files_caller), db: Session = Depends(get_db)
) -> list[dict]:
    """The caller's folders with how many files each holds and their size (a token: the ones it may
    list). A source folder its files have all left stays (count 0): the client decides whether to
    show it."""
    done = (DownloadJob.folder_id == FileFolder.id) & (DownloadJob.status == JobStatus.DONE)
    stmt = select(
        FileFolder,
        func.count(DownloadJob.id),
        func.coalesce(func.sum(MediaAsset.size_bytes), 0),
    ).where(FileFolder.user_id == caller.user.id)
    listable = caller.folders_with(Right.LIST)
    if listable is not None:
        stmt = stmt.where(FileFolder.id.in_(listable))
    rows = db.execute(
        stmt.outerjoin(DownloadJob, done)
        .outerjoin(MediaAsset, MediaAsset.id == DownloadJob.asset_id)
        .group_by(FileFolder.id)
        .order_by(FileFolder.kind.desc(), FileFolder.source_key, FileFolder.name, FileFolder.id)
    ).all()
    linked = _linked(db, [f.id for f, _, _ in rows])
    return [_serialize_folder(f, count, int(size), f.id in linked) for f, count, size in rows]


class FolderIn(BaseModel):
    name: str = Field(min_length=1, max_length=DISPLAY_TEXT_MAX)


def _folder_name(raw: str) -> str:
    name = display_text(raw)
    if not name:
        raise refused(400, "file_folder_name_required")
    return name


@router.post("/folders")
def create_folder(
    body: FolderIn, user: User = Depends(current_user), db: Session = Depends(get_db)
) -> dict:
    folder = FileFolder(user_id=user.id, kind=folders.FolderKind.OWN, name=_folder_name(body.name))
    try:
        with db.begin_nested():
            db.add(folder)
            db.flush()
    except IntegrityError as e:  # the unique (user, lower(name)): one folder per name
        raise refused(409, "file_folder_name_taken") from e
    audit.record(
        db, user.id, AuditAction.FILE_FOLDER_CREATE, target_type="file_folder", target_id=folder.id
    )
    db.commit()
    return _serialize_folder(folder, 0, 0)


class UpdateFolderIn(BaseModel):
    # Presence (model_fields_set) decides what is touched; retention_days null = keep forever.
    name: str | None = Field(default=None, min_length=1, max_length=DISPLAY_TEXT_MAX)
    retention_days: int | None = Field(default=None, ge=1, le=_MAX_RETENTION_DAYS)


@router.patch("/folders/{folder_id}")
def update_folder(
    folder_id: int,
    body: UpdateFolderIn,
    user: User = Depends(current_user),
    db: Session = Depends(get_db),
) -> dict:
    """Rename one of the caller's own folders (a source folder's name is its origin's), and/or set
    how long any of their folders keeps a file (`folders.set_retention`)."""
    folder = owned_or_404(db, FileFolder, folder_id, user, what="folder")
    sent = body.model_fields_set
    if "name" in sent:
        if folder.kind != folders.FolderKind.OWN:
            raise refused(409, "file_folder_not_own")
        folder.name = _folder_name(body.name or "")
        try:
            with db.begin_nested():
                db.flush()
        except IntegrityError as e:
            raise refused(409, "file_folder_name_taken") from e
        audit.record(
            db,
            user.id,
            AuditAction.FILE_FOLDER_RENAME,
            target_type="file_folder",
            target_id=folder.id,
        )
    if "retention_days" in sent:
        # The value replaced is the one read under the folder's lock, not the one read above it.
        try:
            before = folders.set_retention(db, folder, body.retention_days)
        except folders.FolderError as e:
            raise refused(409, e.reason) from e
        if before != body.retention_days:
            audit.record(
                db,
                user.id,
                AuditAction.FILE_FOLDER_RETENTION,
                target_type="file_folder",
                target_id=folder.id,
                before={"retention_days": before},
                after={"retention_days": body.retention_days},
            )
    db.commit()
    count, size = _folder_totals(db, folder.id)
    return _serialize_folder(folder, count, size, folder.id in _linked(db, [folder.id]))


def _folder_totals(db: Session, folder_id: int) -> tuple[int, int]:
    count, size = db.execute(
        select(func.count(DownloadJob.id), func.coalesce(func.sum(MediaAsset.size_bytes), 0))
        .select_from(DownloadJob)
        .outerjoin(MediaAsset, MediaAsset.id == DownloadJob.asset_id)
        .where(DownloadJob.folder_id == folder_id, DownloadJob.status == JobStatus.DONE)
    ).one()
    return count, int(size)


@router.delete("/folders/{folder_id}")
def delete_folder(
    folder_id: int, user: User = Depends(current_user), db: Session = Depends(get_db)
) -> dict:
    """Delete one of the caller's own folders; its files go back to their source folders."""
    folder = owned_or_404(db, FileFolder, folder_id, user, what="folder")
    try:
        moved = folders.delete_own(db, folder)
    except folders.FolderError as e:
        raise refused(409, e.reason) from e
    audit.record(
        db,
        user.id,
        AuditAction.FILE_FOLDER_DELETE,
        target_type="file_folder",
        target_id=folder_id,
        after={"files_moved": moved},
    )
    db.commit()
    return {"ok": True, "deleted": folder_id, "files_moved": moved}


@router.get("/usage")
def my_usage(user: User = Depends(current_user), db: Session = Depends(get_db)) -> dict:
    """The caller's storage quota, plus the per-file upload cap.

    The cap rides here rather than in `quota.usage` because it is not a quota value — it is a
    `sysconfig` knob about one route — and this is the route layer, where composing the two is the
    job. The upload dialog needs it to refuse an over-cap file BEFORE sending it: both server-side
    caps answer too late to be pleasant (the edge ceiling refuses the request outright, see
    `bodylimit.ROUTE_MAX_BODY_BYTES`), and making the user push 600 MB up the wire to be told the
    limit is 500 is a bad answer even when it is a correct one. It is a convenience, not the
    boundary: the caps stay where they are and still refuse a client that ignores this.
    """
    return {
        **quota.usage(db, user.id),
        "upload_max_bytes": sysconfig.get_int(db, "download_upload_max_bytes"),
    }


@router.delete("/shared/{job_id}")
def remove_shared_with_me(
    job_id: int, user: User = Depends(current_user), db: Session = Depends(get_db)
) -> dict:
    """Remove a file that was shared WITH this user from their 'Shared with me' list. Deletes
    only the recipient's share grant — the owner's job and the physical file are untouched (this is
    a per-user dismissal, not a delete)."""
    row = db.execute(
        select(DownloadShare).where(
            DownloadShare.job_id == job_id, DownloadShare.to_user_id == user.id
        )
    ).scalar_one_or_none()
    if row is not None:
        db.delete(row)
        db.commit()
    return {"ok": True, "removed": job_id}


# --- files ---------------------------------------------------------------------------------


@router.get("")
def list_files(
    folder_id: int | None = None,
    q: str = Query("", max_length=200),
    sort: Literal["added", "name", "size"] = "added",
    order: Literal["asc", "desc"] = "desc",
    scope: Literal["mine", "shared"] = "mine",
    caller: FilesCaller = Depends(files_caller),
    db: Session = Depends(get_db),
) -> list[dict]:
    """The caller's done files (`scope=mine`, optionally one folder's), or the ones shared with
    them (`scope=shared`); searched by name and channel, sorted by when they were added, by name
    (in the reader's alphabet) or by size. A token lists only in the folders it may list, and never
    the shared ones."""
    user = caller.user
    listable = caller.folders_with(Right.LIST)
    if listable is not None:
        if scope == "shared":
            raise refused(403, "api_token_scope")
        if folder_id is not None and folder_id not in listable:
            raise not_found("folder")
    stmt = (
        select(DownloadJob)
        .join(MediaAsset, MediaAsset.id == DownloadJob.asset_id)
        .where(DownloadJob.status == JobStatus.DONE)
    )
    shared = scope == "shared"
    if shared:
        stmt = stmt.join(DownloadShare, DownloadShare.job_id == DownloadJob.id).where(
            DownloadShare.to_user_id == user.id
        )
    else:
        stmt = stmt.where(DownloadJob.user_id == user.id)
        if folder_id is not None:
            stmt = stmt.where(DownloadJob.folder_id == folder_id)
        elif listable is not None:
            stmt = stmt.where(DownloadJob.folder_id.in_(listable))
    name = func.coalesce(DownloadJob.display_name, MediaAsset.title, "")
    term = q.strip()
    if term:
        like = f"%{like_escape(term)}%"
        stmt = stmt.where(
            or_(
                name.ilike(like),
                func.coalesce(DownloadJob.display_uploader, MediaAsset.uploader, "").ilike(like),
            )
        )
    # A file is added to its owner's list when it is done, not when it was asked for (a download that
    # failed for days and then went through is new); one shared with the caller, when it was shared.
    key = {
        "added": DownloadShare.created_at if shared else DownloadJob.ready_at,
        "name": collated(name, lang_for_user(user)),
        "size": MediaAsset.size_bytes,
    }[sort]
    first = key.asc() if order == "asc" else key.desc()
    tie = DownloadJob.id.asc() if order == "asc" else DownloadJob.id.desc()
    jobs = db.execute(stmt.order_by(first.nulls_last(), tie).limit(MAX_LIST)).scalars().all()
    assets = assets_for(db, jobs)
    positions = positions_for(db, user, jobs)
    shared_at = _shared_at(db, user, jobs) if shared else {}
    sources = source_keys(db, jobs)
    return [
        {
            **serialize(j, assets.get(j.asset_id) if j.asset_id is not None else None),
            "position_seconds": positions.get(j.id, 0),
            "shared": shared,
            "shared_at": iso(shared_at.get(j.id)),
            "source_key": sources[j.id],
        }
        for j in jobs
    ]


def source_keys(db: Session, jobs: Sequence[DownloadJob]) -> dict[int, str]:
    """Where each file came from (its source folder's key), for the list's Source column, the
    "back to its source folder" move and the download tray's site: a file in a source folder has its folder's key; one moved into
    an own folder (or someone else's, shared) is traced back by `folders.source_key_for`."""
    ids = {j.folder_id for j in jobs if j.folder_id is not None}
    by_id = (
        {f.id: f for f in db.execute(select(FileFolder).where(FileFolder.id.in_(ids))).scalars()}
        if ids
        else {}
    )
    out: dict[int, str] = {}
    for j in jobs:
        folder = by_id.get(j.folder_id) if j.folder_id is not None else None
        if folder is not None and folder.kind == folders.FolderKind.SOURCE and folder.source_key:
            out[j.id] = folder.source_key
        else:
            out[j.id] = folders.source_key_for(db, j)
    return out


def _shared_at(db: Session, user: User, jobs: Sequence[DownloadJob]) -> dict[int, datetime]:
    rows = db.execute(
        select(DownloadShare.job_id, DownloadShare.created_at).where(
            DownloadShare.to_user_id == user.id,
            DownloadShare.job_id.in_([j.id for j in jobs]),
        )
    ).all()
    return {job_id: at for job_id, at in rows}


_MAX_EXTRA_LINKS = 8


def _clean_url(raw) -> str | None:
    """Accept only a plausible http(s) URL (these get rendered as clickable links + embedded in a
    public watch page); anything else is dropped rather than trusted."""
    if not isinstance(raw, str):
        return None
    url = raw.strip()
    if not url:
        return None
    if not url.startswith(("http://", "https://")):
        return None
    # `urlparse` raises on a malformed authority; this function already has a "not a plausible URL"
    # answer, so the typo belongs in it.
    try:
        parsed = urlparse(url)
    # silent-ok: a typo in a link someone pasted. None is this function's "not a plausible URL"
    # answer, the caller already has one, and any line here would carry the URL itself.
    except ValueError:
        return None
    if not parsed.netloc:
        return None
    return url[:2048]


class UpdateFileIn(BaseModel):
    # Presence (model_fields_set) decides what is touched; a null/"" text falls back to the system
    # value (the title, the channel). All display-only: the file on disk keeps its own name.
    name: str | None = None
    uploader: str | None = None
    uploader_url: str | None = None
    extra_links: list | None = None
    folder_id: int | None = None
    kept: bool | None = None


@router.patch("/{job_id}")
def update_file(
    job_id: int,
    body: UpdateFileIn,
    user: User = Depends(current_user),
    db: Session = Depends(get_db),
) -> dict:
    """Rename a file and its channel, set its reference links (all display-only: the file on disk
    keeps its own name), move it to another folder (`folders.move`), or keep it until deleted /
    hand it back to its folder's retention."""
    job = owned_or_404(db, DownloadJob, job_id, user, what="download")
    sent = body.model_fields_set
    if "name" in sent:
        job.display_name = display_text(body.name)
    if "uploader" in sent:
        job.display_uploader = display_text(body.uploader)
    if "uploader_url" in sent:
        job.display_uploader_url = _clean_url(body.uploader_url)
    if "extra_links" in sent:
        raw = body.extra_links or []
        cleaned = [u for u in (_clean_url(x) for x in raw) if u][:_MAX_EXTRA_LINKS]
        job.extra_links = cleaned or None
    if "folder_id" in sent:
        if body.folder_id is None:
            raise refused(400, "file_folder_gone")
        before = job.folder_id
        try:
            folders.move(db, job, folders.own_folder(db, user.id, body.folder_id))
        except folders.FolderError as e:
            raise refused(409, e.reason) from e
        if job.folder_id != before:
            audit.record(
                db,
                user.id,
                AuditAction.FILE_MOVE,
                target_type="file",
                target_id=job.id,
                before={"folder_id": before},
                after={"folder_id": job.folder_id},
            )
    if "kept" in sent and body.kept is not None and body.kept != job.kept:
        folders.set_kept(db, job, body.kept)
        action = AuditAction.FILE_KEEP if body.kept else AuditAction.FILE_UNKEEP
        audit.record(db, user.id, action, target_type="file", target_id=job.id)
    db.commit()
    return serialize_job(db, job)


@router.delete("/{job_id}")
def delete_file(
    job_id: int, caller: FilesCaller = Depends(files_caller), db: Session = Depends(get_db)
) -> dict:
    """Delete a file from the caller's library; the bytes go with their last holder. A token
    deletes only in a folder it may delete in — judged on the row as locked, so a file moved out of
    that folder meanwhile is out of its reach."""
    job = own_job_for_update(db, caller.user, job_id)
    if not caller.may(job.folder_id, Right.DELETE):
        db.rollback()  # lets go of the locks; nothing was written
        raise not_found("download")
    audit.record(
        db,
        caller.user.id,
        AuditAction.FILE_DELETE,
        target_type="file",
        target_id=job_id,
        summary=caller.via,
    )
    service.delete(db, job)  # commits, the audit row with it
    return {"ok": True, "deleted": job_id}


@router.post("/upload")
def upload_file(
    upload: SpooledUpload = Depends(spool_upload),
    db: Session = Depends(get_db),
) -> dict:
    """Put a local file in the caller's library — in the folder `UPLOAD_FOLDER_HEADER` names, else
    their Uploads folder. Any file type; media gets the player, a generic file is download-only.
    The body IS the file (see the header note above `UPLOAD_FILENAME_HEADER`); `spool_upload` has
    authenticated the caller, checked the folder and streamed it to disk already.

    A sync (threadpool) handler on purpose: the ingest does blocking work — an ffprobe of up to 30s
    plus sync DB writes — so it must NOT run on the event loop."""
    return serialize_job(db, ingest_spooled(db, upload))


def ingest_spooled(db: Session, upload: SpooledUpload) -> DownloadJob:
    """The spooled upload into the library (`upload.ingest_upload`, which commits its own rows),
    its refusals answered as HTTP."""
    if upload.size == 0:
        raise HTTPException(status_code=400, detail={"code": "upload_empty"})
    try:
        job = uploadmod.ingest_upload(
            db,
            upload.user_id,
            filename=upload.filename,
            src_path=upload.path,
            size=upload.size,
            display_name=upload.display_name,
            sha256=upload.sha256,
            folder_id=upload.folder_id,
            via=upload.via,
        )
    except quota.QuotaExceeded as e:
        raise HTTPException(status_code=422, detail=quota_detail(e)) from e
    except folders.FolderError as e:  # the folder went while the file was on its way
        raise refused(409, e.reason) from e
    return job


def _ready_file(db: Session, job: DownloadJob) -> tuple[MediaAsset, Path]:
    asset = db.get(MediaAsset, job.asset_id) if job.asset_id else None
    if asset is None or asset.status != "ready" or not asset.rel_path:
        raise refused(409, "download_not_ready")
    path = storage.safe_abs_path(settings.files_root, asset.rel_path)
    if path is None:
        raise not_found("file")
    return asset, path


def serve_file(db: Session, job: DownloadJob) -> FileResponse:
    """The file of `job` (the caller may read it), range-aware, named by the user's display name.

    The served Content-Type comes from the ffprobe-verified media_kind + a container allow-list
    (`storage.served_media_type`), NEVER guessed from the file's own extension. A generic 'file' (and
    any media whose container we don't recognise — e.g. a media/HTML polyglot named "evil.html")
    returns None → a neutral force-download attachment, so uploaded HTML/SVG can't execute inline on
    this origin. Recognised media is served with its real type so the in-app player streams it. Both
    are range-aware (FileResponse → 206). A file whose hash is known says so (`Repr-Digest`, RFC
    9530: the digest of the whole file, whichever range is asked for)."""
    asset, path = _ready_file(db, job)
    filename = storage.download_filename(
        job.display_name or asset.title or asset.source_ref, asset.container, path
    )
    headers = {}
    if asset.sha256:
        digest = base64.b64encode(bytes.fromhex(asset.sha256)).decode()
        headers["Repr-Digest"] = f"sha-256=:{digest}:"
    asset.last_access_at = datetime.now(timezone.utc)  # the handler commits it
    media_type = storage.served_media_type(asset.media_kind, asset.container)
    if media_type is None:
        return FileResponse(
            path,
            filename=filename,
            media_type="application/octet-stream",
            content_disposition_type="attachment",
            headers=headers,
        )
    return FileResponse(path, filename=filename, media_type=media_type, headers=headers)


@router.get("/{job_id}/file")
def get_file(
    job_id: int, caller: FilesCaller = Depends(files_caller), db: Session = Depends(get_db)
):
    response = serve_file(db, readable_job(db, caller, job_id))
    db.commit()
    return response


# A preview's own headers. `sandbox` leaves the answer no script and an opaque origin, whatever the
# file turns out to hold; `frame-ancestors 'self'` lets the app's viewer frame a PDF (every other
# answer keeps the app-wide 'none', main.py), with X-Frame-Options saying the same for old engines.
PREVIEW_HEADERS = {
    "Content-Security-Policy": "sandbox; frame-ancestors 'self'",
    "X-Frame-Options": "SAMEORIGIN",
}
# Set on a text preview cut at `preview.TEXT_PREVIEW_BYTES`, so the viewer can say it shows the start.
TRUNCATED_HEADER = "X-Preview-Truncated"


@router.get("/{job_id}/preview")
def preview_file(
    job_id: int, user: User = Depends(current_user), db: Session = Depends(get_db)
) -> Response:
    """The file shown in the library's viewer: an image or a PDF inline, a text format as plain text
    (its first `TEXT_PREVIEW_BYTES`). The type comes from `downloads/preview.py`'s allow-list, so
    an HTML or SVG upload arrives as text, never as a page. Anything else: 415 `file_no_preview`."""
    job = accessible_job(db, user, job_id)
    asset, path = _ready_file(db, job)
    kind = preview.kind(asset.media_kind, asset.container)
    if kind is None:
        raise refused(415, "file_no_preview")
    headers = dict(PREVIEW_HEADERS)
    if kind == "text":
        with path.open("rb") as f:
            head = f.read(preview.TEXT_PREVIEW_BYTES + 1)
        if len(head) > preview.TEXT_PREVIEW_BYTES:
            head = head[: preview.TEXT_PREVIEW_BYTES]
            headers[TRUNCATED_HEADER] = "1"
        text = preview.text_utf8(head)
        if text is None:
            raise refused(415, "file_no_preview")
        asset.last_access_at = datetime.now(timezone.utc)
        db.commit()
        return Response(text, media_type=preview.media_type(kind, asset.container), headers=headers)
    filename = storage.download_filename(
        job.display_name or asset.title or asset.source_ref, asset.container, path
    )
    asset.last_access_at = datetime.now(timezone.utc)
    db.commit()
    return FileResponse(
        path,
        filename=filename,
        media_type=preview.media_type(kind, asset.container),
        content_disposition_type="inline",
        headers=headers,
    )


@router.get("/{job_id}/sha256")
def get_sha256(
    job_id: int, caller: FilesCaller = Depends(files_caller), db: Session = Depends(get_db)
) -> dict:
    """The file's SHA-256 (hex), hashed now if it never was and kept on the asset for every holder.
    A sync handler: hashing a large file is blocking disk work, so it runs in the threadpool — and
    every other sync route shares that pool, so only `_HASHERS` files are hashed at a time (a caller
    past that is told to come back), and none of them holds a database connection while it reads."""
    asset, path = _ready_file(db, readable_job(db, caller, job_id))
    if asset.sha256:
        return {"sha256": asset.sha256}
    asset_id = asset.id
    if not _HASHING.acquire(blocking=False):
        raise refused(429, "file_hash_busy")
    try:
        release_read_connection(db)
        h = hashlib.sha256()
        with path.open("rb") as f:
            while chunk := f.read(_HASH_CHUNK):
                h.update(chunk)
    except OSError as e:
        raise not_found("file") from e
    finally:
        _HASHING.release()
    digest = h.hexdigest()
    db.execute(
        update(MediaAsset)
        .where(MediaAsset.id == asset_id, MediaAsset.sha256.is_(None))
        .values(sha256=digest)
    )
    db.commit()
    return {"sha256": digest}