"""Capture's reads: what the library, the download tray, the share dialogs and the public watch pages
show. Each returns rows or plain values and writes nothing; whose a row is goes through
`userscope.owned_by` / `owned_row`, so a row of someone else's reads as a missing one.

The HTTP layer (`routes.downloads`, `routes.files`, `routes.public`) asks here and serializes; the
writes are the service's (`service`, `folders`, `links`, `quota`)."""

from collections.abc import Sequence
from datetime import datetime, timezone

from sqlalchemy import func, or_, select
from sqlalchemy.orm import Session

from app.apitokens import FilesCaller, Right
from app.collation import collated
from app.downloads import folders, links, quota
from app.downloads.models import (
    DownloadJob,
    DownloadLink,
    DownloadProfile,
    DownloadQuota,
    DownloadShare,
    FileFolder,
    LibraryState,
    MediaAsset,
)
from app.downloads.status import FINISHED, JobStatus
from app.models import User
from app.userscope import owned_by, owned_row
from app.utils import like_escape

# Cap a 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


# --- jobs and their files ------------------------------------------------------------------


def own_job(db: Session, user: User, job_id: int) -> DownloadJob | None:
    return owned_row(db, DownloadJob, job_id, user)


def job(db: Session, job_id: int) -> DownloadJob | None:
    """A job by id, whoever's — for a public link, which already names its job."""
    return db.get(DownloadJob, job_id)


def accessible_job(db: Session, user: User, job_id: int) -> DownloadJob | None:
    """A file the caller may read: their own, or one shared with them."""
    row = db.get(DownloadJob, job_id)
    if row is None:
        return None
    if row.user_id == user.id or shared_with(db, job_id, user) is not None:
        return row
    return None


def readable_job(db: Session, caller: FilesCaller, job_id: int) -> DownloadJob | None:
    """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)
    row = own_job(db, caller.user, job_id)
    if row is None or not caller.may(row.folder_id, Right.READ):
        return None
    return row


def asset_of(db: Session, job: DownloadJob | None) -> MediaAsset | None:
    """The file under a job, if it has one yet."""
    return db.get(MediaAsset, job.asset_id) if job is not None and job.asset_id else None


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(
            owned_by(LibraryState.user_id, user), LibraryState.job_id.in_(ids)
        )
    ).all()
    return {job_id: pos for job_id, pos in rows}


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 queue(db: Session, user: User, recent: datetime) -> list[DownloadJob]:
    """The download tray: what is waiting, running, paused or failed, and what finished (done or
    canceled) since `recent`. A done job is timed from when it became done, never from its last
    write: a rename, a move or the GC's expiry warning touches an old file's row, and the tray would
    announce it as just finished."""
    return list(
        db.execute(
            select(DownloadJob)
            .where(
                owned_by(DownloadJob.user_id, user),
                DownloadJob.status.not_in(FINISHED)
                | ((DownloadJob.status == JobStatus.DONE) & (DownloadJob.ready_at >= recent))
                | ((DownloadJob.status == JobStatus.CANCELED) & (DownloadJob.updated_at >= recent)),
            )
            .order_by(DownloadJob.created_at.desc(), DownloadJob.id.desc())
            .limit(MAX_LIST)
        ).scalars()
    )


def statuses_by_source(db: Session, user: User, statuses: Sequence[str]) -> list[tuple[str, str]]:
    """(source_ref, status) of each of `user`'s jobs in one of `statuses`."""
    return list(
        db.execute(
            select(DownloadJob.source_ref, DownloadJob.status).where(
                owned_by(DownloadJob.user_id, user), DownloadJob.status.in_(tuple(statuses))
            )
        ).tuples()
    )


def library(
    db: Session,
    user: User,
    *,
    folder_id: int | None,
    listable: set[int] | None,
    shared: bool,
    term: str,
    sort: str,
    order: str,
    lang: str,
) -> list[DownloadJob]:
    """The caller's done files (optionally one folder's, or only in the folders a token may list),
    or the ones shared with them; searched by name and channel, sorted by when they were added, by
    name (in the reader's alphabet) or by size. 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."""
    stmt = (
        select(DownloadJob)
        .join(MediaAsset, MediaAsset.id == DownloadJob.asset_id)
        .where(DownloadJob.status == JobStatus.DONE)
    )
    if shared:
        stmt = stmt.join(DownloadShare, DownloadShare.job_id == DownloadJob.id).where(
            owned_by(DownloadShare.to_user_id, user)
        )
    else:
        stmt = stmt.where(owned_by(DownloadJob.user_id, user))
        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, "")
    if term:
        like = f"%{like_escape(term)}%"
        stmt = stmt.where(
            or_(
                name.ilike(like),
                func.coalesce(DownloadJob.display_uploader, MediaAsset.uploader, "").ilike(like),
            )
        )
    key = {
        "added": DownloadShare.created_at if shared else DownloadJob.ready_at,
        "name": collated(name, lang),
        "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()
    return list(db.execute(stmt.order_by(first.nulls_last(), tie).limit(MAX_LIST)).scalars())


def recent_jobs(db: Session) -> list[DownloadJob]:
    """Everyone's newest jobs, for the admin's list."""
    return list(
        db.execute(
            select(DownloadJob)
            .order_by(DownloadJob.created_at.desc(), DownloadJob.id.desc())
            .limit(MAX_LIST)
        ).scalars()
    )


# --- shares --------------------------------------------------------------------------------


def shared_with(db: Session, job_id: int, user: User | int) -> DownloadShare | None:
    """The grant that hands this job to `user`, if there is one."""
    return db.execute(
        select(DownloadShare).where(
            DownloadShare.job_id == job_id, owned_by(DownloadShare.to_user_id, user)
        )
    ).scalar_one_or_none()


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


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


def own_folder(db: Session, user: User, folder_id: int) -> FileFolder | None:
    return owned_row(db, FileFolder, folder_id, user)


def folders_by_id(db: Session, ids: set[int]) -> dict[int, FileFolder]:
    """These folders, by id — for a reader that already knows which ones (a token's grants)."""
    if not ids:
        return {}
    return {f.id: f for f in db.execute(select(FileFolder).where(FileFolder.id.in_(ids))).scalars()}


def folders_with_totals(
    db: Session, user: User, listable: set[int] | None
) -> list[tuple[FileFolder, int, int]]:
    """The user's folders (only `listable` ones, when given) with how many done files each holds and
    their size. A source folder its files have all left stays (count 0)."""
    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(owned_by(FileFolder.user_id, user))
    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)
    ).tuples()
    return [(f, count, int(size or 0)) for f, count, size in rows]


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)


def linked_folders(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}


# --- links ---------------------------------------------------------------------------------


def own_link(db: Session, user: User, link_id: int) -> DownloadLink | None:
    """A link to one of the user's files or folders."""
    link = db.get(DownloadLink, link_id)
    if link is None:
        return None
    target = (
        db.get(DownloadJob, link.job_id)
        if link.job_id is not None
        else db.get(FileFolder, link.folder_id)
    )
    if target is None or target.user_id != user.id:
        return None
    return link


def links_to(
    db: Session, *, job_id: int | None = None, folder_id: int | None = None
) -> list[DownloadLink]:
    """The links to one file or one folder, newest first."""
    target = (
        DownloadLink.job_id == job_id if job_id is not None else DownloadLink.folder_id == folder_id
    )
    return list(
        db.execute(select(DownloadLink).where(target).order_by(DownloadLink.id.desc())).scalars()
    )


def link_folder(db: Session, link: DownloadLink) -> FileFolder | None:
    return db.get(FileFolder, link.folder_id) if link.folder_id is not None else None


def folder_job(db: Session, folder: FileFolder, job_id: int) -> DownloadJob | None:
    """One of the files a link to `folder` reaches (`links.in_folder`), while it is in it."""
    return db.execute(
        select(DownloadJob).where(DownloadJob.id == job_id, *links.in_folder(folder))
    ).scalar_one_or_none()


def owner_suspended(db: Session, job: DownloadJob) -> bool:
    """The job's owner is suspended (or gone): the worker leaves their queued jobs where they are."""
    owner = db.get(User, job.user_id)
    return owner is None or owner.is_suspended


# --- profiles ------------------------------------------------------------------------------


def profiles_for(db: Session, user: User) -> list[DownloadProfile]:
    """The built-in format profiles, then the user's own."""
    return list(
        db.execute(
            select(DownloadProfile)
            .where(DownloadProfile.is_builtin.is_(True) | owned_by(DownloadProfile.user_id, user))
            .order_by(
                DownloadProfile.is_builtin.desc(), DownloadProfile.sort_order, DownloadProfile.id
            )
        ).scalars()
    )


def own_profile(db: Session, user: User, profile_id: int) -> DownloadProfile | None:
    """One of the user's own profiles (a built-in is no one's to change)."""
    p = owned_row(db, DownloadProfile, profile_id, user)
    return None if p is None or p.is_builtin else p


def usable_profile(db: Session, user: User, profile_id: int) -> DownloadProfile | None:
    """A profile the user may enqueue with: a built-in, or their own."""
    p = db.get(DownloadProfile, profile_id)
    if p is None or (not p.is_builtin and p.user_id != user.id):
        return None
    return p


def default_profile(db: Session) -> DownloadProfile | None:
    """The first built-in, for an enqueue that named no format."""
    return db.execute(
        select(DownloadProfile)
        .where(DownloadProfile.is_builtin.is_(True))
        .order_by(DownloadProfile.sort_order)
        .limit(1)
    ).scalar_one_or_none()


# --- storage and quota (admin) -------------------------------------------------------------


def storage_totals(db: Session) -> tuple[int, int, int]:
    """(files on disk, their bytes, every asset row). On disk is `quota.ON_DISK`: ready files, and
    uploads waiting for or failed in their conversion — the same disk the footprint and the GC cap
    count."""
    on_disk = db.execute(
        select(func.count(), func.coalesce(func.sum(MediaAsset.size_bytes), 0)).where(quota.ON_DISK)
    ).one()
    total_assets = db.execute(select(func.count()).select_from(MediaAsset)).scalar_one()
    return on_disk[0], int(on_disk[1]), total_assets


def done_files_per_user(db: Session) -> dict[int, int]:
    """How many finished files each user's Files lists."""
    return dict(
        db.execute(
            select(DownloadJob.user_id, func.count())
            .where(DownloadJob.status == JobStatus.DONE)
            .group_by(DownloadJob.user_id)
        )
        .tuples()
        .all()
    )


def custom_quota(db: Session, user_id: int) -> DownloadQuota | None:
    """The admin's own limits for this user, if any were set."""
    return db.get(DownloadQuota, user_id)