"""Plex playlists: the current user's personal, orderable playlists of playable items."""

from datetime import datetime, timezone

from fastapi import APIRouter, Depends
from typing import Annotated

from pydantic import BaseModel, Field, model_validator
from sqlalchemy import delete, func, select
from sqlalchemy.orm import Session

from app.auth import current_user
from app.db import get_db
from app.models import (
    PlexItem,
    PlexPlaylist,
    PlexPlaylistItem,
    PlexShow,
    PlexState,
    User,
)
from app.plex.cards import leaf_card
from app.plex.lookups import by_rating_key
from app.routes._common import owned_or_404, not_found
from app.refusal import refused

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


def _playlist_card(pl: PlexPlaylist, count: int, thumb_rk: str | None) -> dict:
    return {
        "id": pl.id,
        "title": pl.title,
        "item_count": count,
        "thumb": f"/api/plex/image/{thumb_rk}" if thumb_rk else None,
    }


def _playlist_item_query(pid: int):
    return (
        select(PlexPlaylistItem, PlexItem)
        .join(PlexItem, PlexItem.id == PlexPlaylistItem.item_id)
        .where(PlexPlaylistItem.playlist_id == pid)
        .order_by(PlexPlaylistItem.position, PlexPlaylistItem.id)
    )


@router.get("/playlists")
def playlists(
    contains: str | None = None,
    contains_group: str | None = None,
    user: User = Depends(current_user),
    db: Session = Depends(get_db),
) -> dict:
    """The current user's playlists (newest-touched first), each with an item count + a cover thumb.
    `contains`=an item rating_key adds `has_item` per playlist (for the single 'add to playlist' dialog).
    `contains_group`=a comma-separated list of rating_keys adds `group_in` per playlist (how many of the
    group it already holds) + a top-level `group_size`, for the 'add a whole season/show' dialog."""
    contains_id = None
    if contains:
        contains_id = db.scalar(select(PlexItem.id).where(PlexItem.rating_key == str(contains)))
    group_ids: set[int] | None = None
    if contains_group is not None:
        rks = [s for s in (contains_group or "").split(",") if s]
        group_ids = set(
            db.execute(select(PlexItem.id).where(PlexItem.rating_key.in_(rks or [""]))).scalars()
        )
    out = []
    for pl in db.execute(
        select(PlexPlaylist)
        .where(PlexPlaylist.user_id == user.id)
        .order_by(PlexPlaylist.updated_at.desc())
    ).scalars():
        count = (
            db.scalar(
                select(func.count(PlexPlaylistItem.id)).where(PlexPlaylistItem.playlist_id == pl.id)
            )
            or 0
        )
        first = db.execute(_playlist_item_query(pl.id)).first()
        card = _playlist_card(pl, count, first[1].rating_key if first else None)
        if contains_id is not None:
            card["has_item"] = (
                db.execute(
                    select(PlexPlaylistItem.id).where(
                        PlexPlaylistItem.playlist_id == pl.id,
                        PlexPlaylistItem.item_id == contains_id,
                    )
                ).first()
                is not None
            )
        if group_ids is not None:
            card["group_in"] = (
                db.scalar(
                    select(func.count(PlexPlaylistItem.id)).where(
                        PlexPlaylistItem.playlist_id == pl.id,
                        PlexPlaylistItem.item_id.in_(group_ids or [0]),
                    )
                )
                or 0
            )
        out.append(card)
    resp: dict = {"playlists": out}
    if group_ids is not None:
        resp["group_size"] = len(group_ids)
    return resp


class CreatePlexPlaylistIn(BaseModel):
    title: str = ""
    item_rating_key: str = ""


@router.post("/playlists")
def create_playlist(
    body: CreatePlexPlaylistIn,
    user: User = Depends(current_user),
    db: Session = Depends(get_db),
) -> dict:
    title = body.title.strip()
    if not title:
        raise refused(400, "title_required")
    pl = PlexPlaylist(user_id=user.id, title=title)
    db.add(pl)
    db.flush()
    seed = body.item_rating_key
    count = 0
    thumb_rk = None
    if seed:
        it = by_rating_key(db, PlexItem, seed)
        if it is not None:
            db.add(PlexPlaylistItem(playlist_id=pl.id, item_id=it.id, position=0))
            count, thumb_rk = 1, it.rating_key
    db.commit()
    return _playlist_card(pl, count, thumb_rk)


@router.get("/playlists/{pid}")
def playlist_detail(
    pid: int, user: User = Depends(current_user), db: Session = Depends(get_db)
) -> dict:
    pl = owned_or_404(db, PlexPlaylist, pid, user, what="playlist")
    rows = db.execute(_playlist_item_query(pid)).all()
    items = [it for (_pi, it) in rows]
    states = {
        s.item_id: s
        for s in db.execute(
            select(PlexState).where(
                PlexState.user_id == user.id,
                PlexState.item_id.in_([it.id for it in items] or [0]),
            )
        ).scalars()
    }
    shows = {
        sh.id: sh
        for sh in db.execute(
            select(PlexShow).where(
                PlexShow.id.in_([it.show_id for it in items if it.show_id] or [0])
            )
        ).scalars()
    }
    cards = [
        leaf_card(
            it,
            states.get(it.id),
            shows[it.show_id].title if it.show_id in shows else None,
            shows[it.show_id].rating_key if it.show_id in shows else None,
        )
        for it in items
    ]
    return {"id": pl.id, "title": pl.title, "items": cards}


class RenamePlexPlaylistIn(BaseModel):
    title: str = ""


@router.patch("/playlists/{pid}")
def rename_playlist(
    pid: int,
    body: RenamePlexPlaylistIn,
    user: User = Depends(current_user),
    db: Session = Depends(get_db),
) -> dict:
    pl = owned_or_404(db, PlexPlaylist, pid, user, what="playlist")
    title = body.title.strip()
    if not title:
        raise refused(400, "title_required")
    pl.title = title
    db.commit()
    count = (
        db.scalar(
            select(func.count(PlexPlaylistItem.id)).where(PlexPlaylistItem.playlist_id == pl.id)
        )
        or 0
    )
    first = db.execute(_playlist_item_query(pl.id)).first()
    return _playlist_card(pl, count, first[1].rating_key if first else None)


@router.delete("/playlists/{pid}")
def delete_playlist(
    pid: int, user: User = Depends(current_user), db: Session = Depends(get_db)
) -> dict:
    pl = owned_or_404(db, PlexPlaylist, pid, user, what="playlist")
    db.delete(pl)
    db.commit()
    return {"deleted": pid}


class PlexItemRefIn(BaseModel):
    item_rating_key: str = ""


@router.post("/playlists/{pid}/items")
def playlist_add_item(
    pid: int,
    body: PlexItemRefIn,
    user: User = Depends(current_user),
    db: Session = Depends(get_db),
) -> dict:
    # Locked (like every add / reorder here): two adds otherwise read the same max position.
    pl = owned_or_404(db, PlexPlaylist, pid, user, what="playlist", lock=True)
    it = by_rating_key(db, PlexItem, body.item_rating_key)
    if it is None:
        raise not_found("item")
    exists = (
        db.execute(
            select(PlexPlaylistItem).where(
                PlexPlaylistItem.playlist_id == pid, PlexPlaylistItem.item_id == it.id
            )
        )
        .scalars()
        .first()
    )
    if exists is None:
        maxpos = db.scalar(
            select(func.coalesce(func.max(PlexPlaylistItem.position), -1)).where(
                PlexPlaylistItem.playlist_id == pid
            )
        )
        db.add(PlexPlaylistItem(playlist_id=pid, item_id=it.id, position=int(maxpos) + 1))
        pl.updated_at = datetime.now(timezone.utc)
    db.commit()
    return {"ok": True}


@router.delete("/playlists/{pid}/items/{item_rating_key}")
def playlist_remove_item(
    pid: int,
    item_rating_key: str,
    user: User = Depends(current_user),
    db: Session = Depends(get_db),
) -> dict:
    pl = owned_or_404(db, PlexPlaylist, pid, user, what="playlist")
    it = by_rating_key(db, PlexItem, item_rating_key)
    if it is not None:
        db.execute(
            delete(PlexPlaylistItem).where(
                PlexPlaylistItem.playlist_id == pid, PlexPlaylistItem.item_id == it.id
            )
        )
        pl.updated_at = datetime.now(timezone.utc)
    db.commit()
    return {"ok": True}


class PlexItemKeysIn(BaseModel):
    item_rating_keys: list[str] = []


def _items_by_rks(db: Session, rks: list) -> list[PlexItem]:
    """Resolve rating_keys to PlexItems, preserving the input order (drops unknown keys)."""
    order = [str(k) for k in rks if str(k)]
    if not order:
        return []
    by_rk = {
        it.rating_key: it
        for it in db.execute(select(PlexItem).where(PlexItem.rating_key.in_(order))).scalars()
    }
    seen: set[str] = set()
    out: list[PlexItem] = []
    for rk in order:
        it = by_rk.get(rk)
        if it is not None and rk not in seen:
            seen.add(rk)
            out.append(it)
    return out


class PlexItemAddBulkIn(PlexItemKeysIn):
    # Where each key goes back (E28 S3e2, the list page's "Undo" of a removal): an index over the
    # ORDERED rows, one per key. The two-call shape (append, then send the whole order) leaves the rows
    # at the end whenever the second call fails, and the order it sends would overwrite anything
    # another tab changed in between.
    positions: list[Annotated[int, Field(ge=0)]] | None = None

    @model_validator(mode="after")
    def _one_position_per_key(self):
        if self.positions is not None and len(self.positions) != len(self.item_rating_keys):
            raise ValueError("positions must pair one-to-one with item_rating_keys")
        return self


def _insert_at(db: Session, pid: int, placed: list[tuple[int, PlexItem]]) -> int:
    """Insert new rows at their indices (ascending, so each index is where the row stood when the
    rows before it were back), renumber the whole list 0..n-1, and say how many were added. An item
    already in the list does not move: the add stays idempotent."""
    rows = list(
        db.execute(
            select(PlexPlaylistItem)
            .where(PlexPlaylistItem.playlist_id == pid)
            .order_by(PlexPlaylistItem.position, PlexPlaylistItem.id)
        ).scalars()
    )
    present = {r.item_id for r in rows}
    added = 0
    for at, it in sorted(placed, key=lambda p: p[0]):
        if it.id in present:
            continue
        row = PlexPlaylistItem(playlist_id=pid, item_id=it.id, position=0)
        db.add(row)
        rows.insert(min(at, len(rows)), row)
        present.add(it.id)
        added += 1
    for i, r in enumerate(rows):
        r.position = i
    return added


@router.post("/playlists/{pid}/items/bulk")
def playlist_add_bulk(
    pid: int,
    body: PlexItemAddBulkIn,
    user: User = Depends(current_user),
    db: Session = Depends(get_db),
) -> dict:
    """Append many items at once (a whole season/show). Already-present items are skipped; the input
    order is preserved for the newly-added ones. With `positions`, each key is put back at its index
    instead of appended. Returns how many were added + the new total."""
    pl = owned_or_404(db, PlexPlaylist, pid, user, what="playlist", lock=True)
    if body.positions is not None:
        by_rk = {it.rating_key: it for it in _items_by_rks(db, body.item_rating_keys)}
        placed = [
            (at, by_rk[str(rk)])
            for rk, at in zip(body.item_rating_keys, body.positions, strict=True)
            if str(rk) in by_rk
        ]
        added = _insert_at(db, pid, placed)
        if added:
            pl.updated_at = datetime.now(timezone.utc)
        db.commit()
        total = (
            db.scalar(
                select(func.count(PlexPlaylistItem.id)).where(PlexPlaylistItem.playlist_id == pid)
            )
            or 0
        )
        return {"ok": True, "added": added, "item_count": total}
    items = _items_by_rks(db, body.item_rating_keys)
    existing = set(
        db.execute(
            select(PlexPlaylistItem.item_id).where(PlexPlaylistItem.playlist_id == pid)
        ).scalars()
    )
    pos = int(
        db.scalar(
            select(func.coalesce(func.max(PlexPlaylistItem.position), -1)).where(
                PlexPlaylistItem.playlist_id == pid
            )
        )
    )
    added = 0
    for it in items:
        if it.id in existing:
            continue
        pos += 1
        db.add(PlexPlaylistItem(playlist_id=pid, item_id=it.id, position=pos))
        existing.add(it.id)
        added += 1
    if added:
        pl.updated_at = datetime.now(timezone.utc)
    db.commit()
    total = (
        db.scalar(
            select(func.count(PlexPlaylistItem.id)).where(PlexPlaylistItem.playlist_id == pid)
        )
        or 0
    )
    return {"ok": True, "added": added, "item_count": total}


@router.post("/playlists/{pid}/items/remove-bulk")
def playlist_remove_bulk(
    pid: int,
    body: PlexItemKeysIn,
    user: User = Depends(current_user),
    db: Session = Depends(get_db),
) -> dict:
    """Remove many items at once (a whole season/show, or a multi-select). Returns how many were
    removed + the new total."""
    pl = owned_or_404(db, PlexPlaylist, pid, user, what="playlist")
    ids = [it.id for it in _items_by_rks(db, body.item_rating_keys)]
    removed = 0
    if ids:
        removed = db.execute(
            delete(PlexPlaylistItem).where(
                PlexPlaylistItem.playlist_id == pid, PlexPlaylistItem.item_id.in_(ids)
            ),
            execution_options={"synchronize_session": False},
        ).rowcount
        if removed:
            pl.updated_at = datetime.now(timezone.utc)
    db.commit()
    total = (
        db.scalar(
            select(func.count(PlexPlaylistItem.id)).where(PlexPlaylistItem.playlist_id == pid)
        )
        or 0
    )
    return {"ok": True, "removed": removed, "item_count": total}


@router.put("/playlists/{pid}/order")
def reorder_playlist(
    pid: int,
    body: PlexItemKeysIn,
    user: User = Depends(current_user),
    db: Session = Depends(get_db),
) -> dict:
    """Set the playlist order from an explicit list of item rating_keys (0-based positions)."""
    pl = owned_or_404(db, PlexPlaylist, pid, user, what="playlist", lock=True)
    order = body.item_rating_keys
    id_by_rk = {
        it.rating_key: it.id
        for it in db.execute(
            select(PlexItem).where(PlexItem.rating_key.in_(order or [""]))
        ).scalars()
    }
    rows = {
        r.item_id: r
        for r in db.execute(
            select(PlexPlaylistItem).where(PlexPlaylistItem.playlist_id == pid)
        ).scalars()
    }
    pos = 0
    seen: set[int] = set()
    for rk in order:
        row = rows.get(id_by_rk.get(rk, -1))
        if row is not None and row.item_id not in seen:
            row.position = pos
            pos += 1
            seen.add(row.item_id)
    # Rows the payload omitted (added in another tab meanwhile) keep their relative order after
    # the given ones, so no two rows share a position (the YouTube reorder does the same).
    for row in sorted(
        (r for iid, r in rows.items() if iid not in seen), key=lambda r: (r.position, r.id)
    ):
        row.position = pos
        pos += 1
    pl.updated_at = datetime.now(timezone.utc)
    db.commit()
    return {"ok": True}