import os
from datetime import datetime, timedelta
from typing import Optional

from fastapi import APIRouter, Depends, HTTPException, BackgroundTasks
from pydantic import BaseModel
from sqlalchemy.orm import Session
from sqlalchemy import text

from ..auth_utils import get_current_user
from ..config import settings
from ..database import get_db, SessionLocal
from ..models import Channel, Download, User, UserSettings, UserVideo, Video
from ..services import ytdlp

router = APIRouter()


class DownloadRequest(BaseModel):
    youtube_video_id: str
    quality: Optional[str] = None
    subtitle_langs: Optional[str] = None  # overrides user setting when provided


TRASH_TTL_DAYS = 7

class DownloadOut(BaseModel):
    id: int
    status: str
    progress_percent: float
    video_title: Optional[str]
    video_thumbnail_url: Optional[str]
    youtube_video_id: Optional[str]
    file_url: Optional[str]
    resolution: Optional[str]
    created_at: datetime
    completed_at: Optional[datetime]
    error_message: Optional[str]
    pending_delete_at: Optional[datetime] = None

    model_config = {"from_attributes": True}


def _on_progress(download_id: int, pct: float):
    db = SessionLocal()
    try:
        dl = db.query(Download).filter(Download.id == download_id).first()
        if dl:
            dl.progress_percent = pct
            dl.status = "downloading"
            db.commit()
    finally:
        db.close()


def _on_complete(download_id: int, file_path: Optional[str], resolution: Optional[str] = None):
    db = SessionLocal()
    try:
        dl = db.query(Download).filter(Download.id == download_id).first()
        if dl:
            dl.status = "complete"
            dl.progress_percent = 100.0
            dl.completed_at = datetime.utcnow()
            dl.file_path = file_path
            dl.resolution = resolution
            db.commit()

            uv = db.query(UserVideo).filter_by(user_id=dl.user_id, video_id=dl.video_id).first()
            if not uv:
                uv = UserVideo(user_id=dl.user_id, video_id=dl.video_id)
                db.add(uv)
            uv.downloaded = True
            uv.downloaded_at = datetime.utcnow()
            db.commit()
    finally:
        db.close()


def _on_error(download_id: int, message: str):
    db = SessionLocal()
    try:
        dl = db.query(Download).filter(Download.id == download_id).first()
        if dl:
            dl.status = "failed"
            dl.error_message = message
            db.commit()
    finally:
        db.close()


def _ensure_video(db: Session, youtube_video_id: str) -> Video:
    video = db.query(Video).filter_by(youtube_video_id=youtube_video_id).first()
    if video:
        return video

    meta = ytdlp.fetch_video_metadata(youtube_video_id)
    if not meta:
        raise HTTPException(status_code=404, detail="Video not found on YouTube")

    ch_data = meta.pop("channel", {}) or {}
    yt_channel_id = ch_data.get("youtube_channel_id")
    channel = None
    if yt_channel_id:
        channel = db.query(Channel).filter_by(youtube_channel_id=yt_channel_id).first()
        if not channel:
            channel = Channel(**{k: v for k, v in ch_data.items() if hasattr(Channel, k)})
            db.add(channel)
            db.flush()

    video = Video(
        channel_id=channel.id if channel else None,
        **{k: v for k, v in meta.items() if hasattr(Video, k)},
    )
    db.add(video)
    db.commit()
    db.refresh(video)
    return video


@router.post("", response_model=DownloadOut, status_code=201)
def create_download(
    body: DownloadRequest,
    background_tasks: BackgroundTasks,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    video = _ensure_video(db, body.youtube_video_id)
    user_settings = db.query(UserSettings).filter_by(user_id=current_user.id).first()
    default_quality = user_settings.preferred_quality if user_settings else "best"
    quality = body.quality if body.quality in ytdlp.QUALITY_FORMATS else default_quality
    if body.subtitle_langs is not None:
        subtitle_langs = body.subtitle_langs.strip()
    else:
        subtitle_langs = (user_settings.subtitle_langs or "") if user_settings else ""

    _DL_SELECT = """
        SELECT d.id, d.status, d.progress_percent, d.resolution,
               d.created_at, d.completed_at, d.error_message, d.pending_delete_at,
               v.title AS video_title, v.thumbnail_url AS video_thumbnail_url,
               v.youtube_video_id,
               '/files/' || v.youtube_video_id || '.mp4' AS file_url
        FROM downloads d JOIN videos v ON d.video_id = v.id
        WHERE d.id = :id
    """

    existing = db.query(Download).filter_by(
        user_id=current_user.id,
        video_id=video.id,
    ).filter(Download.status.in_(["pending", "downloading", "complete"])).first()
    if existing:
        row = db.execute(text(_DL_SELECT), {"id": existing.id}).mappings().first()
        return DownloadOut(**dict(row))

    dl = Download(user_id=current_user.id, video_id=video.id, status="pending")
    db.add(dl)
    db.commit()
    db.refresh(dl)

    background_tasks.add_task(
        ytdlp.start_download,
        video.youtube_video_id, dl.id,
        _on_progress, _on_complete, _on_error,
        quality, subtitle_langs,
    )

    row = db.execute(text(_DL_SELECT), {"id": dl.id}).mappings().first()
    return DownloadOut(**dict(row))


@router.get("", response_model=list[DownloadOut])
def list_downloads(
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    _purge_expired_trash(db)
    rows = db.execute(
        text("""
            SELECT d.id, d.status, d.progress_percent, d.created_at, d.completed_at,
                   d.error_message, d.pending_delete_at, d.resolution,
                   v.title AS video_title, v.thumbnail_url AS video_thumbnail_url,
                   v.youtube_video_id,
                   '/files/' || v.youtube_video_id || '.mp4' AS file_url
            FROM downloads d JOIN videos v ON d.video_id = v.id
            WHERE d.user_id = :user_id
            ORDER BY d.created_at DESC
            LIMIT 200
        """),
        {"user_id": current_user.id},
    ).mappings().all()
    return [DownloadOut(**dict(r)) for r in rows]


def _get_quality(db, user_id: int) -> str:
    s = db.query(UserSettings).filter_by(user_id=user_id).first()
    return s.preferred_quality if s else "best"


def _get_subtitle_langs(db, user_id: int) -> str:
    s = db.query(UserSettings).filter_by(user_id=user_id).first()
    return (s.subtitle_langs or "") if s else ""


@router.post("/channel/{channel_id}", status_code=202)
def download_channel_videos(
    channel_id: int,
    background_tasks: BackgroundTasks,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    quality = _get_quality(db, current_user.id)
    subtitle_langs = _get_subtitle_langs(db, current_user.id)
    rows = db.execute(
        text("""
            SELECT v.id, v.youtube_video_id
            FROM videos v
            LEFT JOIN downloads d ON v.id = d.video_id AND d.user_id = :uid
                AND d.status IN ('pending', 'downloading', 'complete')
            WHERE v.channel_id = :cid AND d.id IS NULL
        """),
        {"uid": current_user.id, "cid": channel_id},
    ).mappings().all()

    count = 0
    for row in rows:
        dl = Download(user_id=current_user.id, video_id=row["id"], status="pending")
        db.add(dl)
        db.flush()
        background_tasks.add_task(
            ytdlp.start_download, row["youtube_video_id"], dl.id,
            _on_progress, _on_complete, _on_error, quality, subtitle_langs,
        )
        count += 1
    db.commit()
    return {"queued": count}


@router.post("/following", status_code=202)
def download_following_videos(
    background_tasks: BackgroundTasks,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    quality = _get_quality(db, current_user.id)
    subtitle_langs = _get_subtitle_langs(db, current_user.id)
    rows = db.execute(
        text("""
            SELECT v.id, v.youtube_video_id
            FROM videos v
            JOIN channels c ON v.channel_id = c.id
            JOIN user_channels uc ON c.id = uc.channel_id
                AND uc.user_id = :uid AND uc.status = 'followed'
            LEFT JOIN downloads d ON v.id = d.video_id AND d.user_id = :uid
                AND d.status IN ('pending', 'downloading', 'complete')
            WHERE d.id IS NULL
        """),
        {"uid": current_user.id},
    ).mappings().all()

    count = 0
    for row in rows:
        dl = Download(user_id=current_user.id, video_id=row["id"], status="pending")
        db.add(dl)
        db.flush()
        background_tasks.add_task(
            ytdlp.start_download, row["youtube_video_id"], dl.id,
            _on_progress, _on_complete, _on_error, quality,
        )
        count += 1
    db.commit()
    return {"queued": count}


def _purge_expired_trash(db: Session):
    expired = db.execute(
        text("SELECT id, video_id, user_id FROM downloads WHERE pending_delete_at IS NOT NULL AND pending_delete_at <= :now"),
        {"now": datetime.utcnow()},
    ).mappings().all()
    for row in expired:
        video = db.query(Video).filter_by(id=row["video_id"]).first()
        if video:
            fp = ytdlp.predicted_file_path(video.youtube_video_id)
            if fp.exists():
                try:
                    os.remove(fp)
                except OSError:
                    pass
            uv = db.query(UserVideo).filter_by(user_id=row["user_id"], video_id=row["video_id"]).first()
            if uv:
                uv.downloaded = False
                uv.downloaded_at = None
        db.execute(text("DELETE FROM downloads WHERE id = :id"), {"id": row["id"]})
    if expired:
        db.commit()


def _delete_download_record(db: Session, dl: "Download", user_id: int):
    video = db.query(Video).filter_by(id=dl.video_id).first()
    if video:
        fp = ytdlp.predicted_file_path(video.youtube_video_id)
        if fp.exists():
            try:
                os.remove(fp)
            except OSError:
                pass
        uv = db.query(UserVideo).filter_by(user_id=user_id, video_id=dl.video_id).first()
        if uv:
            uv.downloaded = False
            uv.downloaded_at = None
    db.delete(dl)


@router.delete("/all", status_code=204)
def delete_all_downloads(
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    dls = db.query(Download).filter(
        Download.user_id == current_user.id,
        Download.status.notin_(["pending", "downloading"]),
    ).all()
    for dl in dls:
        _delete_download_record(db, dl, current_user.id)
    db.commit()


@router.post("/{download_id}/restore", status_code=200)
def restore_download(
    download_id: int,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    dl = db.query(Download).filter_by(id=download_id, user_id=current_user.id).first()
    if not dl:
        raise HTTPException(status_code=404, detail="Download not found")
    dl.pending_delete_at = None
    db.commit()
    return {"ok": True}


@router.delete("/{download_id}", status_code=204)
def delete_download(
    download_id: int,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """Delete a download record and its file from disk. Resets downloaded flag on the video."""
    dl = db.query(Download).filter_by(id=download_id, user_id=current_user.id).first()
    if not dl:
        raise HTTPException(status_code=404, detail="Download not found")
    _delete_download_record(db, dl, current_user.id)
    db.commit()


@router.get("/{download_id}", response_model=DownloadOut)
def get_download(
    download_id: int,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    row = db.execute(
        text("""
            SELECT d.id, d.status, d.progress_percent, d.resolution,
                   d.created_at, d.completed_at, d.error_message, d.pending_delete_at,
                   v.title AS video_title, v.thumbnail_url AS video_thumbnail_url,
                   v.youtube_video_id,
                   '/files/' || v.youtube_video_id || '.mp4' AS file_url
            FROM downloads d JOIN videos v ON d.video_id = v.id
            WHERE d.id = :id AND d.user_id = :user_id
        """),
        {"id": download_id, "user_id": current_user.id},
    ).mappings().first()
    if not row:
        raise HTTPException(status_code=404, detail="Download not found")
    return DownloadOut(**dict(row))