import logging

import httpx
from google.oauth2.credentials import Credentials

from app.config import settings

logger = logging.getLogger(__name__)

API_BASE = "https://www.googleapis.com/youtube/v3"
BATCH_SIZE = 50


class YouTubeQuotaExceeded(Exception):
    pass


class YouTubeAPIError(Exception):
    pass


class YouTubeInsufficientScope(Exception):
    """Raised when Google rejects a call because the stored token was granted
    under an older, narrower scope (e.g. readonly tokens issued before the
    unsubscribe feature needed write access) -- the fix is reconnecting."""

    pass


def _headers(credentials: Credentials) -> dict:
    return {"Authorization": f"Bearer {credentials.token}"}


def _raise_for_status(response: httpx.Response) -> None:
    if response.status_code in (200, 204):
        return
    try:
        payload = response.json()
        reason = payload.get("error", {}).get("errors", [{}])[0].get("reason", "")
        message = payload.get("error", {}).get("message", response.text)
    except Exception:
        reason = ""
        message = response.text

    if response.status_code == 403 and reason in ("quotaExceeded", "dailyLimitExceeded", "rateLimitExceeded"):
        raise YouTubeQuotaExceeded(message)

    if response.status_code in (401, 403) and (
        reason == "insufficientPermissions" or "insufficient authentication scopes" in message.lower()
    ):
        raise YouTubeInsufficientScope(message)

    logger.error("YouTube API error %s: %s", response.status_code, message)
    raise YouTubeAPIError(f"{response.status_code}: {message}")


def fetch_subscriptions(credentials: Credentials) -> list[dict]:
    subscriptions: list[dict] = []
    page_token: str | None = None

    with httpx.Client(timeout=settings.metube_request_timeout_seconds) as client:
        while True:
            params = {
                "part": "snippet,contentDetails",
                "mine": "true",
                "maxResults": 50,
            }
            if page_token:
                params["pageToken"] = page_token

            response = client.get(f"{API_BASE}/subscriptions", params=params, headers=_headers(credentials))
            _raise_for_status(response)
            data = response.json()

            for item in data.get("items", []):
                snippet = item.get("snippet", {})
                resource_id = snippet.get("resourceId", {})
                channel_id = resource_id.get("channelId")
                if not channel_id:
                    continue
                thumbnails = snippet.get("thumbnails", {})
                thumbnail = (
                    thumbnails.get("high") or thumbnails.get("medium") or thumbnails.get("default") or {}
                ).get("url")
                subscriptions.append(
                    {
                        "youtube_channel_id": channel_id,
                        # The subscription resource's own id -- distinct from
                        # the channel id, required to later call
                        # subscriptions.delete (unsubscribe).
                        "youtube_subscription_id": item.get("id"),
                        "title": snippet.get("title", ""),
                        "description": snippet.get("description", ""),
                        "thumbnail_url": thumbnail,
                    }
                )

            page_token = data.get("nextPageToken")
            if not page_token:
                break

    return subscriptions


def fetch_playlist_video_ids(credentials: Credentials, playlist_id: str, max_results: int) -> list[str]:
    with httpx.Client(timeout=settings.metube_request_timeout_seconds) as client:
        params = {
            "part": "contentDetails",
            "playlistId": playlist_id,
            "maxResults": min(max_results, 50),
        }
        response = client.get(f"{API_BASE}/playlistItems", params=params, headers=_headers(credentials))
        if response.status_code == 404:
            return []
        _raise_for_status(response)
        data = response.json()

    video_ids = []
    for item in data.get("items", []):
        video_id = item.get("contentDetails", {}).get("videoId")
        if video_id:
            video_ids.append(video_id)
    return video_ids


def fetch_videos_details(credentials: Credentials, video_ids: list[str]) -> list[dict]:
    results: list[dict] = []

    with httpx.Client(timeout=settings.metube_request_timeout_seconds) as client:
        for i in range(0, len(video_ids), BATCH_SIZE):
            batch = video_ids[i : i + BATCH_SIZE]
            params = {
                "part": "snippet,contentDetails,status",
                "id": ",".join(batch),
                "maxResults": BATCH_SIZE,
            }
            response = client.get(f"{API_BASE}/videos", params=params, headers=_headers(credentials))
            _raise_for_status(response)
            data = response.json()

            for item in data.get("items", []):
                snippet = item.get("snippet", {})
                thumbnails = snippet.get("thumbnails", {})
                thumbnail = (
                    thumbnails.get("high") or thumbnails.get("medium") or thumbnails.get("default") or {}
                ).get("url")
                results.append(
                    {
                        "youtube_video_id": item.get("id"),
                        "youtube_channel_id": snippet.get("channelId"),
                        "title": snippet.get("title", ""),
                        "description": snippet.get("description", ""),
                        "thumbnail_url": thumbnail,
                        "published_at": snippet.get("publishedAt"),
                        "duration_iso8601": item.get("contentDetails", {}).get("duration"),
                    }
                )

    return results


def unsubscribe(credentials: Credentials, youtube_subscription_id: str) -> None:
    with httpx.Client(timeout=settings.metube_request_timeout_seconds) as client:
        response = client.delete(
            f"{API_BASE}/subscriptions",
            params={"id": youtube_subscription_id},
            headers=_headers(credentials),
        )
    if response.status_code == 404:
        # Already gone (unsubscribed elsewhere, or stale id) -- treat as success.
        return
    _raise_for_status(response)


def fetch_uploads_playlists(credentials: Credentials, channel_ids: list[str]) -> dict[str, str]:
    result: dict[str, str] = {}

    with httpx.Client(timeout=settings.metube_request_timeout_seconds) as client:
        for i in range(0, len(channel_ids), BATCH_SIZE):
            batch = channel_ids[i : i + BATCH_SIZE]
            params = {
                "part": "snippet,contentDetails",
                "id": ",".join(batch),
                "maxResults": BATCH_SIZE,
            }
            response = client.get(f"{API_BASE}/channels", params=params, headers=_headers(credentials))
            _raise_for_status(response)
            data = response.json()

            for item in data.get("items", []):
                channel_id = item.get("id")
                uploads = (
                    item.get("contentDetails", {}).get("relatedPlaylists", {}).get("uploads")
                )
                if channel_id and uploads:
                    result[channel_id] = uploads

    return result