"""Radio Browser: the community's own station directory.

``https://de1.api.radio-browser.info/json/stations/search`` is keyless, CORS-open
and public-domain data.  It knows nothing about what a station is playing —
there is no per-station history — so this catalogue is a *directory*: the most
clicked working stations, a page at a time.  Whatever the relay puts in its
stream is what you hear; the app has no metadata to show.
"""

from __future__ import annotations

import asyncio
import re
from typing import Any
from urllib.parse import urlencode

import httpx

from ... import config
from ...models import Station, to_int
from ..base import StationPage, fetch_json

API_URL = "https://de1.api.radio-browser.info/json/stations/search"
BY_UUID_URL = "https://de1.api.radio-browser.info/json/stations/byuuid"

#: Stations per directory page.  The app loads the first page at startup and
#: the next ones as the station list nears its end.
PAGE_SIZE = 100

#: Results per field for a directory search.  The four fields are merged.
SEARCH_LIMIT = 100

#: The search endpoint has no full-text parameter, so a free-text query is
#: sent once per field and the answers are merged.
_SEARCH_FIELDS = ("name", "tag", "country", "language")

#: Radio Browser ids are UUIDs; anything else is another catalogue's favourite.
_UUID_PATTERN = re.compile(
    r"^[0-9a-fA-F]{8}(?:-[0-9a-fA-F]{4}){3}-[0-9a-fA-F]{12}$"
)

#: How many UUIDs to ask for in one ``byuuid`` request.
LOOKUP_BATCH = 50

_PARAMS = {
    "hidebroken": "true",
    "order": "clickcount",
    "reverse": "true",
}

_CODECS = {"mp3": "mp3", "aac": "aac", "aac+": "aacp", "ogg": "ogg", "opus": "opus"}


def _quality(bitrate: int) -> str:
    if bitrate >= 192:
        return "highest"
    if bitrate >= 96:
        return "high"
    return "low" if bitrate else ""


def station_from_entry(entry: dict[str, Any]) -> Station | None:
    if not isinstance(entry, dict):
        return None
    name = str(entry.get("name") or "").strip()
    url = str(entry.get("url_resolved") or entry.get("url") or "").strip()
    station_id = str(entry.get("stationuuid") or "").strip()
    if not name or not station_id or not url.startswith(("http://", "https://")):
        return None

    bitrate = to_int(entry.get("bitrate"))
    codec = str(entry.get("codec") or "").strip().lower()
    tags = [
        tag.strip()
        for tag in str(entry.get("tags") or "").split(",")
        if tag.strip()
    ][:3]
    country = str(entry.get("country") or "").strip()
    language = str(entry.get("language") or "").strip()
    description = " · ".join(part for part in (country, language) if part)

    favicon = str(entry.get("favicon") or "").strip()

    return Station(
        id=station_id,
        title=name,
        description=description or "internet radio",
        genre="|".join(tags),
        image=favicon if favicon.startswith(("http://", "https://")) else "",
        playlists=[
            {
                "url": url,
                "format": _CODECS.get(codec, codec),
                "quality": _quality(bitrate),
                "bitrate": str(bitrate) if bitrate else "",
            }
        ],
        provider="radiobrowser",
    )


def parse_stations(payload: Any, *, sort: bool = True) -> list[Station]:
    if not isinstance(payload, list):
        return []
    stations: list[Station] = []
    seen: set[str] = set()
    for entry in payload:
        station = station_from_entry(entry)
        if station is None or station.id in seen:
            continue
        seen.add(station.id)
        stations.append(station)
    if sort:
        stations.sort(key=lambda station: station.title.casefold())
    return stations


def _page_url(offset: int) -> str:
    params = {**_PARAMS, "limit": str(PAGE_SIZE), "offset": str(offset)}
    return f"{API_URL}?{urlencode(params)}"


async def fetch_station_page(
    client: httpx.AsyncClient, offset: int = 0
) -> StationPage:
    """One page of the directory, most-clicked first."""
    try:
        payload = await fetch_json(client, _page_url(offset))
    except RuntimeError as exc:
        raise RuntimeError(f"could not fetch the Radio Browser directory: {exc}") from None

    stations = parse_stations(payload, sort=False)
    rows = len(payload) if isinstance(payload, list) else 0
    next_offset = offset + PAGE_SIZE if rows >= PAGE_SIZE else None
    if offset == 0 and stations and isinstance(payload, list):
        config.write_json(config.channels_cache_path("radiobrowser"), payload)
    return StationPage(stations=stations, next_offset=next_offset)


async def fetch_stations(client: httpx.AsyncClient) -> list[Station]:
    page = await fetch_station_page(client, 0)
    if not page.stations:
        raise RuntimeError("Radio Browser returned no stations")
    return page.stations


def load_cached_stations() -> list[Station]:
    return parse_stations(
        config.read_json(config.channels_cache_path("radiobrowser")), sort=False
    )


async def _search_field(
    client: httpx.AsyncClient, query: str, field: str
) -> list[Station]:
    params = {**_PARAMS, "limit": str(SEARCH_LIMIT), field: query}
    payload = await fetch_json(client, f"{API_URL}?{urlencode(params)}")
    return parse_stations(payload, sort=False)


async def search_stations(client: httpx.AsyncClient, query: str) -> list[Station]:
    """Search the directory by name, tag, country and language.

    The API has no single full-text search, so the query is sent once per field
    and the results are merged.  A station that matches a genre rarely has that
    genre in its name, and vice versa.  Fields that fail are ignored as long as
    one of them still answers; only a complete failure is raised.
    """
    text = query.strip()
    if not text:
        return []

    batches = await asyncio.gather(
        *(_search_field(client, text, field) for field in _SEARCH_FIELDS),
        return_exceptions=True,
    )

    stations: list[Station] = []
    seen: set[str] = set()
    failures = 0
    for batch in batches:
        if isinstance(batch, BaseException):
            failures += 1
            continue
        for station in batch:
            if station.id in seen:
                continue
            seen.add(station.id)
            stations.append(station)

    if failures == len(batches):
        raise RuntimeError("could not search the Radio Browser directory")

    return stations


async def _fetch_by_uuids(
    client: httpx.AsyncClient, station_ids: list[str]
) -> list[Station]:
    params = urlencode({"uuids": ",".join(station_ids)}, safe=",")
    payload = await fetch_json(client, f"{BY_UUID_URL}?{params}")
    return parse_stations(payload, sort=False)


async def fetch_stations_by_ids(
    client: httpx.AsyncClient, station_ids: list[str]
) -> list[Station]:
    """Look up specific stations, for favourites outside the first page."""
    ids = list(
        dict.fromkeys(
            station_id.strip()
            for station_id in station_ids
            if _UUID_PATTERN.match(station_id.strip())
        )
    )
    if not ids:
        return []

    batches = [
        ids[index : index + LOOKUP_BATCH]
        for index in range(0, len(ids), LOOKUP_BATCH)
    ]
    results = await asyncio.gather(
        *(_fetch_by_uuids(client, batch) for batch in batches),
        return_exceptions=True,
    )

    stations: list[Station] = []
    seen: set[str] = set()
    for batch in results:
        if isinstance(batch, BaseException):
            continue
        for station in batch:
            if station.id in seen:
                continue
            seen.add(station.id)
            stations.append(station)
    return stations