from fastapi import APIRouter, Depends, HTTPException, Query
from sqlalchemy.ext.asyncio import AsyncSession

from app.db.session import get_db
from app.services.earth_news import (
    ALLOWED_NEWS_CATEGORY_KEYS,
    SUPPORTED_NEWS_LOCALES,
    REGION_ANCHORS,
    get_earth_news_payload,
)

router = APIRouter()


def _parse_categories(raw: str | None) -> set[str] | None:
    if raw is None or not raw.strip():
        return None
    requested = {item.strip().lower() for item in raw.split(",") if item.strip()}
    invalid = sorted(requested - set(ALLOWED_NEWS_CATEGORY_KEYS))
    if invalid:
        raise HTTPException(
            status_code=422,
            detail={
                "message": "Unsupported news categories.",
                "invalid_categories": invalid,
                "allowed_categories": list(ALLOWED_NEWS_CATEGORY_KEYS),
            },
        )
    return requested or None


def _parse_source_ids(raw: str | None) -> set[str] | None:
    if raw is None or not raw.strip():
        return None
    return {item.strip() for item in raw.split(",") if item.strip()} or None


def _parse_limit(raw: int | None) -> int:
    if raw is None:
        return 12
    if raw < 1:
        raise HTTPException(status_code=422, detail={"message": "News limit must be greater than 0."})
    return min(raw, 100)


def _parse_locale(raw: str | None) -> str:
    if raw is None or not raw.strip():
        return "zh-CN"
    requested = raw.strip()
    if requested not in SUPPORTED_NEWS_LOCALES:
        raise HTTPException(
            status_code=422,
            detail={
                "message": "Unsupported news locale.",
                "invalid_locale": requested,
                "allowed_locales": sorted(SUPPORTED_NEWS_LOCALES),
            },
        )
    return requested


@router.get("/earth-feed")
async def get_earth_feed(
    lat: float | None = Query(None, description="Current Earth view center latitude"),
    lon: float | None = Query(None, description="Current Earth view center longitude"),
    region: str | None = Query(None, description="Explicit Earth news region for UE/client integrations"),
    categories: str | None = Query(None, description="Comma-separated news category keys"),
    sources: str | None = Query(None, description="Comma-separated news source ids"),
    limit: int | None = Query(None, description="Maximum news items to return, capped at 100"),
    locale: str | None = Query(None, description="Display locale, zh-CN or en-US"),
    db: AsyncSession = Depends(get_db),
):
    normalized_region = region.strip().lower() if isinstance(region, str) and region.strip() else None
    if normalized_region is not None and normalized_region not in REGION_ANCHORS:
        raise HTTPException(
            status_code=422,
            detail={
                "message": "Unsupported news region.",
                "invalid_region": normalized_region,
                "allowed_regions": list(REGION_ANCHORS.keys()),
            },
        )
    return await get_earth_news_payload(
        lat=lat,
        lon=lon,
        region=normalized_region,
        categories=_parse_categories(categories),
        source_ids=_parse_source_ids(sources),
        limit=_parse_limit(limit),
        locale=_parse_locale(locale),
        db=db,
    )