"""Platform → download-backend dispatch (one place that knows which platforms
are served by the native FC ingester vs. the gallery-dl subprocess).

gallery-dl wasn't built to be driven by an automated scheduler — no native
checkpoint/resume, no structured logs, per-file HEADs that dominate wall-clock.
The native ingester (services/patreon_ingester.py, plan #697) replaces it for
Patreon and is the path we grow as more platforms migrate. To keep that
migration DRY, every caller that has to behave differently per backend —
download routing, the credential-verify probe, cursor handling — asks THIS
module instead of testing ``platform == "patreon"`` inline. When a platform gets
a native ingester, it moves into ``NATIVE_INGESTER_PLATFORMS`` here and both the
download path and verify switch over together.

The backend surfaces share a UNIFORM signature so a caller invokes the same
function regardless of platform:
  - verify_credential(...)  → (ok: bool|None, message: str)
  - (download stays in download_service for now; uses_native_ingester() is the
    shared predicate it routes on, so the decision lives here too.)
"""

from __future__ import annotations

from pathlib import Path

# Platforms whose download + verify go through the native ingester rather than
# gallery-dl. gallery-dl still serves every other platform (subscribestar,
# hentaifoundry, discord, pixiv, deviantart) unchanged.
NATIVE_INGESTER_PLATFORMS = frozenset({"patreon"})


def uses_native_ingester(platform: str) -> bool:
    """True when `platform` is served by the native ingester (not gallery-dl).
    The single predicate the download path and verify both route on."""
    return platform in NATIVE_INGESTER_PLATFORMS


async def verify_source_credential(
    *,
    platform: str,
    url: str,
    artist_slug: str,
    config_overrides: dict | None,
    cookies_path: str | None,
    auth_token: str | None,
    images_root: Path,
) -> tuple[bool | None, str]:
    """Uniform credential probe across backends. Returns `(ok, message)`:
    True = authenticated, False = rejected, None = inconclusive (drift /
    network / nothing to test). Callers don't branch on platform — they call
    this and render the result.
    """
    if uses_native_ingester(platform):
        # Native ingester platforms verify via their own lightweight auth probe
        # (resolve campaign id + one authenticated API page). Patreon today.
        from .patreon_ingester import verify_patreon_credential

        return await verify_patreon_credential(url, cookies_path, config_overrides)

    # gallery-dl platforms: --simulate one item; the extractor errors before it
    # can list if auth is bad.
    from .gallery_dl import GalleryDLService, SourceConfig

    gdl = GalleryDLService(images_root=images_root)
    return await gdl.verify(
        url=url,
        artist_slug=artist_slug,
        platform=platform,
        source_config=SourceConfig.from_dict(config_overrides or {}),
        cookies_path=cookies_path,
        auth_token=auth_token,
    )