FabledCurator/backend/app/services/download_service.py

"""FC-3c download orchestrator.

Three-phase pipeline:
  Phase 1 — DB setup (brief session): load source, mark event running,
            fetch credentials + settings.
  Phase 2 — Execute (no DB connection): call GalleryDLService; on
            Patreon campaign-ID failure, resolve vanity and retry once.
  Phase 3 — Import + persist (fresh session): attach_in_place each
            written file; clean up duplicates; persist rich metadata.
"""

from __future__ import annotations

import asyncio
import logging
import re
from datetime import UTC, datetime
from pathlib import Path
from typing import Any

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.orm import Session as SyncSession
from sqlalchemy.orm import joinedload

from ..models import Artist, DownloadEvent, Source
from .credential_service import CredentialService
from .gallery_dl import (
    BACKFILL_SKIP_VALUE,
    BACKFILL_TIMEOUT_SECONDS,
    TICK_SKIP_VALUE,
    ErrorType,
    GalleryDLService,
    SourceConfig,
)
from .importer import Importer
from .patreon_resolver import resolve_campaign_id
from .scheduler_service import set_platform_cooldown

log = logging.getLogger(__name__)


_PATREON_VANITY_RE = re.compile(
    r"^https?://(?:www\.)?patreon\.com/(?:c/)?(?!id:)([^/?#]+)",
    re.IGNORECASE,
)
_CAMPAIGN_ID_FAILURE_PATTERN = "failed to extract campaign id"


def _extract_patreon_vanity(url: str) -> str | None:
    m = _PATREON_VANITY_RE.match(url)
    return m.group(1) if m else None


def _looks_like_campaign_id_failure(stdout: str, stderr: str) -> bool:
    return _CAMPAIGN_ID_FAILURE_PATTERN in f"{stdout}\n{stderr}".lower()


def _effective_url(platform: str, source_url: str, overrides: dict) -> str:
    if platform == "patreon" and overrides.get("patreon_campaign_id"):
        return f"https://www.patreon.com/id:{overrides['patreon_campaign_id']}"
    return source_url


class DownloadService:
    """Async orchestrator. The Celery task runs `asyncio.run(svc.download_source(N))`.

    The Importer is sync (existing FC convention); calls to attach_in_place
    happen via run_in_executor.
    """

    def __init__(
        self,
        async_session: AsyncSession,
        sync_session: SyncSession,
        gdl: GalleryDLService,
        importer: Importer,
        cred_service: CredentialService,
    ):
        self.async_session = async_session
        self.sync_session = sync_session
        self.gdl = gdl
        self.importer = importer
        self.cred_service = cred_service

    async def download_source(self, source_id: int) -> int:
        """Returns DownloadEvent.id. Idempotent: in-flight events are returned as-is."""
        setup = await self._phase1_setup(source_id)
        if setup["status"] in ("skipped", "in_flight"):
            return setup["event_id"]
        ctx = setup

        source_config = SourceConfig.from_dict(ctx["config_overrides"] or {})
        # alembic 0031 / plan #544: derive skip_value + timeout from the
        # source's backfill_runs_remaining counter. When > 0, walk the full
        # post history (skip: True + 1800s); when 0, exit gallery-dl after
        # 20 contiguous archived items (skip: "exit:20" + the default
        # 870s). Operator sets backfill via POST /api/sources/{id}/backfill.
        backfill_remaining = ctx.get("backfill_runs_remaining", 0) or 0
        if backfill_remaining > 0:
            skip_value: bool | str = BACKFILL_SKIP_VALUE
            source_config.timeout = BACKFILL_TIMEOUT_SECONDS
        else:
            skip_value = TICK_SKIP_VALUE

        effective_url = _effective_url(
            ctx["platform"], ctx["url"], ctx["config_overrides"] or {}
        )

        dl_result = await self.gdl.download(
            url=effective_url,
            artist_slug=ctx["artist_slug"],
            platform=ctx["platform"],
            source_config=source_config,
            cookies_path=ctx["cookies_path"],
            auth_token=ctx["auth_token"],
            skip_value=skip_value,
        )

        resolved_campaign_id: str | None = None
        if (
            ctx["platform"] == "patreon"
            and not dl_result.success
            and "patreon_campaign_id" not in (ctx["config_overrides"] or {})
            and _looks_like_campaign_id_failure(dl_result.stdout, dl_result.stderr)
        ):
            vanity = _extract_patreon_vanity(ctx["url"])
            if vanity:
                log.info(
                    "Attempting campaign-ID resolution for %s (%s)",
                    ctx["artist_slug"], vanity,
                )
                resolved_campaign_id = await resolve_campaign_id(
                    vanity, ctx["cookies_path"]
                )
                if resolved_campaign_id:
                    dl_result = await self.gdl.download(
                        url=f"https://www.patreon.com/id:{resolved_campaign_id}",
                        artist_slug=ctx["artist_slug"],
                        platform=ctx["platform"],
                        source_config=source_config,
                        cookies_path=ctx["cookies_path"],
                        auth_token=ctx["auth_token"],
                        skip_value=skip_value,
                    )

        return await self._phase3_persist(
            ctx["event_id"], ctx, dl_result, resolved_campaign_id,
        )

    async def _phase1_setup(self, source_id: int) -> dict[str, Any]:
        source = (await self.async_session.execute(
            select(Source).options(joinedload(Source.artist)).where(Source.id == source_id)
        )).scalar_one_or_none()
        if source is None:
            raise LookupError(f"source {source_id} not found")

        if not source.enabled:
            ev = DownloadEvent(source_id=source_id, status="pending")
            self.async_session.add(ev)
            await self.async_session.commit()
            await self.async_session.refresh(ev)
            await self._finalize_event_and_source(
                event_id=ev.id, source_id=source_id, status="skipped",
                error_message="source disabled",
            )
            return {"status": "skipped", "event_id": ev.id}

        existing = (await self.async_session.execute(
            select(DownloadEvent).where(
                DownloadEvent.source_id == source_id,
                DownloadEvent.status.in_(["pending", "running"]),
            ).order_by(DownloadEvent.id.desc()).limit(1)
        )).scalar_one_or_none()

        if existing and existing.status == "running":
            return {"status": "in_flight", "event_id": existing.id}
        if existing and existing.status == "pending":
            existing.status = "running"
            # Reset started_at on the pending→running transition so the
            # recovery sweep (DOWNLOAD_STALL_THRESHOLD_MINUTES, 30 min)
            # measures from real start, not from enqueue. On heavy-queue
            # days a freshly-promoted event whose original started_at
            # predated the cutoff would otherwise get swept mid-flight,
            # racing phase3's commit. Audit 2026-06-02.
            existing.started_at = datetime.now(UTC)
            await self.async_session.commit()
            event_id = existing.id
        else:
            ev = DownloadEvent(source_id=source_id, status="running")
            self.async_session.add(ev)
            await self.async_session.commit()
            await self.async_session.refresh(ev)
            event_id = ev.id

        artist = source.artist
        if source.platform in ("discord", "pixiv"):
            cookies_path = None
            auth_token = await self.cred_service.get_token(source.platform)
        else:
            cookies_path_obj = await self.cred_service.get_cookies_path(source.platform)
            cookies_path = str(cookies_path_obj) if cookies_path_obj else None
            auth_token = None

        return {
            "status": "ok",
            "event_id": event_id,
            "source_id": source_id,
            "url": source.url,
            "platform": source.platform,
            "artist_slug": artist.slug if artist else "_unknown",
            "artist_id": artist.id if artist else None,
            "config_overrides": dict(source.config_overrides or {}),
            "cookies_path": cookies_path,
            "auth_token": auth_token,
            "backfill_runs_remaining": source.backfill_runs_remaining or 0,
        }

    async def _phase3_persist(
        self,
        event_id: int,
        ctx: dict,
        dl_result,
        resolved_campaign_id: str | None,
    ) -> int:
        # Cache Patreon campaign id on the source.
        if resolved_campaign_id:
            src = self.sync_session.get(Source, ctx["source_id"])
            if src is not None:
                src.config_overrides = {
                    **(src.config_overrides or {}),
                    "patreon_campaign_id": resolved_campaign_id,
                }
                self.sync_session.commit()

        artist = None
        source_row = None
        if ctx.get("artist_id"):
            artist = self.sync_session.get(Artist, ctx["artist_id"])
        source_row = self.sync_session.get(Source, ctx["source_id"])

        import_summary = {"attached": 0, "skipped": 0, "errors": 0}
        bytes_downloaded = 0

        loop = asyncio.get_running_loop()

        for path_str in dl_result.written_paths or []:
            if path_str in (dl_result.quarantined_paths or []):
                continue
            path = Path(path_str)
            # Sync stdlib filesystem ops are intentional here: this orchestrator
            # runs under `asyncio.run` inside a Celery task — no other awaitables
            # compete for the loop. ASYNC240 suppressed below.
            if not path.exists():  # noqa: ASYNC240
                continue

            def _attach(p=path):
                return self.importer.attach_in_place(
                    p, artist=artist, source=source_row,
                )

            result = await loop.run_in_executor(None, _attach)

            if result.status in ("imported", "superseded"):
                import_summary["attached"] += 1
                try:
                    bytes_downloaded += path.stat().st_size  # noqa: ASYNC240
                except OSError:
                    pass
                # Enqueue thumbnail + ML for newly-attached images, matching
                # the filesystem-import path (tasks/import_file.py:228-239).
                # Importer.attach_in_place deliberately skips inline thumb
                # generation to keep the import queue moving; the calling
                # task is responsible for the enqueue. Operator-flagged
                # 2026-06-01: without this, every downloaded image stayed
                # at thumbnail_path=NULL until a periodic backfill swept
                # it up, surfacing as broken-thumbnail tiles in the gallery
                # for hours after a download landed. Lazy import to avoid
                # circular-import risk between this service and the
                # tasks/* modules that import it.
                from ..tasks.ml import tag_and_embed
                from ..tasks.thumbnail import generate_thumbnail
                ids = list(result.member_image_ids)
                if result.image_id is not None and result.image_id not in ids:
                    ids.append(result.image_id)
                for img_id in ids:
                    generate_thumbnail.delay(img_id)
                    tag_and_embed.delay(img_id)
            elif result.status == "attached":
                # Non-media or extracted archive captured as PostAttachment
                # (FC-2d-iii). The canonical copy lives in the attachments
                # store; the original download path is now redundant —
                # mirror duplicate_hash cleanup so we don't keep two copies.
                # Operator-flagged 2026-06-02 (Lustria OST zip).
                import_summary["attached"] += 1
                try:
                    bytes_downloaded += path.stat().st_size  # noqa: ASYNC240
                except OSError:
                    pass
                try:
                    path.unlink(missing_ok=True)  # noqa: ASYNC240
                except OSError:
                    pass
            elif result.status == "skipped" and result.skip_reason and result.skip_reason.value in (
                "duplicate_hash", "duplicate_phash",
            ):
                import_summary["skipped"] += 1
                try:
                    path.unlink(missing_ok=True)  # noqa: ASYNC240
                except OSError:
                    pass
            elif result.status == "skipped":
                # Soft skip (too_small, too_transparent, invalid_image) —
                # the file just didn't qualify, not a download/ingest
                # failure. Don't flag the run as error; the file stays
                # on disk for operator inspection.
                import_summary["skipped"] += 1
            else:
                import_summary["errors"] += 1

        ev = (await self.async_session.execute(
            select(DownloadEvent).where(DownloadEvent.id == event_id)
        )).scalar_one()

        run_stats = self.gdl._compute_run_stats(
            dl_result.return_code, dl_result.stdout, dl_result.stderr
        )
        run_stats["quarantined_count"] = dl_result.files_quarantined
        stderr_summary = self.gdl._extract_errors_warnings(dl_result.stderr)

        # Plan #544: PARTIAL means the run downloaded ≥1 file but the
        # subprocess didn't finish in budget (typically wall-clock timeout
        # mid-walk). Real work happened; the next tick continues via
        # gallery-dl's archive. NOT a failure for status purposes.
        if dl_result.success and import_summary["errors"] == 0:
            status = "ok"
        elif dl_result.error_type == ErrorType.PARTIAL and import_summary["errors"] == 0:
            status = "ok"
        else:
            status = "error"
        ev.status = status
        ev.finished_at = datetime.now(UTC)
        ev.files_count = import_summary["attached"]
        ev.bytes_downloaded = bytes_downloaded
        ev.error = dl_result.error_message if status == "error" else None
        ev.metadata_ = {
            "run_stats": run_stats,
            "error_type": dl_result.error_type.value if dl_result.error_type else None,
            "stdout": self.gdl._truncate_log(dl_result.stdout) or None,
            "stderr": self.gdl._truncate_log(dl_result.stderr) or None,
            "stderr_errors_warnings": stderr_summary or None,
            "duration_seconds": dl_result.duration_seconds,
            "quarantined_paths": dl_result.quarantined_paths or None,
            "import_summary": import_summary,
        }
        await self._update_source_health(
            source_id=ctx["source_id"], status=status, error_message=ev.error,
            error_type=dl_result.error_type.value if dl_result.error_type else None,
        )
        # Plan #544: backfill lifecycle — auto-complete when a clean
        # backfill run drained the queue (gallery-dl exited 0 + zero files
        # downloaded means there was nothing to fetch); otherwise decrement
        # the counter. Next tick falls back to tick mode once it hits 0.
        backfill_remaining = ctx.get("backfill_runs_remaining", 0) or 0
        if backfill_remaining > 0:
            src = (await self.async_session.execute(
                select(Source).where(Source.id == ctx["source_id"])
            )).scalar_one()
            if dl_result.return_code == 0 and dl_result.files_downloaded == 0:
                src.backfill_runs_remaining = 0
            else:
                src.backfill_runs_remaining = max(0, backfill_remaining - 1)
        await self.async_session.commit()
        return event_id

    async def _update_source_health(
        self, *, source_id: int, status: str, error_message: str | None,
        error_type: str | None = None,
    ) -> None:
        """FC-3d: update Source.{consecutive_failures, last_error, last_checked_at}.

        ok      -> failures = 0, error = None, checked_at = now
        error   -> failures += 1, error = error_message, checked_at = now
        skipped -> failures unchanged, error = None, checked_at = now

        When error_type == 'rate_limited', also stamps a platform-wide
        cooldown via scheduler_service.set_platform_cooldown so the next
        scan tick skips every source on this platform until the cooldown
        expires. Preventive half of the burst-prevention pair —
        consecutive_failures still backs the offending source off across
        ticks.
        """
        source = (await self.async_session.execute(
            select(Source).where(Source.id == source_id)
        )).scalar_one()
        now = datetime.now(UTC)
        if status == "ok":
            source.consecutive_failures = 0
            source.last_error = None
        elif status == "error":
            source.consecutive_failures = (source.consecutive_failures or 0) + 1
            source.last_error = error_message
            if error_type == "rate_limited":
                await set_platform_cooldown(self.async_session, source.platform)
        elif status == "skipped":
            source.last_error = None
        source.last_checked_at = now

    async def _finalize_event_and_source(
        self, *, event_id: int, source_id: int, status: str,
        error_message: str | None,
    ) -> None:
        """Finalize the event AND the source-health columns in one
        transactional step. Used by the skipped early-out path and by
        unit tests that exercise the source-health writes directly.
        """
        ev = (await self.async_session.execute(
            select(DownloadEvent).where(DownloadEvent.id == event_id)
        )).scalar_one()
        ev.status = status
        ev.finished_at = datetime.now(UTC)
        ev.error = error_message
        await self._update_source_health(
            source_id=source_id, status=status, error_message=error_message,
        )
        await self.async_session.commit()