"""WorkflowService — stage readiness for the Workflow home.

Totals are DERIVED from the source tables (assets, duplicate_clusters,
safety_reviews, analysis_results) rather than a separately-maintained counter, so
the home page can never drift from reality. Each stage card carries a machine
``status`` plus human ``status_label`` and ``blocker`` text — the UI communicates
state with text/icons as well as color (concept §Workflow home).

``active_job`` is the one-mutating-job indicator: when a job holds the
``library_write`` lock, mutating actions across the app are disabled with a reason,
while read-only browsing stays available.
"""

from __future__ import annotations

from sqlalchemy import func, select
from sqlalchemy.orm import sessionmaker

from photo_pipeline.jobs.domain_handlers import ANALYSIS, SAFETY_SCORE
from photo_pipeline.models import Asset, DuplicateCluster, Job
from photo_pipeline.services.analysis import AnalysisService
from photo_pipeline.services.jobs import ACTIVE_STATES
from photo_pipeline.services.safety import SafetyService

# Job type that produced each stage's last run.
STAGE_JOB_TYPE = {"inventory": "scan", "safety": SAFETY_SCORE, "analysis": ANALYSIS}


class WorkflowService:
    def __init__(self, session_factory: sessionmaker) -> None:
        self._session_factory = session_factory

    def readiness(self) -> dict:
        with self._session_factory() as session:
            asset_total = session.scalar(
                select(func.count()).select_from(Asset).where(Asset.canonical_asset_id.is_(None))
            )
            missing = session.scalar(
                select(func.count()).select_from(Asset).where(Asset.missing_at.is_not(None))
            )
            cluster_states = dict(
                session.execute(
                    select(DuplicateCluster.state, func.count()).group_by(DuplicateCluster.state)
                ).all()
            )
            last_run = self._last_runs(session)
            active = self._active_job(session)

        safety = SafetyService(self._session_factory).counts()
        # Reuse the confirmed-SFW total just computed: resolving the current decision
        # of every asset is the expensive part of this page (US07-06).
        analysis = AnalysisService(self._session_factory).counts(eligible=safety[_SFW])
        undecided_clusters = cluster_states.get("open", 0) + cluster_states.get("reopened", 0)

        stages = [
            _card(
                "inventory",
                "Inventory",
                status="complete" if asset_total and not missing else ("attention" if missing else "ready"),
                counts={"assets": asset_total or 0, "missing": missing or 0},
                blocker=f"{missing} missing file(s)" if missing else None,
                last_run=last_run.get("inventory"),
                action={"label": "Rescan", "job_type": "scan", "route": "#/inventory"},
            ),
            _card(
                "duplicates",
                "Duplicates",
                status="attention" if undecided_clusters else "complete",
                counts={"undecided": undecided_clusters, "total": sum(cluster_states.values())},
                blocker=f"{undecided_clusters} cluster(s) to review" if undecided_clusters else None,
                last_run=None,
                action={"label": "Review", "route": "#/duplicates"},
            ),
            _card(
                "safety",
                "Safety",
                # Blocked while duplicates are unreviewed (dedup precedes safety).
                status=_safety_status(safety, undecided_clusters),
                counts=safety,
                blocker=(
                    "resolve duplicate clusters first"
                    if undecided_clusters
                    else (f"{safety['undecided']} undecided" if safety["undecided"] else None)
                ),
                last_run=last_run.get("safety"),
                action={"label": "Review safety", "job_type": SAFETY_SCORE, "route": "#/safety"},
                blocked_by="duplicates" if undecided_clusters else None,
            ),
            _card(
                "analysis",
                "Analysis",
                status=_analysis_status(analysis, safety),
                counts=analysis,
                blocker=(
                    "no confirmed-SFW assets yet"
                    if analysis["eligible"] == 0
                    else (f"{analysis['pending']} pending" if analysis["pending"] else None)
                ),
                last_run=last_run.get("analysis"),
                action={"label": "Analyze", "job_type": ANALYSIS, "route": "#/analyze"},
                blocked_by="safety" if analysis["eligible"] == 0 else None,
            ),
        ]
        return {"active_job": active, "stages": stages}

    def _last_runs(self, session) -> dict[str, str | None]:
        out: dict[str, str | None] = {}
        for stage, job_type in STAGE_JOB_TYPE.items():
            finished = session.scalar(
                select(func.max(Job.finished_at)).where(Job.job_type == job_type)
            )
            out[stage] = finished.isoformat() if finished else None
        return out

    def _active_job(self, session) -> dict | None:
        job = session.scalars(
            select(Job).where(Job.state.in_(ACTIVE_STATES)).order_by(Job.created_at.desc())
        ).first()
        if job is None:
            return None
        return {"id": job.id, "job_type": job.job_type, "state": job.state, "lock": job.lock_key}


def _safety_status(safety: dict, undecided_clusters: int) -> str:
    if undecided_clusters:
        return "blocked"
    if safety["undecided"]:
        return "attention"
    if safety[_SFW] or safety[_NSFW]:
        return "complete"
    return "ready"


def _analysis_status(analysis: dict, safety: dict) -> str:
    if analysis["eligible"] == 0:
        return "blocked"
    if analysis["pending"]:
        return "attention"
    return "complete"


def _card(key, title, *, status, counts, blocker, last_run, action, blocked_by=None) -> dict:
    return {
        "key": key,
        "title": title,
        "status": status,
        "status_label": _STATUS_LABEL[status],
        "counts": counts,
        "blocker": blocker,
        "blocked_by": blocked_by,
        "last_run": last_run,
        "action": action,
    }


_SFW = "sfw"
_NSFW = "nsfw"
_STATUS_LABEL = {
    "complete": "Complete",
    "ready": "Ready",
    "attention": "Needs review",
    "blocked": "Blocked",
}