"""Built-in reports: counts, cost of nonconformance, aging, cycle times,
top jobs. All queries respect the shared date-range/department/category
filters."""
from collections import defaultdict
from decimal import Decimal

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

from app.auth.deps import CurrentUser, get_current_user
from app.database import get_db
from app.domain import STAGE_LABELS, Stage
from app.models import Department, DeviationCategory, Ncr, StageTransition
from app.models.base import utcnow
from app.schemas.report import (
    AgingBucket,
    CostByMonth,
    CountByMonth,
    CountByName,
    ReportsSummaryOut,
    StageCycleTime,
    TopJob,
)

router = APIRouter(tags=["reports"])

_AGING_BUCKETS = [(0, 7, "0–7 days"), (8, 14, "8–14 days"), (15, 30, "15–30 days"),
                  (31, 60, "31–60 days"), (61, None, "60+ days")]


def _base_filters(stmt, date_from, date_to, department_id, category_id):
    if date_from:
        stmt = stmt.where(Ncr.created_at >= date_from)
    if date_to:
        stmt = stmt.where(Ncr.created_at <= f"{date_to} 23:59:59")
    if department_id:
        stmt = stmt.where(Ncr.department_id == department_id)
    if category_id:
        stmt = stmt.where(Ncr.deviation_category_id == category_id)
    return stmt


@router.get("/reports/summary", response_model=ReportsSummaryOut)
async def reports_summary(
    date_from: str | None = Query(default=None, description="YYYY-MM-DD"),
    date_to: str | None = Query(default=None, description="YYYY-MM-DD"),
    department_id: int | None = None,
    category_id: int | None = None,
    _: CurrentUser = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
) -> ReportsSummaryOut:
    filters = dict(
        date_from=date_from,
        date_to=date_to,
        department_id=department_id,
        category_id=category_id,
    )

    # Load the filtered NCR set once; aggregate in Python. NCR volume is a few
    # thousand rows a year, so this stays cheap and keeps the SQL portable.
    ncrs = (
        (await db.execute(_base_filters(select(Ncr), **filters))).scalars().unique().all()
    )

    dept_names = {
        d.id: d.name for d in (await db.execute(select(Department))).scalars().all()
    }
    cat_names = {
        c.id: c.name
        for c in (await db.execute(select(DeviationCategory))).scalars().all()
    }

    by_dept: dict[str, int] = defaultdict(int)
    by_cat: dict[str, int] = defaultdict(int)
    by_month: dict[str, int] = defaultdict(int)
    cost_by_month: dict[str, dict[str, Decimal]] = defaultdict(
        lambda: {"labor": Decimal(0), "material": Decimal(0), "service": Decimal(0), "other": Decimal(0)}
    )
    aging_counts: dict[str, int] = {label: 0 for _, _, label in _AGING_BUCKETS}
    job_counts: dict[str, int] = defaultdict(int)
    total_cost = Decimal(0)
    open_count = 0
    closed_count = 0
    now = utcnow()

    for n in ncrs:
        by_dept[dept_names.get(n.department_id, "?")] += 1
        by_cat[cat_names.get(n.deviation_category_id, "?")] += 1
        by_month[n.created_at.strftime("%Y-%m")] += 1
        job_counts[n.job_number] += 1
        if n.stage == Stage.CLOSED.value:
            closed_count += 1
            month = (n.closed_at or n.created_at).strftime("%Y-%m")
            bucket = cost_by_month[month]
            bucket["labor"] += n.labor_cost or 0
            bucket["material"] += n.material_cost or 0
            bucket["service"] += n.service_cost or 0
            bucket["other"] += n.other_cost or 0
            total_cost += n.total_cost or 0
        else:
            open_count += 1
            days = max(0, (now - n.stage_entered_at).days)
            for lo, hi, label in _AGING_BUCKETS:
                if days >= lo and (hi is None or days <= hi):
                    aging_counts[label] += 1
                    break

    # ── cycle times from the transition history ─────────────────────────────
    ncr_ids = [n.id for n in ncrs]
    stage_durations: dict[str, list[float]] = defaultdict(list)
    end_to_end: list[float] = []
    if ncr_ids:
        transitions = (
            (
                await db.execute(
                    select(StageTransition)
                    .where(StageTransition.ncr_id.in_(ncr_ids))
                    .order_by(StageTransition.ncr_id, StageTransition.acted_at)
                )
            )
            .scalars()
            .all()
        )
        per_ncr: dict[int, list[StageTransition]] = defaultdict(list)
        for t in transitions:
            per_ncr[t.ncr_id].append(t)
        for items in per_ncr.values():
            for prev, nxt in zip(items, items[1:]):
                delta_days = (nxt.acted_at - prev.acted_at).total_seconds() / 86400
                stage_durations[prev.to_stage].append(delta_days)
            first, last = items[0], items[-1]
            if last.to_stage == Stage.CLOSED.value:
                end_to_end.append(
                    (last.acted_at - first.acted_at).total_seconds() / 86400
                )

    cycle_times = [
        StageCycleTime(
            stage=s.value,
            stage_label=STAGE_LABELS[s],
            avg_days=round(sum(v) / len(v), 2),
            samples=len(v),
        )
        for s in Stage
        if s != Stage.CLOSED and (v := stage_durations.get(s.value))
    ]

    months = sorted(set(by_month) | set(cost_by_month))
    return ReportsSummaryOut(
        total_ncrs=len(ncrs),
        open_ncrs=open_count,
        closed_ncrs=closed_count,
        total_cost=total_cost,
        by_department=sorted(
            (CountByName(name=k, count=v) for k, v in by_dept.items()),
            key=lambda x: -x.count,
        ),
        by_category=sorted(
            (CountByName(name=k, count=v) for k, v in by_cat.items()),
            key=lambda x: -x.count,
        ),
        by_month=[CountByMonth(month=m, count=by_month.get(m, 0)) for m in months],
        cost_over_time=[
            CostByMonth(
                month=m,
                labor=c["labor"],
                material=c["material"],
                service=c["service"],
                other=c["other"],
                total=c["labor"] + c["material"] + c["service"] + c["other"],
            )
            for m in months
            if (c := cost_by_month.get(m))
        ],
        aging=[AgingBucket(bucket=label, count=aging_counts[label]) for _, _, label in _AGING_BUCKETS],
        cycle_times=cycle_times,
        end_to_end_avg_days=(
            round(sum(end_to_end) / len(end_to_end), 2) if end_to_end else None
        ),
        top_jobs=sorted(
            (TopJob(job_number=j, count=c) for j, c in job_counts.items()),
            key=lambda x: -x.count,
        )[:10],
    )