/**
 * Plan-tab body — Wave 2 chart-first redesign.
 *
 * Layout (chart is the SoT for editing life events):
 *   ┌────────────────────────────────────────┐
 *   │ NW fan + floating stats badges (top-R) │
 *   │   year-scrubber along the bottom        │
 *   ├────────────────────────────────────────┤
 *   │ Spending profile (stacked area)         │
 *   ├────────────────────────────────────────┤
 *   │ Event Gantt (drag/click to edit)        │
 *   ├────────────────────────────────────────┤
 *   │ Flex rules editor                       │
 *   ├────────────────────────────────────────┤
 *   │ Drawer: legacy form sections (collapsed)│
 *   └────────────────────────────────────────┘
 */
import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
import { useEffect, useMemo, useState } from 'react';
import { Link, useNavigate, useParams, useSearchParams } from 'react-router-dom';

import { api, lifeEventsApi, type Scenario, type SimulateRequest } from '@/api/client';
import { ApiError } from '@/api/client';
import { EventGantt } from '@/components/EventGantt';
import { FanChart } from '@/components/FanChart';
import { FlexRulesEditor } from '@/components/FlexRulesEditor';
import { GoalsSection } from '@/components/GoalsSection';
import { IncomeStreamsSection } from '@/components/IncomeStreamsSection';
import { LifeEventsSection } from '@/components/LifeEventsSection';
import { SpendingProfileChart } from '@/components/SpendingProfileChart';
import { YearScrubber } from '@/components/YearScrubber';
import { gbp, pct } from '@/lib/format';
import { emojiFor } from '@/lib/milestone';

export function ScenarioDetail() {
  const params = useParams<{ id: string }>();
  const id = Number(params.id);
  const navigate = useNavigate();
  const qc = useQueryClient();
  const [searchParams, setSearchParams] = useSearchParams();

  const scen = useQuery({
    queryKey: ['scenarios', id],
    queryFn: () => api.scenarios.get(id),
    enabled: Number.isFinite(id),
  });
  const proj = useQuery({
    queryKey: ['scenarios', id, 'projection'],
    queryFn: () => api.scenarios.projection(id),
    enabled: Number.isFinite(id),
    retry: (count, err) => {
      if (err instanceof ApiError && err.status === 404) return false;
      return count < 2;
    },
  });

  const events = useQuery({
    queryKey: ['scenarios', id, 'life-events'],
    queryFn: () => lifeEventsApi.list(id),
    enabled: Number.isFinite(id),
  });

  const profile = useQuery({
    queryKey: ['spending-profile', id],
    queryFn: () => api.spendingProfile(id),
    enabled: Number.isFinite(id),
    staleTime: 0,
    refetchOnWindowFocus: true,
  });

  const yearStats = useQuery({
    queryKey: ['year-stats', id, parseInt(searchParams.get('year') ?? '0', 10)],
    queryFn: () => api.yearStats(id, parseInt(searchParams.get('year') ?? '0', 10)),
    enabled: Number.isFinite(id) && proj.isSuccess,
    staleTime: 0,
  });

  const del = useMutation({
    mutationFn: () => api.scenarios.delete(id),
    onSuccess: () => {
      qc.invalidateQueries({ queryKey: ['scenarios'] });
      navigate('/scenarios');
    },
  });

  const sim = useMutation({
    mutationFn: (req: SimulateRequest) => api.simulate(req),
  });

  const horizonYears = scen.data?.horizon_years ?? proj.data?.yearly.length ?? 60;
  const maxYear = (proj.data?.yearly.length ?? horizonYears) - 1;

  const yearFromUrl = Number(searchParams.get('year'));
  const initialYear = Number.isFinite(yearFromUrl) && yearFromUrl >= 0 ? yearFromUrl : 0;
  const [year, setYear] = useState<number>(initialYear);

  useEffect(() => {
    if (year > maxYear && maxYear >= 0) setYear(maxYear);
  }, [maxYear, year]);

  const setYearAndUrl = (y: number) => {
    setYear(y);
    const next = new URLSearchParams(searchParams);
    next.set('year', String(y));
    setSearchParams(next, { replace: true });
  };

  const milestones = useMemo(
    () =>
      (events.data ?? [])
        .filter((e) => e.enabled)
        .map((e) => ({
          year_idx: e.year_start,
          emoji: emojiFor(e.kind),
          label: e.name,
          delta_gbp: Number(e.delta_gbp_per_year) !== 0 ? gbp(e.delta_gbp_per_year) : null,
        })),
    [events.data],
  );

  const onDelete = () => {
    if (!scen.data) return;
    if (!confirm(`Delete scenario "${scen.data.name ?? id}"? This can't be undone.`)) return;
    del.mutate();
  };

  const onRunNow = async (s: Scenario) => {
    const fresh = await lifeEventsApi.list(s.id);
    const flexRules = readFlexRules(s);
    sim.mutate({
      jurisdiction: s.jurisdiction,
      strategy: s.strategy,
      leave_uk_year: s.leave_uk_year,
      spending_gbp: s.spending_gbp,
      nw_seed_gbp: s.nw_seed_gbp,
      savings_per_year_gbp: s.savings_per_year_gbp,
      horizon_years: s.horizon_years,
      n_paths: 5000,
      seed: 42,
      life_events: fresh.map((e) => ({
        year_start: e.year_start,
        year_end: e.year_end,
        delta_gbp_per_year: e.delta_gbp_per_year,
        one_time_amount_gbp: e.one_time_amount_gbp,
        category: e.category,
        enabled: e.enabled,
      })),
      flex_rules: flexRules,
    });
  };

  if (!Number.isFinite(id)) return <p className="text-red-700">Invalid scenario id.</p>;
  if (scen.isLoading) return <p className="text-slate-500">Loading…</p>;
  if (scen.isError || !scen.data) {
    return (
      <div className="rounded-md border border-red-200 bg-red-50 p-4 text-red-800 text-sm">
        Couldn&apos;t load scenario {id}.
      </div>
    );
  }

  const s = scen.data;
  const projection = proj.data;
  const projection404 =
    proj.isError && proj.error instanceof ApiError && proj.error.status === 404;

  return (
    <section className="space-y-6">
      <div className="text-sm">
        <Link to="/scenarios" className="text-slate-500 hover:text-slate-900">
          ← Scenarios
        </Link>
      </div>

      <header className="flex items-start justify-between gap-4">
        <div>
          <h1 className="text-3xl font-semibold tracking-tight">{s.name ?? s.external_id}</h1>
          <p className="text-sm text-slate-500 mt-1">
            {s.kind} · {s.jurisdiction} · {s.strategy} · leave UK y{s.leave_uk_year} ·{' '}
            {s.glide_path} glide · {s.horizon_years}y horizon
          </p>
          {s.description && <p className="text-sm text-slate-600 mt-2">{s.description}</p>}
        </div>
        <div className="flex items-center gap-2">
          <button
            type="button"
            onClick={() => void onRunNow(s)}
            disabled={sim.isPending}
            className="rounded-md border border-slate-300 bg-white text-sm px-3 py-1.5 hover:bg-slate-50 disabled:opacity-60"
            title="Run a fresh MC including this scenario's life events + flex rules"
          >
            {sim.isPending ? 'Running…' : 'Run now'}
          </button>
          {s.kind === 'user' && (
            <>
              <Link
                to={`/scenarios/${s.id}/edit`}
                className="rounded-md border border-slate-300 bg-white text-sm px-3 py-1.5 hover:bg-slate-50"
              >
                Edit
              </Link>
              <button
                type="button"
                onClick={onDelete}
                disabled={del.isPending}
                className="rounded-md border border-red-300 text-red-700 text-sm px-3 py-1.5 hover:bg-red-50 disabled:opacity-60"
              >
                {del.isPending ? 'Deleting…' : 'Delete'}
              </button>
            </>
          )}
        </div>
      </header>
      {del.isError && (
        <div className="rounded-md border border-red-200 bg-red-50 p-3 text-red-800 text-sm">
          {String((del.error as Error)?.message ?? del.error)}
        </div>
      )}

      {projection ? (
        <>
          {/* NW fan with floating stat badges */}
          <div className="relative rounded-lg border border-slate-200 bg-white p-5">
            <div className="flex items-baseline justify-between mb-2">
              <h2 className="text-lg font-semibold">Portfolio fan</h2>
              <span className="text-xs text-slate-500">
                p10/p50/p90 over {projection.yearly.length}y · {projection.n_paths.toLocaleString()} paths
              </span>
            </div>
            <FanChart
              yearly={projection.yearly}
              height={460}
              showWithdrawal
              milestones={milestones}
              selectedYear={year}
              onSelectYear={setYearAndUrl}
            />
            <div className="mt-3">
              <YearScrubber value={year} min={0} max={maxYear} onChange={setYearAndUrl} />
            </div>
            <FloatingStats
              year={year}
              maxYear={maxYear}
              successRate={projection.success_rate}
              p50End={projection.p50_ending_gbp}
              netWorth={yearStats.data?.net_worth_p50}
              changeNw={yearStats.data?.change_in_nw}
              spending={yearStats.data?.spending}
              taxes={yearStats.data?.taxes}
              effectiveRate={yearStats.data?.effective_tax_rate}
              age={yearStats.data?.age ?? null}
              calendarYear={yearStats.data?.calendar_year}
            />
          </div>

          {/* Spending profile */}
          <div className="rounded-lg border border-slate-200 bg-white p-5">
            <div className="flex items-baseline justify-between mb-2">
              <h2 className="text-lg font-semibold">Spending profile</h2>
              <Legend />
            </div>
            {profile.data ? (
              <SpendingProfileChart
                points={profile.data.points}
                selectedYear={year}
                onSelectYear={setYearAndUrl}
              />
            ) : (
              <p className="text-sm text-slate-500">Loading…</p>
            )}
          </div>

          {/* Interactive Gantt */}
          <div className="rounded-lg border border-slate-200 bg-white p-5">
            <div className="flex items-baseline justify-between mb-2">
              <h2 className="text-lg font-semibold">Life events</h2>
              <span className="text-xs text-slate-500">
                Click empty space to add · drag bars to move · drag edges to resize
              </span>
            </div>
            <EventGantt
              scenarioId={id}
              events={events.data ?? []}
              horizonYears={horizonYears}
            />
          </div>

          <FlexRulesEditor scenario={s} />
        </>
      ) : projection404 ? (
        <div className="rounded-lg border border-slate-200 bg-white p-8 text-center text-slate-500">
          <p className="font-medium text-slate-700">No projection yet.</p>
          <p className="text-sm mt-2">
            Run <code className="px-1">python -m fire_planner recompute-all</code> or{' '}
            <code>POST /recompute</code> to fill in MC projections for all scenarios.
          </p>
        </div>
      ) : proj.isLoading ? (
        <p className="text-slate-500">Loading projection…</p>
      ) : (
        <div className="rounded-md border border-red-200 bg-red-50 p-4 text-red-800 text-sm">
          {String((proj.error as Error)?.message ?? proj.error)}
        </div>
      )}

      {sim.data && (
        <div className="rounded-lg border border-slate-200 bg-white p-5">
          <div className="flex items-baseline justify-between mb-3">
            <h2 className="text-lg font-semibold">Live preview run</h2>
            <span className="text-xs text-slate-500">
              {sim.data.elapsed_seconds}s · 5,000 paths · success {pct(sim.data.success_rate)}
            </span>
          </div>
          <FanChart yearly={sim.data.yearly} height={360} showWithdrawal />
        </div>
      )}
      {sim.isError && (
        <div className="rounded-md border border-red-200 bg-red-50 p-3 text-red-800 text-sm">
          {String((sim.error as Error)?.message ?? sim.error)}
        </div>
      )}

      {/* Legacy form sections — collapsed by default. The chart UI above
          is the primary editor; these stay for bulk edit + accessibility. */}
      <details className="rounded-lg border border-slate-200 bg-white">
        <summary className="cursor-pointer select-none px-5 py-3 text-sm font-medium text-slate-700">
          Form-based editors (income streams · goals · life events table)
        </summary>
        <div className="p-5 space-y-5 border-t border-slate-100">
          <IncomeStreamsSection scenarioId={id} />
          <GoalsSection scenarioId={id} probabilities={projection?.goals_probability} />
          <LifeEventsSection scenarioId={id} />
        </div>
      </details>
    </section>
  );
}

function FloatingStats(props: {
  year: number;
  maxYear: number;
  successRate: string;
  p50End: string;
  netWorth?: string;
  changeNw?: string;
  spending?: string;
  taxes?: string;
  effectiveRate?: string;
  age: number | null;
  calendarYear?: number;
}) {
  return (
    <div className="absolute top-3 right-3 grid grid-cols-2 gap-2 max-w-xs pointer-events-none">
      <Badge label="Year" value={String(props.calendarYear ?? `y${props.year}`)} />
      <Badge label="Age" value={props.age != null ? String(props.age) : '—'} />
      <Badge label="Net Worth" value={props.netWorth ? gbp(props.netWorth) : '—'} accent />
      <Badge
        label="Δ NW"
        value={props.changeNw ? gbp(props.changeNw) : '—'}
        signed={props.changeNw}
      />
      <Badge label="Spending" value={props.spending ? gbp(props.spending) : '—'} />
      <Badge label="Eff. tax" value={props.effectiveRate ? pct(props.effectiveRate) : '—'} />
    </div>
  );
}

function Badge({
  label,
  value,
  accent,
  signed,
}: {
  label: string;
  value: string;
  accent?: boolean;
  signed?: string;
}) {
  let cls = 'text-slate-700';
  if (accent) cls = 'text-emerald-700';
  if (signed != null) {
    const n = Number(signed);
    if (n > 0) cls = 'text-emerald-700';
    else if (n < 0) cls = 'text-red-600';
  }
  return (
    <div className="rounded-md border border-slate-200 bg-white/90 backdrop-blur px-2 py-1 shadow-sm pointer-events-auto">
      <div className="text-[9px] uppercase tracking-wide text-slate-500">{label}</div>
      <div className={`text-xs font-semibold tabular-nums ${cls}`}>{value}</div>
    </div>
  );
}

function Legend() {
  return (
    <div className="flex items-center gap-3 text-xs">
      <Swatch color="rgb(100, 116, 139)" label="Base" />
      <Swatch color="rgb(16, 185, 129)" label="Essential" />
      <Swatch color="rgb(245, 158, 11)" label="Discretionary" />
      <Swatch color="rgb(239, 68, 68)" label="Flex cut" />
    </div>
  );
}

function Swatch({ color, label }: { color: string; label: string }) {
  return (
    <span className="flex items-center gap-1.5">
      <span className="inline-block w-2.5 h-2.5 rounded-sm" style={{ background: color }} />
      <span className="text-slate-600">{label}</span>
    </span>
  );
}

function readFlexRules(s: Scenario): { from_ath_pct: string; cut_discretionary_pct: string }[] {
  const blob = s.config_json as Record<string, unknown>;
  const raw = blob?.flex_rules;
  if (!Array.isArray(raw)) return [];
  return raw
    .filter((r): r is Record<string, unknown> => typeof r === 'object' && r !== null)
    .map((r) => ({
      from_ath_pct: String(r.from_ath_pct ?? 0),
      cut_discretionary_pct: String(r.cut_discretionary_pct ?? 0),
    }));
}