import { useEffect, useMemo, useState } from 'react';
import type { ComponentProps, ComponentType, ReactNode } from 'react';
import { useParams } from 'react-router-dom';
import { Tabs, TabsContent, TabsList, TabsTrigger } from '@/components/ui/tabs';
import { Skeleton } from '@/components/ui/skeleton';
import { TermScope } from '@/components/site/Term';
import { listRuns, loadEpisode, rewardTotal } from '@/lib/demo-kit/episode';
import { usePlayer } from '@/lib/demo-kit/player';
import { loadDemoModule } from '@/lib/demo-kit/registry';
import type { AnyDemoModule } from '@/lib/demo-kit/registry';
import type { DemoEpisode, DemoStep, DemoTabId, RewardValues, RunRef } from '@/lib/demo-kit/types';
import { useRunParam, useSpeedParam, useStepParam, useTabParam } from '@/lib/url-state';
import * as st from '@/content/styles';
import { cn } from '@/lib/utils';
import { BlindCompare } from './BlindCompare';
import { Chip, Label, StatusPill } from './chrome';
import { CodeReceipt } from './CodeReceipt';
import { DemoErrorBoundary } from './DemoErrorBoundary';
import { DemoTabBar, TabClaim, resolveTab, visibleTabs } from './DemoTabs';
import { EnvAnatomy } from './EnvAnatomy';
import { LimitsCallout } from './LimitsCallout';
import { MetricMover } from './MetricMover';
import { ModelCallPanel } from './ModelCallPanel';
import { PlayYourself } from './PlayYourself';
import { ProvenanceCard } from './ProvenanceCard';
import { ReasoningDrawer } from './ReasoningDrawer';
import { ReasoningPanel } from './ReasoningPanel';
import { RewardBreakdown } from './RewardBreakdown';
import { RewardEditor } from './RewardEditor';
import type { RewardArm } from './RewardEditor';
import { SegmentedControl } from './SegmentedControl';
import { SlotRegion } from './SlotRegion';
import { StepTimeline } from './StepTimeline';
import { StatStrip } from './StatStrip';
import type { Stat } from './StatStrip';
import { RecordedBadge, TracePlayer } from './TracePlayer';
import { VerifyBadge } from './VerifyBadge';
import { formatDate, formatOrDash, useIsDesktop } from './format';

const REPO_BLOB = 'https://git.karti.ai/PIG/PIG-Demo/src/branch/main/';

/**
 * The panel the step-detail strip inside the Watch tab opens on.
 *
 * This control is deliberately NOT in the URL. `?tab=` belongs to the page's
 * four top-level tabs, and one param cannot address two nested controls without
 * one of them silently winning; a permalink to `?tab=call` would land the reader
 * on a page with no such top-level tab.
 */
const DEFAULT_DETAIL_PANEL = 'reasoning';

/** Reserved slug for the shell's own hand-written demo. Dev builds only. */
const MOCK_SLUG = '__mock';

/**
 * A top-level tab panel. Each one is its own `TermScope`, so "first occurrence
 * per panel gets the underline" is literally per panel rather than per page.
 */
function Panel({ children, ...props }: ComponentProps<typeof TabsContent>) {
  return (
    <TabsContent {...props}>
      <TermScope>{children}</TermScope>
    </TabsContent>
  );
}

export interface DemoBundle {
  demo: AnyDemoModule;
  runs: RunRef[];
  episodes: Record<string, DemoEpisode>;
}

type LoadState =
  | { status: 'loading' }
  | { status: 'ready'; bundle: DemoBundle; dropped: number }
  | { status: 'error'; message: string };

/**
 * A demo's module plus every recorded run it has.
 *
 * `loadDemoModule` and `loadEpisode` both cache their promises, so the route
 * loader having already fetched the module makes this resolve without a second
 * request. Runs are loaded with `allSettled` on purpose: one unreadable trace
 * drops that arm rather than blanking the page — and the page SAYS it dropped
 * one, because a missing arm that goes unmentioned is a missing arm nobody can
 * ask about.
 */
async function loadBundle(slug: string): Promise<{ bundle: DemoBundle; dropped: number }> {
  if (slug === MOCK_SLUG) {
    // Dynamic, so the mock lands in its own chunk and production never fetches
    // it. A static import would ship several hundred lines of fake trace to
    // every visitor of every real demo.
    const mock = await import('./mock');
    return {
      bundle: { demo: mock.mockDemo, runs: mock.mockRuns, episodes: mock.mockEpisodes },
      dropped: 0,
    };
  }

  const demo = await loadDemoModule(slug);
  const runs = await listRuns(slug).catch(() => [] as RunRef[]);
  const settled = await Promise.allSettled(runs.map((run) => loadEpisode(run)));

  const episodes: Record<string, DemoEpisode> = {};
  let dropped = 0;
  settled.forEach((outcome, index) => {
    const run = runs[index];
    if (!run) return;
    if (outcome.status === 'fulfilled') episodes[run.id] = outcome.value;
    else {
      dropped += 1;
      console.error(`[pig-demo] dropped run "${run.id}":`, outcome.reason);
    }
  });

  return {
    bundle: { demo, runs: runs.filter((run) => episodes[run.id] !== undefined), episodes },
    dropped,
  };
}

export interface DemoShellProps {
  /** Overrides the route param. Useful for previews and tests. */
  slug?: string;
  /** Skips loading entirely when the caller already has the bundle. */
  bundle?: DemoBundle;
}

/**
 * The route component every demo is rendered through.
 *
 * It owns four things and no more: loading, which tabs exist, the URL state,
 * and the page's single polite live region. Everything visual is delegated to
 * the surfaces in this directory, and the demo module is never reached into —
 * the shell only ever calls `adapt` and renders `Surface`.
 */
export function DemoShell({ slug: slugProp, bundle }: DemoShellProps) {
  const params = useParams();
  const slug = slugProp ?? params['slug'] ?? '';
  const [state, setState] = useState<LoadState>(
    bundle ? { status: 'ready', bundle, dropped: 0 } : { status: 'loading' },
  );

  useEffect(() => {
    if (bundle) {
      setState({ status: 'ready', bundle, dropped: 0 });
      return;
    }
    let live = true;
    setState({ status: 'loading' });
    loadBundle(slug)
      .then((loaded) => {
        if (live) setState({ status: 'ready', bundle: loaded.bundle, dropped: loaded.dropped });
      })
      .catch((error: unknown) => {
        if (!live) return;
        setState({
          status: 'error',
          message: error instanceof Error ? error.message : String(error),
        });
      });
    return () => {
      live = false;
    };
  }, [slug, bundle]);

  if (state.status === 'loading') return <ShellSkeleton />;
  if (state.status === 'error') {
    return (
      <main className={cn(st.shell, 'py-16')}>
        <div role="alert" className="max-w-xl rounded-xl border border-border bg-surface p-5 sm:p-6">
          <h1 className="text-h2 text-fg">That environment is not here</h1>
          <p className="mt-3 max-w-measure text-prose text-fg-2">{state.message}</p>
          <a href="/gallery" className={cn(st.btnSecondary, 'mt-6')}>
            All environments
          </a>
        </div>
      </main>
    );
  }

  return (
    // A second boundary inside the route's own: this one is keyed to the demo
    // so a crash names it, and resetting re-renders the surfaces rather than
    // re-navigating.
    <DemoErrorBoundary demoTitle={state.bundle.demo.meta.title}>
      <DemoBody bundle={state.bundle} dropped={state.dropped} />
    </DemoErrorBoundary>
  );
}

function DemoBody({ bundle, dropped }: { bundle: DemoBundle; dropped: number }) {
  const { demo, runs, episodes } = bundle;
  const isDesktop = useIsDesktop();

  const [runParam, setRunParam] = useRunParam();
  const [stepParam, setStepParam] = useStepParam();
  const [speedParam, setSpeedParam] = useSpeedParam();

  const run = useMemo(
    () => runs.find((candidate) => candidate.id === runParam) ?? defaultRun(runs, episodes),
    [runs, runParam],
  );
  const episode = run ? episodes[run.id] : undefined;

  const steps = useMemo<DemoStep<unknown>[]>(
    () => (episode ? demo.adapt(episode) : []),
    [demo, episode],
  );

  const player = usePlayer(steps, {
    initialIndex: stepParam,
    initialSpeed: speedParam,
    onIndexChange: setStepParam,
  });

  // The URL is the other writer of this state — Back, a pasted permalink, the
  // run switcher. The player is the source of truth while it is running, so it
  // only follows the URL when the two have actually diverged.
  const { seek } = player;
  useEffect(() => {
    if (stepParam !== player.index) seek(stepParam);
    // Intentionally keyed on the URL only: including `player.index` here would
    // re-run the effect on the player's own advance and fight it.
  }, [stepParam, seek]);

  // Derived, never declared. A demo that ships no interactive mode has no Play
  // tab and opens on Watch; one whose traces failed to load has no Watch tab
  // and opens on Reward.
  const hasRecording = Boolean(run && episode && steps.length > 0);
  const tabs = useMemo(
    () => visibleTabs({ play: Boolean(demo.interactive), watch: hasRecording }),
    [demo.interactive, hasRecording],
  );
  // `visibleTabs` always keeps `reward` and `evidence`, so index 0 exists; the
  // fallback is here only so the type does not need an assertion.
  const defaultTab: DemoTabId = tabs[0] ?? 'evidence';
  const [tabParam, setTabParam] = useTabParam(defaultTab);
  const activeTab = resolveTab(tabParam, tabs, defaultTab);

  // React-only, not a URL param. See DEFAULT_DETAIL_PANEL.
  const [detailPanel, setDetailPanel] = useState(DEFAULT_DETAIL_PANEL);

  // One arm per AGENT, not per run. Four agents over eight seeds is thirty-two
  // runs, and a ranking of thirty-two rows carrying four distinct labels buries
  // the one thing the Reward tab exists to show: move a slider, the order
  // flips. Each component is averaged over the agent's scored runs; a component
  // no run scored stays null rather than becoming a zero, because a zero is a
  // claim about the agent and a null is an admission we do not know.
  const arms = useMemo<RewardArm[]>(() => {
    const byLabel = new Map<string, { runs: RunRef[]; note?: string }>();
    for (const candidate of runs) {
      const group = byLabel.get(candidate.label) ?? { runs: [] };
      group.runs.push(candidate);
      if (candidate.intervention && !group.note) group.note = candidate.intervention;
      byLabel.set(candidate.label, group);
    }
    return [...byLabel.entries()].map(([label, group]) => {
      const values: RewardValues = {};
      for (const component of demo.reward.components) {
        const scored = group.runs
          .map((r) => episodes[r.id]?.rewards[component.key])
          .filter((v): v is number => typeof v === 'number' && Number.isFinite(v));
        values[component.key] =
          scored.length === 0 ? null : scored.reduce((a, b) => a + b, 0) / scored.length;
      }
      const arm: RewardArm = { id: label, label, values };
      if (group.note) arm.note = `${group.note} Mean over ${group.runs.length} recorded runs.`;
      else arm.note = `Mean over ${group.runs.length} recorded runs.`;
      return arm;
    });
  }, [runs, episodes, demo.reward.components]);

  const blindPair = useMemo(() => {
    for (let i = 0; i < runs.length; i += 1) {
      for (let j = i + 1; j < runs.length; j += 1) {
        const left = runs[i];
        const right = runs[j];
        if (!left || !right || left.seed !== right.seed) continue;
        const leftEpisode = episodes[left.id];
        const rightEpisode = episodes[right.id];
        if (!leftEpisode || !rightEpisode) continue;
        return { left, right, leftEpisode, rightEpisode };
      }
    }
    // Two runs on different seeds are two different puzzles; showing them side
    // by side would be a comparison of luck.
    return null;
  }, [runs, episodes]);

  const Surface = demo.Surface as ComponentType<{ state: unknown; compact?: boolean }>;
  const current = steps[player.index];
  const claims = demo.narrative.claims;
  const extras = demo.tabs ?? [];

  // The seed is the shared coordinate between the visitor's board and the
  // agent's. With no recording to match, the demo's own first board will do.
  const playSeed = run?.seed ?? 0;

  // The newest capture, for the Evidence readout. `runs` is manifest order,
  // which is not date order.
  const newestCapture = useMemo(
    () =>
      runs.reduce<string | null>(
        (newest, candidate) =>
          newest === null || candidate.capturedAt > newest ? candidate.capturedAt : newest,
        null,
      ),
    [runs],
  );

  const headerStats: Stat[] = episode
    ? [
        {
          label: 'Outcome',
          value: episode.outcome,
          tone: episode.outcome === 'solved' ? 'positive' : 'warning',
          title: episode.truncated
            ? 'Truncated before a terminal state'
            : 'How the recorded run ended',
        },
        {
          label: 'Reward',
          value: formatOrDash(rewardTotal(episode.rewards, demo.reward.components)),
          tone: 'brand',
          title: 'Reward — total under the shipped weights',
        },
        { label: 'Steps', value: steps.length, title: 'Steps — model calls in this run' },
        {
          label: 'Seed',
          value: episode.seed,
          title: 'Seed — the same seed reproduces this board',
        },
      ]
    : [];

  const detailPanels: { id: string; label: string; content: ReactNode }[] = [
    {
      id: 'reasoning',
      label: 'Reasoning',
      content: isDesktop ? (
        <ReasoningPanel
          reasoning={current?.reasoning ?? null}
          durationMs={current?.call?.durationMs ?? null}
          playing={player.isPlaying}
          speed={player.speed}
          stepIndex={player.index}
        />
      ) : (
        // Under `lg` there is no column for this, and putting it below the
        // board means watching the run with the thinking off-screen. The sheet
        // is mounted only here, so vaul never locks body scroll on desktop.
        <ReasoningDrawer
          reasoning={current?.reasoning ?? null}
          durationMs={current?.call?.durationMs ?? null}
          playing={player.isPlaying}
          speed={player.speed}
          stepIndex={player.index}
        />
      ),
    },
    {
      id: 'call',
      label: 'Model call',
      content: <ModelCallPanel call={current?.call ?? null} reply={current?.reply ?? null} />,
    },
    // A demo's own extra panels ride alongside the step detail, where they sit
    // next to the step they are almost always about. With no recording there is
    // no step detail, so the Evidence tab picks them up instead.
    ...(hasRecording
      ? extras.map((tab) => ({ id: tab.id, label: tab.label, content: <tab.Component /> }))
      : []),
  ];
  const activeDetail = detailPanels.some((panel) => panel.id === detailPanel)
    ? detailPanel
    : DEFAULT_DETAIL_PANEL;

  return (
    <main className={cn(st.shell, 'pb-16')}>
      {/*
        The page's ONE live region. Every step change lands here and nowhere
        else: with reduced motion the board animation is gone, so this sentence
        is the only thing that tells a screen-reader user what just happened.
      */}
      <div aria-live="polite" aria-atomic="true" className="sr-only">
        {current?.announce ?? ''}
      </div>

      <header className="pt-6">
        <div className="flex flex-wrap items-center gap-2">
          <Label className="text-accent-fg">For {demo.meta.persona}</Label>
          <StatusPill status={demo.meta.status} />
        </div>
        <h1 className="mt-1.5 text-h1 text-fg lg:text-h1-lg">{demo.meta.title}</h1>
        <p className="mt-2 max-w-measure-wide text-pretty text-lede text-fg-2 lg:text-lede-lg">
          {demo.meta.tagline}
        </p>
        {/* The buyer's question, kept quiet on purpose: it is the thing they
            walked in with, not the thing this page is asserting. */}
        <div className="mt-4 border-l-2 border-border-strong pl-3">
          <Label>The question you walked in with</Label>
          <p className="mt-0.5 max-w-[60ch] text-pretty text-prose text-fg-2">
            {demo.narrative.anxiety}
          </p>
        </div>
        {/*
          The stats describe the RECORDED RUN, so they only belong on the tabs
          whose subject is that run. On Play they sat above the visitor's own
          empty board reading "Outcome: failed", which parses as *your* game
          having already failed before you have touched a key.
        */}
        {run && headerStats.length > 0 && activeTab !== 'play' ? (
          <div className="mt-4 flex flex-wrap items-center gap-x-4 gap-y-2">
            <StatStrip stats={headerStats} />
            <RecordedBadge
              model={run.model}
              capturedAt={run.capturedAt}
              {...(run.intervention ? { intervention: run.intervention } : {})}
              {...(player.timingIsReal || activeTab !== 'watch'
                ? {}
                : { timingNote: 'pacing approximate' })}
            />
          </div>
        ) : null}
        <SlotRegion id="hero-aside" />
      </header>

      <Tabs value={activeTab} onValueChange={setTabParam} className="mt-5 sm:mt-6">
        <DemoTabBar tabs={tabs} />

        {tabs.includes('play') ? (
          // `forceMount` keeps the visitor's half-finished board alive while
          // they read the other tabs, so a game in progress survives a trip to
          // Reward and back. Radix leaves the hiding to the author under
          // `forceMount`, which is what the `data-[state=inactive]` class does —
          // it is load-bearing, not belt-and-braces.
          <Panel
            value="play"
            forceMount
            className="mt-5 space-y-6 data-[state=inactive]:hidden sm:mt-6"
          >
            <TabClaim>{claims.play}</TabClaim>
            <PlayYourself
              demo={demo}
              seed={playSeed}
              // The bridge to Watch, rendered only once the visitor has acted
              // and only when there is a Watch tab to bridge to. No slug, no
              // narrative literal: the same sentence on every environment.
              {...(tabs.includes('watch')
                ? {
                    afterMove: (
                      <p className="max-w-measure text-prose text-fg-2">
                        The score on this board comes from the grader, not from us.{' '}
                        <button
                          type="button"
                          onClick={() => setTabParam('watch')}
                          className="font-medium text-accent-fg underline decoration-border-strong underline-offset-4 hover:decoration-accent-fg"
                        >
                          Watch a model take the same board →
                        </button>
                      </p>
                    ),
                  }
                : {})}
            />
            <SlotRegion id="below-board" />
            <div className="space-y-3">
              <Label as="h2">The machine you are inside</Label>
              <EnvAnatomy anatomy={demo.anatomy} rewardLine={demo.meta.rewardLine} compact />
            </div>
          </Panel>
        ) : null}

        {tabs.includes('watch') && run && episode ? (
          <Panel value="watch" className="mt-5 space-y-4 sm:mt-6">
            <TabClaim>{claims.watch}</TabClaim>

            {runs.length > 1 ? (
              <RunSwitcher
                runs={runs}
                activeId={run.id}
                onSelect={(id) => {
                  player.pause();
                  // The run param setter also zeroes `step`: step 6 of a
                  // nine-turn rollout is not step 6 of a three-turn one.
                  setRunParam(id);
                }}
              />
            ) : null}

            <TracePlayer
              playing={player.isPlaying}
              onPlayingChange={(next) => (next ? player.play() : player.pause())}
              speed={player.speed}
              onSpeedChange={(next) => {
                player.setSpeed(next);
                setSpeedParam(next);
                // `instant` is a destination, not a rate. The player only
                // consumes it while running, so choosing it from a paused
                // transport has to start the run — otherwise the button
                // visibly does nothing, which reads as broken.
                if (next === 'instant') player.play();
              }}
              onRestart={player.restart}
              step={player.index}
              stepCount={steps.length}
              onStepChange={(next) => {
                player.pause();
                player.seek(next);
              }}
              progress={player.progress}
              timingIsReal={player.timingIsReal}
              model={run.model}
              capturedAt={run.capturedAt}
              {...(run.intervention ? { intervention: run.intervention } : {})}
            />

            <div className="grid grid-cols-1 gap-3 lg:grid-cols-[auto_minmax(0,1fr)] lg:items-start">
              <div className="w-fit max-w-full rounded-xl border border-border bg-surface p-3 sm:p-4">
                {current ? <Surface state={current.state} /> : null}
              </div>

              <div className="min-w-0">
                <Tabs value={activeDetail} onValueChange={setDetailPanel}>
                  {/* The nested list keeps the PILL segment style, so the
                      primary underline bar and this never look alike. */}
                  <TabsList aria-label="Details for this step" className="max-w-full overflow-x-auto">
                    {detailPanels.map((panel) => (
                      <TabsTrigger key={panel.id} value={panel.id}>
                        {panel.label}
                      </TabsTrigger>
                    ))}
                  </TabsList>
                  {detailPanels.map((panel) => (
                    <TabsContent key={panel.id} value={panel.id} className="mt-3">
                      {panel.content}
                    </TabsContent>
                  ))}
                </Tabs>
              </div>
            </div>

            <StepTimeline
              steps={steps}
              current={player.index}
              onSelect={(next) => {
                player.pause();
                player.seek(next);
              }}
              Surface={Surface}
              onTogglePlay={player.toggle}
            />
            {player.timingIsReal ? null : (
              <p className="max-w-measure text-small text-muted">
                Some steps in this run carried no recorded latency, so their dwell on the timeline
                is the player's fallback rather than a measurement.
              </p>
            )}
            {dropped > 0 ? (
              <p className="font-mono text-caption text-muted">
                {dropped} recorded {dropped === 1 ? 'run' : 'runs'} could not be loaded
              </p>
            ) : null}
            <SlotRegion id="below-timeline" />

            {blindPair ? (
              <BlindCompare
                seed={blindPair.left.seed}
                Surface={Surface}
                a={{
                  runId: blindPair.left.id,
                  label: blindPair.left.label,
                  model: blindPair.left.model,
                  ...(blindPair.left.intervention
                    ? { intervention: blindPair.left.intervention }
                    : {}),
                  steps: demo.adapt(blindPair.leftEpisode),
                  total: rewardTotal(blindPair.leftEpisode.rewards, demo.reward.components),
                }}
                b={{
                  runId: blindPair.right.id,
                  label: blindPair.right.label,
                  model: blindPair.right.model,
                  ...(blindPair.right.intervention
                    ? { intervention: blindPair.right.intervention }
                    : {}),
                  steps: demo.adapt(blindPair.rightEpisode),
                  total: rewardTotal(blindPair.rightEpisode.rewards, demo.reward.components),
                }}
              />
            ) : null}
          </Panel>
        ) : null}

        <Panel value="reward" className="mt-5 space-y-4 sm:mt-6">
          <TabClaim>{claims.reward}</TabClaim>

          {episode ? (
            <RewardBreakdown
              spec={demo.reward}
              values={episode.rewards}
              {...(episode.metrics ? { metrics: episode.metrics } : {})}
            />
          ) : (
            <>
              <p className="max-w-measure text-prose text-fg-2">
                No recorded run has been scored for this environment yet, so every term below
                reads as not scored rather than as zero. The weights are the ones the environment
                ships.
              </p>
              <RewardBreakdown spec={demo.reward} values={{}} />
            </>
          )}

          {/* The editor carries the ranking it re-orders in its own right-hand
              column, so the two are never on screen apart. Absent, not greyed,
              when there is nothing to rank. */}
          {arms.length > 1 ? <RewardEditor spec={demo.reward} arms={arms} /> : null}

          {run && episode ? (
            <HeadlineMetric
              label={`Total reward — ${run.label}`}
              arms={arms}
              components={demo.reward.components}
              currentRewards={episode.rewards}
            />
          ) : null}

          <SlotRegion id="beside-reward" />
        </Panel>

        <Panel value="evidence" className="mt-5 space-y-6 sm:mt-6">
          <TabClaim>{claims.evidence}</TabClaim>

          {/*
            `narrative.thesis` is a required field of the contract and the only
            paragraph on a demo that argues for the environment as a whole
            rather than for one tab. It has to be SOMEWHERE, and this is the
            tab a visitor opens to read rather than to do — Play stays a board
            above the fold, which is the one thing a paragraph here would cost.
          */}
          <div className="space-y-3">
            <p className="max-w-measure text-pretty text-prose text-fg-2">{demo.narrative.thesis}</p>
            {/* The readout that left the landing. Every value is data. */}
            <p className="flex flex-wrap gap-x-2 gap-y-1 font-mono text-caption text-muted">
              <span>
                <span className="uppercase tracking-label">verifiers</span>{' '}
                <span className="text-fg">{demo.provenance.verifiersVersion}</span>
              </span>
              {newestCapture ? (
                <>
                  <span aria-hidden="true">·</span>
                  <span>
                    <span className="uppercase tracking-label">captured</span>{' '}
                    <span className="text-fg">{formatDate(newestCapture)}</span>
                  </span>
                </>
              ) : null}
              {run ? (
                <>
                  <span aria-hidden="true">·</span>
                  <span title="The same seed reproduces this board">
                    <span className="uppercase tracking-label">seed</span>{' '}
                    <span className="text-fg">{run.seed}</span>
                  </span>
                </>
              ) : null}
            </p>
          </div>

          <EnvAnatomy anatomy={demo.anatomy} rewardLine={demo.meta.rewardLine} />

          {/*
            The receipt sits on Evidence, not Reward: the Evidence claim both
            demos make is "here is the grader, and here is proof your browser
            ran it", and that proof belongs next to the printed grader rather
            than under a slider. Reward keeps the breakdown and the editor.
          */}
          {episode ? <VerifyBadge demo={demo} episode={episode} /> : null}

          <div className="grid grid-cols-1 gap-4 lg:grid-cols-2 lg:items-start">
            <ProvenanceCard provenance={demo.provenance} {...(run ? { run } : {})} />
            <CodeReceipt
              code={demo.reward.source.code}
              path={demo.reward.source.path}
              {...(demo.reward.source.marker ? { marker: demo.reward.source.marker } : {})}
              href={`${REPO_BLOB}${demo.reward.source.path}`}
            />
            <SlotRegion id="after-receipts" className="lg:col-span-2" />
          </div>

          {!hasRecording && extras.length > 0 ? (
            <div className="space-y-4">
              {extras.map((tab) => (
                <tab.Component key={tab.id} />
              ))}
            </div>
          ) : null}

          <SlotRegion id="before-limits" />
          <LimitsCallout limits={demo.narrative.limits} />
        </Panel>
      </Tabs>
    </main>
  );
}

/**
 * The headline metric, with every recorded arm on the same line.
 *
 * Arms that were never scored are dropped rather than plotted at zero — the
 * difference between "scored badly" and "not scored" is the site's whole
 * argument, and a chart is the easiest place in the world to lose it.
 */
function HeadlineMetric({
  label,
  arms,
  components,
  currentRewards,
}: {
  label: string;
  arms: RewardArm[];
  components: AnyDemoModule['reward']['components'];
  currentRewards: DemoEpisode['rewards'];
}) {
  const points = arms
    .map((arm) => ({ x: arm.label, y: rewardTotal(arm.values, components) }))
    .filter((point): point is { x: string; y: number } => point.y !== null);
  const baselineArm = arms[0];
  const baselineValue = baselineArm ? rewardTotal(baselineArm.values, components) : null;

  return (
    <MetricMover
      label={label}
      value={rewardTotal(currentRewards, components) ?? 0}
      {...(baselineArm && baselineValue !== null && arms.length > 1
        ? { baseline: { value: baselineValue, label: baselineArm.label } }
        : {})}
      series={points}
      caption="Every point is a recorded run scored by the same grader. Nothing here is a projection."
    />
  );
}

function RunSwitcher({
  runs,
  activeId,
  onSelect,
}: {
  runs: RunRef[];
  activeId: string;
  onSelect: (id: string) => void;
}) {
  // Two axes, not one list. With four arms over eight seeds a flat control is
  // thirty buttons carrying four distinct labels, which reads as a bug. Arms
  // are grouped by `label` because that is what an arm IS in the manifest —
  // the shell has no other notion of one, and inventing a field for it would
  // put demo-specific structure into the contract.
  const arms = useMemo(() => {
    const byLabel = new Map<string, RunRef[]>();
    for (const run of runs) {
      const list = byLabel.get(run.label);
      if (list) list.push(run);
      else byLabel.set(run.label, [run]);
    }
    return [...byLabel.entries()].map(([label, group]) => ({ label, runs: group }));
  }, [runs]);

  const active = runs.find((r) => r.id === activeId) ?? runs[0];
  if (!active) return null;
  const activeArm = arms.find((a) => a.label === active.label) ?? arms[0];
  if (!activeArm) return null;

  const pickArm = (label: string) => {
    const arm = arms.find((a) => a.label === label);
    if (!arm) return;
    // Hold the seed across an arm change where the arm has it. Comparing two
    // agents means comparing them on the SAME hidden word; silently jumping to
    // a different seed would make the comparison meaningless while looking fine.
    const sameSeed = arm.runs.find((r) => r.seed === active.seed);
    onSelect((sameSeed ?? arm.runs[0])!.id);
  };

  return (
    <div className="flex flex-wrap items-center gap-x-4 gap-y-2">
      <div className="flex flex-wrap items-center gap-2">
        <Label as="span">Agent</Label>
        <SegmentedControl
          label="Agent"
          options={arms.map((arm) => {
            const intervention = arm.runs.find((r) => r.intervention)?.intervention;
            return {
              value: arm.label,
              label: intervention ? (
                <span className="inline-flex items-center gap-1.5">
                  {arm.label}
                  {/* PROMPTED: this arm's runs were intervened on. The chip
                      travels with the arm so a switch never hides it. */}
                  <Chip variant="default">prompted</Chip>
                </span>
              ) : (
                arm.label
              ),
              ...(intervention ? { title: intervention } : {}),
            };
          })}
          value={activeArm.label}
          onChange={pickArm}
        />
      </div>
      {activeArm.runs.length > 1 ? (
        <div className="flex flex-wrap items-center gap-2">
          <Label as="span">Seed</Label>
          <SegmentedControl
            label="Seed"
            options={activeArm.runs.map((run) => ({
              value: run.id,
              label: `#${run.seed}`,
              title: `Seed ${run.seed} — the same seed reproduces this board`,
            }))}
            value={active.id}
            onChange={onSelect}
            optionClassName="px-2.5 font-mono text-caption"
          />
        </div>
      ) : null}
    </div>
  );
}

/**
 * The loading state. Shaped like the page it becomes, and with no spinner: a
 * spinner here would imply a live model call, which is the one thing the whole
 * page is at pains to say is not happening.
 */
function ShellSkeleton() {
  return (
    <div className={cn(st.shell, 'py-10')} aria-busy="true">
      <p className="sr-only">Loading the recorded run.</p>
      <Skeleton className="h-3 w-40" />
      <Skeleton className="mt-3 h-8 w-64" />
      <Skeleton className="mt-3 h-5 w-full max-w-md" />
      <Skeleton className="mt-6 h-11 w-full max-w-md" />
      <Skeleton className="mt-6 h-80" />
    </div>
  );
}

/**
 * The run a visitor sees before choosing one.
 *
 * `runs[0]` is the manifest's first entry — the weakest agent on seed 0, which
 * for the first demo shipped was a failed game with thinking off. So the Watch
 * tab opened on a loss with an empty reasoning panel and the Reward tab on a
 * row of zeros: the model's least interesting attempt, chosen by accident of
 * sort order.
 *
 * Prefer, in order: a run with recorded reasoning (there is something to
 * stream), then a solved one (the board reaches a conclusion), then the
 * earliest seed so the choice is stable across deploys. The visitor can still
 * pick any run; this only decides what the page leads with.
 */
function defaultRun(runs: RunRef[], episodes: Record<string, DemoEpisode>): RunRef | undefined {
  const score = (run: RunRef): number => {
    const ep = episodes[run.id];
    if (!ep) return -1;
    const hasReasoning = ep.turns.some((t) => t.reasoning && t.reasoning.length > 0);
    const solved = ep.outcome === 'solved';
    return (hasReasoning ? 2 : 0) + (solved ? 1 : 0);
  };
  return [...runs].sort((a, b) => score(b) - score(a) || a.seed - b.seed)[0];
}