// ArenaPane — live view for an Arena battle.
// Mirrors OrchestratorPane: header with status/winner, contestant roster
// (collapsed rows, expand-one), analysis panel, cross-examination control.
//
// Subscribes to the coder user channel (via useCoderUserEvents → sessionEvents)
// for battle_started / contestant_updated / battle_updated frames.

import { useCallback, useEffect, useRef, useState } from 'react';
import { ChevronDown, ChevronRight, Loader2, MoreHorizontal, RotateCcw, Swords, Trophy, X } from 'lucide-react';
import { toast } from 'sonner';
import { api } from '@/api/client';
import type { ArenaState, BattleShape, ContestantShape, CrossExaminationShape, ProviderSnapshotEntry } from '@/api/types';
import { sessionEvents } from '@/hooks/sessionEvents';
import { useProviderSnapshot } from '@/hooks/useProviderSnapshot';
import {
  DropdownMenu,
  DropdownMenuContent,
  DropdownMenuItem,
  DropdownMenuTrigger,
} from '@/components/ui/dropdown-menu';
import { cn } from '@/lib/utils';

// ─── Status dot (mirrors FlowStepStatusDot) ───────────────────────────────────

function ContestantStatusDot({ status }: { status: ContestantShape['status'] }) {
  if (status === 'running') {
    return (
      <span
        aria-label="running"
        className="inline-block w-3 h-3 rounded-full border-2 border-emerald-500 border-t-transparent animate-spin shrink-0"
      />
    );
  }
  const cls =
    status === 'done'
      ? 'bg-emerald-500'
      : status === 'error'
        ? 'bg-destructive'
        : 'bg-muted-foreground/40'; // queued
  return <span aria-label={status} className={cn('inline-block w-1.5 h-1.5 rounded-full shrink-0', cls)} />;
}

// ─── Lane badge ───────────────────────────────────────────────────────────────

function LaneBadge({ lane }: { lane: ContestantShape['lane'] }) {
  return (
    <span
      className={cn(
        'text-[10px] px-1 py-0.5 rounded shrink-0',
        lane === 'local'
          ? 'bg-sky-500/10 text-sky-600 dark:text-sky-400'
          : 'bg-violet-500/10 text-violet-600 dark:text-violet-400',
      )}
    >
      {lane}
    </span>
  );
}

// ─── Duration formatter ───────────────────────────────────────────────────────

function formatDuration(ms: number | null): string {
  if (ms == null) return '';
  const s = Math.round(ms / 1000);
  if (s < 60) return `${s}s`;
  return `${Math.floor(s / 60)}m${String(s % 60).padStart(2, '0')}s`;
}

// ─── Live ticker for running contestants ─────────────────────────────────────

function LiveDuration({ startedAt }: { startedAt: number }) {
  const [elapsed, setElapsed] = useState(() => Date.now() - startedAt);
  useEffect(() => {
    const id = setInterval(() => setElapsed(Date.now() - startedAt), 1000);
    return () => clearInterval(id);
  }, [startedAt]);
  return <span>{formatDuration(elapsed)}</span>;
}

// ─── DiffView ─────────────────────────────────────────────────────────────────

function DiffView({ diff }: { diff: string }) {
  const lines = diff.split('\n');
  return (
    <div className="border-t border-border/50">
      <div className="px-3 pt-2 pb-1 text-[10px] font-medium uppercase tracking-wide text-muted-foreground">
        Diff
      </div>
      <pre className="px-3 pb-3 text-xs font-mono whitespace-pre leading-relaxed overflow-x-auto">
        {lines.map((line, i) => {
          const cls =
            line.startsWith('+') && !line.startsWith('+++')
              ? 'text-emerald-600 dark:text-emerald-400'
              : line.startsWith('-') && !line.startsWith('---')
                ? 'text-destructive'
                : line.startsWith('@@')
                  ? 'text-violet-500 dark:text-violet-400'
                  : 'text-muted-foreground';
          return (
            <span key={i} className={cn('block', cls)}>
              {line || ' '}
            </span>
          );
        })}
      </pre>
    </div>
  );
}

// ─── ContestantRow ────────────────────────────────────────────────────────────

interface ContestantRowState {
  data: ContestantShape;
  output: string;
  startedAt: number | null;
}

function ContestantRow({
  row,
  isExpanded,
  onToggle,
  isWinner,
  battleId,
  battleType,
}: {
  row: ContestantRowState;
  isExpanded: boolean;
  onToggle: () => void;
  isWinner: boolean;
  battleId: string;
  battleType: 'coding' | 'qa';
}) {
  const { data, output, startedAt } = row;
  const label = `${data.identity} / ${data.model}`;

  // Lazy-fetch diff for coding contestants once they are done and expanded.
  const [diff, setDiff] = useState<string | null>(null);
  useEffect(() => {
    if (!isExpanded || battleType !== 'coding' || data.status !== 'done') return;
    if (diff !== null) return;
    api.battles.getDiff(battleId, data.id)
      .then(({ diff: d }) => setDiff(d))
      .catch(() => setDiff(''));
  }, [isExpanded, battleType, data.status, data.id, battleId, diff]);

  async function handleSetWinner(contestantId: string | null) {
    try {
      await api.battles.setWinner(battleId, { winner_contestant_id: contestantId });
    } catch {
      // WS frame updates the badge; a failed call just leaves it unchanged
    }
  }

  return (
    <div>
      <button
        type="button"
        onClick={onToggle}
        className="w-full flex items-center gap-2 px-3 py-2.5 text-left hover:bg-muted/30 transition-colors"
      >
        <ContestantStatusDot status={data.status} />
        <span className="text-sm flex-1 truncate min-w-0">{label}</span>
        {isWinner && (
          <Trophy size={11} className="shrink-0 text-emerald-500" aria-label="winner" />
        )}
        <LaneBadge lane={data.lane} />
        {data.status === 'running' && startedAt != null ? (
          <span className="text-xs text-muted-foreground shrink-0 tabular-nums">
            <LiveDuration startedAt={startedAt} />
          </span>
        ) : data.duration_ms != null ? (
          <span className="text-xs text-muted-foreground shrink-0 tabular-nums">
            {formatDuration(data.duration_ms)}
          </span>
        ) : null}
        {data.tokens_per_sec != null && (
          <span className="text-xs text-muted-foreground shrink-0 hidden sm:block tabular-nums">
            {data.tokens_per_sec.toFixed(1)} tok/s
          </span>
        )}
        {data.status === 'error' && (
          <span className="text-xs text-destructive shrink-0 hidden sm:block truncate max-w-[100px]" title={data.error ?? ''}>
            {data.error ?? 'error'}
          </span>
        )}
        {isExpanded ? (
          <ChevronDown size={12} className="shrink-0 text-muted-foreground" />
        ) : (
          <ChevronRight size={12} className="shrink-0 text-muted-foreground" />
        )}
        {/* Row menu: winner override. Stop propagation so the row toggle isn't triggered. */}
        <span onClick={(e) => e.stopPropagation()}>
          <DropdownMenu>
            <DropdownMenuTrigger asChild>
              <button
                type="button"
                className="shrink-0 p-0.5 rounded text-muted-foreground hover:text-foreground hover:bg-muted"
                aria-label="Contestant options"
              >
                <MoreHorizontal size={12} />
              </button>
            </DropdownMenuTrigger>
            <DropdownMenuContent align="end">
              {!isWinner && (
                <DropdownMenuItem onSelect={() => void handleSetWinner(data.id)}>
                  <Trophy size={12} /> Set as winner
                </DropdownMenuItem>
              )}
              {isWinner && (
                <DropdownMenuItem onSelect={() => void handleSetWinner(null)}>
                  Clear winner
                </DropdownMenuItem>
              )}
            </DropdownMenuContent>
          </DropdownMenu>
        </span>
      </button>

      {isExpanded && (
        <div className="border-t border-border/50 bg-muted/10 max-h-[55vh] overflow-y-auto">
          {data.token_breakdown && (
            <div className="flex items-center gap-1.5 px-3 py-2 text-xs text-muted-foreground border-b border-border/30">
              {data.token_breakdown.system > 0 && <span title="system">{data.token_breakdown.system}s</span>}
              {data.token_breakdown.user > 0 && <span title="user">{data.token_breakdown.user}u</span>}
              {data.token_breakdown.assistant > 0 && <span title="assistant">{data.token_breakdown.assistant}a</span>}
              {data.token_breakdown.tools > 0 && <span title="tools">{data.token_breakdown.tools}t</span>}
              {data.token_breakdown.reasoning > 0 && <span title="reasoning" className="text-amber-500">{data.token_breakdown.reasoning}r</span>}
              {data.token_breakdown.total > 0 && <span className="font-medium tabular-nums ml-1">∑{data.token_breakdown.total}</span>}
            </div>
          )}
          {output.length === 0 ? (
            <div className="flex items-center justify-center py-6 text-sm text-muted-foreground">
              {data.status === 'queued'
                ? 'Waiting to start…'
                : data.status === 'error'
                  ? data.error ?? 'Error'
                  : 'Connecting…'}
            </div>
          ) : (
            <pre className="p-3 text-xs font-mono whitespace-pre-wrap leading-relaxed break-all text-foreground">
              {output}
            </pre>
          )}
          {battleType === 'coding' && data.status === 'done' && diff && (
            <DiffView diff={diff} />
          )}
        </div>
      )}
    </div>
  );
}

// ─── CrossExaminationPanel ────────────────────────────────────────────────────

function CrossExaminationPanel({
  battleId,
  crossExams,
  snapshot,
}: {
  battleId: string;
  crossExams: CrossExaminationShape[];
  snapshot: ProviderSnapshotEntry[] | null;
}) {
  const [identity, setIdentity] = useState('');
  const [model, setModel] = useState('');
  const [running, setRunning] = useState(false);

  const identityOptions = (snapshot ?? [])
    .filter((e) => e.installed && e.enabled)
    .map((e) => ({ value: e.name, label: e.label }));

  const modelOptions = (() => {
    const provider = (snapshot ?? []).find((e) => e.name === identity);
    return (provider?.models ?? []).map((m) => ({ value: m.id, label: m.label }));
  })();

  async function handleRun() {
    if (!identity || !model || running) return;
    setRunning(true);
    try {
      await api.battles.crossExamine(battleId, { identity, model });
      // The verdict arrives via battle_updated frame; ArenaPane will refetch.
    } catch (err) {
      toast.error(err instanceof Error ? err.message : 'Cross-examination failed');
    } finally {
      setRunning(false);
    }
  }

  return (
    <div className="border-t border-border p-4 flex flex-col gap-3">
      <div className="text-xs font-medium text-muted-foreground uppercase tracking-wide">
        Cross-examination
      </div>
      <p className="text-xs text-muted-foreground">
        Challenge the results with any model. The verdict is advisory and never changes the recorded winner.
      </p>
      <div className="flex gap-2 items-center flex-wrap">
        <select
          value={identity}
          onChange={(e) => { setIdentity(e.target.value); setModel(''); }}
          className="flex-1 min-w-[120px] text-xs border border-border rounded bg-background px-2 py-1.5 text-foreground focus:outline-none focus:ring-1 focus:ring-ring"
          aria-label="Backend"
        >
          <option value="">Backend…</option>
          {identityOptions.map((o) => (
            <option key={o.value} value={o.value}>{o.label}</option>
          ))}
        </select>
        <select
          value={model}
          onChange={(e) => setModel(e.target.value)}
          disabled={!identity}
          className="flex-1 min-w-[120px] text-xs border border-border rounded bg-background px-2 py-1.5 text-foreground focus:outline-none focus:ring-1 focus:ring-ring disabled:opacity-50"
          aria-label="Model"
        >
          <option value="">Model…</option>
          {modelOptions.map((o) => (
            <option key={o.value} value={o.value}>{o.label}</option>
          ))}
        </select>
        <button
          type="button"
          onClick={() => void handleRun()}
          disabled={!identity || !model || running}
          className="inline-flex items-center gap-1 text-xs px-2 py-1.5 rounded border border-border text-foreground hover:bg-muted disabled:opacity-50"
        >
          {running && <Loader2 size={10} className="animate-spin" />}
          Run
        </button>
      </div>

      {crossExams.length > 0 && (
        <div className="flex flex-col gap-3 mt-1">
          {crossExams.map((xe) => (
            <div key={xe.id} className="rounded border border-border/50 bg-muted/20 p-3">
              <div className="text-xs font-medium text-muted-foreground mb-1.5">
                {xe.identity} / {xe.model}
              </div>
              {xe.verdict ? (
                <div className="text-sm whitespace-pre-wrap leading-relaxed">{xe.verdict}</div>
              ) : (
                <div className="text-xs text-muted-foreground flex items-center gap-1.5">
                  <Loader2 size={10} className="animate-spin" /> Running…
                </div>
              )}
            </div>
          ))}
        </div>
      )}
    </div>
  );
}

// ─── ArenaPane ────────────────────────────────────────────────────────────────

interface Props {
  state: ArenaState;
  projectId: string; // available for future use (e.g. file browser affordance)
  onClose: () => void;
}

export function ArenaPane({ state, onClose }: Props) {
  const [battle, setBattle] = useState<BattleShape | null>(null);
  const [contestantRows, setContestantRows] = useState<ContestantRowState[]>([]);
  const [crossExams, setCrossExams] = useState<CrossExaminationShape[]>([]);
  const [analysis, setAnalysis] = useState<string | null>(null);
  const [expandedId, setExpandedId] = useState<string | null>(null);
  const [stopping, setStopping] = useState(false);
  const [reanalyzing, setReanalyzing] = useState(false);
  const startTimesRef = useRef<Map<string, number>>(new Map());

  const snapshot = useProviderSnapshot();

  // Fetch current battle state on mount / battle_id change.
  useEffect(() => {
    setBattle(null);
    setContestantRows([]);
    setCrossExams([]);
    setAnalysis(null);
    setExpandedId(null);

    api.battles.get(state.battle_id)
      .then(({ battle: b, contestants, cross_examinations }) => {
        setBattle(b);
        setContestantRows(
          contestants.map((c) => ({
            data: c,
            output: '',
            startedAt: c.status === 'running' ? Date.now() : null,
          })),
        );
        setCrossExams(cross_examinations);
        // Fetch analysis text if battle is already completed.
        if (b.status === 'completed') {
          api.battles.getAnalysis(state.battle_id)
            .then(({ text }) => setAnalysis(text))
            .catch(() => {});
        }
        // Auto-expand first running contestant.
        const firstRunning = contestants.find((c) => c.status === 'running');
        if (firstRunning) setExpandedId(firstRunning.id);
      })
      .catch(() => {});
  }, [state.battle_id]);

  // Subscribe to live battle/contestant frames.
  useEffect(() => {
    return sessionEvents.subscribe((ev) => {
      if (ev.type === 'battle_started' && ev.battle_id === state.battle_id) {
        setContestantRows((prev) => {
          if (prev.length > 0) return prev;
          return ev.contestants.map((c) => ({
            data: {
              id: c.id,
              battle_id: ev.battle_id,
              identity: c.identity,
              model: c.model,
              lane: c.lane,
              task_id: null,
              worktree_id: null,
              status: 'queued' as const,
              duration_ms: null,
              tokens_per_sec: null,
              cost_tokens: null,
              token_breakdown: null,
              result_path: null,
              error: null,
              created_at: new Date().toISOString(),
              updated_at: new Date().toISOString(),
            },
            output: '',
            startedAt: null,
          }));
        });
      } else if (ev.type === 'contestant_updated' && ev.battle_id === state.battle_id) {
        setContestantRows((prev) =>
          prev.map((row) => {
            if (row.data.id !== ev.contestant_id) return row;
            const updatedData: ContestantShape = {
              ...row.data,
              ...(ev.status != null ? { status: ev.status } : {}),
              ...(ev.duration_ms != null ? { duration_ms: ev.duration_ms } : {}),
              ...(ev.tokens_per_sec != null ? { tokens_per_sec: ev.tokens_per_sec } : {}),
              ...(ev.error != null ? { error: ev.error } : {}),
            };
            const newStartedAt =
              ev.status === 'running' && row.startedAt == null
                ? Date.now()
                : ev.status === 'done' || ev.status === 'error'
                  ? null
                  : row.startedAt;
            if (ev.status === 'running') {
              startTimesRef.current.set(ev.contestant_id, newStartedAt ?? Date.now());
              setExpandedId(ev.contestant_id);
            }
            return {
              data: updatedData,
              output: ev.delta ? row.output + ev.delta : row.output,
              startedAt: newStartedAt,
            };
          }),
        );
        if (ev.battle_status) {
          setBattle((prev) => prev ? { ...prev, status: ev.battle_status! } : prev);
        }
      } else if (ev.type === 'battle_updated' && ev.battle_id === state.battle_id) {
        setBattle((prev) => {
          if (!prev) return prev;
          return {
            ...prev,
            ...(ev.status != null ? { status: ev.status } : {}),
            ...(ev.winner_contestant_id !== undefined ? { winner_contestant_id: ev.winner_contestant_id } : {}),
          };
        });
        if (ev.analysis_ready) {
          api.battles.getAnalysis(state.battle_id)
            .then(({ text }) => setAnalysis(text))
            .catch(() => setAnalysis('Analysis ready — failed to load text.'));
        }
        if (ev.cross_exam_id) {
          // Refetch cross-exams to get the latest verdict.
          api.battles.get(state.battle_id)
            .then(({ cross_examinations }) => setCrossExams(cross_examinations))
            .catch(() => {});
        }
      }
    });
  }, [state.battle_id]);

  const toggleExpand = useCallback((id: string) => {
    setExpandedId((prev) => (prev === id ? null : id));
  }, []);

  async function handleStop() {
    if (stopping) return;
    setStopping(true);
    try {
      await api.battles.stop(state.battle_id);
    } catch {
      // non-fatal
    } finally {
      setStopping(false);
    }
  }

  async function handleReanalyze() {
    if (reanalyzing) return;
    setReanalyzing(true);
    try {
      await api.battles.analyze(state.battle_id);
      toast.success('Re-analysis triggered');
    } catch (err) {
      toast.error(err instanceof Error ? err.message : 'Re-analysis failed');
    } finally {
      setReanalyzing(false);
    }
  }

  function handleOpenResults() {
    if (!battle?.results_path) return;
    sessionEvents.emit({ type: 'open_file_in_browser', path: battle.results_path });
  }

  function handleCopyAnalysis() {
    if (!analysis) return;
    navigator.clipboard.writeText(analysis).catch(() => toast.error('Clipboard write failed'));
  }

  const battleStatus = battle?.status ?? 'running';
  const isRunning = battleStatus === 'running' || battleStatus === 'pending';
  const isCompleted = battleStatus === 'completed';
  const winnerId = battle?.winner_contestant_id;
  const winnerRow = winnerId ? contestantRows.find((r) => r.data.id === winnerId) : null;
  const winnerLabel = winnerRow ? `${winnerRow.data.identity} / ${winnerRow.data.model}` : null;

  return (
    <div className="flex flex-col h-full min-h-0 overflow-hidden">
      {/* Header */}
      <div className="flex items-center gap-2 border-b border-border bg-muted/20 px-3 py-2 shrink-0">
        <Swords size={13} className="text-muted-foreground shrink-0" />
        <span className="text-sm font-medium truncate min-w-0 flex-1" title={state.prompt}>
          {state.prompt.length > 60 ? state.prompt.slice(0, 60) + '…' : state.prompt}
        </span>
        <span className="text-xs text-muted-foreground shrink-0 capitalize">{state.battle_type}</span>

        {winnerLabel && (
          <span
            className="text-xs px-1.5 py-0.5 rounded bg-emerald-500/10 text-emerald-600 dark:text-emerald-400 shrink-0 hidden sm:block truncate max-w-[130px]"
            title={`Winner: ${winnerLabel}`}
          >
            ✓ {winnerLabel}
          </span>
        )}

        <div className="ml-auto flex items-center gap-1 shrink-0">
          {isRunning ? (
            <button
              type="button"
              onClick={() => void handleStop()}
              disabled={stopping}
              className="inline-flex items-center gap-1 text-xs px-1.5 py-0.5 rounded border border-border text-muted-foreground hover:text-foreground hover:bg-muted disabled:opacity-50"
              title="Stop battle"
            >
              Stop
            </button>
          ) : (
            <span
              className={cn(
                'text-xs px-1.5 py-0.5 rounded',
                isCompleted
                  ? 'text-emerald-600 bg-emerald-500/10'
                  : battleStatus === 'failed' || battleStatus === 'cancelled'
                    ? 'text-destructive bg-destructive/10'
                    : 'text-muted-foreground bg-muted/40',
              )}
            >
              {battleStatus}
            </span>
          )}

          {isCompleted && (
            <DropdownMenu>
              <DropdownMenuTrigger asChild>
                <button
                  type="button"
                  className="inline-flex items-center justify-center p-1 rounded text-muted-foreground hover:bg-muted hover:text-foreground"
                  aria-label="Battle options"
                >
                  <MoreHorizontal size={14} />
                </button>
              </DropdownMenuTrigger>
              <DropdownMenuContent align="end">
                <DropdownMenuItem onSelect={() => void handleReanalyze()} disabled={reanalyzing}>
                  <RotateCcw size={14} /> Re-analyze
                </DropdownMenuItem>
                {battle?.results_path && (
                  <DropdownMenuItem onSelect={handleOpenResults}>
                    Open results folder
                  </DropdownMenuItem>
                )}
                {analysis && (
                  <DropdownMenuItem onSelect={handleCopyAnalysis}>
                    Copy analysis
                  </DropdownMenuItem>
                )}
              </DropdownMenuContent>
            </DropdownMenu>
          )}

          <button
            type="button"
            onClick={onClose}
            className="inline-flex items-center justify-center p-1 rounded text-muted-foreground hover:bg-muted hover:text-foreground"
            aria-label="Close pane"
            title="Close pane"
          >
            <X size={12} />
          </button>
        </div>
      </div>

      {/* Body */}
      <div className="flex-1 min-h-0 overflow-y-auto">
        {/* Analysis panel */}
        {analysis && (
          <div className="border-b border-border p-4">
            <div className="text-xs font-medium text-muted-foreground uppercase tracking-wide mb-2 pb-1 border-b border-border/50">
              Analysis
            </div>
            <div className="text-sm text-foreground whitespace-pre-wrap leading-relaxed">
              {analysis}
            </div>
            {winnerLabel && (
              <div className="mt-2 text-sm font-medium text-emerald-600 dark:text-emerald-400">
                Winner: {winnerLabel}
              </div>
            )}
          </div>
        )}

        {/* Empty state */}
        {contestantRows.length === 0 && !analysis && (
          <div className="flex items-center justify-center h-24 text-sm text-muted-foreground">
            Starting battle…
          </div>
        )}

        {/* Contestant roster */}
        <div className="divide-y divide-border">
          {contestantRows.map((row) => (
            <ContestantRow
              key={row.data.id}
              row={row}
              isExpanded={expandedId === row.data.id}
              onToggle={() => toggleExpand(row.data.id)}
              isWinner={winnerId === row.data.id}
              battleId={state.battle_id}
              battleType={battle?.battle_type ?? state.battle_type}
            />
          ))}
        </div>

        {/* Cross-examination panel — available after battle finishes */}
        {!isRunning && (
          <CrossExaminationPanel
            battleId={state.battle_id}
            crossExams={crossExams}
            snapshot={snapshot}
          />
        )}
      </div>
    </div>
  );
}