import { useEffect, useState } from 'react';
import { useQueryClient } from '@tanstack/react-query';
import { dashboardQueryKeys, useSetModeMutation, useStatsQuery, useTimersQuery } from '../../api/queries.js';
import type { BotMode, BotStats, Timers } from '../../api/contracts.js';
import type { AccountStatus } from '../../../../../packages/api-contracts/src/index.js';
import { ConfirmationDialog } from '../../components/confirmation-dialog.js';
import { RedditUserText } from '../../components/reddit-user-text.js';
import { OriginPostButton } from '../../components/origin-post.js';
import { RecentMessagesPanel } from './recent-messages.js';
import { AccountOwnerBadge } from '../../components/account-owner-badge.js';

const MODE_ORDER: readonly BotMode[] = ['running', 'scan', 'stopped'];

const modeCopy: Record<BotMode, { label: string; action: string; dot: string; buttonTone: string }> = {
  running: { label: 'Running', action: 'Start bot', dot: 'running', buttonTone: 'button primary' },
  scan: { label: 'Scanning', action: 'Scan mode', dot: 'scanning', buttonTone: 'button secondary' },
  stopped: { label: 'Stopped', action: 'Stop bot', dot: 'stopped', buttonTone: 'button danger' },
};

function errorMessage(error: Error | null): string {
  return error?.message ?? 'Something went wrong.';
}

function formatTime(timestamp: number): string {
  return new Intl.DateTimeFormat(undefined, { hour: '2-digit', minute: '2-digit' }).format(timestamp);
}

function formatMetricValue(value: number): string {
  return value.toLocaleString();
}

function formatCountdown(remainingMs: number): string {
  const totalSeconds = Math.max(0, Math.ceil(remainingMs / 1_000));
  const minutes = Math.floor(totalSeconds / 60);
  const seconds = totalSeconds % 60;
  return minutes > 0 ? `${minutes}m ${seconds}s` : `${seconds}s`;
}

/** Ticks a client clock so time-derived UI flips without a refetch. */
function useNow(intervalMs = 1_000): number {
  const [now, setNow] = useState(() => Date.now());
  useEffect(() => {
    const timer = globalThis.setInterval(() => setNow(Date.now()), intervalMs);
    return () => globalThis.clearInterval(timer);
  }, [intervalMs]);
  return now;
}

function MetricCard({ label, value, detail, metric }: { label: string; value: string | number; detail: string; metric: string }) {
  return (
    <article className="metric-card">
      <span>{label}</span>
      <strong data-metric={metric}>{value}</strong>
      <small>{detail}</small>
    </article>
  );
}

function TimersPanel({ timers }: { timers: Timers }) {
  const now = useNow();
  const isReady = timers.nextMessageAvailableAt === null || timers.nextMessageAvailableAt <= now;
  return (
    <section aria-labelledby="timers-heading" className="panel">
      <div className="panel-heading">
        <div>
          <span className="eyebrow">Rate limits</span>
          <h2 id="timers-heading">Sending window</h2>
        </div>
        <span className={isReady ? 'pill success' : 'pill warning'}>{isReady ? 'Ready' : 'Cooling down'}</span>
      </div>
      <dl className="definition-list">
        <div>
          <dt>Next message</dt>
          <dd>{isReady
            ? 'Available now'
            : `Ready in ${formatCountdown((timers.nextMessageAvailableAt ?? now) - now)} (${formatTime(timers.nextMessageAvailableAt ?? now)})`}</dd>
        </div>
        <div>
          <dt>Hourly allowance</dt>
          <dd>{timers.messagesRemaining} messages remaining</dd>
        </div>
        <div>
          <dt>Allowance resets</dt>
          <dd>{formatTime(timers.hourlyResetAt)}</dd>
        </div>
      </dl>
    </section>
  );
}

const sendingStateCopy: Record<AccountStatus['sendingState'], { label: string; tone: 'success' | 'warning' | 'neutral'; detail: string }> = {
  ready: { label: 'Ready', tone: 'success', detail: 'Available for the next outbound candidate.' },
  'bot-stopped': { label: 'Bot stopped', tone: 'neutral', detail: 'Global sending is stopped.' },
  'scan-only': { label: 'Scan only', tone: 'neutral', detail: 'Conversations stay in sync, but nothing is sent.' },
  'runtime-stopped': { label: 'Runtime stopped', tone: 'warning', detail: 'This account runtime is not running.' },
  'runtime-failed': { label: 'Runtime failed', tone: 'warning', detail: 'This account runtime needs attention.' },
  'login-required': { label: 'Login required', tone: 'warning', detail: 'Refresh this account session before it can send.' },
  'matrix-cooldown': { label: 'Matrix cooldown', tone: 'warning', detail: 'Only this account is paused by Reddit chat throttling.' },
  'replies-prioritized': { label: 'Replies first', tone: 'neutral', detail: 'Inbound replies are being handled before new outreach.' },
  pacing: { label: 'Pacing', tone: 'neutral', detail: 'Waiting for the account sending window.' },
  unestablished: { label: 'Not established', tone: 'warning', detail: 'Reddit will not accept chat invitations from this account yet.' },
};

function AccountStatusPanel({ accounts }: { accounts: readonly AccountStatus[] }) {
  return (
    <section aria-labelledby="account-status-heading" className="panel account-status-panel">
      <div className="panel-heading">
        <div><span className="eyebrow">Multi-account delivery</span><h2 id="account-status-heading">Account status</h2></div>
        <span className="pill neutral">{accounts.length} configured</span>
      </div>
      {accounts.length === 0 ? <div className="empty-state"><strong>No accounts configured.</strong><span>Add an account under Settings → Access.</span></div> : (
        <div className="account-status-grid">
          {accounts.map((account) => {
            const state = sendingStateCopy[account.sendingState];
            return (
              <article aria-label={`Status for u/${account.redditUsername}`} className="account-status-card" key={account.accountId}>
                <div className="account-status-heading">
                  <AccountOwnerBadge owner={account} />
                  <span className={`pill ${state.tone}`}>{state.label}</span>
                </div>
                <p>{state.detail}</p>
                <dl className="account-status-details">
                  <div><dt>Runtime</dt><dd>{account.runtimeState}</dd></div>
                  <div><dt>Authentication</dt><dd>{account.authenticated ? 'Authenticated' : 'Unavailable'}</dd></div>
                  <div><dt>Hourly usage</dt><dd>{account.messagesThisHour} of {account.maxMessagesPerHour}</dd></div>
                  <div><dt>Remaining</dt><dd>{account.messagesRemaining}</dd></div>
                  <div><dt>Allowance resets</dt><dd>{formatTime(account.hourlyResetAt)}</dd></div>
                  <div><dt>Pending replies</dt><dd>{account.actionableReplies}</dd></div>
                </dl>
                {account.nextMessageAvailableAt && account.nextMessageAvailableAt > Date.now() && !account.invitationCooldown
                  ? <p className="account-status-note">Next send: {formatTime(account.nextMessageAvailableAt)}</p>
                  : null}
                {account.invitationCooldown ? (
                  <div className="account-status-warning">
                    <strong>Cooldown until {formatTime(account.invitationCooldown.until)}</strong>
                    <span>{account.invitationCooldown.reason}</span>
                    {account.invitationCooldown.redditCode ? <code>{account.invitationCooldown.redditCode}</code> : null}
                  </div>
                ) : null}
                {account.failure ? <div className="account-status-warning is-error" role="alert"><strong>Runtime failure</strong><span>{account.failure}</span></div> : null}
              </article>
            );
          })}
        </div>
      )}
    </section>
  );
}

function ActivityPanel({ stats }: { stats: BotStats }) {
  return (
    <section aria-labelledby="activity-heading" className="panel activity-panel">
      <div className="panel-heading">
        <div>
          <span className="eyebrow">Latest signals</span>
          <h2 id="activity-heading">Recent activity</h2>
        </div>
      </div>
      {stats.recentActivity.length === 0 ? (
        <div className="empty-state">
          <strong>No recent activity yet.</strong>
          <span>New bot events will appear here.</span>
        </div>
      ) : (
        <ol className="activity-list">
          {stats.recentActivity.map((item, index) => (
            <li key={`${item.timestamp}-${index}`}>
              <span className={`activity-marker ${item.type}`} aria-hidden="true" />
              <div><strong>{item.postUrl && item.postTitle ? (
                <OriginPostButton post={{ title: item.postTitle, url: item.postUrl, imageUrl: item.imageUrl }}>
                  {item.message}
                </OriginPostButton>
              ) : <RedditUserText>{item.message}</RedditUserText>}</strong><AccountOwnerBadge owner={item.owner} /><small>{formatTime(item.timestamp)}</small></div>
            </li>
          ))}
        </ol>
      )}
    </section>
  );
}

export function OverviewPage() {
  const queryClient = useQueryClient();
  const statsQuery = useStatsQuery();
  const timersQuery = useTimersQuery();
  const controlMutation = useSetModeMutation();
  const [confirmationAction, setConfirmationAction] = useState<BotMode | null>(null);
  const isRefreshing = (statsQuery.isFetching || timersQuery.isFetching) && !statsQuery.isPending;

  async function refreshOverview() {
    await Promise.all([
      queryClient.invalidateQueries({ queryKey: dashboardQueryKeys.stats }),
      queryClient.invalidateQueries({ queryKey: dashboardQueryKeys.timers }),
    ]);
  }

  function confirmControl() {
    if (!confirmationAction) return;
    controlMutation.mutate(confirmationAction, {
      onSuccess: () => setConfirmationAction(null),
    });
  }

  if (statsQuery.isPending) {
    if (statsQuery.isPaused) {
      return (
        <div className="page-state error-state" role="alert">
          <strong>You appear to be offline</strong>
          <span>The overview will load once the connection returns.</span>
          <button className="button secondary" onClick={() => void statsQuery.refetch()} type="button">Retry overview</button>
        </div>
      );
    }
    return <div aria-label="Loading overview" className="page-state" role="status"><span className="spinner" />Loading overview…</div>;
  }

  if (statsQuery.isError) {
    return (
      <div className="page-state error-state" role="alert">
        <strong>Overview unavailable</strong>
        <span>{errorMessage(statsQuery.error)}</span>
        <button className="button secondary" onClick={() => void statsQuery.refetch()} type="button">Retry overview</button>
      </div>
    );
  }

  const stats = statsQuery.data;
  // Offer the two modes the bot is not currently in, in a stable order.
  const offeredModes = MODE_ORDER.filter((mode) => mode !== stats.mode);

  return (
    <div className="page">
      <header className="page-header">
        <div>
          <span className="eyebrow">Control room</span>
          <h1>Overview</h1>
          <p>System health, sending limits, and the signals that need attention.</p>
        </div>
        <div className="header-actions">
          <button
            aria-busy={isRefreshing ? 'true' : undefined}
            aria-label={isRefreshing ? 'Refreshing overview' : 'Refresh overview'}
            className="button secondary"
            disabled={isRefreshing}
            onClick={() => void refreshOverview()}
            type="button"
          >
            {isRefreshing ? 'Refreshing…' : 'Refresh'}
          </button>
          {offeredModes.map((mode) => (
            <button
              className={modeCopy[mode].buttonTone}
              key={mode}
              onClick={() => setConfirmationAction(mode)}
              type="button"
            >
              {modeCopy[mode].action}
            </button>
          ))}
        </div>
      </header>

      <section aria-label="Bot state" className="status-strip">
        <div>
          <span className={`status-dot ${modeCopy[stats.mode].dot}`} aria-hidden="true" />
          <div><small>Bot status</small><strong data-bot-status>{modeCopy[stats.mode].label}</strong></div>
        </div>
        {stats.dryRunMode ? <span className="pill neutral">Dry run</span> : null}
        <span className="status-note">{stats.messagesThisHour} of {stats.maxMessagesPerHour} messages used this hour</span>
      </section>

      {stats.invitationCooldown ? (
        <div className="cooldown-banner" role="status">
          <strong>{stats.invitationCooldown.redditUsername
            ? `u/${stats.invitationCooldown.redditUsername} invitation cooldown`
            : 'Reddit invitation cooldown'}</strong>
          <span>{stats.invitationCooldown.reason}</span>
        </div>
      ) : null}

      <section aria-label="Key metrics" className="metrics-grid">
        <MetricCard detail="All recorded sends" label="Messages sent" metric="messages-sent" value={formatMetricValue(stats.totalMessagesSent)} />
        <MetricCard detail={`${stats.responseRate}% response rate`} label="Responses" metric="responses" value={formatMetricValue(stats.totalResponses)} />
        <MetricCard detail="Posts evaluated" label="Processed" metric="processed" value={formatMetricValue(stats.totalProcessed)} />
        <MetricCard detail={`Limit ${formatMetricValue(stats.maxMessagesPerHour)}`} label="This hour" metric="messages-hour" value={formatMetricValue(stats.messagesThisHour)} />
      </section>

      <AccountStatusPanel accounts={stats.accounts} />

      <div className="overview-grid">
        {timersQuery.isPending ? (
          <section aria-label="Loading timers" className="panel panel-loading" role="status"><span className="spinner" />Loading sending window…</section>
        ) : timersQuery.isError ? (
          <section className="panel error-panel" role="alert">
            <strong>Sending window unavailable</strong>
            <span>{errorMessage(timersQuery.error)}</span>
            <button className="button secondary" onClick={() => void timersQuery.refetch()} type="button">Retry timers</button>
          </section>
        ) : (
          <TimersPanel timers={timersQuery.data} />
        )}
        <ActivityPanel stats={stats} />
      </div>
      <RecentMessagesPanel />

      {confirmationAction ? (
        <ConfirmationDialog
          action={confirmationAction}
          errorMessage={controlMutation.isError ? errorMessage(controlMutation.error) : null}
          isPending={controlMutation.isPending}
          onCancel={() => { setConfirmationAction(null); controlMutation.reset(); }}
          onConfirm={confirmControl}
        />
      ) : null}
    </div>
  );
}