import { useEffect, useMemo, useState } from 'react'
import { useQuery } from '@tanstack/react-query'
import { useNavigate } from '@tanstack/react-router'
import {
  fetchLocalMeetings,
  fetchRaceHub,
  fetchSeasons,
  fetchWeekend,
} from '../api'
import { DatasetStrip } from '../components/DatasetStrip'
import { RaceStoryCanvas } from '../components/RaceStoryCanvas'
import { TabBar, type Tab } from '../components/TabBar'
import { DatasetStatusView } from '../components/DatasetStatusView'
import { StrategyView } from '../components/StrategyView'
import { LapsView } from '../components/LapsView'
import { CompareView } from '../components/CompareView'
import { RaceControlView } from '../components/RaceControlView'
import { WeatherView } from '../components/WeatherView'
import { OverviewView } from '../components/OverviewView'
import { PreSessionView } from '../components/PreSessionView'
import { WeekendSwitcher } from '../components/WeekendSwitcher'
import { SourceBadge } from '../components/SourceBadge'
import { countryAccent, countryDecal, formatGpDateRange } from '../lib/gpIdentity'
import { sessionTypeAbbrev } from '../lib/coverage'
import {
  formatSessionScheduleTime,
  pickAnalysisFocusMeeting,
  sessionStartTime,
  sortSessionsByStart,
} from '../lib/schedule'
import {
  isPreSession,
  sessionState,
  sessionStateDotClass,
  sessionStateLabel,
} from '../lib/sessionState'
import type { Weekend, WeekendSession } from '../types'

interface Props {
  sessionKey: number
}

/**
 * Resolve the session a bare `/race-hub` should open. Prefers the canonical
 * Weekend Context `default_analysis_session` (which never points at a future
 * session), then any completed session with the richest coverage. Returns
 * `undefined` when every session is still upcoming so the caller can fall back
 * to the switcher instead of opening empty analysis.
 */
function pickAnalysisSession(weekend: Weekend | undefined, now: Date): number | undefined {
  if (!weekend) return undefined
  if (weekend.default_analysis_session && weekend.default_analysis_session > 0) {
    return weekend.default_analysis_session
  }

  const started = weekend.sessions.filter((s) => {
    const start = sessionStartTime(s.session)
    return !start || start <= now
  })
  if (started.length === 0) return undefined

  const local = started.filter((s) => s.source === 'local')
  const partial = started.filter((s) => s.source === 'partial')
  const pool = local.length > 0 ? local : partial.length > 0 ? partial : started
  const race = pool.find((s) => s.session.session_type?.toLowerCase().includes('race'))
  if (race) return race.session.session_key
  const qual = pool.find((s) => s.session.session_type?.toLowerCase().includes('qualifying'))
  if (qual) return qual.session.session_key
  return pool[pool.length - 1]?.session.session_key
}

export function RaceHubPage({ sessionKey }: Props) {
  const navigate = useNavigate()
  const [activeTab, setActiveTab] = useState<Tab>('overview')
  const [switcherOpen, setSwitcherOpen] = useState(false)
  const now = useMemo(() => new Date(), [])

  // ─── Auto-redirect when no session_key is supplied ───
  const seasonsQuery = useQuery({
    queryKey: ['seasons'],
    queryFn: fetchSeasons,
    enabled: sessionKey === 0,
  })

  const latestSeason = seasonsQuery.data?.[0] ?? null

  const meetingsQuery = useQuery({
    queryKey: ['meetings', latestSeason],
    queryFn: () => fetchLocalMeetings(latestSeason!),
    enabled: sessionKey === 0 && latestSeason != null,
  })

  const focusMeeting = useMemo(() => {
    if (sessionKey !== 0 || !meetingsQuery.data) return null
    return pickAnalysisFocusMeeting(meetingsQuery.data, now)
  }, [sessionKey, meetingsQuery.data, now])

  const fallbackWeekendQuery = useQuery({
    queryKey: ['weekend', focusMeeting?.meeting_key],
    queryFn: () => fetchWeekend(focusMeeting!.meeting_key),
    enabled: sessionKey === 0 && focusMeeting != null,
  })

  useEffect(() => {
    if (sessionKey !== 0) return
    const weekend = fallbackWeekendQuery.data
    if (!weekend) return
    const target = pickAnalysisSession(weekend, now)
    if (target) {
      navigate({ to: '/race-hub', search: { session_key: target }, replace: true })
    }
  }, [sessionKey, fallbackWeekendQuery.data, navigate, now])

  // ─── Active session payload ───
  const raceHubQuery = useQuery({
    queryKey: ['race-hub', sessionKey],
    queryFn: () => fetchRaceHub(sessionKey),
    enabled: sessionKey > 0,
    staleTime: 30_000,
  })

  const meetingKey = raceHubQuery.data?.meeting?.meeting_key
  const weekendQuery = useQuery({
    queryKey: ['weekend', meetingKey],
    queryFn: () => fetchWeekend(meetingKey!),
    enabled: meetingKey != null && meetingKey > 0,
    staleTime: 60_000,
  })

  const data = raceHubQuery.data
  const weekend = weekendQuery.data
  const accent = countryAccent(data?.meeting ?? null)
  const accentStyle = { '--gp-accent': accent } as React.CSSProperties

  const [showDiagnostics, setShowDiagnostics] = useState(false)

  // ─── No session_key: show resolving state, fall back to switcher if no local data ───
  if (sessionKey === 0) {
    if (seasonsQuery.isLoading || meetingsQuery.isLoading || fallbackWeekendQuery.isLoading) {
      return (
        <div className="rh-page" style={accentStyle}>
          <div className="loading-state">resolving latest local weekend…</div>
        </div>
      )
    }
    const seasons = seasonsQuery.data ?? []
    if (seasons.length === 0) {
      return (
        <div className="rh-page rh-empty" data-testid="race-hub-empty" style={accentStyle}>
          <div className="rh-empty-band">
            <span className="rh-empty-eyebrow mono">box-box · race hub</span>
            <h1 className="rh-empty-title">No local sessions yet</h1>
            <p className="rh-empty-sub">
              The Race Hub reads from local ingest only. Once a weekend is ingested
              it will open here automatically.
            </p>
            <div className="rh-empty-actions">
              <a href="/admin" className="rh-empty-action">Open Admin · Data Health</a>
              <a href="/" className="rh-empty-action">Back to Command Center</a>
            </div>
          </div>
        </div>
      )
    }
    // Weekend resolved but every session is upcoming — offer the switcher instead
    // of silently opening empty analysis.
    if (fallbackWeekendQuery.data && !pickAnalysisSession(fallbackWeekendQuery.data, now)) {
      return (
        <div className="rh-page rh-empty" data-testid="race-hub-no-analysis" style={accentStyle}>
          <div className="rh-empty-band">
            <span className="rh-empty-eyebrow mono">box-box · race hub</span>
            <h1 className="rh-empty-title">No completed session to analyse yet</h1>
            <p className="rh-empty-sub">
              The next weekend hasn’t run. Pick a past session to review, or check
              back once it’s complete.
            </p>
            <div className="rh-empty-actions">
              <button
                type="button"
                className="rh-empty-action"
                onClick={() => setSwitcherOpen(true)}
              >
                Browse Weekends
              </button>
              <a href="/" className="rh-empty-action">Back to Command Center</a>
            </div>
          </div>
          {switcherOpen && (
            <WeekendSwitcher
              currentMeetingKey={fallbackWeekendQuery.data.meeting_key}
              onClose={() => setSwitcherOpen(false)}
            />
          )}
        </div>
      )
    }
    return (
      <div className="rh-page" style={accentStyle}>
        <div className="loading-state">resolving latest local weekend…</div>
      </div>
    )
  }

  // ─── Loading / error for the requested session_key (retry + back to weekend) ───
  if (raceHubQuery.isLoading) {
    return (
      <div className="rh-page" style={accentStyle}>
        <div className="loading-state">loading session {sessionKey}…</div>
      </div>
    )
  }
  if (raceHubQuery.isError || !data) {
    return (
      <div className="rh-page" data-testid="race-hub-error" style={accentStyle}>
        <div className="rh-recover">
          <div className="error-box">
            {raceHubQuery.error instanceof Error
              ? raceHubQuery.error.message
              : `Failed to load session ${sessionKey}.`}
          </div>
          <div className="rh-recover-actions">
            <button
              type="button"
              className="rh-recover-btn primary"
              onClick={() => raceHubQuery.refetch()}
              data-testid="rh-retry"
            >
              Retry
            </button>
            <a href="/race-hub" className="rh-recover-btn" data-testid="rh-back-weekend">
              Back to Weekend
            </a>
          </div>
        </div>
      </div>
    )
  }

  const decal = countryDecal(data.meeting ?? null)
  const sessions = weekend ? sortSessionsByStart(weekend.sessions.map((w) => w.session)) : []
  const sessionMeta = weekend
    ? Object.fromEntries(weekend.sessions.map((w) => [w.session.session_key, w]))
    : {}
  const activeSessionMeta: WeekendSession | undefined = sessionMeta[sessionKey]
  const activeState = activeSessionMeta ? sessionState(activeSessionMeta, now) : undefined
  const preSession = activeState != null && isPreSession(activeState)

  return (
    <div className="rh-page" data-testid="race-hub" style={accentStyle}>
      {/* Topbar */}
      <div className="rh-topbar">
        <span className="rh-topbar-label mono">
          box-box · race hub
          {data.meeting?.year ? ` · ${data.meeting.year}` : ''}
        </span>
        <span className="rh-topbar-spacer" />
        <SourceBadge source={data.source} />
        <button
          type="button"
          className={`rh-switcher-toggle${switcherOpen ? ' active' : ''}`}
          onClick={() => setSwitcherOpen((v) => !v)}
          aria-expanded={switcherOpen}
          data-testid="rh-switch-weekend"
        >
          {switcherOpen ? 'Close' : 'Switch Weekend'}
        </button>
      </div>

      {switcherOpen && (
        <WeekendSwitcher
          currentMeetingKey={meetingKey}
          currentSessionKey={sessionKey}
          onClose={() => setSwitcherOpen(false)}
        />
      )}

      {/* GP Identity band */}
      {data.meeting && (
        <section className="rh-identity" data-testid="rh-identity">
          <div className="rh-identity-accent" aria-hidden="true" />
          <div className="rh-identity-body">
            <span className="rh-identity-decal mono">{decal}</span>
            <div className="rh-identity-titles">
              <h1 className="rh-identity-name">{data.meeting.meeting_name}</h1>
              <div className="rh-identity-sub mono">
                {[data.meeting.location, data.meeting.circuit_short_name]
                  .filter(Boolean)
                  .join(' · ')}
              </div>
              <div className="rh-identity-sub mono rh-identity-dates">
                {formatGpDateRange(data.meeting)}
              </div>
            </div>
          </div>
        </section>
      )}

      {/* Session rail */}
      {sessions.length > 0 && (
        <nav className="rh-session-rail" aria-label="Weekend sessions" data-testid="rh-session-rail">
          {sessions.map((session) => {
            const meta = sessionMeta[session.session_key]
            const active = session.session_key === sessionKey
            const state = meta ? sessionState(meta, now) : undefined
            return (
              <button
                key={session.session_key}
                type="button"
                className={`rh-session-chip${active ? ' active' : ''}`}
                onClick={() =>
                  navigate({
                    to: '/race-hub',
                    search: { session_key: session.session_key },
                  })
                }
                aria-current={active ? 'page' : undefined}
                data-testid={`rh-session-${session.session_key}`}
              >
                <span className="rh-session-abbrev mono">
                  {sessionTypeAbbrev(session.session_type, session.session_name)}
                </span>
                <span className="rh-session-name">{session.session_name}</span>
                <span className="rh-session-time mono">
                  {formatSessionScheduleTime(session.date_start)}
                </span>
                {state && (
                  <span className="rh-session-cov mono">
                    <span
                      className={`cc-cov-dot ${sessionStateDotClass(state)}`}
                      aria-hidden="true"
                    />
                    {sessionStateLabel(state)}
                  </span>
                )}
              </button>
            )
          })}
        </nav>
      )}

      {/* Active session sub-bar */}
      {data.session && (
        <div className="rh-active-bar" data-testid="rh-active-bar">
          <span className="rh-active-name">{data.session.session_name}</span>
          <span className="rh-active-meta mono">
            {formatSessionScheduleTime(data.session.date_start)}
          </span>
          {activeState && (
            <span className="rh-active-cov mono" data-testid="rh-active-state">
              <span
                className={`cc-cov-dot ${sessionStateDotClass(activeState)}`}
                aria-hidden="true"
              />
              {sessionStateLabel(activeState)}
            </span>
          )}
          <span className="rh-active-key mono">key {sessionKey}</span>
        </div>
      )}

      {preSession && data.session ? (
        <PreSessionView session={data.session} sessionName={data.session.session_name} />
      ) : (
        <>
          <TabBar active={activeTab} onChange={setActiveTab} />

          {activeTab === 'overview' && <OverviewView data={data} />}

          {activeTab === 'race_story' && (
            <div className="data-section">
              <RaceStoryCanvas data={data} />
            </div>
          )}

          {activeTab === 'strategy' && (
            <div className="data-section">
              <div className="sec-header">
                <span className="sec-title">Race Strategy</span>
              </div>
              <StrategyView
                results={data.results}
                stints={data.stints}
                pit_stops={data.pit_stops}
                hasStints={data.datasets['stints']?.status === 'available'}
              />
            </div>
          )}

          {activeTab === 'compare' && (
            <div className="data-section">
              <div className="sec-header">
                <span className="sec-title">Driver Compare</span>
              </div>
              <CompareView
                sessionKey={sessionKey}
                results={data.results}
                drivers={data.drivers}
              />
            </div>
          )}

          {activeTab === 'lap_data' && (
            <div className="data-section">
              <div className="sec-header">
                <span className="sec-title">Lap Data</span>
                {data.laps.length > 0 && (
                  <span className="sec-meta mono">{data.laps.length} samples</span>
                )}
              </div>
              <LapsView laps={data.laps} drivers={data.drivers} />
            </div>
          )}

          {activeTab === 'conditions' && (
            <div className="data-section">
              <div className="sec-header">
                <span className="sec-title">Conditions</span>
                {data.weather.length > 0 && (
                  <span className="sec-meta mono">{data.weather.length} samples</span>
                )}
              </div>
              <WeatherView weather={data.weather} />
            </div>
          )}

          {activeTab === 'race_control' && (
            <div className="data-section">
              <div className="sec-header">
                <span className="sec-title">Race Control</span>
                {data.race_control.length > 0 && (
                  <span className="sec-meta mono">{data.race_control.length} messages</span>
                )}
              </div>
              <RaceControlView messages={data.race_control} />
            </div>
          )}

          {activeTab === 'data_status' && (
            <div className="data-section">
              <div className="sec-header">
                <span className="sec-title">Diagnostics</span>
                <button
                  type="button"
                  className={`rh-diagnostics-toggle${showDiagnostics ? ' active' : ''}`}
                  onClick={() => setShowDiagnostics((v) => !v)}
                  aria-expanded={showDiagnostics}
                  data-testid="rh-diagnostics-toggle"
                >
                  {showDiagnostics ? 'Hide dataset coverage' : 'Show dataset coverage'}
                </button>
              </div>
              <DatasetStatusView datasets={data.datasets} />
              {showDiagnostics && (
                <div style={{ marginTop: 'var(--s5)' }} data-testid="rh-dataset-strip">
                  <DatasetStrip datasets={data.datasets} />
                </div>
              )}
            </div>
          )}
        </>
      )}
    </div>
  )
}