import { useCallback, useEffect, useState } from 'react'
import { Link, useNavigate } from 'react-router-dom'
import { Loading, ErrorState } from '../../../components/PageState.jsx'
import { useAuth } from '../../../contexts/AuthContext.jsx'
import { api } from '../../../api/client.js'
import { runStatusWord, isTerminalRun } from '../../../lib/eventAuthoring.js'

// Admin → Events (EVENTS.md §I, Phase 3).
//
// Two tables on one screen: the definitions an operator authors, and the runs
// those definitions have produced. They are together rather than on two nav rows
// because the question this screen exists to answer is one question — "what is
// scheduled, and what is happening right now" — and the second half of it is the
// one somebody opens at 8pm on a Friday.
//
// **The waiting badge is the whole reason the run table is here rather than
// buried a click away.** A run parked on a GM cue looks perfectly healthy: it is
// `running`, nothing has failed, and it will stay that way for ever because it
// is waiting for a person who does not know they are being waited for. The count
// comes from the run row itself (`waitingSteps`), so a run needs nobody to open
// it before it can say so.
//
// **The calendar is a separate screen, not a third table here.** It answers
// "when", this one answers "what" — and Phase 4, which built it, also made a
// definition able to carry a recurrence, so the two questions stopped having the
// same answer the moment an occurrence could exist before anybody pressed Start.

const STATE_WORD = { draft: 'Draft', ready: 'Ready', archived: 'Archived' }

const STATUS_COLOR = {
  failed: '#d98b84',
  missed: '#d98b84',
  paused: '#d9c184',
  cancelled: 'var(--muted)',
  running: '#8fc79a',
}

const HEALTH_COLOR = { degraded: '#d9c184', stalled: '#d98b84' }

const when = (value) => (value ? new Date(value).toLocaleString() : '—')

export default function EventsAdmin() {
  const { user } = useAuth()
  const navigate = useNavigate()
  const [events, setEvents] = useState([])
  const [runs, setRuns] = useState([])
  const [state, setState] = useState('')
  const [loading, setLoading] = useState(true)
  const [error, setError] = useState(null)
  const [busy, setBusy] = useState(false)
  const [notice, setNotice] = useState(null)

  const isAdmin = user?.role === 'admin'
  const mayAuthor = isAdmin || user?.role === 'editor'

  const load = useCallback(async (nextState) => {
    const [defs, runList] = await Promise.all([
      api.admin.listEvents(nextState || undefined),
      api.admin.listEventRuns({ limit: 50 }),
    ])
    setEvents(defs.events || [])
    setRuns(runList.runs || [])
  }, [])

  useEffect(() => {
    let alive = true
    ;(async () => {
      setLoading(true)
      try {
        await load(state)
        if (alive) setError(null)
      } catch (err) {
        if (alive) setError(err.message)
      } finally {
        if (alive) setLoading(false)
      }
    })()
    return () => {
      alive = false
    }
  }, [load, state])

  // "Start now" is an occurrence whose instant is the present, not a separate
  // concept — the same route a scheduled occurrence will use in Phase 4. Admin
  // only, deliberately (§N2): starting commits the deployment to everything the
  // definition contains, unattended.
  const startNow = async (event) => {
    setBusy(true)
    setNotice(null)
    try {
      const result = await api.admin.startEventRun(event.id, {})
      navigate(`/admin/events/runs/${result.run.id}`)
    } catch (err) {
      setNotice(err.message)
    } finally {
      setBusy(false)
    }
  }

  if (loading && !events.length && !runs.length) return <Loading />
  if (error) return <ErrorState message={error} />

  const live = runs.filter((r) => !isTerminalRun(r.status))
  const waiting = live.filter((r) => r.waitingSteps > 0)

  return (
    <section>
      <div style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center', gap: 16, marginBottom: 16, flexWrap: 'wrap' }}>
        <p className="sans" style={{ margin: 0, fontSize: '0.86rem', color: 'var(--muted)', maxWidth: 620 }}>
          Scheduled, bounded, audited changes to the live world. A definition is authored as a draft,
          published as an immutable version, and every occurrence of it runs against the version it
          pinned. A definition can repeat — once, weekly, or on the nth weekday of the month, in its
          own timezone — and the <Link to="/admin/events/calendar">calendar</Link> is where those
          occurrences are read.
        </p>
        <div style={{ display: 'flex', gap: 8, alignItems: 'flex-end' }}>
          <label>
            <span className="field-label">Show</span>
            <select className="select" value={state} onChange={(e) => setState(e.target.value)}>
              <option value="">All definitions</option>
              <option value="draft">Drafts</option>
              <option value="ready">Ready</option>
              <option value="archived">Archived</option>
            </select>
          </label>
          <Link className="pill" style={{ fontSize: '0.74rem' }} to="/admin/events/calendar">
            Calendar
          </Link>
          {mayAuthor && (
            <Link className="pill" style={{ fontSize: '0.74rem' }} to="/admin/events/new">
              New event
            </Link>
          )}
        </div>
      </div>

      {notice && (
        <p className="sans" style={{ fontSize: '0.84rem', color: '#d98b84', marginTop: 0 }}>{notice}</p>
      )}

      {waiting.length > 0 && (
        <div className="panel-flat" style={{ padding: '12px 14px', marginBottom: 16, borderLeft: '3px solid #d9c184' }}>
          <p className="sans" style={{ margin: 0, fontSize: '0.86rem' }}>
            <strong>{waiting.length === 1 ? 'One run is' : `${waiting.length} runs are`} waiting on a
            person.</strong>{' '}
            <span className="dim">
              A cue holds its phase until somebody confirms it was done in-client — nothing else will
              move it.
            </span>
          </p>
          <div style={{ display: 'flex', gap: 8, flexWrap: 'wrap', marginTop: 8 }}>
            {waiting.map((r) => (
              <Link key={r.id} className="pill" style={{ fontSize: '0.74rem' }} to={`/admin/events/runs/${r.id}`}>
                {r.definitionTitle} · {r.waitingSteps} waiting
              </Link>
            ))}
          </div>
        </div>
      )}

      <h3 className="sans" style={{ fontSize: '0.95rem', margin: '0 0 8px' }}>Definitions</h3>
      {events.length === 0 ? (
        <p className="sans dim" style={{ fontSize: '0.85rem' }}>
          {state ? 'Nothing matches that filter.' : 'No events have been authored yet.'}
        </p>
      ) : (
        <div className="panel-flat">
          <table className="adm-table">
            <thead>
              <tr>
                <th className="adm-th">Event</th>
                <th className="adm-th">State</th>
                <th className="adm-th">Version</th>
                <th className="adm-th">Series</th>
                <th className="adm-th">Updated</th>
                <th className="adm-th" />
              </tr>
            </thead>
            <tbody>
              {events.map((e) => (
                <tr key={e.id}>
                  <td className="adm-td" style={{ fontSize: '0.85rem' }}>
                    <Link to={`/admin/events/${e.id}`}>{e.title}</Link>
                    <div className="dim" style={{ fontSize: '0.76rem' }}>{e.slug}</div>
                  </td>
                  <td className="adm-td" style={{ fontSize: '0.82rem' }}>{STATE_WORD[e.state] || e.state}</td>
                  <td className="adm-td" style={{ fontSize: '0.82rem' }}>
                    {e.currentVersion ? `v${e.currentVersion}` : <span className="dim">unpublished</span>}
                  </td>
                  <td className="adm-td" style={{ fontSize: '0.82rem' }}>
                    {e.seriesName || <span className="dim">—</span>}
                  </td>
                  <td className="adm-td" style={{ fontSize: '0.8rem', whiteSpace: 'nowrap' }}>{when(e.updatedAt)}</td>
                  <td className="adm-td" style={{ textAlign: 'right' }}>
                    {/* Start is admin only and the button follows the route: an
                        editor sees the definition and cannot commit the
                        deployment to running it. */}
                    {isAdmin && e.state === 'ready' && (
                      <button type="button" className="pill" style={{ fontSize: '0.72rem' }}
                        disabled={busy} onClick={() => startNow(e)}>
                        Start now
                      </button>
                    )}
                  </td>
                </tr>
              ))}
            </tbody>
          </table>
        </div>
      )}

      <h3 className="sans" style={{ fontSize: '0.95rem', margin: '22px 0 8px' }}>
        Recent runs
        {live.length > 0 && <span className="dim" style={{ fontWeight: 400 }}> · {live.length} in flight</span>}
      </h3>
      {runs.length === 0 ? (
        <p className="sans dim" style={{ fontSize: '0.85rem' }}>Nothing has run yet.</p>
      ) : (
        <div className="panel-flat">
          <table className="adm-table">
            <thead>
              <tr>
                <th className="adm-th">Occurrence</th>
                <th className="adm-th">Event</th>
                <th className="adm-th">Status</th>
                <th className="adm-th">Phase</th>
                <th className="adm-th">Health</th>
                <th className="adm-th" />
              </tr>
            </thead>
            <tbody>
              {runs.map((r) => (
                <tr key={r.id}>
                  <td className="adm-td" style={{ fontSize: '0.8rem', whiteSpace: 'nowrap' }}>
                    <Link to={`/admin/events/runs/${r.id}`}>{when(r.scheduledFor)}</Link>
                    {r.rehearsal && <span className="dim" style={{ fontSize: '0.74rem' }}> · rehearsal</span>}
                  </td>
                  <td className="adm-td" style={{ fontSize: '0.82rem' }}>
                    {r.definitionTitle} <span className="dim">v{r.version}</span>
                  </td>
                  <td className="adm-td" style={{ fontSize: '0.82rem', color: STATUS_COLOR[r.status] || undefined }}>
                    {runStatusWord(r.status)}
                  </td>
                  <td className="adm-td" style={{ fontSize: '0.82rem' }}>
                    {r.currentPhase || <span className="dim">—</span>}
                  </td>
                  <td className="adm-td" style={{ fontSize: '0.82rem', color: HEALTH_COLOR[r.health] || undefined }}>
                    {r.health === 'ok' ? <span className="dim">ok</span> : r.health}
                  </td>
                  <td className="adm-td" style={{ textAlign: 'right', fontSize: '0.78rem' }}>
                    {r.waitingSteps > 0 && (
                      <span style={{ color: '#d9c184' }}>
                        waiting on {r.waitingSteps === 1 ? 'a person' : `${r.waitingSteps} people`}
                      </span>
                    )}
                  </td>
                </tr>
              ))}
            </tbody>
          </table>
        </div>
      )}
    </section>
  )
}