import { useCallback, useEffect, useState } from 'react'
import { Loading, ErrorState } from '../../../components/PageState.jsx'
import { api } from '../../../api/client.js'

// Admin → Engagement → Retention (ENGAGEMENT.md Phase 14).
//
// Three of the four engagement tables grew on every fire and nothing had ever
// deleted from any of them. This screen is the policy: how long the deployment
// keeps a cooldown row, a finished outbox row and a send-log entry.
//
// **Why it is a screen, when the other two retention workers in this codebase
// (`team_activity`, `user_notifications`) are invisible settings rows.** The
// send-log horizon changes what an operator-facing page is *able to show* — the
// Send Log is the only answer to "was this person told" — so an operator has to
// be able to see it and set it, not discover it by finding rows missing. Having
// made one visible, hiding the other two would be the worse split: "what does
// this deployment keep" is one question and deserves one answer.
//
// **The fourth table is on this page as prose, not as a control.** Suppressions
// do not expire (org lead, 2026-09-01), and saying so here is the point: an
// operator reading a retention screen that lists three tables would reasonably
// assume the fourth was an oversight.

const FIELDS = [
  {
    name: 'sends',
    label: 'Send log',
    table: 'engagement_sends',
    // The one horizon the org lead asked to be pickable rather than typed —
    // and `custom` stays, because a deployment with a compliance answer to
    // give should not be limited to three numbers somebody chose.
    presets: [90, 180, 365],
    help:
      'One row per delivery attempt. This is what Admin → Engagement → Send Log reads, so the '
      + 'horizon is also how far back "was this person told" can be answered. The per-rule hourly '
      + 'ceiling counts this table too, which is why it can never go below a week.',
  },
  {
    name: 'cooldowns',
    label: 'Cooldowns',
    table: 'engagement_cooldowns',
    presets: [7, 30, 90],
    help:
      'One row per rule, user, subject and channel, written on every fire. Deleting a row that '
      + 'is still in force makes the next fire count as a first fire — that is a duplicate '
      + 'message — so this must stay longer than the longest cooldown on any enabled rule.',
  },
  {
    name: 'outbox',
    label: 'Outbox',
    table: 'engagement_outbox',
    presets: [7, 30, 90],
    help:
      'Only finished rows are ever removed: sent, failed, cancelled and not-sent. A scheduled '
      + 'row is a message this deployment still intends to send and is never swept, however old '
      + 'the horizon.',
  },
]

export default function EngagementRetention() {
  const [policy, setPolicy] = useState(null)
  const [limits, setLimits] = useState({})
  const [warnings, setWarnings] = useState([])
  const [longestCooldown, setLongestCooldown] = useState(0)
  const [draft, setDraft] = useState({})
  const [saving, setSaving] = useState(false)
  const [note, setNote] = useState(null)
  const [loading, setLoading] = useState(true)
  const [error, setError] = useState(null)

  const apply = useCallback((result) => {
    setPolicy(result.retention)
    setDraft(result.retention)
    setLimits(result.limits || {})
    setWarnings(result.warnings || [])
    setLongestCooldown(result.longestCooldownSeconds || 0)
  }, [])

  useEffect(() => {
    let alive = true
    ;(async () => {
      try {
        const result = await api.admin.getEngagementRetention()
        if (alive) apply(result)
      } catch (err) {
        if (alive) setError(err.message)
      } finally {
        if (alive) setLoading(false)
      }
    })()
    return () => { alive = false }
  }, [apply])

  async function save() {
    setSaving(true)
    setNote(null)
    try {
      // The whole draft, not the changed field: this screen is the one place the
      // three are set together, and a partial save would leave the warning line
      // (which is computed from the cooldown horizon) describing a policy that is
      // half saved. The route itself is sparse, so sending three is legal.
      const result = await api.admin.setEngagementRetention(draft)
      apply(result)
      setNote('Saved.')
    } catch (err) {
      setNote(err.message)
    } finally {
      setSaving(false)
    }
  }

  if (loading) return <Loading />
  if (error) return <ErrorState message={error} />

  const dirty = policy && FIELDS.some((f) => Number(draft[f.name]) !== Number(policy[f.name]))

  return (
    <section>
      <p className="sans dim" style={{ fontSize: '0.88rem', maxWidth: 720, marginTop: 0 }}>
        How long this deployment keeps the engagement system&rsquo;s own records. A nightly sweep
        removes anything older, in batches, and skips a table it cannot read rather than failing
        the run.
      </p>

      {warnings.map((w) => (
        <p
          key={w}
          className="sans"
          style={{
            fontSize: '0.85rem',
            maxWidth: 720,
            padding: '10px 12px',
            borderLeft: '3px solid #d98b84',
            background: 'rgba(217, 139, 132, 0.08)',
          }}
        >
          {w}
        </p>
      ))}

      <div style={{ display: 'grid', gap: 22, maxWidth: 720, marginTop: 20 }}>
        {FIELDS.map((f) => {
          const spec = limits[f.name] || {}
          const value = draft[f.name] ?? ''
          const isPreset = f.presets.includes(Number(value))
          return (
            <div key={f.name}>
              <div style={{ display: 'flex', gap: 10, alignItems: 'baseline', flexWrap: 'wrap' }}>
                <span className="field-label" style={{ fontWeight: 600 }}>{f.label}</span>
                <code className="dim" style={{ fontSize: '0.74rem' }}>{f.table}</code>
              </div>
              <p className="sans dim" style={{ fontSize: '0.82rem', margin: '4px 0 8px' }}>
                {f.help}
              </p>
              <div style={{ display: 'flex', gap: 8, alignItems: 'flex-end', flexWrap: 'wrap' }}>
                <label>
                  <span className="field-label">Keep for</span>
                  <select
                    className="select"
                    value={isPreset ? String(value) : 'custom'}
                    onChange={(e) => {
                      const next = e.target.value
                      // Choosing "custom" must not blank the field — the number
                      // box below is what the operator is about to edit, and an
                      // empty one would post NaN.
                      if (next === 'custom') return
                      setDraft({ ...draft, [f.name]: Number(next) })
                    }}
                  >
                    {f.presets.map((d) => (
                      <option key={d} value={String(d)}>{d} days</option>
                    ))}
                    <option value="custom">Custom…</option>
                  </select>
                </label>
                <label>
                  <span className="field-label">Days</span>
                  <input
                    className="input"
                    type="number"
                    min={spec.min ?? 2}
                    max={spec.max ?? 3650}
                    style={{ width: 110 }}
                    value={value}
                    onChange={(e) => setDraft({ ...draft, [f.name]: e.target.value === '' ? '' : Number(e.target.value) })}
                  />
                </label>
                {spec.min !== undefined && (
                  <span className="sans dim" style={{ fontSize: '0.78rem', paddingBottom: 8 }}>
                    {spec.min}–{spec.max} days
                  </span>
                )}
              </div>
            </div>
          )
        })}
      </div>

      <div style={{ display: 'flex', gap: 10, alignItems: 'center', marginTop: 24 }}>
        <button type="button" className="pill" disabled={!dirty || saving} onClick={save}>
          {saving ? 'Saving…' : 'Save'}
        </button>
        {dirty && (
          <button type="button" className="pill" disabled={saving} onClick={() => setDraft(policy)}>
            Discard
          </button>
        )}
        {note && <span className="sans" style={{ fontSize: '0.82rem' }}>{note}</span>}
      </div>

      <div style={{ maxWidth: 720, marginTop: 32 }}>
        <h3 className="sans" style={{ fontSize: '0.95rem', marginBottom: 6 }}>
          Suppressed addresses do not expire
        </h3>
        <p className="sans dim" style={{ fontSize: '0.84rem', margin: 0 }}>
          A suppression is a standing decision, not a record of something that happened. Ageing one
          out would re-mail an address that already hard-bounced or asked to be left alone, which is
          how a sender loses a domain&rsquo;s reputation. The way out of that list stays a
          deliberate act:{' '}
          <strong>Lift</strong> on the row, in Admin → Engagement → Suppressions.
        </p>
        {longestCooldown > 0 && (
          <p className="sans dim" style={{ fontSize: '0.84rem', marginBottom: 0 }}>
            The longest cooldown on an enabled rule right now is {longestCooldown} seconds.
          </p>
        )}
      </div>
    </section>
  )
}