'use client'

import { useCallback, useEffect, useRef, useState, type FormEvent } from 'react'
import { useRouter } from 'next/navigation'
import AdminShell from '../../ui/AdminShell'
import { authFetch, getApiBase } from '../../lib/auth'
import '../../email-recaps/recaps.css'

type Settings = { enabled: boolean; day: number; hour: number; public_url: string; next_send_at?: number | null }
type Delivery = { id: string; month: string; kind: string; email: string; username: string | null; state: string; attempts: number; created_at: number; updated_at: number; next_attempt_at: number; detail: string }
type Overview = { settings: Settings; ready: boolean; detail: string; months: string[]; deliveries: Delivery[]; total: number; subscribers: number; worker_enabled: boolean }
type Preview = { month: string; subject: string; body_html: string; body_text: string; email: string | null }
const monthLabel = (month: string) => new Date(`${month}-01T00:00:00Z`).toLocaleDateString(undefined, { month: 'long', year: 'numeric', timeZone: 'UTC' })
const dateLabel = (value?: number | null) => value ? `${new Date(value * 1000).toLocaleString(undefined, { dateStyle: 'medium', timeStyle: 'short', timeZone: 'UTC' })} UTC` : 'Not scheduled'
const stateLabels: Record<string, string> = { queued: 'Queued', preparing: 'Preparing report', sending: 'Sending', sent: 'Accepted by mail server', retry: 'Retry scheduled', failed: 'Failed', unknown: 'Needs review', cancelled: 'Cancelled' }

export default function EmailRecapsAdminPage() {
  const router = useRouter()
  const [data, setData] = useState<Overview | null>(null)
  const [settings, setSettings] = useState<Settings>({ enabled: false, day: 2, hour: 9, public_url: '' })
  const [month, setMonth] = useState('')
  const [preview, setPreview] = useState<Preview | null>(null)
  const [previewMode, setPreviewMode] = useState<'html' | 'text'>('html')
  const [error, setError] = useState('')
  const [notice, setNotice] = useState('')
  const [busy, setBusy] = useState('')
  const [offset, setOffset] = useState(0)
  const [revision, setRevision] = useState(0)
  const testRequest = useRef<{ month: string; id: string } | null>(null)
  const initialized = useRef(false)
  const previewController = useRef<AbortController | null>(null)

  const responseData = useCallback(async (response: Response) => {
    if (response.status === 401) { router.replace('/login?next=%2Fadmin%2Frecaps'); throw new Error('Sign in to continue.') }
    if (response.status === 403) { router.replace('/'); throw new Error('Administrator access is required.') }
    const result = await response.json().catch(() => ({}))
    if (!response.ok) throw new Error(typeof result.detail === 'string' ? result.detail : 'Could not complete this action. Check your settings and try again.')
    return result
  }, [router])

  useEffect(() => {
    const abort = new AbortController()
    void authFetch(`${getApiBase()}/admin/email-recaps?offset=${offset}`, { signal: abort.signal }).then(responseData).then((result: Overview) => {
      if (abort.signal.aborted) return
      setData(result)
      if (!initialized.current) { setSettings(result.settings); setMonth(result.months[0] || ''); initialized.current = true }
    }).catch((err: Error) => { if (!abort.signal.aborted) setError(err.message) })
    return () => abort.abort()
  }, [offset, revision, responseData])

  useEffect(() => {
    if (!data?.deliveries.some((delivery) => ['queued', 'preparing', 'sending', 'retry'].includes(delivery.state))) return
    const timer = window.setInterval(() => setRevision((value) => value + 1), 10000)
    return () => window.clearInterval(timer)
  }, [data])
  useEffect(() => () => previewController.current?.abort(), [])

  const dirty = !!data && (settings.enabled !== data.settings.enabled || settings.day !== data.settings.day || settings.hour !== data.settings.hour || settings.public_url !== data.settings.public_url)
  const save = async (event: FormEvent) => {
    event.preventDefault()
    if (busy) return
    setBusy('save'); setError(''); setNotice('')
    try {
      const { enabled, day, hour, public_url } = settings
      const result = await responseData(await authFetch(`${getApiBase()}/admin/email-recaps`, { method: 'PUT', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ enabled, day, hour, public_url }) })) as Settings
      setSettings(result); setData((current) => current ? { ...current, settings: result } : current)
      setPreview(null)
      setNotice(result.enabled ? `Schedule saved. Next send: ${dateLabel(result.next_send_at)}.` : 'Settings saved. Scheduled delivery is paused.')
      setRevision((value) => value + 1)
    } catch (err) { setError(err instanceof Error ? err.message : 'Could not save the schedule.') }
    finally { setBusy('') }
  }

  const loadPreview = async () => {
    if (busy || !month) return
    const abort = new AbortController()
    previewController.current?.abort(); previewController.current = abort
    setBusy('preview'); setError(''); setNotice(''); setPreview(null)
    try {
      const result = await responseData(await authFetch(`${getApiBase()}/admin/email-recaps/preview?month=${month}`, { signal: abort.signal })) as Preview
      if (!abort.signal.aborted) setPreview(result)
    } catch (err) { if (!abort.signal.aborted) setError(err instanceof Error ? err.message : 'Could not prepare your preview.') }
    finally { if (!abort.signal.aborted) setBusy('') }
  }

  const sendTest = async () => {
    if (busy || !preview || preview.month !== month) return
    if (!testRequest.current || testRequest.current.month !== month) testRequest.current = { month, id: crypto.randomUUID() }
    setBusy('test'); setError(''); setNotice('')
    try {
      const result = await responseData(await authFetch(`${getApiBase()}/admin/email-recaps/test`, { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ month, request_id: testRequest.current.id }) }))
      setNotice(result.message); testRequest.current = null; setOffset(0); setRevision((value) => value + 1)
    } catch (err) { setError(err instanceof Error ? err.message : 'Could not queue your test.') }
    finally { setBusy('') }
  }

  return <AdminShell title="Monthly email recaps" subtitle="Give each user a personal look back at their month in viewing." actions={<a className="ghost-button" href="/admin/notifications">Email settings ↗</a>}>
    <div className="recap-admin">
      {error && <p className="error-banner" role="alert">{error}</p>}
      {notice && <p className="status-banner" role="status">{notice}</p>}
      {!data && !error && <p role="status">Loading email recaps…</p>}
      {!data && error && <button className="ghost-button" type="button" onClick={() => { setError(''); setRevision((value) => value + 1) }}>Try again</button>}
      {data && <>
        <div className="recap-overview-strip"><div><span className={`recap-pill ${data.settings.enabled ? 'is-enabled' : ''}`}>{data.settings.enabled ? 'Schedule running' : 'Schedule paused'}</span><p>{data.settings.enabled ? `Next send ${dateLabel(data.settings.next_send_at)}` : 'Start the schedule when you’re ready for monthly delivery.'}</p></div><div className="recap-subscriber-count"><strong>{data.subscribers}</strong><span>confirmed {data.subscribers === 1 ? 'subscriber' : 'subscribers'}</span></div></div>
        <div className="recap-admin-grid">
          <section className="admin-panel recap-panel"><div className="recap-section-heading"><div><span className="recap-eyebrow">Set the rhythm</span><h2>Monthly schedule</h2></div></div>
            <p>Send the previous month’s report to users who have opted in and confirmed their email. All report periods and send times use UTC.</p>
            <form className="recap-schedule-form" onSubmit={save}>
              <label htmlFor="recap-public-url">Public Magent address<input id="recap-public-url" type="url" placeholder="https://magent.example.com" maxLength={500} value={settings.public_url} onChange={(event) => setSettings({ ...settings, public_url: event.target.value })} disabled={!!busy} required={settings.enabled} /><small>The address users open from this environment’s emails.</small></label>
              <div className="recap-schedule-fields"><label htmlFor="recap-day">Day of the month<select id="recap-day" value={settings.day} onChange={(event) => setSettings({ ...settings, day: Number(event.target.value) })} disabled={!!busy}>{Array.from({ length: 28 }, (_, index) => <option key={index + 1} value={index + 1}>{index + 1}</option>)}</select></label><label htmlFor="recap-hour">Send time (UTC)<select id="recap-hour" value={settings.hour} onChange={(event) => setSettings({ ...settings, hour: Number(event.target.value) })} disabled={!!busy}>{Array.from({ length: 24 }, (_, hour) => <option key={hour} value={hour}>{String(hour).padStart(2, '0')}:00 UTC</option>)}</select></label></div>
              <label className="recap-checkbox"><input type="checkbox" checked={settings.enabled} disabled={!!busy} onChange={(event) => setSettings({ ...settings, enabled: event.target.checked })} /><span>Enable scheduled monthly recaps</span></label>
              <p className="recap-muted">Starting or changing the schedule begins at its next future send time. Pausing cancels queued monthly emails.</p>
              <button className="account-primary" type="submit" disabled={!!busy || !dirty}>{busy === 'save' ? 'Saving…' : 'Save schedule'}</button>
            </form>
            {!data.ready && <p className="recap-setup-note">{data.detail} <a href="/admin/notifications">Review email settings ↗</a></p>}
          </section>
          <section className="admin-panel recap-panel"><span className="recap-eyebrow">Make it yours</span><h2>Preview your recap</h2><p>See your own viewing highlights in the email design. A test goes only to your confirmed profile email.</p>
            <label className="recap-month-label" htmlFor="recap-month">Report month<select id="recap-month" value={month} disabled={!!busy} onChange={(event) => { setMonth(event.target.value); setPreview(null); testRequest.current = null }}>{data.months.map((value) => <option key={value} value={value}>{monthLabel(value)}</option>)}</select></label>
            <div className="recap-actions"><button type="button" className="account-primary" onClick={() => void loadPreview()} disabled={!!busy || dirty || !month}>{busy === 'preview' ? 'Preparing preview…' : 'Preview my recap'}</button><button type="button" className="account-secondary" onClick={() => void sendTest()} disabled={!!busy || dirty || !preview || !data.ready}>{busy === 'test' ? 'Queuing test…' : 'Send test to me'}</button></div>
            {dirty && <p className="recap-muted">Save your settings before previewing or sending a test.</p>}
            <div className="recap-preview-guidance"><h3>One email. Your month.</h3><ul><li>Minutes, movies, episodes and requests</li><li>Changes from the previous month</li><li>Most watched titles and your longest run</li><li>A link to the full report and easy unsubscribe</li></ul><a href="/profile#monthly-recaps">Confirm your email in Profile ↗</a></div>
          </section>
        </div>
        {preview && <section className="admin-panel recap-panel recap-preview"><div className="recap-section-heading"><div><span className="recap-eyebrow">Email preview</span><h2>{preview.subject}</h2><p>For {preview.email || 'your profile email'} · Preview links use your saved public address.</p></div><div className="recap-mode-buttons"><button type="button" aria-pressed={previewMode === 'html'} onClick={() => setPreviewMode('html')}>Email design</button><button type="button" aria-pressed={previewMode === 'text'} onClick={() => setPreviewMode('text')}>Plain text</button></div></div>{previewMode === 'html' ? <iframe title="Monthly recap email preview" sandbox="" referrerPolicy="no-referrer" srcDoc={preview.body_html} /> : <pre className="recap-plain-preview">{preview.body_text}</pre>}</section>}
        <section className="admin-panel recap-panel"><div className="recap-section-heading"><div><span className="recap-eyebrow">From queue to inbox</span><h2>Delivery history</h2><p>Server acceptance is recorded here. Inbox placement depends on your mail provider.</p></div><button type="button" className="ghost-button" disabled={!!busy} onClick={() => { setError(''); setRevision((value) => value + 1) }}>Refresh history</button></div>
          {data.deliveries.length ? <><div className="recap-history-scroll"><table className="recap-history"><thead><tr><th scope="col">Recipient</th><th scope="col">Report</th><th scope="col">Delivery</th><th scope="col">Updated</th></tr></thead><tbody>{data.deliveries.map((delivery) => <tr key={delivery.id}><td><strong>{delivery.username || 'Removed account'}</strong><small>{delivery.email}</small></td><td>{monthLabel(delivery.month)}<small>{delivery.kind === 'test' ? 'Test email' : 'Scheduled recap'}</small></td><td><span className={`recap-pill ${delivery.state === 'sent' ? 'is-enabled' : ['failed', 'unknown'].includes(delivery.state) ? 'is-attention' : ''}`}>{stateLabels[delivery.state] || delivery.state}</span><small>{delivery.attempts} {delivery.attempts === 1 ? 'attempt' : 'attempts'} · {delivery.detail || 'Waiting for the next worker check.'}</small>{delivery.state === 'retry' && <small>Next attempt {dateLabel(delivery.next_attempt_at)}</small>}{delivery.state === 'unknown' && <small>Automatic retries are stopped to avoid a duplicate email.</small>}</td><td>{dateLabel(delivery.updated_at)}</td></tr>)}</tbody></table></div><div className="recap-pagination"><span>{offset + 1}–{Math.min(offset + 50, data.total)} of {data.total}</span><div className="recap-actions"><button className="ghost-button" type="button" disabled={!offset} onClick={() => setOffset(Math.max(0, offset - 50))}>Previous</button><button className="ghost-button" type="button" disabled={offset + 50 >= data.total} onClick={() => setOffset(offset + 50)}>Next</button></div></div></> : <div className="recap-empty"><span aria-hidden="true">✉</span><h3>Your first recap starts here</h3><p>Preview your email, send yourself a test, then start the monthly schedule. Delivery results will appear here.</p></div>}
        </section>
      </>}
    </div>
  </AdminShell>
}