import { useEffect, useState } from 'react'
import type { ReactNode } from 'react'
import { Link } from 'react-router-dom'
import type { SiteContent } from '../content'
import { StoreLink } from './StoreLink'

type TabKey = 'downloads' | 'books' | 'recommended'

interface Props {
  content: SiteContent
  downloadPath: (resourceId: string) => string
  // Shown when there are no downloads, books or recommended resources at all
  fallback: ReactNode
}

// A description that stays short in the grid; long ones get a Read more toggle
function ClampedText({ text, className, lines = 3, threshold = 150 }: { text: string; className: string; lines?: number; threshold?: number }) {
  const [open, setOpen] = useState(false)
  const long = text.length > threshold
  return (
    <>
      <p
        className={`${className}${long && !open ? ' res-clamped' : ''}`}
        style={long && !open ? { WebkitLineClamp: lines } : undefined}
      >
        {text}
      </p>
      {long && (
        <button type="button" className="res-more" onClick={() => setOpen(o => !o)} aria-expanded={open}>
          {open ? 'Show less' : 'Read more'}
        </button>
      )}
    </>
  )
}

export function ResourcesHub({ content, downloadPath, fallback }: Props) {
  const links = content.customLinks ?? []
  // Ask for name and email before sending visitors to Amazon / Apple Books (on unless switched off in the admin)
  const gated = content.gateStoreLinks !== false
  const resources = links.filter(l => l.placement === 'resources')
  const books = links.filter(l => l.placement === 'books')
  const recommended = links.filter(l => l.placement === 'recommended')

  const featured: { key: string; to: string; title: string; description: string; image: string; alt: string }[] = []
  if (content.studyGuideTitle) {
    featured.push({
      key: 'primary',
      to: '/downloads/primary-guide',
      title: content.studyGuideTitle,
      description: content.studyGuideDescription ?? '',
      image: content.seriesImageUrl || '/images/titus-cover.png',
      alt: content.seriesTitle,
    })
  }
  if (content.secondSeries?.guide?.title) {
    featured.push({
      key: 'second',
      to: '/downloads/second-guide',
      title: content.secondSeries.guide.title,
      description: content.secondSeries.guide.description ?? '',
      image: content.secondSeries.imageUrl ?? '',
      alt: content.secondSeries.title,
    })
  }

  const counts: Record<TabKey, number> = {
    downloads: featured.length + resources.length,
    books: books.length,
    recommended: recommended.length,
  }
  const available = (Object.keys(counts) as TabKey[]).filter(k => counts[k] > 0)

  const fromHash = (): TabKey | null => {
    const h = typeof window !== 'undefined' ? window.location.hash.replace('#', '') : ''
    return h === 'downloads' || h === 'books' || h === 'recommended' ? h : null
  }
  const [picked, setPicked] = useState<TabKey | null>(fromHash)
  const [activeTag, setActiveTag] = useState<string | null>(null)

  // Links like /resources#books, and the browser's back/forward buttons, switch the tab too
  useEffect(() => {
    const onHash = () => setPicked(fromHash())
    window.addEventListener('hashchange', onHash)
    return () => window.removeEventListener('hashchange', onHash)
  }, [])

  if (available.length === 0) return <>{fallback}</>

  const tab: TabKey = picked && counts[picked] > 0 ? picked : available[0]
  const choose = (k: TabKey) => {
    setPicked(k)
    try { window.history.replaceState(null, '', `#${k}`) } catch { /* ignore */ }
  }

  const tags = Array.from(new Set(resources.flatMap(r => r.tags ?? []))).filter(Boolean)
  const shownResources = resources.filter(r => !activeTag || (r.tags ?? []).includes(activeTag))
  const labels: Record<TabKey, string> = { downloads: 'Downloads', books: 'Reading List', recommended: 'Recommended' }

  return (
    <section className="res-hub" aria-label="Resources">
      <div className="section-inner">
        {available.length > 1 && (
          <div className="res-tabs" role="tablist" aria-label="Resource types">
            {available.map(k => (
              <button
                key={k}
                type="button"
                role="tab"
                id={`res-tab-${k}`}
                aria-selected={tab === k}
                aria-controls="res-panel"
                className={`res-tab${tab === k ? ' res-tab--on' : ''}`}
                onClick={() => choose(k)}
              >
                {labels[k]} <span>{counts[k]}</span>
              </button>
            ))}
          </div>
        )}

        <div id="res-panel" role="tabpanel" aria-labelledby={`res-tab-${tab}`}>
          {tab === 'downloads' && (
            <>
              {featured.length > 0 && (
                <div className="res-featured">
                  {featured.map(f => (
                    <Link key={f.key} to={f.to} className="res-feature">
                      {f.image && <img src={f.image} alt={f.alt} className="res-feature-img" loading="lazy" />}
                      <div className="res-feature-body">
                        <span className="res-badge">Featured</span>
                        <span className="res-title">{f.title}</span>
                        {f.description && <p className="res-desc res-clamped" style={{ WebkitLineClamp: 2 }}>{f.description}</p>}
                        <span className="res-action">Download free guide →</span>
                      </div>
                    </Link>
                  ))}
                </div>
              )}

              {tags.length > 0 && (
                <div className="res-tags" role="group" aria-label="Filter by topic">
                  <button type="button" className={`res-chip${activeTag === null ? ' res-chip--on' : ''}`} onClick={() => setActiveTag(null)}>All topics</button>
                  {tags.map(t => (
                    <button key={t} type="button" className={`res-chip${activeTag === t ? ' res-chip--on' : ''}`} onClick={() => setActiveTag(prev => (prev === t ? null : t))}>{t}</button>
                  ))}
                </div>
              )}

              {shownResources.length > 0 ? (
                <div className="res-grid">
                  {shownResources.map(r => (
                    <Link key={r.id} to={downloadPath(r.id)} className="res-card">
                      {r.imageUrl && <img src={r.imageUrl} alt={r.label} className="res-card-img" loading="lazy" />}
                      <div className="res-card-body">
                        <span className="res-title">{r.label}</span>
                        {r.description && <p className="res-desc res-clamped" style={{ WebkitLineClamp: 3 }}>{r.description}</p>}
                        {(r.tags ?? []).length > 0 && <span className="res-card-tags">{(r.tags ?? []).join(' · ')}</span>}
                        <span className="res-action">Open download →</span>
                      </div>
                    </Link>
                  ))}
                </div>
              ) : (
                resources.length > 0 && <p className="res-empty">No downloads tagged &quot;{activeTag}&quot;.</p>
              )}
            </>
          )}

          {tab === 'books' && (
            <div className="res-grid">
              {books.map(book => (
                <div key={book.id} className="res-book">
                  {book.imageUrl && <img src={book.imageUrl} alt={book.label} className="res-book-cover" loading="lazy" />}
                  <div className="res-book-body">
                    <span className="res-title">{book.label}</span>
                    {book.description && <ClampedText text={book.description} className="res-desc" lines={3} />}
                    <div className="res-book-actions">
                      {(book.amazonUrl || book.url) && (
                        <StoreLink
                          source={`book:${book.id}`}
                          store="amazon"
                          href={book.amazonUrl || book.url}
                          gated={gated}
                          className="btn-primary res-btn"
                        >
                          {book.amazonUrl ? (book.amazonLabel || 'View on Amazon') : (book.amazonLabel || 'Learn More')}
                        </StoreLink>
                      )}
                      {book.appleBooksUrl && (
                        <StoreLink
                          source={`book:${book.id}`}
                          store="apple"
                          href={book.appleBooksUrl}
                          gated={gated}
                          className="btn-secondary res-btn"
                        >
                          {book.appleBooksLabel || 'Apple Books'}
                        </StoreLink>
                      )}
                    </div>
                  </div>
                </div>
              ))}
            </div>
          )}

          {tab === 'recommended' && (
            <div className="res-grid">
              {recommended.map(item => (
                <a key={item.id} href={item.url} target="_blank" rel="noopener noreferrer" className="res-card">
                  {item.imageUrl && <img src={item.imageUrl} alt={item.label} className="res-card-img" loading="lazy" />}
                  <div className="res-card-body">
                    <span className="res-title">{item.label}</span>
                    {item.description && <p className="res-desc res-clamped" style={{ WebkitLineClamp: 3 }}>{item.description}</p>}
                    <span className="res-action">Visit →</span>
                  </div>
                </a>
              ))}
            </div>
          )}
        </div>
      </div>
    </section>
  )
}