import { useEffect, useRef, useState } from 'react'

interface Comment {
  id: string
  displayName: string
  text: string
  createdAt: string
}

interface Props {
  studySlug: string
  sectionId: string
  isEnrolled: boolean
}

function formatDate(iso: string) {
  try {
    return new Date(iso).toLocaleDateString('en-US', { year: 'numeric', month: 'short', day: 'numeric' })
  } catch {
    return ''
  }
}

export function StudySectionComments({ studySlug, sectionId, isEnrolled }: Props) {
  const [comments, setComments] = useState<Comment[]>([])
  const [loading, setLoading] = useState(true)
  const [text, setText] = useState('')
  const [submitting, setSubmitting] = useState(false)
  const [error, setError] = useState<string | null>(null)
  const [success, setSuccess] = useState(false)
  const [deletingId, setDeletingId] = useState<string | null>(null)
  const textRef = useRef<HTMLTextAreaElement>(null)

  useEffect(() => {
    setLoading(true)
    fetch(`/api/study-comments/${studySlug}/${sectionId}`)
      .then(r => r.json())
      .then(data => setComments(Array.isArray(data.comments) ? data.comments : []))
      .catch(() => setComments([]))
      .finally(() => setLoading(false))
  }, [studySlug, sectionId])

  async function handleSubmit(e: React.FormEvent) {
    e.preventDefault()
    if (!text.trim()) return
    setSubmitting(true)
    setError(null)
    setSuccess(false)
    try {
      const res = await fetch(`/api/study-comments/${studySlug}/${sectionId}`, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ text: text.trim() }),
      })
      const data = await res.json()
      if (!res.ok) {
        setError(data.message ?? 'Failed to post comment.')
        return
      }
      setComments(prev => [...prev, data.comment])
      setText('')
      setSuccess(true)
      setTimeout(() => setSuccess(false), 3000)
    } catch {
      setError('Network error. Please try again.')
    } finally {
      setSubmitting(false)
    }
  }

  async function handleDelete(commentId: string) {
    setDeletingId(commentId)
    try {
      const res = await fetch(`/api/study-comments/${commentId}`, { method: 'DELETE' })
      if (!res.ok) {
        setError('Could not delete that comment.')
        return
      }
      setComments(prev => prev.filter(c => c.id !== commentId))
    } catch {
      setError('Network error. Please try again.')
    } finally {
      setDeletingId(null)
    }
  }

  return (
    <section className="study-comments">
      <h3 className="study-comments-heading">Share Your Thoughts</h3>

      {loading ? (
        <p className="study-comments-loading">Loading comments…</p>
      ) : comments.length === 0 ? (
        <p className="study-comments-empty">No comments yet. Be the first to share a thought!</p>
      ) : (
        <ul className="study-comments-list">
          {comments.map(comment => (
            <li key={comment.id} className="study-comment">
              <div className="study-comment-header">
                <span className="study-comment-author">{comment.displayName}</span>
                <span className="study-comment-date">{formatDate(comment.createdAt)}</span>
              </div>
              <p className="study-comment-text">{comment.text}</p>
              <button
                type="button"
                className="study-comment-delete"
                onClick={() => handleDelete(comment.id)}
                disabled={deletingId === comment.id}
                aria-label="Delete comment"
              >
                {deletingId === comment.id ? 'Deleting…' : 'Delete'}
              </button>
            </li>
          ))}
        </ul>
      )}

      {isEnrolled ? (
        <form className="study-comment-form" onSubmit={handleSubmit}>
          <label htmlFor="study-comment-input" className="study-comment-form-label">
            Leave a comment
          </label>
          <textarea
            id="study-comment-input"
            ref={textRef}
            className="study-comment-textarea"
            value={text}
            onChange={e => setText(e.target.value)}
            placeholder="Share a thought, question, or encouragement…"
            rows={3}
            maxLength={2000}
            disabled={submitting}
          />
          <div className="study-comment-form-footer">
            <span className="study-comment-char-count">{text.length}/2000</span>
            {error && <span className="study-comment-error">{error}</span>}
            {success && <span className="study-comment-success">Comment posted!</span>}
            <button
              type="submit"
              className="study-comment-submit"
              disabled={submitting || !text.trim()}
            >
              {submitting ? 'Posting…' : 'Post Comment'}
            </button>
          </div>
        </form>
      ) : (
        <p className="study-comments-enroll-note">
          <a href="/study">Enroll in this study</a> to join the discussion.
        </p>
      )}
    </section>
  )
}