import { useEffect, useRef, useState } from 'react'
import { Helmet } from 'react-helmet-async'
import { useNavigate } from 'react-router-dom'

import FieldError from '@/components/common/FieldError'
import Form from '@/components/common/Form'
import FormField from '@/components/common/FormField'
import PageTitle from '@/components/common/PageTitle'
import MainArea from '@/components/layout/MainArea'
import { Button } from '@/components/ui/button'
import { toast } from '@/components/ui/use-toast'
import { SITE_TITLE } from '@/config'
import { apiPost, isApiError } from '@/lib/api'
import { canEditContent } from '@/lib/users'
import { inputClass } from '@/lib/utils'
import { countImportSourceLines,
	 cleanupExpiredPostImportSessions,
	 createPostImportSessionId,
	 initialisePreviewRows,
	 loadPostImportSourceDraft,
	 savePostImportSession,
	 savePostImportSourceDraft,
	 validateImportSource } from '@/lib/postImportSession'
import Forbidden from '@/pages/Forbidden'

import type { FC } from 'react'

import type { PostImportRow } from '@/lib/postImportSession'
import type { User } from '@/types'

type Props = { user: User | null }

const MAX_ROWS = 100
const SOURCE_ERROR_ID = 'post-import-source-error'
const SOURCE_ISSUES_ID = 'post-import-source-issues'

const urlIssuesFromRows = (rows: PostImportRow[], source: string) => {
  const sourceLines = source.split (/\r\n|\n|\r/)

  return rows.flatMap (row =>
      (row.validationErrors.url ?? []).map (message => ({
	  sourceRow: row.sourceRow,
	  message,
	  url: sourceLines[row.sourceRow - 1]?.trim () ?? row.url })))
}


const PostImportSourcePage: FC<Props> = ({ user }) => {
  const editable = canEditContent (user)
  const navigate = useNavigate ()
  const [source, setSource] = useState ('')
  const [loading, setLoading] = useState (false)
  const [sourceIssues, setSourceIssues] = useState<ReturnType<typeof validateImportSource>> ([])
  const [sourceError, setSourceError] = useState<string | null> (null)
  const saveTimer = useRef<number | null> (null)
  const editedRef = useRef (false)

  const lineCount = countImportSourceLines (source)
  const messages = sourceError != null ? [sourceError] : []
  const sourceDescribedBy =
      [sourceError != null ? SOURCE_ERROR_ID : null,
       sourceIssues.length > 0 ? SOURCE_ISSUES_ID : null]
      .filter (_1 => _1 != null)
      .join (' ')

  useEffect (() => {
    cleanupExpiredPostImportSessions (message =>
	toast ({ title: '保存済みデータを整理できませんでした', description: message }))

    const draft = loadPostImportSourceDraft (message =>
	toast ({ title: '保存済み入力を復元できませんでした', description: message }))

    if (!(editedRef.current))
      setSource (current => current === '' ? draft.source : current)
  }, [])

  useEffect (() => {
    if (saveTimer.current != null)
      window.clearTimeout (saveTimer.current)

    saveTimer.current = window.setTimeout (() => {
      savePostImportSourceDraft (source, message =>
	  toast ({ title: '入力内容を保存できませんでした', description: message }))
    }, 300)

    return () => {
      if (saveTimer.current != null)
	window.clearTimeout (saveTimer.current)
    }
  }, [source])

  const preview = async () => {
    if (lineCount === 0)
      {
	setSourceIssues ([])
	setSourceError ('URL を入力してください．')
	return
      }

    const issues = validateImportSource (source)
    if (issues.length > 0)
      {
	setSourceIssues (issues)
	setSourceError (null)
	return
      }

    setLoading (true)
    setSourceIssues ([])
    setSourceError (null)
    try
    {
      const data = await apiPost<{ rows: PostImportRow[] }> ('/posts/import/preview', { source })
      const urlIssues = urlIssuesFromRows (data.rows, source)
      if (urlIssues.length > 0)
	{
	  setSourceIssues (urlIssues)
	  return
	}
      const sessionId = createPostImportSessionId ()
      const saved = savePostImportSession (
	  sessionId,
	  { source,
	    rows: initialisePreviewRows (data.rows),
	    repairMode: 'all' },
	  message => toast ({ title: '取込状態を保存できませんでした', description: message }))
      if (!(saved))
	return
      navigate (`/posts/import/${ sessionId }/review`)
    }
    catch (requestError)
    {
      const message =
	  isApiError<{ message?: string, baseErrors?: string[] }> (requestError)
	  ? (requestError.response?.data?.message
	     ?? requestError.response?.data?.baseErrors?.[0])
	  : undefined
      setSourceError (message ?? '入力を確認してください．')
      toast ({ title: '投稿情報の取得に失敗しました',
	       description: message ?? '入力を確認してください．' })
    }
    finally
    {
      setLoading (false)
    }
  }

  if (!(editable))
    return <Forbidden/>

  return (
      <MainArea>
	<Helmet>
	  <title>{`投稿インポート | ${ SITE_TITLE }`}</title>
	</Helmet>

	<Form className="max-w-4xl">
	  <PageTitle>投稿インポート</PageTitle>
	  <FormField label="URL リスト">
	    {() => (
		<textarea
		    value={source}
		    rows={14}
		    aria-invalid={messages.length > 0 || sourceIssues.length > 0}
		    aria-describedby={sourceDescribedBy || undefined}
		    className={inputClass (
			messages.length > 0 || sourceIssues.length > 0,
			'font-mono text-sm')}
		    onBlur={() => {
		      savePostImportSourceDraft (source, message =>
			  toast ({ title: '入力内容を保存できませんでした',
				   description: message }))
		    }}
		    onChange={ev => {
		      editedRef.current = true
		      setSource (ev.target.value)
		      setSourceError (null)
		      setSourceIssues ([])
		    }}/>)}
	  </FormField>
	  <div id={messages.length > 0 ? SOURCE_ERROR_ID : undefined}>
	    <FieldError messages={messages}/>
	  </div>
	  <ul
	      id={SOURCE_ISSUES_ID}
	      className="space-y-2 text-sm text-red-700 dark:text-red-300">
	    {sourceIssues.map (issue => (
		<li key={`${ issue.sourceRow }-${ issue.message }-${ issue.url }`}>
		  <div>{issue.sourceRow} 行目: {issue.message}</div>
		  <div className="break-all font-mono text-xs">{issue.url}</div>
		</li>))}
	  </ul>

	  <div className="flex items-center justify-between gap-3">
	    <div className="text-sm text-neutral-600 dark:text-neutral-300">
	      入力行数 {lineCount} / {MAX_ROWS}
	    </div>
	    <Button
		type="button"
		className="shrink-0"
		onClick={preview}
		disabled={loading}>
	      次へ
	    </Button>
	  </div>
	</Form>
      </MainArea>)
}

export default PostImportSourcePage