import { useEffect, useMemo, useState } from 'react'
import Alert from '@mui/material/Alert'
import Box from '@mui/material/Box'
import Button from '@mui/material/Button'
import Chip from '@mui/material/Chip'
import List from '@mui/material/List'
import ListItem from '@mui/material/ListItem'
import ListItemButton from '@mui/material/ListItemButton'
import ListItemText from '@mui/material/ListItemText'
import Stack from '@mui/material/Stack'
import Typography from '@mui/material/Typography'
import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query'
import { Link as RouterLink } from 'react-router-dom'
import { fetchMyOrder, postOrderMessage } from '@/entities/order/api/order-api'
import { fetchMyConversations, markOrderMessagesRead } from '@/entities/user/api/messages-api'
import { orderStatusLabelRu } from '@/shared/lib/order-status-labels'
import { ChatMessageBubble } from '@/shared/ui/ChatMessageBubble'
import { OrderMessageBody } from '@/shared/ui/OrderMessageBody'
import { RichTextMessageContent } from '@/shared/ui/RichTextMessageContent'
import { RichTextMessageEditor } from '@/shared/ui/RichTextMessageEditor'

export function MessagesPage() {
  const qc = useQueryClient()
  const [selectedId, setSelectedId] = useState<string | null>(null)
  const [text, setText] = useState('')

  const listQuery = useQuery({
    queryKey: ['me', 'conversations'],
    queryFn: fetchMyConversations,
  })

  const conversationsList = useMemo(() => listQuery.data?.items ?? [], [listQuery.data?.items])

  const activeThreadId = useMemo(() => {
    return selectedId ?? conversationsList[0]?.orderId ?? null
  }, [selectedId, conversationsList])

  const orderQuery = useQuery({
    queryKey: ['me', 'orders', activeThreadId],
    queryFn: () => fetchMyOrder(activeThreadId!),
    enabled: Boolean(activeThreadId),
  })

  useEffect(() => {
    if (!activeThreadId || orderQuery.status !== 'success') return
    void (async () => {
      await markOrderMessagesRead(activeThreadId).catch(() => undefined)
      await qc.invalidateQueries({ queryKey: ['me', 'messages', 'unread-count'] })
      await qc.invalidateQueries({ queryKey: ['me', 'conversations'] })
    })()
  }, [activeThreadId, orderQuery.status, qc])

  const msgMut = useMutation({
    mutationFn: () => postOrderMessage(activeThreadId!, text.trim()),
    onSuccess: async () => {
      setText('')
      await qc.invalidateQueries({ queryKey: ['me', 'orders', activeThreadId] })
      await qc.invalidateQueries({ queryKey: ['me', 'conversations'] })
    },
  })

  const order = orderQuery.data?.item
  const canSendMessage = text.replace(/<[^>]*>/g, ' ').trim().length > 0

  return (
    <Box>
      <Typography variant="h4" gutterBottom>
        Сообщения
      </Typography>

      <Typography color="text.secondary" variant="body2" sx={{ mb: 2 }}>
        Переписка по всем заказам. Последнее сообщение в каждом заказе — в списке слева.
      </Typography>

      {listQuery.isError && <Alert severity="error">Не удалось загрузить переписки.</Alert>}
      {listQuery.isSuccess && conversationsList.length === 0 && (
        <Alert severity="info">
          Пока нет сообщений в заказах. Их отправит администратор — или напишите сами на странице заказа.
        </Alert>
      )}

      {conversationsList.length > 0 && (
        <Stack direction={{ xs: 'column', md: 'row' }} spacing={2} sx={{ alignItems: 'flex-start' }}>
          <Box
            sx={{
              width: { xs: '100%', md: 320 },
              flexShrink: 0,
              border: 1,
              borderColor: 'divider',
              borderRadius: 2,
              bgcolor: 'background.paper',
              maxHeight: 520,
              overflow: 'auto',
            }}
          >
            <List disablePadding>
              {conversationsList.map((c) => (
                <ListItem
                  key={c.orderId}
                  disablePadding
                  secondaryAction={
                    c.unreadCount > 0 ? (
                      <Chip sx={{ mr: 1 }} size="small" color="error" label={String(c.unreadCount)} />
                    ) : null
                  }
                >
                  <ListItemButton selected={activeThreadId === c.orderId} onClick={() => setSelectedId(c.orderId)}>
                    <ListItemText
                      primary={
                        <Stack direction="row" spacing={1} sx={{ alignItems: 'center', flexWrap: 'wrap' }}>
                          <Typography component="span" sx={{ fontWeight: 700 }}>
                            №{c.orderId.slice(-6)}
                          </Typography>
                          <Typography component="span" variant="caption" color="text.secondary">
                            · {orderStatusLabelRu(c.status)}
                          </Typography>
                        </Stack>
                      }
                      slotProps={{
                        secondary: {
                          sx: {
                            mt: 0.5,
                            overflow: 'hidden',
                            display: '-webkit-box',
                            WebkitLineClamp: 2,
                            WebkitBoxOrient: 'vertical',
                          },
                        },
                      }}
                      secondary={<RichTextMessageContent value={c.preview} tone="chat" />}
                    />
                  </ListItemButton>
                </ListItem>
              ))}
            </List>
          </Box>

          <Box
            sx={{
              flexGrow: 1,
              minWidth: 0,
              border: 1,
              borderColor: 'divider',
              borderRadius: 2,
              p: 2,
              bgcolor: 'background.paper',
            }}
          >
            {!activeThreadId && <Typography color="text.secondary">Выберите заказ.</Typography>}
            {activeThreadId && orderQuery.isLoading && <Typography>Загрузка чата…</Typography>}
            {activeThreadId && orderQuery.isError && <Alert severity="error">Не удалось загрузить заказ.</Alert>}
            {order && (
              <>
                <Stack direction="row" sx={{ mb: 2, justifyContent: 'space-between', flexWrap: 'wrap', gap: 1 }}>
                  <Typography variant="h6">
                    Чат заказа №{order.id.slice(-6)}{' '}
                    <Typography component="span" variant="body2" color="text.secondary">
                      ({orderStatusLabelRu(order.status)})
                    </Typography>
                  </Typography>
                  <Button component={RouterLink} to={`/me/orders/${order.id}`} size="small" variant="outlined">
                    Открыть заказ
                  </Button>
                </Stack>
                <Stack spacing={1} sx={{ mb: 2, maxHeight: 360, overflow: 'auto' }}>
                  {order.messages.map((m) => (
                    <ChatMessageBubble key={m.id} authorType={m.authorType === 'admin' ? 'admin' : 'user'}>
                      <Typography variant="caption" color="text.secondary">
                        {m.authorType === 'admin' ? 'Админ' : 'Вы'} · {new Date(m.createdAt).toLocaleString()}
                      </Typography>
                      <OrderMessageBody text={m.text} attachmentUrl={m.attachmentUrl} />
                    </ChatMessageBubble>
                  ))}
                  {order.messages.length === 0 && <Typography color="text.secondary">Нет сообщений.</Typography>}
                </Stack>
                <Stack direction={{ xs: 'column', sm: 'row' }} spacing={2} sx={{ alignItems: { sm: 'flex-end' } }}>
                  <Box sx={{ flexGrow: 1, width: '100%' }}>
                    <RichTextMessageEditor value={text} onChange={setText} placeholder="Сообщение" />
                  </Box>
                  <Button
                    variant="contained"
                    sx={{ minWidth: 140 }}
                    onClick={() => msgMut.mutate()}
                    disabled={msgMut.isPending || !canSendMessage}
                  >
                    Отправить
                  </Button>
                </Stack>
              </>
            )}
          </Box>
        </Stack>
      )}
    </Box>
  )
}
