'use client'

import type { FC } from 'react'
import { memo, useCallback, useEffect, useMemo, useRef, useState } from 'react'
import { createPortal } from 'react-dom'
import { useParams } from 'next/navigation'
import { RiArrowUpLine, RiAtLine } from '@remixicon/react'
import Textarea from 'react-textarea-autosize'
import Button from '@/app/components/base/button'
import Avatar from '@/app/components/base/avatar'
import cn from '@/utils/classnames'
import { type UserProfile, fetchMentionableUsers } from '@/service/workflow-comment'

type MentionInputProps = {
  value: string
  onChange: (value: string) => void
  onSubmit: (content: string, mentionedUserIds: string[]) => void
  onCancel?: () => void
  placeholder?: string
  disabled?: boolean
  loading?: boolean
  className?: string
  isEditing?: boolean
  autoFocus?: boolean
}

export const MentionInput: FC<MentionInputProps> = memo(({
  value,
  onChange,
  onSubmit,
  onCancel,
  placeholder = 'Add a comment',
  disabled = false,
  loading = false,
  className,
  isEditing = false,
  autoFocus = false,
}) => {
  const params = useParams()
  const appId = params.appId as string
  const textareaRef = useRef<HTMLTextAreaElement>(null)

  const [mentionUsers, setMentionUsers] = useState<UserProfile[]>([])
  const [showMentionDropdown, setShowMentionDropdown] = useState(false)
  const [mentionQuery, setMentionQuery] = useState('')
  const [mentionPosition, setMentionPosition] = useState(0)
  const [selectedMentionIndex, setSelectedMentionIndex] = useState(0)
  const [mentionedUserIds, setMentionedUserIds] = useState<string[]>([])

  const loadMentionableUsers = useCallback(async () => {
    if (!appId) return
    try {
      const users = await fetchMentionableUsers(appId)
      setMentionUsers(users)
    }
    catch (error) {
      console.error('Failed to load mentionable users:', error)
    }
  }, [appId])

  useEffect(() => {
    loadMentionableUsers()
  }, [loadMentionableUsers])

  const filteredMentionUsers = useMemo(() => {
    if (!mentionQuery) return mentionUsers
    return mentionUsers.filter(user =>
      user.name.toLowerCase().includes(mentionQuery.toLowerCase())
      || user.email.toLowerCase().includes(mentionQuery.toLowerCase()),
    )
  }, [mentionUsers, mentionQuery])

  const dropdownPosition = useMemo(() => {
    if (!showMentionDropdown || !textareaRef.current)
      return { x: 0, y: 0 }

    const textareaRect = textareaRef.current.getBoundingClientRect()
    return {
      x: textareaRect.left,
      y: textareaRect.bottom + 4,
    }
  }, [showMentionDropdown])

  const handleContentChange = useCallback((newValue: string) => {
    onChange(newValue)

    setTimeout(() => {
      const cursorPosition = textareaRef.current?.selectionStart || 0
      const textBeforeCursor = newValue.slice(0, cursorPosition)
      const mentionMatch = textBeforeCursor.match(/@(\w*)$/)

      if (mentionMatch) {
        setMentionQuery(mentionMatch[1])
        setMentionPosition(cursorPosition - mentionMatch[0].length)
        setShowMentionDropdown(true)
        setSelectedMentionIndex(0)
      }
      else {
        setShowMentionDropdown(false)
      }
    }, 0)
  }, [onChange])

  const handleMentionButtonClick = useCallback((e: React.MouseEvent) => {
    e.preventDefault()
    e.stopPropagation()

    const textarea = textareaRef.current
    if (!textarea) return

    const cursorPosition = textarea.selectionStart || 0
    const newContent = `${value.slice(0, cursorPosition)}@${value.slice(cursorPosition)}`

    onChange(newContent)

    setTimeout(() => {
      const newCursorPos = cursorPosition + 1
      textarea.setSelectionRange(newCursorPos, newCursorPos)
      textarea.focus()

      setMentionQuery('')
      setMentionPosition(cursorPosition)
      setShowMentionDropdown(true)
      setSelectedMentionIndex(0)
    }, 0)
  }, [value, onChange])

  const insertMention = useCallback((user: UserProfile) => {
    const textarea = textareaRef.current
    if (!textarea) return

    const beforeMention = value.slice(0, mentionPosition)
    const afterMention = value.slice(textarea.selectionStart || 0)
    const newContent = `${beforeMention}@${user.name} ${afterMention}`

    onChange(newContent)
    setShowMentionDropdown(false)

    const newMentionedUserIds = [...mentionedUserIds, user.id]
    setMentionedUserIds(newMentionedUserIds)

    setTimeout(() => {
      const newCursorPos = mentionPosition + user.name.length + 2 // @ + name + space
      textarea.setSelectionRange(newCursorPos, newCursorPos)
      textarea.focus()
    }, 0)
  }, [value, mentionPosition, onChange, mentionedUserIds])

  const handleSubmit = useCallback((e?: React.MouseEvent) => {
    if (e) {
      e.preventDefault()
      e.stopPropagation()
    }

    if (value.trim()) {
      onSubmit(value.trim(), mentionedUserIds)
      setMentionedUserIds([])
      setShowMentionDropdown(false)
    }
  }, [value, mentionedUserIds, onSubmit])

  const handleKeyDown = useCallback((e: React.KeyboardEvent) => {
    if (showMentionDropdown) {
      if (e.key === 'ArrowDown') {
        e.preventDefault()
        setSelectedMentionIndex(prev =>
          prev < filteredMentionUsers.length - 1 ? prev + 1 : 0,
        )
      }
      else if (e.key === 'ArrowUp') {
        e.preventDefault()
        setSelectedMentionIndex(prev =>
          prev > 0 ? prev - 1 : filteredMentionUsers.length - 1,
        )
      }
      else if (e.key === 'Enter') {
        e.preventDefault()
        if (filteredMentionUsers[selectedMentionIndex])
          insertMention(filteredMentionUsers[selectedMentionIndex])

        return
      }
      else if (e.key === 'Escape') {
        e.preventDefault()
        setShowMentionDropdown(false)
        return
      }
    }

    if (e.key === 'Enter' && !e.shiftKey && !showMentionDropdown) {
      e.preventDefault()
      handleSubmit()
    }
  }, [showMentionDropdown, filteredMentionUsers, selectedMentionIndex, insertMention, handleSubmit])

  const resetMentionState = useCallback(() => {
    setMentionedUserIds([])
    setShowMentionDropdown(false)
    setMentionQuery('')
    setMentionPosition(0)
    setSelectedMentionIndex(0)
  }, [])

  useEffect(() => {
    if (!value)
      resetMentionState()
  }, [value, resetMentionState])

  useEffect(() => {
    if (autoFocus && textareaRef.current) {
      const textarea = textareaRef.current
      setTimeout(() => {
        textarea.focus()
        const length = textarea.value.length
        textarea.setSelectionRange(length, length)
      }, 0)
    }
  }, [autoFocus])

  return (
    <>
      <div className={cn('relative flex items-center', className)}>
        <Textarea
          ref={textareaRef}
          className={cn(
            'body-lg-regular w-full resize-none bg-transparent p-1 leading-6 text-text-primary caret-primary-500 outline-none',
          )}
          placeholder={placeholder}
          autoFocus={autoFocus}
          minRows={isEditing ? 4 : 1}
          maxRows={4}
          value={value}
          disabled={disabled || loading}
          onChange={e => handleContentChange(e.target.value)}
          onKeyDown={handleKeyDown}
        />

        {!isEditing && (
          <div className="absolute bottom-0 right-1 z-20 flex items-end gap-1">
            <div
              className="z-20 flex h-8 w-8 cursor-pointer items-center justify-center rounded-lg bg-components-button-secondary-bg hover:bg-state-base-hover"
              onClick={handleMentionButtonClick}
            >
              <RiAtLine className="h-4 w-4" />
            </div>
            <Button
              className='z-20 ml-2 w-8 px-0'
              variant='primary'
              disabled={!value.trim() || disabled || loading}
              onClick={handleSubmit}
            >
              <RiArrowUpLine className='h-4 w-4' />
            </Button>
          </div>
        )}

        {isEditing && (
          <div className="absolute bottom-0 left-1 right-1 z-20 flex items-end justify-between">
            <div
              className="z-20 flex h-8 w-8 cursor-pointer items-center justify-center rounded-lg bg-components-button-secondary-bg hover:bg-state-base-hover"
              onClick={handleMentionButtonClick}
            >
              <RiAtLine className="h-4 w-4" />
            </div>
            <div className='flex items-center gap-2'>
              <Button variant='secondary' size='small' onClick={onCancel} disabled={loading}>
                Cancel
              </Button>
              <Button
                variant='primary'
                size='small'
                disabled={loading || !value.trim()}
                onClick={() => handleSubmit()}
              >
                Save
              </Button>
            </div>
          </div>
        )}
      </div>

      {showMentionDropdown && filteredMentionUsers.length > 0 && typeof document !== 'undefined' && createPortal(
        <div
          className="fixed z-[9999] max-h-40 w-64 overflow-y-auto rounded-lg border border-components-panel-border bg-white shadow-lg"
          style={{
            left: dropdownPosition.x,
            top: dropdownPosition.y,
          }}
          data-mention-dropdown
        >
          {filteredMentionUsers.map((user, index) => (
            <div
              key={user.id}
              className={cn(
                'flex cursor-pointer items-center gap-2 p-2 hover:bg-state-base-hover',
                index === selectedMentionIndex && 'bg-state-base-hover',
              )}
              onClick={() => insertMention(user)}
            >
              <Avatar
                avatar={user.avatar_url || null}
                name={user.name}
                size={24}
                className="shrink-0"
              />
              <div className="min-w-0 flex-1">
                <div className="truncate text-sm font-medium text-text-primary">
                  {user.name}
                </div>
                <div className="truncate text-xs text-text-tertiary">
                  {user.email}
                </div>
              </div>
            </div>
          ))}
        </div>,
        document.body,
      )}
    </>
  )
})

MentionInput.displayName = 'MentionInput'