import { useState } from 'react'
import {
  Box,
  TextField,
  Button,
  FormControl,
  InputLabel,
  Select,
  MenuItem,
  Paper,
  Typography,
  Alert,
  type SelectChangeEvent,
} from '@mui/material'
import { useNavigate } from 'react-router'
import type { CreateTaskRequest, Task } from '~/types/task'
import { TaskStatus } from '~/types/task'
import { useTasks } from '~/hooks/useTasks'

interface TaskFormProps {
  task?: Task
  onSuccess?: (task: Task) => void
  onCancel?: () => void
  inline?: boolean
}

interface FormData {
  title: string
  description: string
  status: TaskStatus
}

interface FormErrors {
  title?: string
  description?: string
}

export function TaskForm({
  task,
  onSuccess,
  onCancel,
  inline = false,
}: TaskFormProps) {
  const navigate = useNavigate()
  const { createTask, loading, error } = useTasks({ autoFetch: false })

  const [formData, setFormData] = useState<FormData>({
    title: task?.title || '',
    description: task?.description || '',
    status: task?.status || TaskStatus.Todo,
  })

  const [errors, setErrors] = useState<FormErrors>({})
  const [isSubmitting, setIsSubmitting] = useState(false)

  const validateForm = (): boolean => {
    const newErrors: FormErrors = {}

    if (!formData.title.trim()) {
      newErrors.title = 'Title is required'
    } else if (formData.title.trim().length < 3) {
      newErrors.title = 'Title must be at least 3 characters long'
    } else if (formData.title.trim().length > 200) {
      newErrors.title = 'Title must be less than 200 characters'
    }

    if (formData.description.length > 1000) {
      newErrors.description = 'Description must be less than 1000 characters'
    }

    setErrors(newErrors)
    return Object.keys(newErrors).length === 0
  }

  const handleSubmit = async (e: React.FormEvent) => {
    e.preventDefault()

    if (!validateForm()) {
      return
    }

    setIsSubmitting(true)

    try {
      if (task) {
        // Update existing task - for now we only support create
        // This would use updateTask hook when implemented
        console.log('Update not implemented yet')
      } else {
        // Create new task
        const createData: CreateTaskRequest = {
          title: formData.title.trim(),
          description: formData.description.trim() || undefined,
        }

        const newTask = await createTask(createData)

        if (newTask) {
          if (onSuccess) {
            onSuccess(newTask)
          } else {
            navigate('/')
          }
        }
      }
    } catch (err) {
      console.error('Form submission error:', err)
    } finally {
      setIsSubmitting(false)
    }
  }

  const handleCancel = () => {
    if (onCancel) {
      onCancel()
    } else {
      navigate('/')
    }
  }

  const handleInputChange =
    (field: keyof FormData) =>
    (e: React.ChangeEvent<HTMLInputElement | HTMLTextAreaElement>) => {
      setFormData(prev => ({
        ...prev,
        [field]: e.target.value,
      }))

      // Clear error for this field when user starts typing
      if (errors[field as keyof FormErrors]) {
        setErrors(prev => ({
          ...prev,
          [field]: undefined,
        }))
      }
    }

  const handleStatusChange = (event: SelectChangeEvent<TaskStatus>) => {
    setFormData(prev => ({
      ...prev,
      status: event.target.value as TaskStatus,
    }))
  }

  const content = (
    <Box component="form" onSubmit={handleSubmit} sx={{ width: '100%' }}>
      <Typography variant="h4" component="h1" gutterBottom>
        {task ? 'Edit Task' : 'Create New Task'}
      </Typography>

      {error && (
        <Alert severity="error" sx={{ mb: 2 }}>
          {error}
        </Alert>
      )}

      <TextField
        fullWidth
        label="Title"
        value={formData.title}
        onChange={handleInputChange('title')}
        error={!!errors.title}
        helperText={errors.title}
        margin="normal"
        required
        autoFocus
        disabled={isSubmitting || loading}
      />

      <TextField
        fullWidth
        label="Description"
        value={formData.description}
        onChange={handleInputChange('description')}
        error={!!errors.description}
        helperText={errors.description}
        margin="normal"
        multiline
        rows={4}
        disabled={isSubmitting || loading}
      />

      {task && (
        <FormControl fullWidth margin="normal">
          <InputLabel>Status</InputLabel>
          <Select
            value={formData.status}
            onChange={handleStatusChange}
            label="Status"
            disabled={isSubmitting || loading}
          >
            <MenuItem value={TaskStatus.Todo}>Todo</MenuItem>
            <MenuItem value={TaskStatus.Done}>Done</MenuItem>
            <MenuItem value={TaskStatus.Backlog}>Backlog</MenuItem>
          </Select>
        </FormControl>
      )}

      <Box sx={{ display: 'flex', gap: 2, mt: 3 }}>
        <Button
          type="submit"
          variant="contained"
          disabled={isSubmitting || loading}
          sx={{ minWidth: 120 }}
        >
          {isSubmitting ? 'Saving...' : task ? 'Update' : 'Create'}
        </Button>

        <Button
          type="button"
          variant="outlined"
          onClick={handleCancel}
          disabled={isSubmitting || loading}
        >
          Cancel
        </Button>
      </Box>
    </Box>
  )

  if (inline) {
    return content
  }

  return (
    <Paper elevation={2} sx={{ p: 3, maxWidth: 600, mx: 'auto' }}>
      {content}
    </Paper>
  )
}