'use client'

import {
  type ComponentProps,
  createContext,
  memo,
  useContext,
  useEffect,
  useState,
} from 'react'
import { useControllableState } from '@radix-ui/react-use-controllable-state'
import { BrainIcon, ChevronDownIcon } from 'lucide-react'
import { cn } from '@/lib/utils'
import {
  Collapsible,
  CollapsibleContent,
  CollapsibleTrigger,
} from '@/components/ui/collapsible'
import { Response } from './response'
import { Shimmer } from './shimmer'

type ReasoningContextValue = {
  isStreaming: boolean
  isOpen: boolean
  setIsOpen: (open: boolean) => void
  duration: number
}

const ReasoningContext = createContext<ReasoningContextValue | null>(null)

const useReasoning = () => {
  const context = useContext(ReasoningContext)
  if (!context) {
    throw new Error('Reasoning components must be used within Reasoning')
  }
  return context
}

export type ReasoningProps = ComponentProps<typeof Collapsible> & {
  isStreaming?: boolean
  open?: boolean
  defaultOpen?: boolean
  onOpenChange?: (open: boolean) => void
  duration?: number
}

const AUTO_CLOSE_DELAY = 1000
const MS_IN_S = 1000

export const Reasoning = memo(
  ({
    className,
    isStreaming = false,
    open,
    defaultOpen = true,
    onOpenChange,
    duration: durationProp,
    children,
    ...props
  }: ReasoningProps) => {
    const [isOpen, setIsOpen] = useControllableState({
      prop: open,
      defaultProp: defaultOpen,
      onChange: onOpenChange,
    })
    const [duration, setDuration] = useControllableState({
      prop: durationProp,
      defaultProp: 0,
    })

    const [hasAutoClosed, setHasAutoClosed] = useState(false)
    const [startTime, setStartTime] = useState<number | null>(null)

    // Track duration when streaming starts and ends
    useEffect(() => {
      if (isStreaming) {
        if (startTime === null) {
          // eslint-disable-next-line react-hooks/set-state-in-effect
          setStartTime(Date.now())
        }
      } else if (startTime !== null) {
        setDuration(Math.ceil((Date.now() - startTime) / MS_IN_S))
        setStartTime(null)
      }
    }, [isStreaming, startTime, setDuration])

    // Auto-open when streaming starts, auto-close when streaming ends (once only)
    useEffect(() => {
      if (defaultOpen && !isStreaming && isOpen && !hasAutoClosed) {
        // Add a small delay before closing to allow user to see the content
        const timer = setTimeout(() => {
          setIsOpen(false)
          setHasAutoClosed(true)
        }, AUTO_CLOSE_DELAY)

        return () => clearTimeout(timer)
      }
    }, [isStreaming, isOpen, defaultOpen, setIsOpen, hasAutoClosed])

    const handleOpenChange = (newOpen: boolean) => {
      setIsOpen(newOpen)
    }

    return (
      <ReasoningContext.Provider
        value={{ isStreaming, isOpen, setIsOpen, duration }}
      >
        <Collapsible
          className={cn('not-prose mb-4', className)}
          onOpenChange={handleOpenChange}
          open={isOpen}
          {...props}
        >
          {children}
        </Collapsible>
      </ReasoningContext.Provider>
    )
  }
)

export type ReasoningTriggerProps = ComponentProps<typeof CollapsibleTrigger>

const getThinkingMessage = (isStreaming: boolean, duration?: number) => {
  if (isStreaming) {
    return <Shimmer duration={1}>Thinking...</Shimmer>
  }
  // When duration is unknown or 0 (e.g., non-streaming responses), show a generic message
  if (duration === undefined || duration === 0) {
    return <p>Thought for a few seconds</p>
  }
  return <p>Thought for {duration} seconds</p>
}

export const ReasoningTrigger = memo(
  ({ className, children, ...props }: ReasoningTriggerProps) => {
    const { isStreaming, isOpen, duration } = useReasoning()

    return (
      <CollapsibleTrigger
        className={cn(
          'text-muted-foreground hover:text-foreground flex w-full items-center gap-2 text-sm transition-colors',
          className
        )}
        {...props}
      >
        {children ?? (
          <>
            <BrainIcon className='size-4' />
            {getThinkingMessage(isStreaming, duration)}
            <ChevronDownIcon
              className={cn(
                'size-4 transition-transform',
                isOpen ? 'rotate-180' : 'rotate-0'
              )}
            />
          </>
        )}
      </CollapsibleTrigger>
    )
  }
)

export type ReasoningContentProps = ComponentProps<
  typeof CollapsibleContent
> & {
  children: string
}

export const ReasoningContent = memo(
  ({ className, children, ...props }: ReasoningContentProps) => (
    <CollapsibleContent
      className={cn(
        'mt-4 text-sm',
        'data-[state=closed]:fade-out-0 data-[state=closed]:slide-out-to-top-2 data-[state=open]:slide-in-from-top-2 text-muted-foreground data-[state=closed]:animate-out data-[state=open]:animate-in outline-none',
        className
      )}
      {...props}
    >
      <Response className='grid gap-2'>{children}</Response>
    </CollapsibleContent>
  )
)

Reasoning.displayName = 'Reasoning'
ReasoningTrigger.displayName = 'ReasoningTrigger'
ReasoningContent.displayName = 'ReasoningContent'
