"use client"

import type { ComponentProps, ReactNode } from "react"

import { useControllableState } from "@radix-ui/react-use-controllable-state"
import { useTranslations } from "next-intl"
import {
  Collapsible,
  CollapsibleContent,
  CollapsibleTrigger,
} from "@/components/ui/collapsible"
import { cn } from "@/lib/utils"
import { cjk } from "@streamdown/cjk"
import { code } from "@streamdown/code"
import { math } from "@streamdown/math"
import { mermaid } from "@streamdown/mermaid"
import { BrainIcon, ChevronDownIcon } from "lucide-react"
import {
  createContext,
  memo,
  useCallback,
  useContext,
  useEffect,
  useMemo,
  useRef,
  useState,
} from "react"
import { Streamdown } from "streamdown"

import { Shimmer } from "./shimmer"
import { useStreamdownLinkSafety } from "./link-safety"

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

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

export 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,
    onOpenChange,
    duration: durationProp,
    children,
    ...props
  }: ReasoningProps) => {
    const resolvedDefaultOpen = defaultOpen ?? isStreaming
    // Track if defaultOpen was explicitly set to false (to prevent auto-open)
    const isExplicitlyClosed = defaultOpen === false

    const [isOpen, setIsOpen] = useControllableState<boolean>({
      defaultProp: resolvedDefaultOpen,
      onChange: onOpenChange,
      prop: open,
    })
    const [duration, setDuration] = useControllableState<number | undefined>({
      defaultProp: undefined,
      prop: durationProp,
    })

    const hasEverStreamedRef = useRef(isStreaming)
    const [hasAutoClosed, setHasAutoClosed] = useState(false)
    const startTimeRef = useRef<number | null>(null)

    // Track when streaming starts and compute duration
    useEffect(() => {
      if (isStreaming) {
        hasEverStreamedRef.current = true
        if (startTimeRef.current === null) {
          startTimeRef.current = Date.now()
        }
      } else if (startTimeRef.current !== null) {
        setDuration(Math.ceil((Date.now() - startTimeRef.current) / MS_IN_S))
        startTimeRef.current = null
      }
    }, [isStreaming, setDuration])

    // Auto-open when streaming starts (unless explicitly closed)
    useEffect(() => {
      if (isStreaming && !isOpen && !isExplicitlyClosed) {
        setIsOpen(true)
      }
    }, [isStreaming, isOpen, setIsOpen, isExplicitlyClosed])

    // Auto-close when streaming ends (once only, and only if it ever streamed)
    useEffect(() => {
      if (
        hasEverStreamedRef.current &&
        !isStreaming &&
        isOpen &&
        !hasAutoClosed
      ) {
        const timer = setTimeout(() => {
          setIsOpen(false)
          setHasAutoClosed(true)
        }, AUTO_CLOSE_DELAY)

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

    const handleOpenChange = useCallback(
      (newOpen: boolean) => {
        setIsOpen(newOpen)
      },
      [setIsOpen]
    )

    const contextValue = useMemo(
      () => ({ duration, isOpen, isStreaming, setIsOpen }),
      [duration, isOpen, isStreaming, setIsOpen]
    )

    return (
      <ReasoningContext.Provider value={contextValue}>
        <Collapsible
          className={cn("not-prose", className)}
          onOpenChange={handleOpenChange}
          open={isOpen}
          {...props}
        >
          {children}
        </Collapsible>
      </ReasoningContext.Provider>
    )
  }
)

export type ReasoningTriggerProps = ComponentProps<
  typeof CollapsibleTrigger
> & {
  getThinkingMessage?: (isStreaming: boolean, duration?: number) => ReactNode
}

export const ReasoningTrigger = memo(
  ({
    className,
    children,
    getThinkingMessage,
    ...props
  }: ReasoningTriggerProps) => {
    const t = useTranslations("Folder.chat.reasoning")
    const { isStreaming, isOpen, duration } = useReasoning()
    const defaultGetThinkingMessage = useCallback(
      (nextIsStreaming: boolean, nextDuration?: number) => {
        if (nextIsStreaming || nextDuration === 0) {
          return <Shimmer duration={1}>{t("thinking")}</Shimmer>
        }
        if (nextDuration === undefined) {
          return <p>{t("thoughtForFewSeconds")}</p>
        }
        return <p>{t("thoughtForSeconds", { duration: nextDuration })}</p>
      },
      [t]
    )
    const thinkingMessageBuilder =
      getThinkingMessage ?? defaultGetThinkingMessage

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

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

const streamdownPlugins = { cjk, code, math, mermaid }

export const ReasoningContent = memo(
  ({ className, children, ...props }: ReasoningContentProps) => {
    const linkSafety = useStreamdownLinkSafety()

    return (
      <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 outline-none data-[state=closed]:animate-out data-[state=open]:animate-in",
          className
        )}
        {...props}
      >
        <Streamdown
          linkSafety={linkSafety}
          plugins={streamdownPlugins}
          {...props}
        >
          {children}
        </Streamdown>
      </CollapsibleContent>
    )
  }
)

Reasoning.displayName = "Reasoning"
ReasoningTrigger.displayName = "ReasoningTrigger"
ReasoningContent.displayName = "ReasoningContent"