"use client"

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

type 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 = true,
        onOpenChange,
        duration: durationProp,
        children,
        ...props
    }: ReasoningProps) => {
        const [isOpen, setIsOpen] = useControllableState({
            prop: open,
            defaultProp: defaultOpen,
            onChange: onOpenChange,
        })
        const [duration, setDuration] = useControllableState({
            prop: durationProp,
            defaultProp: undefined,
        })

        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) {
                    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
> & {
    getThinkingMessage?: (isStreaming: boolean, duration?: number) => ReactNode
}

const defaultGetThinkingMessage = (isStreaming: boolean, duration?: number) => {
    if (isStreaming || duration === 0) {
        return <Shimmer duration={1}>Thinking...</Shimmer>
    }
    if (duration === undefined) {
        return <p>Thought for a few seconds</p>
    }
    return <p>Thought for {duration} seconds</p>
}

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

        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" />
                        {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 outline-none data-[state=closed]:animate-out data-[state=open]:animate-in",
                className,
            )}
            {...props}
        >
            <div className="whitespace-pre-wrap">{children}</div>
        </CollapsibleContent>
    ),
)

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