Message

// Shared motion tokens. Easing curves mirror the CSS custom properties in
// globals.css; springs are the canonical physics used across components.
// Strong custom variants — defaults like `ease-in`/`ease-out` feel weak.

export const EASE_OUT = [0.16, 1, 0.3, 1] as const;
export const EASE_IN_OUT = [0.77, 0, 0.175, 1] as const;
export const EASE_DRAWER = [0.32, 0.72, 0, 1] as const;

/** CSS string form of EASE_OUT for inline style transitions. */
export const EASE_OUT_CSS = "cubic-bezier(0.16, 1, 0.3, 1)";

/** Press feedback on buttons and other tappable surfaces. */
export const SPRING_PRESS = {
  type: "spring",
  stiffness: 500,
  damping: 30,
  mass: 0.6,
} as const;

/** Content swaps — label/icon slots trading places inside a control. */
export const SPRING_SWAP = {
  type: "spring",
  stiffness: 460,
  damping: 30,
  mass: 0.55,
} as const;

/** Overlay panel entrances — modals and sheets summoned by pointer. */
export const SPRING_PANEL = {
  type: "spring",
  stiffness: 420,
  damping: 40,
  mass: 0.5,
} as const;

/** Shared-layout glides — pills, indicators and panels morphing between positions. */
export const SPRING_LAYOUT = {
  type: "spring",
  stiffness: 360,
  damping: 32,
  mass: 0.6,
} as const;

/** Cursor-follow physics for decorative mouse tracking (magnetic, tilt, dock). */
export const SPRING_MOUSE = {
  stiffness: 200,
  damping: 15,
  mass: 0.3,
} as const;

/** Dragged handles and fills (sliders) — critically damped `useSpring` config,
 * so the value follows the pointer butterily and never rebounds off an end. */
export const SPRING_GLIDE = {
  stiffness: 700,
  damping: 50,
  mass: 0.5,
} as const;

import { clsx, type ClassValue } from "clsx"
import { twMerge } from "tailwind-merge"

export function cn(...inputs: ClassValue[]) {
  return twMerge(clsx(inputs))
}

"use client";

import { useEffect, useState } from "react";

/**
 * Returns true only on devices that have a true hover (mouse / trackpad).
 * Touch devices fire phantom `:hover` on tap that sticks until tap-elsewhere
 * — gate hover-only effects (scale lifts, magnetic pulls) behind this.
 */
export function useHoverCapable() {
  const [canHover, setCanHover] = useState(false);

  useEffect(() => {
    if (typeof window === "undefined" || !window.matchMedia) return;
    const mq = window.matchMedia("(hover: hover) and (pointer: fine)");
    const update = () => setCanHover(mq.matches);
    update();
    mq.addEventListener?.("change", update);
    return () => mq.removeEventListener?.("change", update);
  }, []);

  return canHover;
}

/** Resolve a website URL to its conventional root favicon location. */
export function getFaviconUrl(value: string) {
  try {
    return new URL("/favicon.ico", value).toString();
  } catch {
    return null;
  }
}

"use client";
// beui.dev/components/agents/message

import { motion, useReducedMotion } from "motion/react";
import {
  type ComponentPropsWithRef,
  createContext,
  type ReactNode,
  useContext,
} from "react";
import { EASE_OUT } from "@/lib/ease";
import { cn } from "@/lib/utils";
import { MessageSideContext } from "@/components/agents/message-context";

export {
  MessageBubble,
  MessageBubbleCollapsible,
  MessageBubbleContent,
  MessageBubbleGroup,
} from "@/components/agents/message-bubble";
export { MessageScroller } from "@/components/agents/message-scroller";
export type { MessageScrollerProps } from "@/components/agents/message-scroller";

export type MessageFrom = "user" | "assistant";

interface MessageContextValue {
  from: MessageFrom;
}

const MessageContext = createContext<MessageContextValue>({
  from: "assistant",
});

export interface MessageProps
  extends Omit<ComponentPropsWithRef<typeof motion.article>, "children"> {
  from: MessageFrom;
  /** Plays a trailing-edge pop-up once when this message row mounts. */
  animateIn?: boolean;
  children: ReactNode;
}

export interface MessageGroupProps extends ComponentPropsWithRef<"div"> {
  spacing?: "compact" | "default";
}

export interface MessageAvatarProps extends ComponentPropsWithRef<"div"> {
  /** Keep an empty avatar slot so grouped messages remain aligned. */
  placeholder?: boolean;
}

export type MessageContentProps = ComponentPropsWithRef<"div">;
export type MessageHeaderProps = ComponentPropsWithRef<"div">;
export type MessageFooterProps = ComponentPropsWithRef<"div">;

export type MessageMarkerProps = ComponentPropsWithRef<"div">;

export interface MessageTypingProps extends ComponentPropsWithRef<"span"> {
  label?: string;
}

// A sent row should rise from the live edge without changing measured layout.
const MESSAGE_POP_UP = {
  type: "spring",
  stiffness: 480,
  damping: 32,
  mass: 0.62,
} as const;

export function Message({
  from,
  animateIn = false,
  children,
  className,
  initial,
  animate,
  transition,
  exit,
  style,
  ...props
}: MessageProps) {
  const reduce = useReducedMotion() ?? false;

  return (
    <MessageSideContext.Provider value={from === "user" ? "end" : "start"}>
      <MessageContext.Provider value={{ from }}>
        <motion.article
          data-slot="message"
          data-from={from}
          aria-label={props["aria-label"] ?? `${from} message`}
          initial={
            initial ??
            (animateIn && !reduce
              ? {
                  opacity: 0,
                  transform: "translateY(8px) scale(0.95)",
                }
              : false)
          }
          animate={
            animate ??
            (animateIn && !reduce
              ? {
                  opacity: 1,
                  transform: "translateY(0px) scale(1)",
                }
              : { opacity: 1 })
          }
          exit={
            exit ??
            (reduce
              ? { opacity: 0 }
              : {
                  opacity: 0,
                  transform: "translateY(-3px) scale(0.99)",
                })
          }
          transition={
            transition ?? (reduce ? { duration: 0.12 } : MESSAGE_POP_UP)
          }
          style={{
            transformOrigin: from === "user" ? "100% 100%" : "0% 100%",
            ...style,
          }}
          className={cn(
            "group/message flex w-full items-start gap-2",
            from === "user" ? "flex-row-reverse" : "flex-row",
            className,
          )}
          {...props}
        >
          {children}
        </motion.article>
      </MessageContext.Provider>
    </MessageSideContext.Provider>
  );
}

export function MessageGroup({
  spacing = "compact",
  className,
  ...props
}: MessageGroupProps) {
  return (
    <div
      data-slot="message-group"
      className={cn(
        "flex w-full flex-col",
        spacing === "compact" ? "gap-1.5" : "gap-4",
        className,
      )}
      {...props}
    />
  );
}

export function MessageAvatar({
  placeholder = false,
  children,
  className,
  ...props
}: MessageAvatarProps) {
  return (
    <div
      data-slot="message-avatar"
      aria-hidden={placeholder || undefined}
      className={cn(
        "grid size-7 shrink-0 place-items-center overflow-hidden rounded-full bg-muted text-xs font-medium text-muted-foreground [&_img]:size-full [&_img]:object-cover [&_svg]:size-3.5",
        placeholder && "invisible",
        className,
      )}
      {...props}
    >
      {children}
    </div>
  );
}

export function MessageContent({ className, ...props }: MessageContentProps) {
  const { from } = useContext(MessageContext);

  return (
    <div
      data-slot="message-content"
      className={cn(
        "flex min-w-0 flex-1 flex-col gap-1.5",
        from === "user" ? "items-end" : "items-start",
        className,
      )}
      {...props}
    />
  );
}

export function MessageHeader({ className, ...props }: MessageHeaderProps) {
  const { from } = useContext(MessageContext);

  return (
    <div
      data-slot="message-header"
      className={cn(
        "flex items-center gap-1.5 px-1 text-[11px] leading-none text-muted-foreground",
        from === "user" ? "justify-end" : "justify-start",
        className,
      )}
      {...props}
    />
  );
}

export function MessageFooter({ className, ...props }: MessageFooterProps) {
  const { from } = useContext(MessageContext);

  return (
    <div
      data-slot="message-footer"
      className={cn(
        "flex min-h-5 items-center gap-1 px-1 text-[11px] text-muted-foreground",
        from === "user" ? "justify-end" : "justify-start",
        className,
      )}
      {...props}
    />
  );
}

export function MessageMarker({ className, ...props }: MessageMarkerProps) {
  return (
    <div
      data-slot="message-marker"
      className={cn(
        "mx-auto flex w-fit max-w-[88%] items-center gap-1.5 rounded-full bg-muted/70 px-2.5 py-1 text-center text-xs text-muted-foreground",
        className,
      )}
      {...props}
    />
  );
}

export function MessageTyping({
  label = "Responding",
  className,
  ...props
}: MessageTypingProps) {
  const reduce = useReducedMotion() ?? false;

  return (
    <span
      data-slot="message-typing"
      className={cn("inline-flex h-5 items-center gap-1", className)}
      {...props}
    >
      <span className="sr-only">{label}</span>
      {[0, 1, 2].map((index) => (
        <motion.span
          key={index}
          aria-hidden="true"
          className="size-1 rounded-full bg-current"
          animate={
            reduce
              ? { opacity: 0.45 }
              : { opacity: [0.28, 0.85, 0.28], y: [0, -2, 0] }
          }
          transition={{
            duration: 1.05,
            ease: EASE_OUT,
            repeat: Number.POSITIVE_INFINITY,
            delay: index * 0.14,
          }}
        />
      ))}
    </span>
  );
}

"use client";

import { ChevronDown } from "lucide-react";
import {
  type HTMLMotionProps,
  motion,
  useReducedMotion,
} from "motion/react";
import {
  cloneElement,
  type ComponentPropsWithRef,
  createContext,
  type ReactElement,
  type ReactNode,
  type Ref,
  useCallback,
  useContext,
  useId,
  useState,
} from "react";
import {
  EASE_OUT,
  SPRING_LAYOUT,
  SPRING_SWAP,
} from "@/lib/ease";
import { cn } from "@/lib/utils";
import { MessageSideContext } from "@/components/agents/message-context";

export type MessageBubbleVariant =
  | "solid"
  | "soft"
  | "tint"
  | "outline"
  | "ghost"
  | "danger";
export type MessageBubbleAlign = "start" | "end";

interface MessageBubbleContextValue {
  align?: MessageBubbleAlign;
  animateIn: boolean;
  variant: MessageBubbleVariant;
}

const MessageBubbleContext = createContext<MessageBubbleContextValue>({
  animateIn: true,
  variant: "soft",
});
const MessageBubbleLayoutContext = createContext<() => void>(() => {});

export interface MessageBubbleProps
  extends Omit<HTMLMotionProps<"div">, "children"> {
  variant?: MessageBubbleVariant;
  /** Defaults to the surrounding Message alignment when omitted. */
  align?: MessageBubbleAlign;
  /** Plays the bubble entrance once when this component mounts. */
  animateIn?: boolean;
  children?: ReactNode;
}

export interface MessageBubbleContentProps
  extends ComponentPropsWithRef<"div"> {
  /** Replaces the content element while preserving bubble styling. */
  render?: ReactElement;
}

export interface MessageBubbleGroupProps extends ComponentPropsWithRef<"div"> {
  spacing?: "compact" | "default";
}

export interface MessageBubbleCollapsibleProps
  extends ComponentPropsWithRef<"div"> {
  open?: boolean;
  defaultOpen?: boolean;
  onOpenChange?: (open: boolean) => void;
  collapsedLines?: 2 | 3 | 4 | 5 | 6;
  moreLabel?: ReactNode;
  lessLabel?: ReactNode;
  contentClassName?: string;
  triggerClassName?: string;
  children?: ReactNode;
}

function mergeRefs<T>(...refs: Array<Ref<T> | undefined>) {
  return (node: T | null) => {
    for (const ref of refs) {
      if (typeof ref === "function") ref(node);
      else if (ref) ref.current = node;
    }
  };
}

const BUBBLE_CONTENT_REVEAL = {
  duration: 0.12,
  ease: EASE_OUT,
  delay: 0.04,
} as const;

// Sent bubbles should pop into place quickly with one restrained overshoot.
const BUBBLE_POP = {
  type: "spring",
  stiffness: 520,
  damping: 27,
  mass: 0.52,
} as const;

export function MessageBubble({
  variant = "soft",
  align,
  animateIn = false,
  className,
  children,
  initial,
  animate,
  exit,
  transition,
  layout,
  ...props
}: MessageBubbleProps) {
  const reduce = useReducedMotion() ?? false;
  const messageSide = useContext(MessageSideContext);
  const resolvedAlign = align ?? messageSide ?? "start";

  return (
    <MessageBubbleContext.Provider
      value={{ align: resolvedAlign, animateIn, variant }}
    >
      <motion.div
        data-slot="message-bubble"
        data-align={resolvedAlign}
        data-variant={variant}
        layout={layout}
        initial={initial ?? false}
        animate={animate}
        exit={
          exit ??
          (reduce ? { opacity: 0 } : { opacity: 0, y: -3, scale: 0.99 })
        }
        transition={transition ?? (reduce ? { duration: 0.12 } : SPRING_LAYOUT)}
        className={cn(
          "group/bubble flex w-full flex-col",
          resolvedAlign === "end" ? "items-end" : "items-start",
          className,
        )}
        {...props}
      >
        {children}
      </motion.div>
    </MessageBubbleContext.Provider>
  );
}

function bubbleContentClass(
  variant: MessageBubbleVariant,
  interactive: boolean,
) {
  return cn(
    "relative z-0 min-w-9 max-w-[82%] rounded-2xl px-3.5 py-2.5 text-sm leading-6 text-foreground",
    "[&_a]:font-medium [&_a]:underline [&_a]:underline-offset-4 [&_code]:rounded [&_code]:bg-background/60 [&_code]:px-1 [&_code]:py-0.5 [&_code]:font-mono [&_code]:text-[0.9em] [&_ol]:my-2 [&_ol]:list-decimal [&_ol]:pl-5 [&_p+p]:mt-2 [&_pre]:my-2 [&_pre]:overflow-x-auto [&_pre]:rounded-xl [&_pre]:bg-background/60 [&_pre]:p-3 [&_ul]:my-2 [&_ul]:list-disc [&_ul]:pl-5",
    variant === "solid" && "text-background",
    variant === "ghost" && "w-full max-w-none rounded-none px-0 py-0",
    variant === "danger" && "text-destructive",
    interactive &&
      "cursor-pointer text-left outline-none transition-[background-color,color,transform] duration-150 hover:brightness-[0.98] focus-visible:ring-2 focus-visible:ring-ring active:scale-[0.99]",
  );
}

function bubbleSurfaceClass(
  variant: MessageBubbleVariant,
  align: MessageBubbleAlign,
) {
  return cn(
    "pointer-events-none absolute inset-0 -z-10 rounded-[inherit]",
    align === "end" ? "origin-bottom-right" : "origin-bottom-left",
    variant === "solid" && "bg-foreground",
    variant === "soft" && "bg-muted",
    variant === "tint" && "bg-primary/10",
    variant === "outline" && "border border-border/70 bg-background",
    variant === "danger" && "bg-destructive/10",
  );
}

export function MessageBubbleContent({
  render,
  className,
  children,
  ref,
  ...props
}: MessageBubbleContentProps) {
  const reduce = useReducedMotion() ?? false;
  const { align = "start", animateIn, variant } =
    useContext(MessageBubbleContext);
  const [layoutVersion, setLayoutVersion] = useState(0);
  const notifyLayout = useCallback(
    () => setLayoutVersion((version) => version + 1),
    [],
  );
  const interactive =
    render?.type === "button" || render?.type === "a";
  const classes = cn(bubbleContentClass(variant, interactive), className);
  const composedChildren = (
    <>
      {variant !== "ghost" ? (
        <motion.span
          aria-hidden="true"
          layout={reduce ? false : "size"}
          layoutDependency={layoutVersion}
          initial={
            animateIn && !reduce
              ? {
                  opacity: 0,
                  scale: 0.92,
                }
              : false
          }
          animate={{ opacity: 1, scale: 1 }}
          transition={
            reduce
              ? { duration: 0 }
              : {
                  opacity: { duration: 0.12, ease: EASE_OUT },
                  scale: BUBBLE_POP,
                  layout: SPRING_LAYOUT,
                }
          }
          className={bubbleSurfaceClass(variant, align)}
        />
      ) : null}
      <MessageBubbleLayoutContext.Provider value={notifyLayout}>
        <motion.div
          initial={
            animateIn
              ? reduce
                ? { opacity: 0 }
                : { opacity: 0 }
              : false
          }
          animate={{ opacity: 1 }}
          transition={
            reduce ? { duration: 0.12, ease: EASE_OUT } : BUBBLE_CONTENT_REVEAL
          }
          className="relative"
        >
          {children}
        </motion.div>
      </MessageBubbleLayoutContext.Provider>
    </>
  );

  if (render) {
    const child = render as ReactElement<
      Record<string, unknown> & { className?: string; ref?: Ref<HTMLElement> }
    >;

    return cloneElement(child, {
      ...props,
      ref: mergeRefs(child.props.ref, ref as Ref<HTMLElement> | undefined),
      className: cn(classes, child.props.className),
      children: composedChildren,
      "data-slot": "message-bubble-content",
    });
  }

  return (
    <div
      ref={ref}
      data-slot="message-bubble-content"
      className={classes}
      {...props}
    >
      {composedChildren}
    </div>
  );
}

export function MessageBubbleGroup({
  spacing = "compact",
  className,
  ...props
}: MessageBubbleGroupProps) {
  return (
    <div
      data-slot="message-bubble-group"
      className={cn(
        "flex w-full flex-col",
        spacing === "compact" ? "gap-1.5" : "gap-3",
        className,
      )}
      {...props}
    />
  );
}

const LINE_CLAMP_CLASS = {
  2: "line-clamp-2",
  3: "line-clamp-3",
  4: "line-clamp-4",
  5: "line-clamp-5",
  6: "line-clamp-6",
} as const;

export function MessageBubbleCollapsible({
  open,
  defaultOpen = false,
  onOpenChange,
  collapsedLines = 4,
  moreLabel = "Show more",
  lessLabel = "Show less",
  contentClassName,
  triggerClassName,
  className,
  children,
  ...props
}: MessageBubbleCollapsibleProps) {
  const reduce = useReducedMotion() ?? false;
  const contentId = useId();
  const notifyLayout = useContext(MessageBubbleLayoutContext);
  const [internalOpen, setInternalOpen] = useState(defaultOpen);
  const currentOpen = open ?? internalOpen;

  const setOpen = useCallback(
    (next: boolean) => {
      notifyLayout();
      if (open === undefined) setInternalOpen(next);
      onOpenChange?.(next);
    },
    [notifyLayout, onOpenChange, open],
  );

  return (
    <div
      data-slot="message-bubble-collapsible"
      data-state={currentOpen ? "open" : "closed"}
      className={cn("w-full", className)}
      {...props}
    >
      <div
        id={contentId}
        className={cn(
          "transition-[mask-image] duration-200",
          !currentOpen && LINE_CLAMP_CLASS[collapsedLines],
          !currentOpen &&
            "[mask-image:linear-gradient(to_bottom,#000_68%,transparent_100%)]",
          contentClassName,
        )}
      >
        {children}
      </div>
      <button
        type="button"
        aria-expanded={currentOpen}
        aria-controls={contentId}
        onClick={() => setOpen(!currentOpen)}
        className={cn(
          "mt-2 inline-flex h-7 items-center gap-1 rounded-full px-2 text-xs font-medium text-muted-foreground outline-none transition-colors hover:bg-muted hover:text-foreground focus-visible:ring-2 focus-visible:ring-ring",
          triggerClassName,
        )}
      >
        <span>{currentOpen ? lessLabel : moreLabel}</span>
        <motion.span
          aria-hidden="true"
          animate={{ rotate: currentOpen ? 180 : 0 }}
          transition={reduce ? { duration: 0 } : SPRING_SWAP}
        >
          <ChevronDown className="size-3.5" />
        </motion.span>
      </button>
    </div>
  );
}

"use client";

import { createContext } from "react";

export type MessageSide = "start" | "end";

export const MessageSideContext = createContext<MessageSide | undefined>(
  undefined,
);

"use client";

import { useReducedMotion } from "motion/react";
import {
  type ComponentPropsWithRef,
  type Ref,
  useCallback,
  useEffect,
  useLayoutEffect,
  useRef,
  useState,
} from "react";
import {
  PreviewRail,
  type PreviewRailItem,
} from "@/components/motion/preview-rail";
import { cn } from "@/lib/utils";

const PREVIEW_TITLE_LENGTH = 56;
const PREVIEW_DESCRIPTION_LENGTH = 88;

function truncateMessageText(text: string, limit: number) {
  if (text.length <= limit) return text;
  const excerpt = text.slice(0, limit);
  const boundary = excerpt.lastIndexOf(" ");
  return `${excerpt.slice(0, boundary > limit * 0.65 ? boundary : limit).trim()}…`;
}

function getMessageText(message: HTMLElement) {
  const surface =
    message.querySelector<HTMLElement>('[data-slot="message-bubble-content"]') ??
    message.querySelector<HTMLElement>('[data-slot="message-content"]') ??
    message;
  return (surface.textContent ?? "").replace(/\s+/g, " ").trim();
}

function getMessagePreview(
  message: HTMLElement,
  assistantResponse?: HTMLElement,
) {
  const text = getMessageText(message);
  if (!text) {
    return { label: "Message", description: undefined };
  }

  if (text.length <= PREVIEW_TITLE_LENGTH) {
    const responseText = assistantResponse
      ? getMessageText(assistantResponse)
      : "";
    return {
      label: text,
      description: responseText
        ? truncateMessageText(responseText, PREVIEW_DESCRIPTION_LENGTH)
        : undefined,
    };
  }

  const titleExcerpt = text.slice(0, PREVIEW_TITLE_LENGTH);
  const titleBoundary = titleExcerpt.lastIndexOf(" ");
  const titleEnd =
    titleBoundary > PREVIEW_TITLE_LENGTH * 0.65
      ? titleBoundary
      : PREVIEW_TITLE_LENGTH;
  const label = `${text.slice(0, titleEnd).trim()}…`;
  const responseText = assistantResponse
    ? getMessageText(assistantResponse)
    : text.slice(titleEnd).trim();
  return {
    label,
    description: responseText
      ? truncateMessageText(responseText, PREVIEW_DESCRIPTION_LENGTH)
      : undefined,
  };
}

export interface MessageScrollerProps extends ComponentPropsWithRef<"div"> {
  /** Keep streamed output pinned while the reader remains near the end. */
  followOutput?: boolean;
  /** Distance from the end that still counts as following the output. */
  followThreshold?: number;
  /** Smoothly follow growing content. */
  smooth?: boolean;
  /** Reports when the reader leaves or returns to the live edge. */
  onFollowChange?: (following: boolean) => void;
  /** Accessible label for the scrollable transcript. */
  label?: string;
  /** Marks the transcript as waiting for more streamed content. */
  busy?: boolean;
  /** Adds a compact rail for navigating between rendered Message rows. */
  navigation?: "rail";
  /** Accessible label for the optional message navigation rail. */
  navigationLabel?: string;
  viewportClassName?: string;
  contentClassName?: string;
  railClassName?: string;
  viewportRef?: Ref<HTMLElement>;
  viewportProps?: Omit<
    ComponentPropsWithRef<"section">,
    "children" | "className" | "ref"
  >;
  contentProps?: Omit<
    ComponentPropsWithRef<"div">,
    "children" | "className" | "ref"
  >;
}

export function MessageScroller({
  followOutput = true,
  followThreshold = 56,
  smooth = true,
  onFollowChange,
  label = "Conversation",
  busy,
  navigation,
  navigationLabel = "Message navigation",
  viewportClassName,
  contentClassName,
  railClassName,
  viewportRef: externalViewportRef,
  viewportProps,
  contentProps,
  className,
  children,
  ...props
}: MessageScrollerProps) {
  const reduce = useReducedMotion() ?? false;
  const viewportRef = useRef<HTMLElement>(null);
  const contentRef = useRef<HTMLDivElement>(null);
  const followingRef = useRef(followOutput);
  const programmaticScrollRef = useRef(false);
  const scrollTimerRef = useRef<number | undefined>(undefined);
  const frameRef = useRef<number | undefined>(undefined);
  const railFrameRef = useRef<number | undefined>(undefined);
  const railIdRef = useRef(new WeakMap<HTMLElement, string>());
  const railIdCounterRef = useRef(0);
  const railTargetsRef = useRef(new Map<string, HTMLElement>());
  const [railItems, setRailItems] = useState<PreviewRailItem[]>([]);
  const [activeRailId, setActiveRailId] = useState("");
  const [railOverflowing, setRailOverflowing] = useState(false);
  const {
    onScroll: onViewportScroll,
    onWheel: onViewportWheel,
    onTouchStart: onViewportTouchStart,
    onKeyDown: onViewportKeyDown,
    ...restViewportProps
  } = viewportProps ?? {};

  const setViewportRef = useCallback(
    (node: HTMLElement | null) => {
      viewportRef.current = node;
      if (typeof externalViewportRef === "function") {
        externalViewportRef(node);
      } else if (externalViewportRef) {
        externalViewportRef.current = node;
      }
    },
    [externalViewportRef],
  );

  const setFollowing = useCallback(
    (next: boolean) => {
      if (followingRef.current === next) return;
      followingRef.current = next;
      onFollowChange?.(next);
    },
    [onFollowChange],
  );

  const updateActiveRailItem = useCallback(() => {
    if (navigation !== "rail") return;
    const viewport = viewportRef.current;
    const targets = [...railTargetsRef.current.entries()];
    if (!viewport || targets.length === 0) return;

    const viewportRect = viewport.getBoundingClientRect();
    if (viewport.scrollTop <= followThreshold) {
      const firstId = targets[0]?.[0] ?? "";
      setActiveRailId((current) => (current === firstId ? current : firstId));
      return;
    }

    const distanceFromEnd =
      viewport.scrollHeight - viewport.scrollTop - viewport.clientHeight;
    if (distanceFromEnd <= followThreshold) {
      const lastId = targets.at(-1)?.[0] ?? "";
      setActiveRailId((current) => (current === lastId ? current : lastId));
      return;
    }

    const viewportCenter = viewportRect.top + viewportRect.height / 2;
    let nearestId = targets[0]?.[0] ?? "";
    let nearestDistance = Number.POSITIVE_INFINITY;

    for (const [id, element] of targets) {
      const rect = element.getBoundingClientRect();
      const messageCenter = rect.top + rect.height / 2;
      const distance = Math.abs(messageCenter - viewportCenter);
      if (distance < nearestDistance) {
        nearestDistance = distance;
        nearestId = id;
      }
    }

    setActiveRailId((current) =>
      current === nearestId ? current : nearestId,
    );
  }, [followThreshold, navigation]);

  const syncRailItems = useCallback(() => {
    if (navigation !== "rail") return;
    const content = contentRef.current;
    const viewport = viewportRef.current;
    if (!content || !viewport) return;

    const messages = Array.from(
      content.querySelectorAll<HTMLElement>('[data-slot="message"]'),
    );
    const targets = new Map<string, HTMLElement>();
    const nextItems = messages.map((message, index) => {
      let id = railIdRef.current.get(message);
      if (!id) {
        railIdCounterRef.current += 1;
        id = `message-rail-${railIdCounterRef.current}`;
        railIdRef.current.set(message, id);
      }
      targets.set(id, message);
      const sender = message.dataset.from ?? "conversation";
      const assistantResponse =
        sender === "user"
          ? messages
              .slice(index + 1)
              .find((candidate) => candidate.dataset.from === "assistant")
          : undefined;
      const preview = getMessagePreview(message, assistantResponse);

      return {
        id,
        label: preview.label,
        description: preview.description,
        ariaLabel: `Go to ${sender} message ${index + 1} of ${messages.length}`,
      };
    });

    railTargetsRef.current = targets;
    setRailItems((current) => {
      const unchanged =
        current.length === nextItems.length &&
        current.every(
          (item, index) =>
            item.id === nextItems[index]?.id &&
            item.label === nextItems[index]?.label &&
            item.description === nextItems[index]?.description &&
            item.ariaLabel === nextItems[index]?.ariaLabel,
        );
      return unchanged ? current : nextItems;
    });
    setRailOverflowing(
      viewport.scrollHeight > viewport.clientHeight + 1 && messages.length > 1,
    );
  }, [navigation]);

  const scheduleRailSync = useCallback(() => {
    if (navigation !== "rail") return;
    if (railFrameRef.current) cancelAnimationFrame(railFrameRef.current);
    railFrameRef.current = requestAnimationFrame(() => {
      syncRailItems();
      updateActiveRailItem();
    });
  }, [navigation, syncRailItems, updateActiveRailItem]);

  const scrollToEnd = useCallback((behavior: ScrollBehavior) => {
    const viewport = viewportRef.current;
    if (!viewport) return;

    programmaticScrollRef.current = true;
    if (typeof viewport.scrollTo === "function") {
      viewport.scrollTo({ top: viewport.scrollHeight, behavior });
    } else {
      viewport.scrollTop = viewport.scrollHeight;
    }
    if (scrollTimerRef.current) window.clearTimeout(scrollTimerRef.current);
    scrollTimerRef.current = window.setTimeout(() => {
      programmaticScrollRef.current = false;
    }, behavior === "smooth" ? 320 : 0);
  }, []);

  const handleScroll = useCallback(() => {
    const viewport = viewportRef.current;
    if (!viewport || programmaticScrollRef.current) return;

    const distance =
      viewport.scrollHeight - viewport.scrollTop - viewport.clientHeight;
    setFollowing(distance <= followThreshold);
    updateActiveRailItem();
  }, [followThreshold, setFollowing, updateActiveRailItem]);

  const leaveLiveEdge = useCallback(() => {
    programmaticScrollRef.current = false;
  }, []);

  useLayoutEffect(() => {
    followingRef.current = followOutput;
    if (!followOutput) return;

    frameRef.current = requestAnimationFrame(() => scrollToEnd("auto"));
    return () => {
      if (frameRef.current) cancelAnimationFrame(frameRef.current);
    };
  }, [followOutput, scrollToEnd]);

  useEffect(() => {
    const content = contentRef.current;
    if (!content || typeof ResizeObserver === "undefined") return;

    const observer = new ResizeObserver(() => {
      scheduleRailSync();
      if (!followOutput || !followingRef.current) return;
      scrollToEnd(reduce || !smooth ? "auto" : "smooth");
    });
    observer.observe(content);

    return () => observer.disconnect();
  }, [followOutput, reduce, scheduleRailSync, scrollToEnd, smooth]);

  useEffect(() => {
    if (navigation !== "rail") {
      railTargetsRef.current.clear();
      setRailItems([]);
      setRailOverflowing(false);
      return;
    }

    const content = contentRef.current;
    const viewport = viewportRef.current;
    if (!content || !viewport) return;

    scheduleRailSync();
    const mutationObserver =
      typeof MutationObserver === "undefined"
        ? null
        : new MutationObserver(scheduleRailSync);
    mutationObserver?.observe(content, {
      childList: true,
      characterData: true,
      subtree: true,
    });

    const resizeObserver =
      typeof ResizeObserver === "undefined"
        ? null
        : new ResizeObserver(scheduleRailSync);
    resizeObserver?.observe(content);
    resizeObserver?.observe(viewport);

    return () => {
      mutationObserver?.disconnect();
      resizeObserver?.disconnect();
    };
  }, [navigation, scheduleRailSync]);

  useEffect(
    () => () => {
      if (scrollTimerRef.current) window.clearTimeout(scrollTimerRef.current);
      if (frameRef.current) cancelAnimationFrame(frameRef.current);
      if (railFrameRef.current) cancelAnimationFrame(railFrameRef.current);
    },
    [],
  );

  const scrollToRailItem = useCallback(
    (item: PreviewRailItem) => {
      const viewport = viewportRef.current;
      const target = railTargetsRef.current.get(item.id);
      if (!viewport || !target) return;

      const lastItem = railItems.at(-1)?.id === item.id;
      setActiveRailId(item.id);
      if (lastItem) {
        setFollowing(true);
        scrollToEnd(reduce || !smooth ? "auto" : "smooth");
        return;
      }

      setFollowing(false);
      programmaticScrollRef.current = true;
      const viewportRect = viewport.getBoundingClientRect();
      const targetRect = target.getBoundingClientRect();
      const top =
        viewport.scrollTop +
        targetRect.top -
        viewportRect.top -
        (viewport.clientHeight - targetRect.height) / 2;
      const behavior = reduce || !smooth ? "auto" : "smooth";

      if (typeof viewport.scrollTo === "function") {
        viewport.scrollTo({ top, behavior });
      } else {
        viewport.scrollTop = top;
      }
      if (scrollTimerRef.current) window.clearTimeout(scrollTimerRef.current);
      scrollTimerRef.current = window.setTimeout(() => {
        programmaticScrollRef.current = false;
      }, behavior === "smooth" ? 320 : 0);
    },
    [railItems, reduce, scrollToEnd, setFollowing, smooth],
  );

  const viewport = (
    <section
      ref={setViewportRef}
      aria-label={label}
      {...restViewportProps}
      onScroll={(event) => {
        handleScroll();
        onViewportScroll?.(event);
      }}
      onWheel={(event) => {
        leaveLiveEdge();
        onViewportWheel?.(event);
      }}
      onTouchStart={(event) => {
        leaveLiveEdge();
        onViewportTouchStart?.(event);
      }}
      onKeyDown={(event) => {
        if (["ArrowUp", "PageUp", "Home"].includes(event.key)) {
          leaveLiveEdge();
        }
        onViewportKeyDown?.(event);
      }}
      className={cn(
        "h-full overflow-y-auto overscroll-contain outline-none [overflow-anchor:none] focus-visible:ring-2 focus-visible:ring-inset focus-visible:ring-ring",
        navigation === "rail"
          ? "[-ms-overflow-style:none] [scrollbar-width:none] [&::-webkit-scrollbar]:hidden"
          : "[scrollbar-gutter:stable]",
        viewportClassName,
        navigation === "rail" && railOverflowing && "pr-10",
      )}
    >
      <div
        ref={contentRef}
        role="log"
        aria-live="polite"
        aria-relevant="additions text"
        aria-busy={busy}
        className={contentClassName}
        {...contentProps}
      >
        {children}
      </div>
    </section>
  );

  return (
    <div
      data-slot="message-scroller"
      className={cn("min-h-0", className)}
      {...props}
    >
      {navigation === "rail" ? (
        <PreviewRail
          items={railOverflowing ? railItems : []}
          label={navigationLabel}
          activeId={activeRailId}
          onItemSelect={scrollToRailItem}
          previewSide="before"
          highlightActive
          itemSize={14}
          className="h-full min-h-0 overflow-hidden"
          previewContainerClassName="right-8 left-3"
          previewClassName="mr-1 w-64 max-w-full [&_[data-slot=preview-rail-card]]:h-20 [&_[data-slot=preview-rail-card]]:overflow-hidden [&_[data-slot=preview-rail-card]]:p-3 [&_[data-slot=preview-rail-title]]:line-clamp-1 [&_[data-slot=preview-rail-title]]:text-xs [&_[data-slot=preview-rail-title]]:leading-4 [&_[data-slot=preview-rail-description]]:line-clamp-2 [&_[data-slot=preview-rail-description]]:text-xs [&_[data-slot=preview-rail-description]]:leading-4"
          railClassName={cn(
            "absolute inset-y-3 right-1 w-7 content-center py-1 [&_[data-slot=preview-rail-item]]:w-7 [&_[data-slot=preview-rail-item]]:justify-end [&_[data-slot=preview-rail-tick]]:h-px [&_[data-slot=preview-rail-tick]]:w-4 [&_[data-slot=preview-rail-tick]]:origin-right",
            railOverflowing
              ? "pointer-events-auto opacity-100"
              : "pointer-events-none opacity-0",
            railClassName,
          )}
        >
          {viewport}
        </PreviewRail>
      ) : (
        viewport
      )}
    </div>
  );
}

"use client";

import { AnimatePresence, motion, useReducedMotion } from "motion/react";
import { useId, useState, type ReactNode } from "react";
import { EASE_OUT, SPRING_LAYOUT } from "@/lib/ease";
import { useHoverCapable } from "@/lib/hooks/use-hover-capable";
import { cn } from "@/lib/utils";

export interface PreviewRailItem {
  id: string;
  label: string;
  ariaLabel?: string;
  description?: ReactNode;
  href?: string;
  target?: "_blank" | "_self" | "_parent" | "_top";
  rel?: string;
}

export interface PreviewRailProps {
  items: PreviewRailItem[];
  label?: string;
  orientation?: "vertical" | "horizontal";
  activeId?: string;
  defaultActiveId?: string;
  onActiveChange?: (id: string) => void;
  onItemSelect?: (item: PreviewRailItem) => void;
  renderPreview?: (item: PreviewRailItem) => ReactNode;
  showPreview?: boolean;
  previewSide?: "before" | "after";
  highlightActive?: boolean;
  itemSize?: number;
  children?: ReactNode;
  className?: string;
  railClassName?: string;
  previewContainerClassName?: string;
  previewClassName?: string;
}

function DefaultPreview({ item }: { item: PreviewRailItem }) {
  return (
    <div
      data-slot="preview-rail-card"
      className="rounded-2xl border border-border bg-card p-4 shadow-sm"
    >
      <p
        data-slot="preview-rail-title"
        className="font-medium text-card-foreground"
      >
        {item.label}
      </p>
      {item.description ? (
        <div
          data-slot="preview-rail-description"
          className="mt-1 text-sm leading-6 text-muted-foreground"
        >
          {item.description}
        </div>
      ) : null}
    </div>
  );
}

export function PreviewRail({
  items,
  label = "Section navigation",
  orientation = "vertical",
  activeId,
  defaultActiveId,
  onActiveChange,
  onItemSelect,
  renderPreview,
  showPreview = true,
  previewSide = "after",
  highlightActive = false,
  itemSize = 24,
  children,
  className,
  railClassName,
  previewContainerClassName,
  previewClassName,
}: PreviewRailProps) {
  const uid = useId();
  const reduce = useReducedMotion();
  const canHover = useHoverCapable();
  const [internalActiveId, setInternalActiveId] = useState(
    defaultActiveId ?? items[0]?.id ?? "",
  );
  const [hoveredId, setHoveredId] = useState<string | null>(null);
  const [focusedId, setFocusedId] = useState<string | null>(null);

  const requestedActiveId = activeId ?? internalActiveId;
  const selectedId = items.some((item) => item.id === requestedActiveId)
    ? requestedActiveId
    : (items[0]?.id ?? "");
  const displayedId = hoveredId ?? focusedId ?? "";
  const highlightedId = displayedId || (highlightActive ? selectedId : "");
  const displayedIndex = items.findIndex((item) => item.id === highlightedId);
  const rowTemplate = items.length
    ? `repeat(${items.length}, ${itemSize}px)`
    : undefined;
  const isHorizontal = orientation === "horizontal";

  const selectItem = (id: string) => {
    if (activeId === undefined) setInternalActiveId(id);
    onActiveChange?.(id);
  };

  return (
    <motion.div
      layoutRoot
      onBlur={(event) => {
        if (!event.currentTarget.contains(event.relatedTarget)) {
          setFocusedId(null);
        }
      }}
      className={cn(
        "isolate relative flex w-full overflow-visible",
        isHorizontal
          ? "min-h-64 flex-col items-center justify-center"
          : "min-h-80",
        className,
      )}
    >
      <nav
        aria-label={label}
        onPointerLeave={() => setHoveredId(null)}
        style={
          isHorizontal
            ? { gridTemplateColumns: rowTemplate }
            : { gridTemplateRows: rowTemplate }
        }
        className={cn(
          "relative z-10 grid shrink-0",
          isHorizontal
            ? "h-12 w-fit max-w-full self-center justify-center"
            : "w-12 content-center",
          railClassName,
        )}
      >
        {items.map((item, index) => {
          const selected = item.id === selectedId;
          const highlighted = item.id === highlightedId;
          const distance =
            displayedIndex < 0 ? Number.POSITIVE_INFINITY : Math.abs(index - displayedIndex);
          const scale = highlighted
            ? 1
            : distance === 1
              ? 0.68
              : distance === 2
                ? 0.44
                : 0.25;

          const itemContent = (
            <>
              <motion.span
                data-slot="preview-rail-tick"
                aria-hidden="true"
                animate={isHorizontal ? { scaleY: scale } : { scaleX: scale }}
                transition={reduce ? { duration: 0 } : SPRING_LAYOUT}
                className={cn(
                  "block bg-current",
                  isHorizontal
                    ? "h-12 w-0.5 origin-bottom"
                    : "h-0.5 w-12 origin-left",
                  highlighted ? "text-foreground" : undefined,
                )}
              />
            </>
          );

          const sharedClassName = cn(
            "relative flex text-muted-foreground focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 focus-visible:ring-offset-background",
            isHorizontal
              ? "h-12 w-6 items-end justify-center"
              : "h-6 w-12 items-center",
          );
          const sharedStyle = isHorizontal
            ? { width: itemSize }
            : { height: itemSize };
          const handlePointerEnter = () => {
            if (canHover) setHoveredId(item.id);
          };
          const handleFocus = (currentTarget: HTMLElement) => {
            if (currentTarget.matches(":focus-visible")) {
              setFocusedId(item.id);
            }
          };
          const handleSelect = () => {
            selectItem(item.id);
            onItemSelect?.(item);
          };

          return item.href ? (
            <a
              key={item.id}
              data-slot="preview-rail-item"
              href={item.href}
              target={item.target}
              rel={
                item.rel ??
                (item.target === "_blank" ? "noreferrer noopener" : undefined)
              }
              aria-label={item.ariaLabel ?? item.label}
              aria-current={selected ? "page" : undefined}
              onPointerEnter={handlePointerEnter}
              onMouseEnter={handlePointerEnter}
              onPointerDown={() => setFocusedId(null)}
              onFocus={(event) => handleFocus(event.currentTarget)}
              onClick={handleSelect}
              style={sharedStyle}
              className={sharedClassName}
            >
              {itemContent}
            </a>
          ) : (
            <button
              key={item.id}
              data-slot="preview-rail-item"
              type="button"
              aria-label={item.ariaLabel ?? item.label}
              aria-current={selected ? "location" : undefined}
              onPointerEnter={handlePointerEnter}
              onMouseEnter={handlePointerEnter}
              onPointerDown={() => setFocusedId(null)}
              onFocus={(event) => handleFocus(event.currentTarget)}
              onClick={handleSelect}
              style={sharedStyle}
              className={sharedClassName}
            >
              {itemContent}
            </button>
          );
        })}
      </nav>

      {showPreview ? (
        <div
          aria-hidden="true"
          style={
            isHorizontal
              ? { gridTemplateColumns: rowTemplate }
              : { gridTemplateRows: rowTemplate }
          }
          className={cn(
            "pointer-events-none absolute z-50 grid",
            isHorizontal
              ? "top-1/2 left-1/2 h-5 w-fit max-w-full -translate-x-1/2 -translate-y-1/2 justify-center"
              : previewSide === "before"
                ? "inset-y-0 right-16 left-4 content-center"
                : "inset-y-0 right-4 left-16 content-center",
            previewContainerClassName,
          )}
        >
          {items.map((item) => (
            <div
              key={item.id}
              style={
                isHorizontal ? { width: itemSize } : { height: itemSize }
              }
              className={cn(
                "relative flex items-center",
                isHorizontal ? "justify-center" : undefined,
              )}
            >
              {item.id === displayedId ? (
                <div
                  className={cn(
                    isHorizontal
                      ? "absolute bottom-12 left-1/2 w-72 -translate-x-1/2"
                      : cn(
                          "w-full max-w-sm",
                          previewSide === "before" && "ml-auto",
                        ),
                    previewClassName,
                  )}
                >
                  <motion.div
                    layoutId={`preview-rail-card-${uid}`}
                    transition={reduce ? { duration: 0 } : SPRING_LAYOUT}
                  >
                    <AnimatePresence mode="wait" initial={false}>
                      <motion.div
                        key={item.id}
                        initial={
                          reduce
                            ? { opacity: 0 }
                            : { opacity: 0, y: 4, filter: "blur(6px)" }
                        }
                        animate={
                          reduce
                            ? { opacity: 1 }
                            : { opacity: 1, y: 0, filter: "blur(0px)" }
                        }
                        exit={
                          reduce
                            ? { opacity: 0 }
                            : {
                                opacity: 0,
                                y: -2,
                                filter: "blur(4px)",
                                transition: {
                                  duration: 0.12,
                                  ease: EASE_OUT,
                                },
                              }
                        }
                        transition={{
                          duration: reduce ? 0 : 0.18,
                          ease: EASE_OUT,
                        }}
                      >
                        {renderPreview ? (
                          renderPreview(item)
                        ) : (
                          <DefaultPreview item={item} />
                        )}
                      </motion.div>
                    </AnimatePresence>
                  </motion.div>
                </div>
              ) : null}
            </div>
          ))}
        </div>
      ) : null}

      {children ? (
        <div className="min-h-0 min-w-0 flex-1">{children}</div>
      ) : null}
    </motion.div>
  );
}