Message Scroller

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

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

// 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;

"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-scroller

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>
  );
}

"use client";

import { Bot, User } from "lucide-react";
import { useReducedMotion } from "motion/react";
import { useCallback, useEffect, useRef, useState } from "react";
import {
  Message,
  MessageAvatar,
  MessageContent,
  MessageFooter,
  MessageGroup,
  MessageHeader,
  MessageTyping,
} from "@/components/agents/message";
import {
  MessageBubble,
  MessageBubbleContent,
  type MessageBubbleVariant,
} from "@/components/agents/message-bubble";
import { MessageScroller } from "@/components/agents/message-scroller";
import { PromptInput } from "@/components/agents/prompt-input";
import { StreamingResponse } from "@/components/agents/streaming-response";
import { cn } from "@/lib/utils";

export interface ChatPreviewMessage {
  id: string;
  from: "user" | "assistant";
  content: string;
}

interface RenderedChatMessage extends ChatPreviewMessage {
  animateIn: boolean;
  streaming?: boolean;
}

export interface ChatPreviewProps {
  initialMessages?: ChatPreviewMessage[];
  reply?: string | ((prompt: string) => string);
  showAvatars?: boolean;
  showMetadata?: boolean;
  showRail?: boolean;
  assistantVariant?: MessageBubbleVariant;
  userVariant?: MessageBubbleVariant;
  placeholder?: string;
  className?: string;
  viewportClassName?: string;
}

const DEFAULT_MESSAGES: ChatPreviewMessage[] = [
  {
    id: "welcome-question",
    from: "user",
    content: "What should we include in the first release?",
  },
  {
    id: "welcome-answer",
    from: "assistant",
    content: "Start with the smallest workflow that still feels complete.",
  },
];

const DEFAULT_REPLY =
  "I’d include composing a prompt, following a streamed answer, recovering from an error, and returning to the latest response without losing the reader’s place.";
const CHARACTERS_PER_SECOND = 96;
const STREAM_DELAY = 140;

export function ChatPreview({
  initialMessages = DEFAULT_MESSAGES,
  reply = DEFAULT_REPLY,
  showAvatars = false,
  showMetadata = false,
  showRail = false,
  assistantVariant = "soft",
  userVariant = "solid",
  placeholder = "Send a message…",
  className,
  viewportClassName,
}: ChatPreviewProps) {
  const reduce = useReducedMotion() ?? false;
  const nextId = useRef(0);
  const replyTimer = useRef<number | undefined>(undefined);
  const [messages, setMessages] = useState<RenderedChatMessage[]>(() =>
    initialMessages.map((message) => ({ ...message, animateIn: false })),
  );
  const [pending, setPending] = useState(false);
  const [activeReply, setActiveReply] = useState<{
    id: string;
    content: string;
  } | null>(null);
  const loading = pending || activeReply !== null;

  useEffect(() => {
    if (!activeReply) return;

    if (reduce) {
      setMessages((current) =>
        current.map((message) =>
          message.id === activeReply.id
            ? { ...message, content: activeReply.content, streaming: false }
            : message,
        ),
      );
      setActiveReply(null);
      return;
    }

    const startedAt = performance.now() + STREAM_DELAY;
    let frame = 0;
    const stream = (now: number) => {
      const cursor = Math.min(
        activeReply.content.length,
        Math.floor(
          (Math.max(0, now - startedAt) / 1000) * CHARACTERS_PER_SECOND,
        ),
      );
      const content = activeReply.content.slice(0, cursor);
      setMessages((current) =>
        current.map((message) =>
          message.id === activeReply.id && message.content !== content
            ? { ...message, content }
            : message,
        ),
      );

      if (cursor < activeReply.content.length) {
        frame = requestAnimationFrame(stream);
      } else {
        setMessages((current) =>
          current.map((message) =>
            message.id === activeReply.id
              ? { ...message, streaming: false }
              : message,
          ),
        );
        setActiveReply(null);
      }
    };

    frame = requestAnimationFrame(stream);
    return () => cancelAnimationFrame(frame);
  }, [activeReply, reduce]);

  useEffect(
    () => () => {
      if (replyTimer.current) window.clearTimeout(replyTimer.current);
    },
    [],
  );

  const submit = useCallback(
    (prompt: string) => {
      if (loading) return;

      const run = nextId.current++;
      const userId = `sent-user-${run}`;
      const assistantId = `sent-assistant-${run}`;
      const response = typeof reply === "function" ? reply(prompt) : reply;

      setMessages((current) => [
        ...current,
        { id: userId, from: "user", content: prompt, animateIn: true },
      ]);
      setPending(true);

      replyTimer.current = window.setTimeout(() => {
        setMessages((current) => [
          ...current,
          {
            id: assistantId,
            from: "assistant",
            content: "",
            animateIn: true,
            streaming: true,
          },
        ]);
        setPending(false);
        setActiveReply({ id: assistantId, content: response });
      }, reduce ? 0 : 420);
    },
    [loading, reduce, reply],
  );

  const stop = useCallback(() => {
    if (replyTimer.current) window.clearTimeout(replyTimer.current);
    replyTimer.current = undefined;
    setPending(false);
    setMessages((current) =>
      current.map((message) =>
        message.streaming ? { ...message, streaming: false } : message,
      ),
    );
    setActiveReply(null);
  }, []);

  return (
    <div
      className={cn(
        "flex h-[440px] w-full max-w-xl flex-col overflow-hidden rounded-2xl border border-border/70 bg-background",
        className,
      )}
    >
      <MessageScroller
        busy={loading}
        navigation={showRail ? "rail" : undefined}
        className="min-h-0 flex-1"
        viewportClassName={cn("px-3 py-4", viewportClassName)}
        contentClassName="min-h-full"
      >
        <MessageGroup spacing="default">
          {messages.map((message) => (
            <Message
              key={message.id}
              id={message.id}
              from={message.from}
              animateIn={message.from === "user" && message.animateIn}
            >
              {showAvatars ? (
                <MessageAvatar>
                  {message.from === "user" ? <User /> : <Bot />}
                </MessageAvatar>
              ) : null}
              <MessageContent>
                {showMetadata ? (
                  <MessageHeader>
                    <span className="font-medium text-foreground/70">
                      {message.from === "user" ? "You" : "Assistant"}
                    </span>
                    <span>{message.streaming ? "Responding" : "Now"}</span>
                  </MessageHeader>
                ) : null}
                <MessageBubble
                  variant={
                    message.from === "user" ? userVariant : assistantVariant
                  }
                  animateIn={false}
                >
                  <MessageBubbleContent>
                    {message.from === "assistant" ? (
                      <StreamingResponse
                        status={message.streaming ? "streaming" : "complete"}
                        showActions={false}
                        announce={false}
                      >
                        {message.content || <MessageTyping />}
                      </StreamingResponse>
                    ) : (
                      message.content
                    )}
                  </MessageBubbleContent>
                </MessageBubble>
                {showMetadata && message.from === "user" ? (
                  <MessageFooter>Sent</MessageFooter>
                ) : null}
              </MessageContent>
            </Message>
          ))}
          {pending ? (
            <Message id="pending-assistant" from="assistant">
              {showAvatars ? (
                <MessageAvatar>
                  <Bot />
                </MessageAvatar>
              ) : null}
              <MessageContent>
                <MessageTyping label="Preparing response" />
              </MessageContent>
            </Message>
          ) : null}
        </MessageGroup>
      </MessageScroller>

      <div className="shrink-0 border-t border-border/60 p-2">
        <PromptInput
          minRows={1}
          maxRows={1}
          loading={loading}
          onSubmit={submit}
          onStop={stop}
          placeholder={placeholder}
          className="border-0 bg-muted shadow-none focus-within:border-transparent"
        />
      </div>
    </div>
  );
}