Switcher

:root {
  --size-control-sm: 2rem;
  --size-control-md: 2.25rem;
  --size-control-lg: 2.5rem;
  --size-icon-sm: 0.875rem;
  --size-icon-md: 1rem;
  --size-icon-lg: 1.25rem;
  --size-roll-fade: 0.25em;
  --size-roll-fade-x: 0.5em;
  --duration-instant: 80ms;
  --duration-fast: 150ms;
  --duration-base: 220ms;
  --duration-slow: 350ms;
  --duration-slower: 500ms;
  --z-overlay: 1200;
  --z-modal: 1300;
  --z-popover: 1400;
  --z-toast: 1500;
  --z-tooltip: 1600;
  --focus-ring-width: 2px;
  --focus-ring-offset: 2px;
  --opacity-disabled: 0.5;
  --ease-spring: linear(0, 0.157, 0.48, 0.77, 0.97, 1.07, 1.1, 1.09, 1.05, 1.02, 1, 0.995, 1);
  --destructive-foreground: oklch(1 0 0);
  --overlay: color-mix(in oklch, oklch(0 0 0) 40%, transparent);
}

.dark {
  --destructive-foreground: oklch(1 0 0);
  --overlay: color-mix(in oklch, oklch(0 0 0) 60%, transparent);
}

@theme inline {
  --animate-popover-in: popover-in var(--duration-fast) cubic-bezier(0.22, 1, 0.36, 1) both;
  --animate-popover-out: popover-out var(--duration-instant) cubic-bezier(0.55, 0, 1, 0.45) both;
  --animate-collapsible-open: collapsible-open var(--duration-slow) cubic-bezier(0.22, 1, 0.36, 1);
  --animate-collapsible-close: collapsible-close var(--duration-base) cubic-bezier(0.55, 0, 1, 0.45) both;
  --color-destructive-foreground: var(--destructive-foreground);
  --color-overlay: var(--overlay);
  @keyframes popover-in {
    from {
      opacity: 0;
      filter: blur(6px);
      transform: scale(0.96);
    }
    to {
      opacity: 1;
      filter: blur(0);
      transform: scale(1);
    }
  }
  @keyframes popover-out {
    from {
      opacity: 1;
      filter: blur(0);
      transform: scale(1);
    }
    to {
      opacity: 0;
      filter: blur(6px);
      transform: scale(0.96);
    }
  }
  @keyframes collapsible-open {
    from {
      height: 0;
      opacity: 0;
      filter: blur(6px);
    }
    to {
      height: var(--collapsible-height);
      opacity: 1;
      filter: blur(0);
    }
  }
  @keyframes collapsible-close {
    from {
      height: var(--collapsible-height);
      opacity: 1;
      filter: blur(0);
    }
    to {
      height: 0;
      opacity: 0;
      filter: blur(6px);
    }
  }
}

@media (prefers-reduced-motion: reduce) {
  :root {
    --duration-instant: 1ms;
    --duration-fast: 1ms;
    --duration-base: 1ms;
    --duration-slow: 1ms;
    --duration-slower: 1ms;
  }
}

import type { Transition } from "motion/react";

/*
 * Motion tokens for JavaScript animations (motion/react).
 * Durations and easings mirror the CSS tokens in src/styles/tokens.css;
 * `pnpm check:tokens` fails if the two drift apart.
 */

/** Durations in seconds. Mirrors --duration-* in tokens.css. */
export const duration = {
  instant: 0.08,
  fast: 0.15,
  base: 0.22,
  slow: 0.35,
  slower: 0.5,
} as const;

/** Cubic-bezier easings. Mirrors --ease-* in tokens.css. */
export const ease = {
  out: [0.22, 1, 0.36, 1],
  in: [0.55, 0, 1, 0.45],
  inOut: [0.65, 0, 0.35, 1],
} as const;

/**
 * Named springs: the library's motion voice.
 * - snappy: quick, almost no overshoot. Toggles, tabs, small controls.
 * - smooth: slow and settled. Panels, sidebars, page sections.
 * - bouncy: playful overshoot. Rare, for moments of delight.
 */
export const spring = {
  snappy: { type: "spring", stiffness: 520, damping: 38, mass: 1 },
  smooth: { type: "spring", stiffness: 120, damping: 20, mass: 1 },
  bouncy: { type: "spring", stiffness: 300, damping: 15, mass: 1 },
} as const satisfies Record<string, Transition>;

export type SpringName = keyof typeof spring;

/**
 * The blur (owner, 2026-10-15): content that appears, leaves or swaps sharpens in from a 6px blur as it
 * fades, instead of only fading. Pair it with the movement the pattern already has. Not for fills,
 * highlights, hover or anything full-screen (those still fade), and with reduced motion it's opacity only.
 * The CSS keyframes in tokens.css use the same 6px (checked by `pnpm check:tokens`).
 */
export const blur = { hidden: "blur(6px)", shown: "blur(0px)" } as const;

/** Swapping content in place (Loading Button, Copy Button): the new rises 6px from blurred; the old lifts away blurring */
export const swap = {
  initial: { opacity: 0, filter: blur.hidden, y: 6 },
  animate: { opacity: 1, filter: blur.shown, y: 0 },
  exit: { opacity: 0, filter: blur.hidden, y: -6 },
} as const;

/**
 * The flow of a changing number (Number Ticker): a spring for the characters' moves, the width and the digits'
 * spin, sampled into CSS linear(), and a fade for characters coming and going. Web Animations timings, in
 * milliseconds. The curve is from number-flow, © 2024 Maxwell Barvian, MIT licence (its full notice is in
 * components/number-ticker/number-ticker.tsx).
 */
export const flow = {
  transform: {
    duration: 900,
    easing:
      "linear(0,.005,.019,.039,.066,.096,.129,.165,.202,.24,.278,.316,.354,.39,.426,.461,.494,.526,.557,.586,.614,.64,.665,.689,.711,.731,.751,.769,.786,.802,.817,.831,.844,.856,.867,.877,.887,.896,.904,.912,.919,.925,.931,.937,.942,.947,.951,.955,.959,.962,.965,.968,.971,.973,.976,.978,.98,.981,.983,.984,.986,.987,.988,.989,.99,.991,.992,.992,.993,.994,.994,.995,.995,.996,.996,.9963,.9967,.9969,.9972,.9975,.9977,.9979,.9981,.9982,.9984,.9985,.9987,.9988,.9989,1)",
  },
  opacity: { duration: 450, easing: "ease-out" },
} as const satisfies Record<string, EffectTiming>;

"use client";

import { spring } from "@/lib/motion";
import { cn } from "@/lib/utils";
import { cva, type VariantProps } from "class-variance-authority";
import { LayoutGroup, motion, useReducedMotion } from "motion/react";
import { ToggleGroup as ToggleGroupPrimitive } from "radix-ui";
import {
  type ComponentProps,
  createContext,
  type Ref,
  useContext,
  useId,
  useLayoutEffect,
  useRef,
  useState,
} from "react";

/*
 * Switcher: one choice from a few, like Day / Week / Month (a segmented control). Owner, 2026-10-14: split
 * from Toggle Group, which switches several options on and off; Lab only until it's approved, so no meta
 * yet.
 * - A pill slides to the active option (layoutId on spring.snappy, .agents/rules/motion.md), scoped to each
 *   Switcher, so two never trade a pill.
 * - There's always a choice: clicking the active option keeps it.
 * - A radiogroup of radio items (Radix Toggle Group, single). Arrow keys move between options; Home and End
 *   jump to the ends.
 * - Flat. The pill takes the page's own colour, dark in dark mode and light in light mode (owner,
 *   2026-10-14). Default: a muted track. Outline: a bordered track, and the pill gets a hairline too, so it
 *   shows on any surface. No shadows and no
 *   scale. Inactive options are muted and brighten on hover.
 * - The pill's corners follow the option's own radius (read from it), so they stay true while it changes
 *   width between options of different sizes.
 */

const switcherVariants = cva("relative isolate inline-flex w-fit items-center gap-0.5 rounded-lg p-0.5", {
  variants: {
    variant: {
      default: "bg-muted",
      outline: "border border-input",
    },
  },
  defaultVariants: { variant: "default" },
});

// The options sit 2px inside the track, so the track is a control height (32, 36 or 40px)
const switcherItemVariants = cva(
  [
    "relative inline-flex shrink-0 cursor-pointer items-center justify-center gap-1.5 rounded-md text-sm font-medium whitespace-nowrap",
    "text-muted-foreground transition-colors duration-(--duration-base) ease-out data-[state=off]:hover:text-foreground data-[state=on]:text-foreground",
    "outline-ring focus-visible:outline-(length:--focus-ring-width) focus-visible:outline-offset-(--focus-ring-offset)",
    "disabled:pointer-events-none disabled:opacity-(--opacity-disabled)",
    "[&_svg]:pointer-events-none [&_svg]:shrink-0 [&_svg:not([class*='size-'])]:size-(--size-icon-md)",
  ],
  {
    variants: {
      size: {
        sm: "h-7 px-2.5",
        md: "h-8 px-3",
        lg: "h-9 px-4",
      },
    },
    defaultVariants: { size: "md" },
  },
);

const SwitcherContext = createContext<{
  value: string;
  variant: "default" | "outline";
  size: "sm" | "md" | "lg";
  reduce: boolean;
} | null>(null);

type RootProps = Omit<
  Extract<ComponentProps<typeof ToggleGroupPrimitive.Root>, { type: "single" }>,
  "type" | "value" | "defaultValue" | "onValueChange"
>;

export type SwitcherProps = RootProps &
  VariantProps<typeof switcherVariants> &
  VariantProps<typeof switcherItemVariants> & {
    /** The chosen option, when you control it */
    value?: string;
    /** The option chosen at first */
    defaultValue?: string;
    /** Called with the new option when the choice changes */
    onValueChange?: (value: string) => void;
  };

function Switcher({
  value,
  defaultValue,
  onValueChange,
  variant,
  size,
  className,
  children,
  ...props
}: SwitcherProps) {
  const groupId = useId();
  const reduce = useReducedMotion() ?? false;
  // Mirror the value, controlled or not, so options know whether they're on
  const [internal, setInternal] = useState(defaultValue ?? "");
  const current = value ?? internal;

  return (
    <SwitcherContext.Provider
      value={{ value: current, variant: variant ?? "default", size: size ?? "md", reduce }}
    >
      <ToggleGroupPrimitive.Root
        data-slot="switcher"
        data-variant={variant ?? "default"}
        type="single"
        value={current}
        onValueChange={(next) => {
          // There's always a choice: Radix sends "" when the active option is clicked again
          if (!next) return;
          setInternal(next);
          onValueChange?.(next);
        }}
        className={cn(switcherVariants({ variant }), className)}
        {...props}
      >
        <LayoutGroup id={groupId}>{children}</LayoutGroup>
      </ToggleGroupPrimitive.Root>
    </SwitcherContext.Provider>
  );
}

/** Hands the option's node to our ref and to the caller's */
function useMergedRef<T>(own: { current: T | null }, theirs?: Ref<T>) {
  return (node: T | null) => {
    own.current = node;
    if (typeof theirs === "function") theirs(node);
    else if (theirs) (theirs as { current: T | null }).current = node;
  };
}

function SwitcherItem({
  className,
  children,
  value,
  ref,
  ...props
}: ComponentProps<typeof ToggleGroupPrimitive.Item>) {
  const switcher = useContext(SwitcherContext);
  const node = useRef<HTMLButtonElement>(null);
  const setRef = useMergedRef(node, ref);
  const [radius, setRadius] = useState(0);

  // A numeric radius lets motion keep the pill's corners true while it changes width
  useLayoutEffect(() => {
    if (node.current) setRadius(Number.parseFloat(getComputedStyle(node.current).borderTopLeftRadius) || 0);
  }, []);

  return (
    <ToggleGroupPrimitive.Item
      ref={setRef}
      data-slot="switcher-item"
      value={value}
      className={cn(switcherItemVariants({ size: switcher?.size }), className)}
      {...props}
    >
      {switcher?.value === value ? (
        // Options aren't stacking contexts: the pill joins the Switcher's layer (it's `isolate`), so it passes
        // behind every option's label as it slides
        <motion.span
          layoutId="switcher-pill"
          aria-hidden
          className={cn(
            "absolute inset-0 -z-10",
            switcher.variant === "outline" ? "border border-input bg-background" : "bg-background",
          )}
          style={{ borderRadius: radius }}
          transition={switcher.reduce ? { duration: 0 } : spring.snappy}
        />
      ) : null}
      {children}
    </ToggleGroupPrimitive.Item>
  );
}

export { Switcher, SwitcherItem, switcherItemVariants, switcherVariants };