Stepper with color-coded bottom bars

"use client"

import { useRef, useState } from "react"
import { Frame, FramePanel } from "@/components/reui/frame"
import { IconStack } from "@/components/reui/icon-stack"
import {
  Stepper,
  StepperContent,
  StepperIndicator,
  StepperItem,
  StepperNav,
  StepperPanel,
  StepperTitle,
  StepperTrigger,
} from "@/components/reui/stepper"
import { cn } from "cn"

import { Button } from "@/components/ui/button"
import { IconPlaceholder } from "@/app/(create)/components/icon-placeholder"

const steps = [
  {
    title: "Company details",
    description: "Legal name and tax ID for your invoices.",
    color: "text-info",
    icon: (
      <IconPlaceholder
        lucide="Building2Icon"
        tabler="IconBuilding"
        hugeicons="Building03Icon"
        phosphor="BuildingsIcon"
        remixicon="RiBuilding2Line"
        className="size-4"
      />
    ),
  },
  {
    title: "Payment method",
    description: "The card charged at each renewal.",
    color: "text-warning",
    icon: (
      <IconPlaceholder
        lucide="CreditCardIcon"
        tabler="IconCreditCard"
        hugeicons="CreditCardIcon"
        phosphor="CreditCardIcon"
        remixicon="RiBankCardLine"
        className="size-4"
      />
    ),
  },
  {
    title: "Billing contact",
    description: "Who receives invoices and receipts.",
    // The theme has no blue token, so this step takes the palette color.
    color: "text-blue-500",
    icon: (
      <IconPlaceholder
        lucide="MailIcon"
        tabler="IconMail"
        hugeicons="Mail01Icon"
        phosphor="EnvelopeIcon"
        remixicon="RiMailLine"
        className="size-4"
      />
    ),
  },
  {
    title: "Review",
    description: "Confirm the plan and start billing.",
    color: "text-success",
    icon: (
      <IconPlaceholder
        lucide="ClipboardCheckIcon"
        tabler="IconClipboardCheck"
        hugeicons="TaskDone01Icon"
        phosphor="ClipboardTextIcon"
        remixicon="RiClipboardLine"
        className="size-4"
      />
    ),
  },
]

// The design's 3:1 dashed ring. pathLength counts the circle as 36 units, so
// the dashes close in nine even segments with no stub at the seam. Loading
// dims the track and lays a 39% arc over it, resting at the design's angle
// (11 to 4 o'clock) when motion is reduced.
function Ring({ spin = false }: { spin?: boolean }) {
  return (
    <svg
      viewBox="0 0 14 14"
      fill="none"
      stroke="currentColor"
      strokeWidth="1.4"
      aria-hidden="true"
      className="size-3.5"
    >
      <circle
        cx="7"
        cy="7"
        r="6"
        strokeDasharray="3 1"
        pathLength={36}
        strokeOpacity={spin ? 0.4 : 1}
      />
      {spin && (
        <circle
          cx="7"
          cy="7"
          r="6"
          strokeDasharray="39 61"
          strokeDashoffset={33}
          pathLength={100}
          className="origin-center motion-safe:animate-spin"
        />
      )}
    </svg>
  )
}

const indicators = {
  // The design draws the 14px ring with a 1.4px line: 2.4 on a 24-unit grid.
  completed: (
    <IconPlaceholder
      lucide="CircleCheckIcon"
      tabler="IconCircleCheck"
      hugeicons="CheckmarkCircle02Icon"
      phosphor="CheckCircleIcon"
      remixicon="RiCheckboxCircleLine"
      strokeWidth={2.4}
      className="size-3.5"
      aria-hidden="true"
    />
  ),
  inactive: <Ring />,
  loading: <Ring spin />,
}

export function Pattern() {
  const [current, setCurrent] = useState(2)
  const prevRef = useRef<HTMLButtonElement>(null)
  const nextRef = useRef<HTMLButtonElement>(null)
  // One past the last step marks every step complete. No tab is selected
  // then, so the last one keeps the tablist's tab stop.
  const allDone = current > steps.length

  function goTo(step: number) {
    setCurrent(step)
    // The pressed button disables itself at either end, so focus moves to
    // its partner.
    if (step === 1) nextRef.current?.focus()
    if (step > steps.length) prevRef.current?.focus()
  }

  return (
    <Stepper
      value={current}
      onValueChange={setCurrent}
      indicators={indicators}
      className="@container max-w-175"
      aria-label="Billing setup"
    >
      <Frame className="w-full" variant="ghost">
        <FramePanel>
          <StepperPanel className="pt-3">
            {steps.map((item, index) => (
              <StepperContent key={item.title} value={index + 1}>
                <div className="flex flex-col items-center text-center">
                  <IconStack aria-hidden="true" className="mb-2">
                    {item.icon}
                  </IconStack>
                  <p className="text-sm font-medium">{item.title}</p>
                  <p className="text-muted-foreground mt-0.5 text-sm text-balance">
                    {item.description}
                  </p>
                </div>
              </StepperContent>
            ))}
            <StepperContent value={steps.length + 1}>
              <div className="flex flex-col items-center text-center">
                <IconStack aria-hidden="true" className="mb-2">
                  <IconPlaceholder
                    lucide="CheckIcon"
                    tabler="IconCheck"
                    hugeicons="Tick02Icon"
                    phosphor="CheckIcon"
                    remixicon="RiCheckLine"
                    className="size-4"
                  />
                </IconStack>
                <p className="text-sm font-medium">Billing ready</p>
                <p className="text-muted-foreground mt-0.5 text-sm text-balance">
                  Invoices start with your next renewal.
                </p>
              </div>
            </StepperContent>
          </StepperPanel>

          <div className="mt-3 flex justify-center gap-2">
            <Button
              ref={prevRef}
              variant="outline"
              size="sm"
              disabled={current === 1}
              onClick={() => goTo(current - 1)}
            >
              Previous
            </Button>
            <Button
              ref={nextRef}
              variant="outline"
              size="sm"
              disabled={allDone}
              onClick={() => goTo(current + 1)}
            >
              Next
            </Button>
          </div>

          {/* Bleeds over the panel's side and bottom padding, so the bars sit
              flush with its edges and its overflow-hidden rounds the outer
              ends to its radius. */}
          <div className="-mx-(--frame-panel-px) mt-4 -mb-(--frame-panel-py) flex">
            <StepperNav>
              {steps.map((item, index) => {
                const step = index + 1
                const status =
                  step < current
                    ? ", completed"
                    : step === current
                      ? ", in progress"
                      : ""

                // Each step owns a color, which the bar and indicator take
                // through currentColor. Off the active step the title turns
                // muted and the indicator dims to 40%. Every step carries the
                // loading flag so the spinner follows the selection.
                return (
                  <StepperItem
                    key={item.title}
                    step={step}
                    loading
                    className="min-w-0 flex-1"
                  >
                    {/* The panel clips anything drawn past its edges, so the
                        focus ring is inset. */}
                    <StepperTrigger
                      tabIndex={
                        allDone && step === steps.length ? 0 : undefined
                      }
                      aria-label={`Step ${step}: ${item.title}${status}`}
                      className="min-w-0 flex-1 rounded-none focus-visible:ring-inset"
                    >
                      {/* 38px: 8px that keeps the ring off the label, the 14px
                          label row, a 12px gap and the 4px bar, so the active
                          bar grows into the gap and the row never moves. */}
                      <span
                        className={cn(
                          "flex h-9.5 min-w-0 flex-1 flex-col justify-between pt-2",
                          item.color
                        )}
                      >
                        <span className="flex items-center justify-between gap-1 px-3 whitespace-nowrap">
                          {/* Under 28rem a quarter row only fits the number;
                              the trigger's aria-label keeps the full name. */}
                          <StepperTitle className="text-current/60 data-[state=active]:text-current">
                            <span className="@max-md:hidden">Step </span>
                            {step}
                          </StepperTitle>
                          <StepperIndicator className="size-3.5 bg-transparent text-current opacity-40 data-[state=active]:bg-transparent data-[state=active]:text-current data-[state=active]:opacity-100 data-[state=completed]:bg-transparent data-[state=completed]:text-current" />
                        </span>

                        {/* The active bar doubles to 8px with rounded top
                            corners, capped at the panel radius so square
                            styles stay square. */}
                        <span
                          aria-hidden="true"
                          className="h-1 bg-current transition-all group-data-[state=active]/step:h-2 group-data-[state=active]/step:rounded-t-[min(calc(var(--radius-sm)-2px),var(--frame-panel-radius))]"
                        />
                      </span>
                    </StepperTrigger>
                  </StepperItem>
                )
              })}
            </StepperNav>
          </div>
        </FramePanel>
      </Frame>
    </Stepper>
  )
}