import React, { useState, useEffect, useCallback } from 'react';

function Section({ title, children }: { title: string; children: React.ReactNode }) {
  return (
    <div className="mb-8">
      <h3 className="text-sm font-bold text-[var(--flux-heading)] mb-3">{title}</h3>
      <div className="rounded border border-[var(--flux-grey-100)] bg-[var(--flux-surface)] overflow-hidden">
        {children}
      </div>
    </div>
  );
}

const shimmerStyle: React.CSSProperties = {
  background:
    'linear-gradient(90deg, var(--flux-grey-100) 25%, var(--flux-grey-50, #f9fafb) 50%, var(--flux-grey-100) 75%)',
  backgroundSize: '200% 100%',
  animation: 'shimmer 1.5s infinite',
};

function Skeleton({ className }: { className: string }) {
  return <div className={className} style={shimmerStyle} />;
}

function KaptioMark({ size = 32 }: { size?: number }) {
  return (
    <svg width={size} height={size} viewBox="0 0 24 24" fill="none">
      <circle cx="12" cy="12" r="10" stroke="var(--flux-primary-400)" strokeWidth="1.5" />
      <circle cx="12" cy="12" r="3" fill="var(--flux-primary-400)" />
    </svg>
  );
}

function SkeletonHeader() {
  return (
    <div
      className="flex items-center justify-between px-4"
      style={{
        height: 'var(--flux-flow-header-height, 3rem)',
        backgroundColor: 'var(--flux-flow-header-bg, #F5F5F5)',
        borderBottom: '1px solid var(--flux-flow-header-border, #EBEBEB)',
      }}
    >
      <div className="flex items-center gap-2.5">
        <Skeleton className="w-5 h-5 rounded-full" />
        <Skeleton className="h-3 w-48 rounded" />
      </div>
      <Skeleton className="h-3 w-20 rounded" />
    </div>
  );
}

function LoadingState({ message, variant = 'document' }: { message: string; variant?: 'document' | 'payment' | 'preferences' }) {
  return (
    <div>
      <SkeletonHeader />
      <div className="p-6">
        <div className="flex items-center gap-3 mb-6">
          <KaptioMark size={28} />
          <p className="text-sm text-[var(--flux-grey-500)]">{message}</p>
        </div>

        {variant === 'document' && (
          <div className="space-y-4 max-w-lg">
            <Skeleton className="h-6 w-3/4 rounded" />
            <Skeleton className="h-3 w-full rounded" />
            <Skeleton className="h-3 w-5/6 rounded" />
            <Skeleton className="h-3 w-2/3 rounded" />
            <div className="pt-4 flex gap-3">
              <Skeleton className="h-40 w-1/2 rounded" />
              <Skeleton className="h-40 w-1/2 rounded" />
            </div>
          </div>
        )}

        {variant === 'payment' && (
          <div className="space-y-4 max-w-sm">
            <Skeleton className="h-5 w-1/2 rounded" />
            <div className="space-y-3 pt-2">
              <Skeleton className="h-10 w-full rounded" />
              <Skeleton className="h-10 w-full rounded" />
              <div className="flex gap-3">
                <Skeleton className="h-10 w-1/2 rounded" />
                <Skeleton className="h-10 w-1/2 rounded" />
              </div>
            </div>
            <Skeleton className="h-11 w-full rounded mt-2" />
          </div>
        )}

        {variant === 'preferences' && (
          <div className="space-y-4 max-w-md">
            <Skeleton className="h-5 w-2/5 rounded" />
            <div className="space-y-3">
              {[1, 2, 3].map((i) => (
                <div key={i} className="flex items-center gap-3">
                  <Skeleton className="w-10 h-10 rounded-full shrink-0" />
                  <div className="flex-1 space-y-2">
                    <Skeleton className="h-3 w-3/4 rounded" />
                    <Skeleton className="h-3 w-1/2 rounded" />
                  </div>
                </div>
              ))}
            </div>
          </div>
        )}
      </div>
    </div>
  );
}

function ErrorState({ message, detail }: { message: string; detail: string }) {
  return (
    <div className="flex flex-col items-center justify-center py-16 gap-4 text-center px-6">
      <div className="w-12 h-12 rounded-full bg-[color:var(--flux-orange-100)] flex items-center justify-center">
        <svg width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="var(--flux-orange-400)" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round">
          <circle cx="12" cy="12" r="10" />
          <line x1="12" y1="8" x2="12" y2="12" />
          <line x1="12" y1="16" x2="12.01" y2="16" />
        </svg>
      </div>
      <div>
        <p className="text-sm font-bold text-[var(--flux-heading)] mb-1">{message}</p>
        <p className="text-xs text-[var(--flux-grey-500)]">{detail}</p>
      </div>
      <button className="mt-2 px-4 py-2 text-sm font-bold rounded bg-[var(--flux-primary-400)] text-white hover:opacity-90 transition-opacity">
        Go Back
      </button>
    </div>
  );
}

function ResolvedState() {
  return (
    <div
      className="flex flex-col items-center justify-center py-16 gap-2"
      style={{
        animation: 'fadeIn var(--flux-flow-entry-duration, 300ms) var(--flux-ease, ease) forwards',
      }}
    >
      <div className="w-10 h-10 rounded-full bg-[color:var(--flux-green-100)] flex items-center justify-center">
        <svg width="20" height="20" viewBox="0 0 20 20" fill="none" stroke="var(--flux-green-400)" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round">
          <polyline points="16 6 8 14 4 10" />
        </svg>
      </div>
      <p className="text-sm text-[var(--flux-grey-500)]">Ready</p>
    </div>
  );
}

type DemoState = 'loading' | 'resolved' | 'error';

function InteractiveDemo() {
  const [state, setState] = useState<DemoState>('loading');

  const cycle = useCallback(() => {
    setState('loading');
    const t1 = setTimeout(() => setState('resolved'), 2500);
    const t2 = setTimeout(() => setState('loading'), 4500);
    return () => { clearTimeout(t1); clearTimeout(t2); };
  }, []);

  useEffect(() => {
    const cleanup = cycle();
    return cleanup;
  }, [cycle]);

  return (
    <div>
      <div className="flex gap-2 p-3 border-b border-[var(--flux-grey-100)]">
        {(['loading', 'resolved', 'error'] as const).map((s) => (
          <button
            key={s}
            onClick={() => setState(s)}
            className={`px-3 py-1 text-xs font-bold rounded transition-colors capitalize ${
              state === s
                ? 'bg-[var(--flux-primary-400)] text-white'
                : 'text-[var(--flux-grey-500)] hover:bg-[var(--flux-grey-100)]'
            }`}
          >
            {s === 'loading' ? 'Arriving' : s === 'resolved' ? 'Ready' : 'Error'}
          </button>
        ))}
      </div>
      {state === 'loading' && <LoadingState message="Opening your proposal..." variant="document" />}
      {state === 'resolved' && <ResolvedState />}
      {state === 'error' && (
        <ErrorState
          message="This link has expired"
          detail="Please go back to your booking and try again."
        />
      )}
    </div>
  );
}

export default function FlowEntryDemo() {
  return (
    <div>
      <style>{`
        @keyframes shimmer {
          0% { background-position: -200% 0; }
          100% { background-position: 200% 0; }
        }
        @keyframes fadeIn {
          from { opacity: 0; transform: translateY(8px); }
          to { opacity: 1; transform: translateY(0); }
        }
      `}</style>

      <Section title="Interactive (cycles through states)">
        <InteractiveDemo />
      </Section>

      <Section title="Document editor (skeleton)">
        <LoadingState message="Opening your proposal..." variant="document" />
      </Section>

      <Section title="Payment form (skeleton)">
        <LoadingState message="Preparing payment..." variant="payment" />
      </Section>

      <Section title="Preferences (skeleton)">
        <LoadingState message="Loading preferences..." variant="preferences" />
      </Section>

      <Section title="Error state (expired)">
        <ErrorState
          message="This link has expired"
          detail="Please go back to your booking and try again."
        />
      </Section>

      <Section title="Error state (generic)">
        <ErrorState
          message="Something went wrong"
          detail="Please close this and try again from your booking."
        />
      </Section>
    </div>
  );
}