import { useRef, useState } from 'react';
import { Modal, ModalHeader, ModalBody, ModalFooter } from '@/components/ui/modal';
import { Button } from '@/components/ui/button';
import { Check, Copy, Download } from 'lucide-react';
import { toast } from '@/components/ui/toast-store';
import { apiFetch } from '@/lib/api';
import { copyToClipboard } from '@/lib/clipboard';
import { TOTP_LENGTH, normalizeTotpInput } from '@/lib/mfa';
import { OtpDigitField } from '@/components/auth/OtpDigitField';
import { ErrorRail } from '@/components/auth/ErrorRail';
import { BackupCodeTicket } from './BackupCodeTicket';

interface MfaBackupCodesDialogProps {
  open: boolean;
  onOpenChange: (open: boolean) => void;
  onRegenerated: () => void;
}

type Step = 'confirm' | 'show';

export function MfaBackupCodesDialog({ open, onOpenChange, onRegenerated }: MfaBackupCodesDialogProps) {
  const [step, setStep] = useState<Step>('confirm');
  const [code, setCode] = useState('');
  const [error, setError] = useState('');
  const [loading, setLoading] = useState(false);
  const [confirmState, setConfirmState] = useState<'idle' | 'loading' | 'error' | 'success'>('idle');
  const [backupCodes, setBackupCodes] = useState<string[]>([]);
  const submittedRef = useRef(false);

  const resetState = () => {
    setStep('confirm');
    setCode('');
    setError('');
    setConfirmState('idle');
    setBackupCodes([]);
    submittedRef.current = false;
  };

  const submitRegenerate = async (valueToSubmit: string) => {
    setError('');
    setConfirmState('loading');
    setLoading(true);
    try {
      const res = await apiFetch('/auth/mfa/backup-codes/regenerate', {
        method: 'POST',
        localOnly: true,
        body: JSON.stringify({ code: valueToSubmit }),
      });
      const data = await res.json().catch(() => ({}));
      if (!res.ok) {
        setError(data?.error || 'Could not regenerate backup codes');
        setCode('');
        setConfirmState('error');
        submittedRef.current = false;
        window.setTimeout(() => setConfirmState('idle'), 600);
        return;
      }
      setBackupCodes(data.backupCodes || []);
      setConfirmState('success');
      setStep('show');
    } catch (err) {
      setError((err as Error)?.message || 'Could not regenerate backup codes');
      setConfirmState('error');
      submittedRef.current = false;
    } finally {
      setLoading(false);
    }
  };

  const handleCodeChange = (raw: string) => {
    const normalized = normalizeTotpInput(raw);
    setCode(normalized);
    if (normalized.length < TOTP_LENGTH) {
      submittedRef.current = false;
      if (confirmState === 'error') setConfirmState('idle');
    }
    if (
      normalized.length === TOTP_LENGTH &&
      !loading &&
      !submittedRef.current
    ) {
      submittedRef.current = true;
      requestAnimationFrame(() => { void submitRegenerate(normalized); });
    }
  };

  const handleCopy = async () => {
    try {
      await copyToClipboard(backupCodes.join('\n'));
      toast.success('Backup codes copied');
    } catch {
      toast.error('Could not copy to clipboard');
    }
  };

  const handleDownload = () => {
    const blob = new Blob([
      'Sencho backup codes\n',
      'Each code can be used once. Keep this file somewhere safe.\n\n',
      backupCodes.join('\n'),
      '\n',
    ], { type: 'text/plain' });
    const url = URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.href = url;
    a.download = 'sencho-backup-codes.txt';
    a.click();
    URL.revokeObjectURL(url);
  };

  const handleFinish = () => {
    resetState();
    onOpenChange(false);
    onRegenerated();
  };

  return (
    <Modal
      size="md"
      open={open}
      onOpenChange={(next) => {
        if (!next) {
          if (step === 'show') onRegenerated();
          resetState();
        }
        onOpenChange(next);
      }}
    >
      <ModalHeader
        kicker="SECURITY · BACKUP CODES"
        title={step === 'confirm' ? 'Confirm identity' : 'New recovery codes'}
        description="Replace your backup codes with a freshly generated set. The previous set stops working immediately."
      />

      {step === 'confirm' && (
        <>
          <ModalBody>
            <p className="text-sm leading-snug text-stat-subtitle">
              Enter a code from your authenticator to generate a new set. The previous codes stop working immediately.
            </p>
            <OtpDigitField
              id="mfa-regen-code"
              value={code}
              onChange={handleCodeChange}
              state={confirmState}
              disabled={loading || confirmState === 'success'}
              autoFocus
            />
            {error && <ErrorRail>{error}</ErrorRail>}
          </ModalBody>
          <ModalFooter
            secondary={
              <Button type="button" variant="ghost" onClick={() => onOpenChange(false)} disabled={loading}>
                Cancel
              </Button>
            }
            primary={null}
          />
        </>
      )}

      {step === 'show' && (
        <>
          <ModalBody>
            <WarningRail>Previous codes have been invalidated.</WarningRail>
            <p className="text-sm leading-snug text-stat-subtitle">
              Each code can be used once. Store them safely. They will not be shown again.
            </p>
            <BackupCodeTicket codes={backupCodes} />
            <div className="flex gap-2">
              <Button type="button" variant="outline" className="flex-1" onClick={handleCopy}>
                <Copy className="h-4 w-4" strokeWidth={1.5} />
                Copy all
              </Button>
              <Button type="button" variant="outline" className="flex-1" onClick={handleDownload}>
                <Download className="h-4 w-4" strokeWidth={1.5} />
                Download
              </Button>
            </div>
          </ModalBody>
          <ModalFooter
            primary={
              <Button
                type="button"
                onClick={handleFinish}
                className="bg-brand text-brand-foreground shadow-btn-glow hover:bg-brand/90"
              >
                <Check strokeWidth={1.5} />
                Done
              </Button>
            }
          />
        </>
      )}
    </Modal>
  );
}

function WarningRail({ children }: { children: React.ReactNode }) {
  return (
    <div className="relative overflow-hidden rounded-md border border-warning/30 bg-warning/8 pl-4 pr-3 py-2">
      <span className="absolute inset-y-0 left-0 w-[3px] bg-warning/70" aria-hidden />
      <div className="font-mono text-[10px] uppercase tracking-[0.18em] text-warning">
        {children}
      </div>
    </div>
  );
}