import React, { useState, useEffect } from 'react';
import { toast } from 'sonner';
import { api } from '@/api';
import { Button } from '@/components/ui/button';
import { Badge } from '@/components/ui/badge';
import { Label } from '@/components/ui/label';
import { Card, CardHeader, CardTitle, CardContent } from '@/components/ui/card';
import {
  Select, SelectTrigger, SelectValue, SelectContent, SelectItem,
} from '@/components/ui/select';
import {
  AlertDialog, AlertDialogContent, AlertDialogHeader, AlertDialogTitle,
  AlertDialogDescription, AlertDialogFooter, AlertDialogCancel, AlertDialogAction,
} from '@/components/ui/alert-dialog';
import { LogIn, UserCheck, ShieldCheck } from 'lucide-react';

export default function LoginModeCard({ users, onModeChange }) {
  const [modeData, setModeData]         = useState(null);
  const [loading, setLoading]           = useState(true);
  const [loadError, setLoadError]       = useState('');
  const [saving, setSaving]             = useState(false);
  const [selected, setSelected]         = useState('multi'); // local UI selection
  const [selectedUser, setSelectedUser] = useState('');
  const [confirmSingle, setConfirmSingle] = useState(false);

  useEffect(() => {
    api.authModeConfig()
      .then(d => {
        setModeData(d);
        const mode = d.auth_mode === 'single' ? 'single' : 'multi';
        setSelected(mode);
        setSelectedUser(d.default_user_id?.toString() || '');
        onModeChange?.(mode);
      })
      .catch(err => setLoadError(err.message || 'Failed to load login mode config'))
      .finally(() => setLoading(false));
  }, []); // eslint-disable-line

  const doSetMode = async (mode, userId) => {
    setSaving(true);
    try {
      await api.setAuthMode({
        auth_mode: mode,
        default_user_id: mode === 'single' ? parseInt(userId, 10) : null,
      });
      const d = await api.authModeConfig();
      setModeData(d);
      const resolved = d.auth_mode === 'single' ? 'single' : 'multi';
      setSelected(resolved);
      setSelectedUser(d.default_user_id?.toString() || '');
      onModeChange?.(resolved);
      toast.success(mode === 'single' ? 'No Login mode enabled.' : 'Login requirement restored.');
    } catch (err) {
      toast.error(err.message || 'Failed to update login mode.');
      // revert UI selection on error
      setSelected(modeData?.auth_mode === 'single' ? 'single' : 'multi');
    } finally {
      setSaving(false);
    }
  };

  const handleSave = () => {
    if (selected === 'single') {
      if (!selectedUser) { toast.error('Select a user account first.'); return; }
      setConfirmSingle(true);
    } else {
      doSetMode('multi', null);
    }
  };

  if (loading)   return <Card><CardContent className="py-8 text-center text-muted-foreground text-sm">Loading…</CardContent></Card>;
  if (loadError) return <Card><CardContent className="py-8 text-center text-sm text-destructive">{loadError}</CardContent></Card>;

  const currentMode    = modeData?.auth_mode === 'single' ? 'single' : 'multi';
  const isDirty        = selected !== currentMode || (selected === 'single' && selectedUser !== (modeData?.default_user_id?.toString() || ''));
  const activeUser     = users?.find(u => u.id === modeData?.default_user_id);
  const pendingUsername = users?.find(u => u.id.toString() === selectedUser)?.username ?? selectedUser;
  const regularUsers   = (users || []).filter(u => u.role === 'user');

  return (
    <>
      <Card>
        <CardHeader className="pb-4">
          <div className="flex items-center justify-between">
            <div>
              <CardTitle>Login Mode</CardTitle>
              <p className="text-sm text-muted-foreground mt-1">
                Choose how users access this app.
              </p>
            </div>
            <Badge className={
              currentMode === 'single'
                ? 'bg-violet-500/15 text-violet-400 border-violet-500/20'
                : 'bg-sky-500/15 text-sky-400 border-sky-500/20'
            }>
              {currentMode === 'single' ? 'No Login' : 'Require Login'}
            </Badge>
          </div>
        </CardHeader>

        <CardContent className="space-y-3">
          {/* Option: Require Login */}
          <button
            type="button"
            onClick={() => setSelected('multi')}
            className={`w-full text-left rounded-lg border px-4 py-3.5 transition-colors focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring ${
              selected === 'multi'
                ? 'border-primary/50 bg-primary/5'
                : 'border-border/60 bg-muted/20 hover:border-border hover:bg-muted/40'
            }`}
          >
            <div className="flex items-start gap-3">
              <div className={`mt-0.5 flex h-4 w-4 shrink-0 items-center justify-center rounded-full border-2 ${
                selected === 'multi' ? 'border-primary' : 'border-muted-foreground/40'
              }`}>
                {selected === 'multi' && <div className="h-2 w-2 rounded-full bg-primary" />}
              </div>
              <div className="min-w-0 flex-1">
                <div className="flex items-center gap-2">
                  <LogIn className="h-4 w-4 text-muted-foreground" />
                  <span className="text-sm font-medium">Require Login</span>
                </div>
                <p className="text-xs text-muted-foreground mt-1">
                  Users must sign in with a username and password, or via OIDC. Authentication methods are configured below.
                </p>
                {currentMode === 'multi' && (
                  <p className="text-xs text-emerald-500 mt-1 font-medium">Currently active</p>
                )}
              </div>
            </div>
          </button>

          {/* Option: No Login */}
          <button
            type="button"
            onClick={() => setSelected('single')}
            className={`w-full text-left rounded-lg border px-4 py-3.5 transition-colors focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring ${
              selected === 'single'
                ? 'border-violet-500/50 bg-violet-500/5'
                : 'border-border/60 bg-muted/20 hover:border-border hover:bg-muted/40'
            }`}
          >
            <div className="flex items-start gap-3">
              <div className={`mt-0.5 flex h-4 w-4 shrink-0 items-center justify-center rounded-full border-2 ${
                selected === 'single' ? 'border-violet-500' : 'border-muted-foreground/40'
              }`}>
                {selected === 'single' && <div className="h-2 w-2 rounded-full bg-violet-500" />}
              </div>
              <div className="min-w-0 flex-1">
                <div className="flex items-center gap-2">
                  <UserCheck className="h-4 w-4 text-muted-foreground" />
                  <span className="text-sm font-medium">No Login — Single User</span>
                </div>
                <p className="text-xs text-muted-foreground mt-1">
                  Anyone who opens the app is automatically signed in as the selected user. No login screen is shown.
                  Admin routes still require a session.
                </p>
                {currentMode === 'single' && (
                  <p className="text-xs text-violet-400 mt-1 font-medium">
                    Currently active — signed in as <span className="text-foreground">{activeUser?.username ?? '—'}</span>
                  </p>
                )}
              </div>
            </div>
          </button>

          {/* User selector — shown only when No Login is selected */}
          {selected === 'single' && (
            <div className="rounded-lg border border-border/60 bg-muted/10 px-4 py-3 space-y-2">
              <Label className="text-xs text-muted-foreground">Auto sign-in as</Label>
              <Select value={selectedUser} onValueChange={setSelectedUser}>
                <SelectTrigger>
                  <SelectValue placeholder="Select a user account…" />
                </SelectTrigger>
                <SelectContent>
                  {regularUsers.map(u => (
                    <SelectItem key={u.id} value={u.id.toString()}>{u.username}</SelectItem>
                  ))}
                </SelectContent>
              </Select>
              {regularUsers.length === 0 && (
                <p className="text-xs text-amber-500">No regular user accounts found. Create a user account first.</p>
              )}
            </div>
          )}

          {/* Security note for single mode */}
          {selected === 'single' && (
            <div className="flex gap-2 rounded-lg border border-amber-500/25 bg-amber-500/10 px-3 py-2.5">
              <ShieldCheck className="h-4 w-4 text-amber-500 shrink-0 mt-0.5" />
              <p className="text-xs text-amber-600 dark:text-amber-400">
                Only use this on trusted private networks. Anyone with access to the URL is signed in automatically.
              </p>
            </div>
          )}

          {isDirty && (
            <Button
              onClick={handleSave}
              disabled={saving || (selected === 'single' && !selectedUser)}
              className="w-full"
              variant={selected === 'single' ? 'default' : 'outline'}
            >
              {saving ? 'Saving…' : selected === 'single' ? 'Enable No Login Mode' : 'Restore Login Requirement'}
            </Button>
          )}
        </CardContent>
      </Card>

      <AlertDialog open={confirmSingle} onOpenChange={setConfirmSingle}>
        <AlertDialogContent>
          <AlertDialogHeader>
            <AlertDialogTitle>Enable No Login Mode?</AlertDialogTitle>
            <AlertDialogDescription>
              Anyone who opens the app will be automatically signed in as{' '}
              <span className="font-medium text-foreground">{pendingUsername}</span>.
              The admin login still requires a password.
            </AlertDialogDescription>
          </AlertDialogHeader>
          <AlertDialogFooter>
            <AlertDialogCancel>Cancel</AlertDialogCancel>
            <AlertDialogAction onClick={() => { setConfirmSingle(false); doSetMode('single', selectedUser); }}>
              Enable No Login Mode
            </AlertDialogAction>
          </AlertDialogFooter>
        </AlertDialogContent>
      </AlertDialog>
    </>
  );
}
