import { useState } from 'react';
import { useTranslation } from 'react-i18next';
import { useQuery, useMutation } from '@tanstack/react-query';
import { Card, CardContent, CardDescription, CardHeader, CardTitle } from '@/components/ui/card';
import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from '@/components/ui/select';
import { Button } from '@/components/ui/button';
import { Input } from '@/components/ui/input';
import { Dialog, DialogContent, DialogHeader, DialogTitle, DialogTrigger } from '@/components/ui/dialog';
import { Globe, Tag, Plus, Edit, Trash2, Layers } from 'lucide-react';
import { Label } from '@shared/schema';
import { queryClient, apiRequest } from '@/lib/queryClient';
import { useToast } from '@/hooks/use-toast';

interface SettingsProps {
  onNavigateToTemplates: () => void;
}

export default function Settings({ onNavigateToTemplates }: SettingsProps) {
  const { t, i18n } = useTranslation();
  const { toast } = useToast();
  
  const [isLabelDialogOpen, setIsLabelDialogOpen] = useState(false);
  const [editingLabel, setEditingLabel] = useState<Label | null>(null);
  const [labelName, setLabelName] = useState('');
  const [labelColor, setLabelColor] = useState('#3B82F6');

  const changeLanguage = (lng: string) => {
    i18n.changeLanguage(lng);
    localStorage.setItem('taskflow-language', lng);
    console.log('Language changed to:', lng);
  };

  // Fetch labels
  const { data: labels = [], isLoading: labelsLoading } = useQuery<Label[]>({
    queryKey: ['/api/labels']
  });

  // Create label mutation
  const createLabelMutation = useMutation({
    mutationFn: (data: { name: string; color: string }) =>
      apiRequest('POST', '/api/labels', data),
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ['/api/labels'] });
      setIsLabelDialogOpen(false);
      setLabelName('');
      setLabelColor('#3B82F6');
      toast({
        title: t('settings.labels.created'),
        description: t('settings.labels.createdDescription'),
      });
    },
  });

  // Update label mutation
  const updateLabelMutation = useMutation({
    mutationFn: ({ id, ...data }: { id: string; name: string; color: string }) =>
      apiRequest('PATCH', `/api/labels/${id}`, data),
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ['/api/labels'] });
      setIsLabelDialogOpen(false);
      setEditingLabel(null);
      setLabelName('');
      setLabelColor('#3B82F6');
      toast({
        title: t('settings.labels.updated'),
        description: t('settings.labels.updatedDescription'),
      });
    },
  });

  // Delete label mutation
  const deleteLabelMutation = useMutation({
    mutationFn: (id: string) => apiRequest('DELETE', `/api/labels/${id}`),
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ['/api/labels'] });
      toast({
        title: t('settings.labels.deleted'),
        description: t('settings.labels.deletedDescription'),
      });
    },
  });

  const handleSaveLabel = () => {
    if (!labelName.trim()) return;

    if (editingLabel) {
      updateLabelMutation.mutate({
        id: editingLabel.id,
        name: labelName,
        color: labelColor,
      });
    } else {
      createLabelMutation.mutate({ name: labelName, color: labelColor });
    }
  };

  const handleEditLabel = (label: Label) => {
    setEditingLabel(label);
    setLabelName(label.name);
    setLabelColor(label.color);
    setIsLabelDialogOpen(true);
  };

  const handleDeleteLabel = (id: string) => {
    if (confirm(t('settings.labels.deleteConfirm'))) {
      deleteLabelMutation.mutate(id);
    }
  };

  return (
    <div className="space-y-6">
      <div>
        <h1 className="text-2xl font-bold" data-testid="text-settings-title">
          {t('settings.title')}
        </h1>
      </div>

      {/* Language Settings */}
      <Card data-testid="card-language-settings">
        <CardHeader>
          <CardTitle className="flex items-center gap-2">
            <Globe className="w-5 h-5" />
            {t('settings.language.title')}
          </CardTitle>
          <CardDescription>
            {t('settings.language.description')}
          </CardDescription>
        </CardHeader>
        <CardContent>
          <Select value={i18n.language} onValueChange={changeLanguage}>
            <SelectTrigger className="w-full sm:w-64" data-testid="select-language">
              <SelectValue />
            </SelectTrigger>
            <SelectContent>
              <SelectItem value="en" data-testid="option-language-en">
                {t('settings.language.english')}
              </SelectItem>
              <SelectItem value="de" data-testid="option-language-de">
                {t('settings.language.german')}
              </SelectItem>
            </SelectContent>
          </Select>
        </CardContent>
      </Card>

      {/* Labels Management */}
      <Card data-testid="card-labels-management">
        <CardHeader>
          <div className="flex items-center justify-between">
            <div>
              <CardTitle className="flex items-center gap-2">
                <Tag className="w-5 h-5" />
                {t('settings.labels.title')}
              </CardTitle>
              <CardDescription>
                {t('settings.labels.description')}
              </CardDescription>
            </div>
            <Dialog open={isLabelDialogOpen} onOpenChange={setIsLabelDialogOpen}>
              <DialogTrigger asChild>
                <Button variant="outline" size="sm" data-testid="button-create-label">
                  <Plus className="w-4 h-4 mr-2" />
                  {t('settings.labels.createLabel')}
                </Button>
              </DialogTrigger>
              <DialogContent>
                <DialogHeader>
                  <DialogTitle>
                    {editingLabel ? t('settings.labels.editLabel') : t('settings.labels.createNewLabel')}
                  </DialogTitle>
                </DialogHeader>
                <div className="space-y-4">
                  <div>
                    <Input
                      placeholder={t('settings.labels.labelNamePlaceholder')}
                      value={labelName}
                      onChange={(e) => setLabelName(e.target.value)}
                      data-testid="input-label-name"
                    />
                  </div>
                  <div>
                    <div className="flex items-center gap-3">
                      <input
                        type="color"
                        value={labelColor}
                        onChange={(e) => setLabelColor(e.target.value)}
                        className="w-12 h-8 rounded border cursor-pointer"
                        data-testid="input-label-color"
                      />
                      <Input
                        value={labelColor}
                        onChange={(e) => setLabelColor(e.target.value)}
                        placeholder="#3B82F6"
                        className="flex-1"
                        data-testid="input-label-color-text"
                      />
                    </div>
                  </div>
                  <div className="flex gap-3 pt-2">
                    <Button 
                      variant="outline" 
                      onClick={() => {
                        setIsLabelDialogOpen(false);
                        setEditingLabel(null);
                        setLabelName('');
                        setLabelColor('#3B82F6');
                      }}
                      className="flex-1"
                      data-testid="button-cancel-label"
                    >
                      {t('settings.labels.cancel')}
                    </Button>
                    <Button 
                      onClick={handleSaveLabel}
                      disabled={!labelName.trim() || createLabelMutation.isPending || updateLabelMutation.isPending}
                      className="flex-1"
                      data-testid="button-save-label"
                    >
                      {editingLabel ? t('settings.labels.update') : t('settings.labels.create')}
                    </Button>
                  </div>
                </div>
              </DialogContent>
            </Dialog>
          </div>
        </CardHeader>
        <CardContent>
          {labelsLoading ? (
            <div className="flex items-center justify-center p-8">
              <div className="text-muted-foreground">{t('settings.labels.loading')}</div>
            </div>
          ) : (
            <div className="grid gap-3 sm:grid-cols-2 lg:grid-cols-3">
              {labels.map((label) => (
                <Card 
                  key={label.id} 
                  className="p-4 hover-elevate active-elevate-2" 
                  style={{ borderLeft: `4px solid ${label.color}` }}
                  data-testid={`label-${label.id}`}
                >
                  <div className="flex items-center justify-between">
                    <div className="flex items-center gap-3">
                      <div 
                        className="w-4 h-4 rounded"
                        style={{ backgroundColor: label.color }}
                      />
                      <span className="font-medium text-sm" data-testid={`text-label-name-${label.id}`}>
                        {label.name}
                      </span>
                    </div>
                    <div className="flex items-center gap-1">
                      <Button
                        variant="ghost"
                        size="icon"
                        onClick={() => handleEditLabel(label)}
                        className="w-6 h-6"
                        data-testid={`button-edit-${label.id}`}
                      >
                        <Edit className="w-3 h-3" />
                      </Button>
                      <Button
                        variant="ghost"
                        size="icon"
                        onClick={() => handleDeleteLabel(label.id)}
                        className="w-6 h-6 text-destructive hover:text-destructive"
                        data-testid={`button-delete-${label.id}`}
                      >
                        <Trash2 className="w-3 h-3" />
                      </Button>
                    </div>
                  </div>
                </Card>
              ))}
              {labels.length === 0 && (
                <div className="col-span-full flex flex-col items-center justify-center p-8 text-center">
                  <Tag className="w-12 h-12 text-muted-foreground mb-4" />
                  <h3 className="font-medium text-muted-foreground mb-2">{t('settings.labels.noLabels')}</h3>
                  <p className="text-sm text-muted-foreground mb-4">
                    {t('settings.labels.noLabelsDescription')}
                  </p>
                  <Button
                    variant="outline"
                    onClick={() => setIsLabelDialogOpen(true)}
                    data-testid="button-create-first-label"
                  >
                    <Plus className="w-4 h-4 mr-2" />
                    {t('settings.labels.createLabel')}
                  </Button>
                </div>
              )}
            </div>
          )}
        </CardContent>
      </Card>

      {/* Project Templates */}
      <Card data-testid="card-project-templates">
        <CardHeader>
          <CardTitle className="flex items-center gap-2">
            <Layers className="w-5 h-5" />
            {t('settings.templates.title')}
          </CardTitle>
          <CardDescription>
            {t('settings.templates.description')}
          </CardDescription>
        </CardHeader>
        <CardContent>
          <Button 
            onClick={onNavigateToTemplates}
            data-testid="button-manage-templates"
          >
            <Layers className="w-4 h-4 mr-2" />
            {t('settings.templates.manageTemplates')}
          </Button>
        </CardContent>
      </Card>
    </div>
  );
}