public class AdapterArticle extends ArrayAdapter<ObjectArticle> implements View.OnClickListener{

    private ArrayList<ObjectArticle> dataSet;
    private Context mContext;
    private FirebaseFirestore mDatabase = FirebaseFirestore.getInstance();

    private static class ViewHolder {
        TextView txtTitle;
        TextView txtVisits;
        ImageView image;
        Button open;
    }

    public AdapterArticle(ArrayList<ObjectArticle> data, Context context) {
        super(context, R.layout.item_article, data);
        dataSet = data;
        mContext = context;
    }

    @Override
    public void onClick(View v) {
        int position = (Integer) v.getTag();
        final ObjectArticle article = getItem(position);

        if (v.getId() == R.id.prevBtn) {
            Intent toContent = new Intent(mContext, Content.class);
            toContent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

            String reference = "";
            ArrayList<String> keywords = article.getKeywords();
            for(String key : keywords){ reference += "_" + key; }

            mDatabase.collection("articles").document(reference)
                    .get()
                    .addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>() {
                        @Override
                        public void onSuccess(DocumentSnapshot documentSnapshot) {
                            ObjectArticle aux = documentSnapshot.toObject(ObjectArticle.class);

                            String auxReference = "";
                            ArrayList<String> auxKeywords = aux.getKeywords();
                            for(String key : auxKeywords){ auxReference += "_" + key; }

                            mDatabase.collection("articles").document(auxReference)
                                    .update("visits", aux.getVisits() + 1);
                        }
                    });

            Bundle b = new Bundle();
            b.putString("title", article.getTitle());
            b.putString("content", article.getContent());
            b.putString("author", article.getAuthor());
            b.putString("image", article.getImageURL());
            b.putLong("visits", article.getVisits());
            b.putStringArrayList("downloadURL", article.getDownloadURL());
            b.putStringArrayList("categories", article.getCategories());
            b.putString("date", convertDate(article.getDate()));

            toContent.putExtras(b);
            mContext.startActivity(toContent);
        }
    }

    private int lastPosition = -1;

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ObjectArticle article = getItem(position);
        ViewHolder viewHolder;

        final View result;

        if (convertView == null) {
            viewHolder = new ViewHolder();
            LayoutInflater inflater = LayoutInflater.from(getContext());
            convertView = inflater.inflate(R.layout.item_article, parent, false);
            viewHolder.txtTitle = convertView.findViewById(R.id.prevTxt);
            viewHolder.txtVisits = convertView.findViewById(R.id.prevVisits);
            viewHolder.image = convertView.findViewById(R.id.prevImg);
            viewHolder.open = convertView.findViewById(R.id.prevBtn);

            result = convertView;

            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
            result = convertView;
        }

        Animation animation = AnimationUtils.loadAnimation(mContext, (position > lastPosition) ? R.anim.up_from_bottom : R.anim.down_from_top);
        result.startAnimation(animation);
        lastPosition = position;

        viewHolder.txtTitle.setText(article.getTitle().equals("") ? "untitled" : article.getTitle());
        viewHolder.txtVisits.setText("Visits: " + article.getVisits());

        if(article.getImageURL().equals("")){ viewHolder.image.setVisibility(View.GONE); }
        else{ loadImageToView(viewHolder.image, article.getImageURL()); }

        viewHolder.open.setOnClickListener(this);
        viewHolder.open.setTag(position);

        return convertView;
    }

    private void loadImageToView(ImageView iv, String url){ Glide.with(mContext).load(url).into(iv); }

    private String convertDate(Timestamp t){
        String day = new SimpleDateFormat("dd/MM/yyyy", Locale.FRANCE).format(t.toDate());
        String hour = new SimpleDateFormat("HH:mm", Locale.FRANCE).format(t.toDate());

        return  day + " at " + hour;
    }
}