using UnityEngine;
using System.Collections;
using System.Collections.Generic;


public static class RectTransformTools {
    public static Vector2 Size(this RectTransform tf) {
        Vector3[] c = new Vector3[4];
        tf.GetLocalCorners(c);
        return new Vector2(c[2].x - c[0].x, c[1].y - c[0].y);
    }
}

public class ItemViewReference : MonoBehaviour {
    public ItemViewController itemView;
}


public delegate void ItemsViewDelegate(ItemsView container);

public class ItemsView : MonoBehaviour {
    public RectTransform container;
    private IEnumerable<PickableItem> _items;
    public GameObject itemViewPrototype;
    private List<ItemViewController> _views = new List<ItemViewController>();
    public List<ItemViewController> Views {
        get { return _views; }
    }
    public float itemsMargin = 5.0f;
    public event ItemsViewDelegate SelectionChanged;
    private ItemViewController _selection;
    public ItemViewController Selection {
        get { return _selection; }
    }

    protected virtual void OnSelectionChanged() {
        ItemsViewDelegate handler = SelectionChanged;
        if (handler != null) {
            handler(this);
        }
    }

    public IEnumerable<PickableItem> Items {
        get { return _items; }
        set {
            _items = value;
            RebuildUI();
        }
    }

    private void Start() {

        var t = itemViewPrototype.GetComponent<RectTransform>();

        var tfSize = t.anchoredPosition;
       
    }

    void OnClick(UnityEngine.UI.Button b) {
        var view = b.gameObject.GetComponent<ItemViewReference>().itemView;
        _selection = view;
        OnSelectionChanged();
    }


    public void RebuildUI() {
        //remove old items view
        foreach (var view in _views) {
            Destroy(view.gameObject);
        }
        _views.Clear();

        //create new views
        if (itemViewPrototype != null) {
            foreach (var item in _items) {
                var view = Instantiate<GameObject>(itemViewPrototype).GetComponent<ItemViewController>();
                view.item = item;
                _views.Add(view);
                view.GetComponent<RectTransform>().parent = container;
                var reference = view.itemButton.gameObject.AddComponent<ItemViewReference>();
                reference.itemView = view;
                view.itemButton.onClick.AddListener(OnClick);
            }
        }
        else {
            Debug.LogWarning("Can't create items view! Prototype not assigned!");
        }

        ArrangeItems();

    }

    
    public void ArrangeItems() {
        var areaSize = container.Size();
        var itemSize = itemViewPrototype.GetComponent<RectTransform>().Size();

        int hCount = (int)((areaSize.x - itemsMargin) / (itemSize.x + itemsMargin));

        for (int i = 0; i < _views.Count; ++i) {
            var view = _views[i];
            var tf = view.GetComponent<RectTransform>();
            int row = i/hCount;
            int column = i%hCount;
            tf.anchoredPosition = new Vector2(column * (itemSize.x + itemsMargin) + itemsMargin + itemSize.x * 0.5f, -(row * (itemSize.y + itemsMargin) + itemsMargin + itemSize.y * 0.5f));
            
        }
    }
	
}