using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using UnityEngine;
using UnityEngine.UI;

public class StatusUI : MonoBehaviour
{
    public StatusIconUI iconPrefab;

    private BattleParticipant battleParticipant;
    private BattleState battleState;

    private Dictionary<BattleStatus, StatusIconUI> statusIcons;

    private Dictionary<Buff, StatusIconUI> buffIcons;

    public void Init(BattleParticipant battleParticipant, BattleState battleState) {
        this.battleParticipant = battleParticipant;
        this.battleState = battleState;

        this.statusIcons = new Dictionary<BattleStatus, StatusIconUI>();
        this.buffIcons = new Dictionary<Buff, StatusIconUI>();
        this.battleParticipant.OnStatusChanged += this.NotifyBattleStatusOrBuffsChanged;
        this.battleParticipant.OnBuffsChanged += this.NotifyBattleStatusOrBuffsChanged;
    }

    // Start is called before the first frame update
    void Start() {
        UpdateAppearance();
    }

    public void NotifyBattleStatusOrBuffsChanged(BattleParticipant updatedParticipant) {
        if (updatedParticipant != this.battleParticipant) {
            throw new System.InvalidOperationException(
                "NotifyBattleStatusOrBuffsChanged was notified about a different participant.");
        }
        UpdateAppearance();
    }

    private void UpdateAppearance() {
        int index = 0;
        foreach (BattleStatus status in Enum.GetValues(typeof(BattleStatus)).Cast<BattleStatus>()) {
            if (status == BattleStatus.None) {
                continue;
            }

            StatusIconUI iconUI = null;
            this.statusIcons.TryGetValue(status, out iconUI);
            if (this.battleParticipant.HasStatus(status)) {
                if (iconUI == null) {
                    iconUI = Instantiate(this.iconPrefab.gameObject, this.transform).GetComponent<StatusIconUI>();
                    iconUI.InitStatus(status);
                    this.statusIcons[status] = iconUI;
                }
                iconUI.UpdateStatusAmount(this.battleParticipant.GetStatusAmount(status));
                iconUI.SetPosition(index++);
            } else {
                if (iconUI != null) {
                    Destroy(iconUI.gameObject);
                    this.statusIcons.Remove(status);
                }
            }
        }

        Dictionary<Buff, StatusIconUI> previousBuffIcons = new Dictionary<Buff, StatusIconUI>(this.buffIcons);
        List<Buff> currentBuffs = this.battleState.BuffManager.GetAllBuffsFor(this.battleParticipant);

        foreach (Buff buff in currentBuffs) {
            StatusIconUI iconUI = null;
            previousBuffIcons.TryGetValue(buff, out iconUI);
            if (iconUI == null) {
                iconUI = Instantiate(this.iconPrefab.gameObject, this.transform).GetComponent<StatusIconUI>();
                iconUI.InitBuff(buff);
                this.buffIcons[buff] = iconUI;
            } else {
                previousBuffIcons.Remove(buff);
            }
            iconUI.SetPosition(index++);
        }

        // If a buff is left in previousBuffIcons, it has been removed.
        foreach (KeyValuePair<Buff, StatusIconUI> p in previousBuffIcons) {
            Buff buff = p.Key;
            StatusIconUI iconUI = p.Value;
            Destroy(iconUI.gameObject);
            this.buffIcons.Remove(buff);
        }
    }
}