PlayerHealth

using UnityEngine;
using UnityEngine.UI;
using System.Collections;

public class PlayerHealth : MonoBehaviour {

    public Texture2D[] screenBloodTextures;                     //container array of the blood screen textures
    public Image hitImage;
    public float flashSpeed = 5f;                               //The speed the damageImage will fade at.
    public Color flashColour = new Color(1f, 0f, 0f, 0.1f);     //The colour the damageImage is set to, to flash.
    public float health;                                        //player's current health
    public float maxHealth;                                     //player's max health
    public float freezeHealingTime;                             //Time to wait for healing again after the player is damaged
    public float repeatDamagePeriod = 1f;                       //How frequently the player can be damaged.
    [HideInInspector]
    public bool isHurting;
    [HideInInspector]
    public bool isDead;
    [Range(0.1f, 100)]
    public float healingPointsPerSecond;                         //Amount of health points the player will recover by second

    private float lastHitTime;                                   //The time at which the player was last hit.

    public float alpha;                                          //Transparency to apply to screen textures
    public int drawDepth;

    // Use this for initialization
    void Start () {

        drawDepth = -1000;
    }

    // Update is called once per frame
    void Update () {
        regenerateHealth();
        hurtFlashing();
    }

    private void regenerateHealth() {
        if (Time.time > lastHitTime + repeatDamagePeriod + freezeHealingTime && !isHurting) {
            if (health < maxHealth) {
                //regenerating health over time
                health += Time.deltaTime * healingPointsPerSecond;

                //Avoid the health to has a value over the maxHealth value
                if (health > maxHealth)
                    health = maxHealth;
            }
        }
    }

    private void hurtFlashing() {
        // If the player has just been damaged...
        if (isHurting) {
            // ... set the colour of the damageImage to the flash colour.
            hitImage.color = flashColour;
        }
        // Otherwise...
        else {
            // ... transition the colour back to clear.
            hitImage.color = Color.Lerp(hitImage.color, Color.clear, flashSpeed * Time.deltaTime);
        }
    }

    public void hurt(int damage) {
        if (Time.time > lastHitTime + repeatDamagePeriod) {
                // ... take damage and reset the lastHitTime.
                StartCoroutine(takeDamage(damage));
                lastHitTime = Time.time;
        }
    }


    private IEnumerator takeDamage(int damage) {

        // Player is getting damage
        isHurting = true;
        // Reduce the player's health by enemy damage.
        health -= damage;

        // If the player has lost all it's health and the death flag hasn't been set yet...
        if (health <= 0 && !isDead) {
            health = 0;
            // ... it should die.
            death();
        }

        // Wait the repeatDamagePeriod until the player can receive damage again
        yield return new WaitForSeconds(repeatDamagePeriod);
        // Player is no longer taking damage
        isHurting = false;
    }

    private void death() {
        isDead = true;

        //TODO Play death transition/animation/sounds/effects and disable the scripts

    }

    void OnGUI() {

        //get the corresponding texture array index
        float percentagePerImage = 100 / screenBloodTextures.Length;
        float takenHealthPercentage = 100 - ((health * 100) / maxHealth);
        int textureIndex = (int)(takenHealthPercentage / percentagePerImage);

        if (textureIndex == screenBloodTextures.Length)
            textureIndex--;

        //adjusting alpha based on player's left health percetage
        alpha = (1 - (health * 100 / maxHealth) / 100);

        //drawing the texture
        GUI.color = new Color(GUI.color.r, GUI.color.g, GUI.color.b, alpha);
        GUI.depth = drawDepth;
        GUI.DrawTexture(new Rect(0, 0, Screen.width, Screen.height), screenBloodTextures[textureIndex]); ;
    }
}