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

public class PlayerHealth : Singleton<PlayerHealth>
{
    public bool isDead { get; private set; }

    [SerializeField] private int maxHealth = 7; // Maximum health of the player
    [SerializeField] private float knockBackThrustAmount = 10f; // Force applied to the player when knocked back
    [SerializeField] private float damageRecoveryTime = 1f; // Time during which the player cannot take damage after being hit

    private Slider healthSlider; // UI Slider to display player's health
    private int currentHealth; // Current health of the player
    private bool canTakeDamage = true; // Flag to check if player can take damage
    private Knockback knockback; // Reference to Knockback component
    private Flash flash; // Reference to Flash component
    
    // The default starting position of the player
    private Vector3 defaultPosition;
    
    // Constants for UI and animation management
    const string HEALTH_SLIDER_TEXT = "Health Slider"; // Name of the health slider in the scene
    const string TOWN_TEXT = "End"; // Name of the scene to load when the player dies
    readonly int DEATH_HASH = Animator.StringToHash("Death"); // Hash for the "Death" animation trigger

    // Initialization of components and setting up the player's default position
    protected override void Awake() {
        base.Awake();

        flash = GetComponent<Flash>();
        knockback = GetComponent<Knockback>();

        // Set the default position to wherever you want the character to start
        defaultPosition = transform.position;
    }

    // Subscribe to scene load events when the script is enabled
    void OnEnable()
    {
        SceneManager.sceneLoaded += OnSceneLoaded;
    }

    // Unsubscribe from scene load events when the script is disabled
    void OnDisable()
    {
        SceneManager.sceneLoaded -= OnSceneLoaded;
    }

    // Resets the player's health and position when a specific scene is loaded
    void OnSceneLoaded(Scene scene, LoadSceneMode mode)
    {
        if (scene.name == "End") 
        {
            ResetHealth();
        }
    }

    // Resets the player's position to the default position
    public void ResetCharacterPosition()
    {
        transform.position = defaultPosition;
    }
    
    // Resets the player's health to the maximum value, updates the UI, and resets the animator and position
    public void ResetHealth()
    {
        isDead = false;
        currentHealth = maxHealth;
        UpdateHealthSlider();
    
        // Reset the animator to the default state
        Animator animator = GetComponent<Animator>();
        if (animator != null)
        {
            animator.ResetTrigger(DEATH_HASH); // Reset the death trigger
            animator.Play("Idle"); // Play the idle animation
        }
        ResetCharacterPosition(); // Reset position when health is reset
    }

    // Sets initial values for the player's health and updates the health UI at the start of the game
    private void Start() {
        isDead = false;
        currentHealth = maxHealth;

        UpdateHealthSlider();
    }

    // Handles damage when the player collides with an enemy and applies knockback
    private void OnCollisionStay2D(Collision2D other) {
        EnemyAI enemy = other.gameObject.GetComponent<EnemyAI>();

        if (enemy) {
            TakeDamage(1, other.transform);
        }
    }

    // Heals the player by one health point if not already at max health, and updates the UI
    public void HealPlayer() {
        if (currentHealth < maxHealth) {
            currentHealth += 1;
            UpdateHealthSlider();
        }
    }

    // Manages the process of taking damage, including knockback, screen flash, and health deduction
    public void TakeDamage(int damageAmount, Transform hitTransform) {
        if (!canTakeDamage) { return; }

        knockback.GetKnockedBack(hitTransform, knockBackThrustAmount); // Apply knockback
        StartCoroutine(flash.FlashRoutine()); // Trigger the flash effect
        canTakeDamage = false; // Temporarily disable taking further damage
        currentHealth -= damageAmount; // Deduct health
        StartCoroutine(DamageRecoveryRoutine()); // Start recovery process
        UpdateHealthSlider(); // Update health UI
        CheckIfPlayerDeath(); // Check if player is dead and handle it
    }

    // Checks if the player's health is 0 or less, and triggers the death sequence if true
    private void CheckIfPlayerDeath() {
        if (currentHealth <= 0 && !isDead) {
            isDead = true;
            currentHealth = 0;
            GetComponent<Animator>().SetTrigger(DEATH_HASH); // Trigger the death animation
            StartCoroutine(DeathLoadSceneRoutine()); // Load the death scene after a delay
        }
    }

    // Coroutine that handles loading the death scene after a short delay
    private IEnumerator DeathLoadSceneRoutine() {
        yield return new WaitForSeconds(2f);
        SceneManager.LoadScene(TOWN_TEXT); // Load the end scene
    }

    // Coroutine that manages the recovery period during which the player cannot take damage
    private IEnumerator DamageRecoveryRoutine() {
        yield return new WaitForSeconds(damageRecoveryTime);
        canTakeDamage = true; // Re-enable taking damage after the recovery period
    }

    // Updates the health slider UI to reflect the player's current health
    private void UpdateHealthSlider() {
        if (healthSlider == null) {
            healthSlider = GameObject.Find(HEALTH_SLIDER_TEXT).GetComponent<Slider>();
        }

        healthSlider.maxValue = maxHealth; // Set the max value of the slider
        healthSlider.value = currentHealth; // Update the slider to the current health
    }
}