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

public class ItemPipe : MonoBehaviour
{
    [Serializable]
    private class GuaranteedItem
    {
        public GameObject prefab;

        [Min(1)]
        public int amount = 1;
    }

    [Serializable]
    private class RandomItem
    {
        public GameObject prefab;

        [Min(0)]
        public float weight = 1f;
    }

    [Header("Pipe")]
    [SerializeField] private Transform spawnPoint;
    [SerializeField, Min(0.05f)] private float spawnInterval = 0.5f;

    [Header("Instant velocity change")]
    [SerializeField] private Vector3 localVelocityChange = Vector3.forward * 4.5f;

    [Header("Guaranteed items")]
    [SerializeField] private List<GuaranteedItem> guaranteedItems = new();

    [Header("Random items")]
    [SerializeField, Min(0)] private int randomItemCount = 5;
    [SerializeField] private List<RandomItem> randomItems = new();

    [Header("Spawn position randomization")]
    [SerializeField, Min(0f)] private float randomSpawnX = 0.2f;
    [SerializeField, Min(0f)] private float randomSpawnZ = 0.2f;

    [Header("Temporary testing")]
    [SerializeField] private bool spawnOnE = true;

    private bool isSpawning;

    private void Update()
    {
        if (!spawnOnE || isSpawning || Keyboard.current == null)
            return;

        if (Keyboard.current.eKey.wasPressedThisFrame)
            StartCoroutine(SpawnSequence());
    }

    private IEnumerator SpawnSequence()
    {
        isSpawning = true;

        List<GameObject> spawnQueue = BuildSpawnQueue();

        foreach (GameObject prefab in spawnQueue)
        {
            Spawn(prefab);
            yield return new WaitForSeconds(spawnInterval);
        }

        isSpawning = false;
    }

    private List<GameObject> BuildSpawnQueue()
    {
        List<GameObject> queue = new();

        // Добавляем предметы в точном количестве.
        foreach (GuaranteedItem item in guaranteedItems)
        {
            if (item.prefab == null)
                continue;

            for (int i = 0; i < item.amount; i++)
                queue.Add(item.prefab);
        }

        // Выбираем указанное количество случайных предметов.
        for (int i = 0; i < randomItemCount; i++)
        {
            GameObject selectedPrefab = ChooseWeightedRandom();

            if (selectedPrefab != null)
                queue.Add(selectedPrefab);
        }

        // Перемешиваем гарантированные и случайные предметы вместе.
        Shuffle(queue);

        return queue;
    }

    private GameObject ChooseWeightedRandom()
    {
        float totalWeight = 0f;

        foreach (RandomItem item in randomItems)
        {
            if (item.prefab != null && item.weight > 0f)
                totalWeight += item.weight;
        }

        if (totalWeight <= 0f)
            return null;

        float roll = UnityEngine.Random.value * totalWeight;
        float currentWeight = 0f;

        foreach (RandomItem item in randomItems)
        {
            if (item.prefab == null || item.weight <= 0f)
                continue;

            currentWeight += item.weight;

            if (roll < currentWeight)
                return item.prefab;
        }

        return null;
    }

    private void Shuffle(List<GameObject> queue)
    {
        for (int i = queue.Count - 1; i > 0; i--)
        {
            int randomIndex = UnityEngine.Random.Range(0, i + 1);

            (queue[i], queue[randomIndex]) =
                (queue[randomIndex], queue[i]);
        }
    }

    private void Spawn(GameObject prefab)
    {
        if (prefab == null || spawnPoint == null)
            return;

        float offsetX = RandomRange(-randomSpawnX, randomSpawnX);
        float offsetZ = RandomRange(-randomSpawnZ, randomSpawnZ);

        Vector3 spawnPosition =
            spawnPoint.position +
            spawnPoint.right * offsetX +
            spawnPoint.forward * offsetZ;

        GameObject item = Instantiate(
            prefab,
            spawnPosition,
            UnityEngine.Random.rotationUniform
        );

        if (item.TryGetComponent(out Rigidbody body))
        {
            Vector3 worldVelocityChange =
                spawnPoint.TransformDirection(localVelocityChange);

            body.AddForce(worldVelocityChange, ForceMode.VelocityChange);
        }
    }

    private float RandomRange(float min, float max)
    {
        return UnityEngine.Random.Range(min, max);
    }
}