using System.Collections.Generic;
using UnityEngine;
using Ashwild.Network;
using Ashwild.Player;

namespace Ashwild.UI
{
    /// <summary>
    /// The in-game feed that spawns a "X a rejoint / a quitté la partie" line whenever a remote player
    /// joins or leaves the session. Listens to the network layer's SessionPresenceEvents (raised on
    /// every client, host or not) and instantiates a PresenceFeedEntry under a holder whose layout group
    /// stacks the lines. Drop this on the holder (or any object referencing it) in the game scene.
    ///
    /// While the local player is tearing the session down (returning to the menu, or the host stopping)
    /// every remote copy despawns at once, which would spam "left" lines; this feed goes quiet on those
    /// bus events so that storm never reaches the screen.
    /// </summary>
    [DisallowMultipleComponent]
    public class PlayerPresenceFeedUI : MonoBehaviour
    {
        #region Serialized Fields

        [Header("References")]
        [Tooltip("Holder the entries are parented to — give it a VerticalLayoutGroup so lines stack.")]
        [SerializeField] private RectTransform holder;

        [Tooltip("Prefab with a PresenceFeedEntry (CanvasGroup + label) instantiated per notification.")]
        [SerializeField] private PresenceFeedEntry entryPrefab;

        [Header("Messages")]
        [Tooltip("Join line format — {0} is the player name.")]
        [SerializeField] private string joinFormat = "{0} a rejoint la partie";

        [Tooltip("Leave line format — {0} is the player name.")]
        [SerializeField] private string leaveFormat = "{0} a quitté la partie";

        [Header("Colours")]
        [SerializeField] private Color joinColor = new Color(0.45f, 1f, 0.45f);
        [SerializeField] private Color leaveColor = new Color(1f, 0.55f, 0.45f);

        [Header("Timing")]
        [Tooltip("Seconds a line stays fully visible before fading out.")]
        [SerializeField] private float holdDuration = 4f;
        [SerializeField] private float fadeInDuration = 0.3f;
        [SerializeField] private float fadeOutDuration = 0.5f;

        [Header("Limits")]
        [Tooltip("Oldest lines are removed once this many are on screen at once.")]
        [SerializeField] private int maxEntries = 5;

        #endregion

        #region State

        /// <summary>
        /// Currently displayed lines, oldest first — trimmed from the front when over the cap.
        /// </summary>
        private readonly List<PresenceFeedEntry> activeEntries = new List<PresenceFeedEntry>();

        /// <summary>
        /// True once the session is tearing down, so the despawn-driven "left" storm is ignored.
        /// </summary>
        private bool suppressed;

        #endregion

        #region Unity Lifecycle

        /// <summary>
        /// Subscribes to presence notifications and the teardown signals that mute the feed.
        /// </summary>
        private void OnEnable()
        {
            SessionPresenceEvents.PlayerJoined += HandlePlayerJoined;
            SessionPresenceEvents.PlayerLeft += HandlePlayerLeft;
            PlayerEvents.ReturningToMenu += HandleTeardown;
            PlayerEvents.SessionStopped += HandleTeardown;
        }

        /// <summary>
        /// Unsubscribes — mirrors OnEnable exactly.
        /// </summary>
        private void OnDisable()
        {
            SessionPresenceEvents.PlayerJoined -= HandlePlayerJoined;
            SessionPresenceEvents.PlayerLeft -= HandlePlayerLeft;
            PlayerEvents.ReturningToMenu -= HandleTeardown;
            PlayerEvents.SessionStopped -= HandleTeardown;
        }

        #endregion

        #region Event Handlers

        /// <summary>
        /// Shows a green arrival line for the named player.
        /// </summary>
        private void HandlePlayerJoined(string playerName) => Push(string.Format(joinFormat, playerName), joinColor);

        /// <summary>
        /// Shows an orange departure line for the named player.
        /// </summary>
        private void HandlePlayerLeft(string playerName) => Push(string.Format(leaveFormat, playerName), leaveColor);

        /// <summary>
        /// Mutes the feed for the rest of its lifetime once the session is being torn down.
        /// </summary>
        private void HandleTeardown() => suppressed = true;

        #endregion

        #region Internal Helpers

        /// <summary>
        /// Instantiates a feed line, trimming the oldest ones past the cap. Ignored while muted or when
        /// a reference is missing (logged once so a mis-wired holder/prefab is obvious).
        /// </summary>
        private void Push(string message, Color color)
        {
            if (suppressed) return;

            if (holder == null || entryPrefab == null)
            {
                Debug.LogError("[PresenceFeed] Holder or entry prefab not assigned — cannot show notifications.", this);
                return;
            }

            activeEntries.RemoveAll(e => e == null);

            while (activeEntries.Count >= maxEntries)
            {
                PresenceFeedEntry oldest = activeEntries[0];
                activeEntries.RemoveAt(0);
                if (oldest != null) Destroy(oldest.gameObject);
            }

            PresenceFeedEntry entry = Instantiate(entryPrefab, holder);
            entry.Play(message, color, holdDuration, fadeInDuration, fadeOutDuration);
            activeEntries.Add(entry);
        }

        #endregion
    }
}