using ProjectM.Simulation;
using Unity.Entities;
using Unity.NetCode;
using UnityEngine;
using UnityEngine.UI;

namespace ProjectM.Client
{
    /// <summary>
    /// Client-only screen HUD. A managed presentation SystemBase (<see cref="PresentationSystemGroup"/>) that builds
    /// a uGUI overlay canvas in code and drives it from the LOCAL player ghost each frame: a health bar
    /// (Health / EffectiveCharacterStats.MaxHealth), an ability-cooldown bar (AbilityCooldown vs NetworkTime
    /// ServerTick + EffectiveAbilityStats.CooldownTicks), a live Husk threat count, and a DOWNED/RESPAWNING overlay
    /// (the derived <see cref="Dead"/> gate). Presentation only — no simulation, client world only. Bars are
    /// RawImages over <c>Texture2D.whiteTexture</c> (always available; the fill width is the RectTransform's
    /// anchorMax.x), so the HUD needs no sprite assets — only a resolved builtin font for the labels.
    /// </summary>
    [WorldSystemFilter(WorldSystemFilterFlags.ClientSimulation)]
    [UpdateInGroup(typeof(PresentationSystemGroup))]
    public partial class HudSystem : SystemBase
    {
        Canvas _canvas;
        RectTransform _healthFill;
        RectTransform _cooldownFill;
        Text _healthText;
        Text _threatText;
        GameObject _respawnOverlay;
        EntityQuery _huskQuery;

        protected override void OnCreate()
        {
            _huskQuery = GetEntityQuery(ComponentType.ReadOnly<EnemyTag>());
        }

        protected override void OnStartRunning()
        {
            if (_canvas == null) BuildHud();
        }

        protected override void OnDestroy()
        {
            if (_canvas != null) Object.Destroy(_canvas.gameObject);
        }

        protected override void OnUpdate()
        {
            if (_canvas == null) return;

            bool haveTick = SystemAPI.TryGetSingleton<NetworkTime>(out var nt);

            bool found = false;
            float hp = 0f, maxHp = 1f, cdFrac = 1f;
            bool dead = false, shielded = false;

            foreach (var (health, effChar, effAbility, cd, invuln, entity) in
                     SystemAPI.Query<RefRO<Health>, RefRO<EffectiveCharacterStats>, RefRO<EffectiveAbilityStats>,
                             RefRO<AbilityCooldown>, RefRO<RespawnInvuln>>()
                         .WithAll<GhostOwnerIsLocal, PlayerTag>().WithEntityAccess())
            {
                found = true;
                hp = health.ValueRO.Current;
                maxHp = effChar.ValueRO.MaxHealth > 0f ? effChar.ValueRO.MaxHealth : health.ValueRO.Max;
                dead = SystemAPI.IsComponentEnabled<Dead>(entity);

                // Cooldown fraction via wrap-safe NetworkTick compare (raw uint subtraction is unsafe across
                // tick wraparound — the project convention, mirroring AbilityFireSystem/EnemyAISystem).
                uint nextFire = cd.ValueRO.NextFireTick;
                int cdTicks = effAbility.ValueRO.CooldownTicks;
                var nextTick = new NetworkTick(nextFire);
                cdFrac = (haveTick && nextFire != 0 && cdTicks > 0 && nextTick.IsValid && nextTick.IsNewerThan(nt.ServerTick))
                    ? Mathf.Clamp01(1f - nextTick.TicksSince(nt.ServerTick) / (float)cdTicks)
                    : 1f;

                uint invulnUntil = invuln.ValueRO.UntilTick;
                var invulnTick = new NetworkTick(invulnUntil);
                shielded = haveTick && invulnUntil != 0 && invulnTick.IsValid && invulnTick.IsNewerThan(nt.ServerTick);
                break;
            }

            _canvas.enabled = found;
            if (!found) return;

            float frac = maxHp > 0f ? Mathf.Clamp01(hp / maxHp) : 0f;
            SetFill(_healthFill, frac);
            var hc = _healthFill.GetComponent<RawImage>();
            if (hc != null)
                hc.color = shielded
                    ? new Color(0.45f, 0.85f, 1f)
                    : Color.Lerp(new Color(0.92f, 0.16f, 0.16f), new Color(0.25f, 0.9f, 0.5f), frac);
            if (_healthText != null)
                _healthText.text = Mathf.CeilToInt(Mathf.Max(0f, hp)) + " / " + Mathf.CeilToInt(maxHp) + (shielded ? "   SHIELDED" : "");

            SetFill(_cooldownFill, cdFrac);

            if (_threatText != null)
                _threatText.text = "HUSKS  " + _huskQuery.CalculateEntityCount();

            _respawnOverlay.SetActive(dead);
        }

        static void SetFill(RectTransform fill, float frac)
        {
            if (fill == null) return;
            var max = fill.anchorMax;
            max.x = Mathf.Clamp01(frac);
            fill.anchorMax = max;
        }

        // ---- uGUI construction (code-built; no prefab/sprite assets) ----

        void BuildHud()
        {
            var go = new GameObject("~HUD");
            _canvas = go.AddComponent<Canvas>();
            _canvas.renderMode = RenderMode.ScreenSpaceOverlay;
            _canvas.sortingOrder = 100;
            var scaler = go.AddComponent<CanvasScaler>();
            scaler.uiScaleMode = CanvasScaler.ScaleMode.ScaleWithScreenSize;
            scaler.referenceResolution = new Vector2(1920, 1080);
            go.AddComponent<GraphicRaycaster>();

            var font = GetFont();

            // Health bar (bottom-left).
            var hpBg = MakeBar("HealthBg", _canvas.transform, new Color(0f, 0f, 0f, 0.6f),
                new Vector2(40, 46), new Vector2(440, 40));
            _healthFill = MakeFill("HealthFill", hpBg, new Color(0.25f, 0.9f, 0.5f));
            _healthText = MakeText("HealthText", hpBg, "100 / 100", 24, TextAnchor.MiddleCenter, Color.white, font);

            // Cooldown bar (just above health).
            var cdBg = MakeBar("CooldownBg", _canvas.transform, new Color(0f, 0f, 0f, 0.55f),
                new Vector2(40, 92), new Vector2(440, 14));
            _cooldownFill = MakeFill("CooldownFill", cdBg, new Color(0.4f, 0.8f, 1f));

            // Threat count (top-right).
            _threatText = MakeText("ThreatText", _canvas.transform, "HUSKS  0", 30, TextAnchor.UpperRight,
                new Color(1f, 0.62f, 0.4f), font);
            var trt = _threatText.rectTransform;
            trt.anchorMin = new Vector2(1, 1); trt.anchorMax = new Vector2(1, 1); trt.pivot = new Vector2(1, 1);
            trt.anchoredPosition = new Vector2(-40, -30); trt.sizeDelta = new Vector2(380, 50);

            // Downed / respawning overlay (full screen, toggled by Dead).
            _respawnOverlay = new GameObject("RespawnOverlay", typeof(RectTransform));
            _respawnOverlay.transform.SetParent(_canvas.transform, false);
            var ov = _respawnOverlay.AddComponent<RawImage>();
            ov.texture = Texture2D.whiteTexture;
            ov.color = new Color(0.35f, 0f, 0f, 0.35f);
            ov.raycastTarget = false;
            Stretch((RectTransform)_respawnOverlay.transform);
            var rtext = MakeText("RespawnText", _respawnOverlay.transform, "DOWNED - RESPAWNING", 56,
                TextAnchor.MiddleCenter, new Color(1f, 0.45f, 0.4f), font);
            Stretch(rtext.rectTransform);
            _respawnOverlay.SetActive(false);
        }

        static RectTransform MakeBar(string name, Transform parent, Color color, Vector2 anchoredPos, Vector2 size)
        {
            var go = new GameObject(name, typeof(RectTransform));
            go.transform.SetParent(parent, false);
            var img = go.AddComponent<RawImage>();
            img.texture = Texture2D.whiteTexture;
            img.color = color;
            img.raycastTarget = false;
            var rt = (RectTransform)go.transform;
            rt.anchorMin = Vector2.zero; rt.anchorMax = Vector2.zero; rt.pivot = Vector2.zero;
            rt.anchoredPosition = anchoredPos; rt.sizeDelta = size;
            return rt;
        }

        static RectTransform MakeFill(string name, RectTransform parent, Color color)
        {
            var go = new GameObject(name, typeof(RectTransform));
            go.transform.SetParent(parent, false);
            var img = go.AddComponent<RawImage>();
            img.texture = Texture2D.whiteTexture;
            img.color = color;
            img.raycastTarget = false;
            var rt = (RectTransform)go.transform;
            rt.anchorMin = Vector2.zero; rt.anchorMax = Vector2.one; rt.pivot = Vector2.zero;
            rt.offsetMin = new Vector2(3, 3); rt.offsetMax = new Vector2(-3, -3);
            return rt;
        }

        static Text MakeText(string name, Transform parent, string text, int size, TextAnchor anchor, Color color, Font font)
        {
            var go = new GameObject(name, typeof(RectTransform));
            go.transform.SetParent(parent, false);
            var t = go.AddComponent<Text>();
            t.text = text;
            t.font = font;
            t.fontSize = size;
            t.alignment = anchor;
            t.color = color;
            t.horizontalOverflow = HorizontalWrapMode.Overflow;
            t.verticalOverflow = VerticalWrapMode.Overflow;
            t.raycastTarget = false;
            Stretch(t.rectTransform);
            return t;
        }

        static void Stretch(RectTransform rt)
        {
            rt.anchorMin = Vector2.zero; rt.anchorMax = Vector2.one;
            rt.offsetMin = Vector2.zero; rt.offsetMax = Vector2.zero;
        }

        static Font GetFont()
        {
            Font f = Resources.GetBuiltinResource<Font>("LegacyRuntime.ttf");
            if (f == null) f = Resources.GetBuiltinResource<Font>("Arial.ttf");
            if (f == null) f = Font.CreateDynamicFontFromOSFont(new[] { "Arial", "Liberation Sans", "DejaVu Sans" }, 28);
            return f;
        }
    }
}