using System.Collections.Generic;
using ProjectM.Simulation;
using Unity.Entities;
using Unity.NetCode;
using UnityEngine;
using UnityEngine.UIElements;

namespace ProjectM.Client
{
    /// <summary>
    /// Client-only screen HUD, rebuilt on UI Toolkit so it reads in the same Aether-cyan visual language as the
    /// menu / pause / settings screens (<see cref="MenuUi"/> / <see cref="HudUi"/>). A managed presentation
    /// SystemBase (<see cref="PresentationSystemGroup"/>) that OBSERVES the local player ghost + the global
    /// cycle / ledger / goal each frame and pushes values into a runtime UIDocument (shared PanelSettings,
    /// sortingOrder 50 so it sits BEHIND the pause overlay's 100). The root is <c>pickingMode = Ignore</c> so the
    /// HUD never eats clicks meant for the game world — only the build-palette buttons pick. Presentation only
    /// (client world, no simulation). The palette buttons set <see cref="BuildPaletteState"/> (client-local UI
    /// state), which BuildSendSystem turns into a ground ghost + click-to-place. The visual tree is built on the
    /// first OnUpdate where the UIDocument's root exists (giving the panel a frame to initialise its PanelSettings).
    /// </summary>
    [WorldSystemFilter(WorldSystemFilterFlags.ClientSimulation)]
    [UpdateInGroup(typeof(PresentationSystemGroup))]
    public partial class HudSystem : SystemBase
    {
        GameObject _hudGo;
        UIDocument _doc;
        bool _built;

        VisualElement _healthFill, _cooldownFill, _goalFill, _downed, _paletteRow;
        Label _healthText, _threatText, _phaseText, _resourceText, _locationText, _goalText;

        bool _paletteBuilt;
        readonly Dictionary<byte, PaletteItem> _palette = new();

        EntityQuery _huskQuery;

        struct PaletteItem { public VisualElement Root; public Label Cost; public int CostAmount; }

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

        protected override void OnStartRunning()
        {
            if (_hudGo != null) return;
            MenuUi.EnsureEventSystem();
            _hudGo = new GameObject("~HUD");
            _doc = _hudGo.AddComponent<UIDocument>();
            _doc.panelSettings = MenuUi.LoadPanelSettings();
            _doc.sortingOrder = 50; // behind the pause overlay (100)
        }

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

        protected override void OnUpdate()
        {
            if (_doc == null) return;
            if (!_built)
            {
                var r = _doc.rootVisualElement;
                if (r == null) return; // panel not initialised yet (next frame)
                BuildTree(r);
                _built = true;
            }

            bool haveTick = SystemAPI.TryGetSingleton<NetworkTime>(out var nt);
            int huskCount = _huskQuery.CalculateEntityCount();

            // ---- Macro loop: phase + cycle + countdown ----
            bool haveCycle = SystemAPI.TryGetSingleton<CycleState>(out var cyc);
            if (haveCycle)
            {
                var endTick = new NetworkTick(cyc.PhaseEndTick);
                string detail;
                if (cyc.Phase == CyclePhase.Siege)
                    detail = "WAVE " + cyc.WaveNumber + "   -   " + huskCount + " HUSKS";
                else if (haveTick && cyc.PhaseEndTick != 0 && endTick.IsValid && endTick.IsNewerThan(nt.ServerTick))
                    detail = "INCURSION IN " + (endTick.TicksSince(nt.ServerTick) / 60 + 1) + "s";
                else
                    detail = "";
                _phaseText.text = PhaseLabel(cyc.Phase) + (detail.Length > 0 ? "   -   " + detail : "");
                _phaseText.style.color = PhaseColor(cyc.Phase);
            }
            else
            {
                _phaseText.text = "";
            }

            // ---- Location + gate hint ----
            var cam = Camera.main;
            bool onExpedition = cam != null && cam.transform.position.x > 500f;
            _locationText.text = onExpedition
                ? "ON EXPEDITION   -   return through the gate"
                : "AT BASE   -   deploy through the gate when you're ready";
            _locationText.style.color = onExpedition ? new Color(1f, 0.8f, 0.4f) : new Color(0.6f, 0.85f, 1f);

            // ---- Goal ----
            if (SystemAPI.TryGetSingleton<GoalProgress>(out var goal))
            {
                float gfrac = goal.Target > 0 ? Mathf.Clamp01(goal.Charge / (float)goal.Target) : 0f;
                HudUi.SetFill(_goalFill, gfrac);
                _goalText.text = "GOAL  " + goal.Charge + " / " + goal.Target;
            }

            // ---- Resources (Ore feeds the palette affordability) ----
            int aether = 0, ore = 0, bio = 0;
            if (SystemAPI.TryGetSingletonEntity<ResourceLedger>(out var ledgerE))
            {
                var buf = SystemAPI.GetBuffer<StorageEntry>(ledgerE);
                for (int i = 0; i < buf.Length; i++)
                {
                    var en = buf[i];
                    if (en.ItemId == ResourceId.Aether) aether = en.Count;
                    else if (en.ItemId == ResourceId.Ore) ore = en.Count;
                    else if (en.ItemId == ResourceId.Biomass) bio = en.Count;
                }
            }
            _resourceText.text = "AETHER " + aether + "     ORE " + ore + "     BIO " + bio;

            // ---- Build palette (lazy-built once the catalog has streamed; hidden off-base) ----
            UpdatePalette(ore, onExpedition);

            // ---- Per-player vitals ----
            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);

                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;
            }

            _doc.rootVisualElement.style.display = (found || haveCycle) ? DisplayStyle.Flex : DisplayStyle.None;
            if (!found) { _downed.style.display = DisplayStyle.None; return; }

            float frac = maxHp > 0f ? Mathf.Clamp01(hp / maxHp) : 0f;
            HudUi.SetFill(_healthFill, frac);
            _healthFill.style.backgroundColor = 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);
            _healthText.text = Mathf.CeilToInt(Mathf.Max(0f, hp)) + " / " + Mathf.CeilToInt(maxHp) + (shielded ? "   SHIELDED" : "");

            HudUi.SetFill(_cooldownFill, cdFrac);
            _threatText.text = "HUSKS  " + huskCount;
            _downed.style.display = dead ? DisplayStyle.Flex : DisplayStyle.None;
        }

        void UpdatePalette(int ore, bool onExpedition)
        {
            if (!_paletteBuilt && SystemAPI.TryGetSingletonEntity<StructureCatalog>(out var catE))
            {
                var cat = SystemAPI.GetBuffer<StructureCatalogEntry>(catE);
                for (int i = 0; i < cat.Length; i++)
                    AddPaletteItem(cat[i].Type, cat[i].CostAmount);
                _paletteBuilt = true;
            }
            if (!_paletteBuilt) { _paletteRow.style.display = DisplayStyle.None; return; }

            _paletteRow.style.display = onExpedition ? DisplayStyle.None : DisplayStyle.Flex;
            foreach (var kv in _palette)
            {
                var item = kv.Value;
                bool affordable = ore >= item.CostAmount;
                bool selected = BuildPaletteState.Selected == kv.Key;
                item.Root.style.opacity = affordable ? 1f : 0.45f;
                item.Cost.style.color = affordable ? new Color(0.7f, 0.95f, 0.8f) : new Color(1f, 0.5f, 0.4f);
                MenuUi.Border(item.Root, selected ? MenuUi.Accent : new Color(1f, 1f, 1f, 0.08f), selected ? 2 : 1);
                item.Root.style.backgroundColor = selected
                    ? new Color(0.16f, 0.26f, 0.32f, 0.95f)
                    : new Color(0.09f, 0.11f, 0.15f, 0.92f);
            }
        }

        void AddPaletteItem(byte type, int cost)
        {
            if (type == 0 || _palette.ContainsKey(type)) return;
            var root = new VisualElement();
            root.style.width = 92;
            root.style.marginLeft = 4; root.style.marginRight = 4;
            root.style.paddingTop = 6; root.style.paddingBottom = 6;
            root.style.alignItems = Align.Center;
            root.style.backgroundColor = new Color(0.09f, 0.11f, 0.15f, 0.92f);
            root.pickingMode = PickingMode.Position;
            MenuUi.Round(root, 6);
            MenuUi.Border(root, new Color(1f, 1f, 1f, 0.08f), 1);

            var nameLabel = HudUi.Text(StructureName(type), 13, MenuUi.TextCol, TextAnchor.MiddleCenter);
            var costLabel = HudUi.Text(cost + " ORE", 12, new Color(0.7f, 0.95f, 0.8f), TextAnchor.MiddleCenter);
            costLabel.style.marginTop = 2;
            root.Add(nameLabel);
            root.Add(costLabel);

            byte t = type;
            root.RegisterCallback<ClickEvent>(_ =>
                BuildPaletteState.Select(BuildPaletteState.Selected == t ? (byte)0 : t));

            _paletteRow.Add(root);
            _palette[type] = new PaletteItem { Root = root, Cost = costLabel, CostAmount = cost };
        }

        // ---- UITK construction ----

        void BuildTree(VisualElement root)
        {
            root.style.position = Position.Absolute;
            root.style.left = 0; root.style.right = 0; root.style.top = 0; root.style.bottom = 0;
            root.pickingMode = PickingMode.Ignore; // never eat game-world clicks

            // Health + cooldown (bottom-left).
            var vitals = HudUi.Group();
            vitals.style.position = Position.Absolute;
            vitals.style.left = 40; vitals.style.bottom = 40;
            var cdBar = HudUi.Bar(440, 12, new Color(0.4f, 0.8f, 1f), out _cooldownFill);
            cdBar.style.marginBottom = 6;
            var hpBar = HudUi.Bar(440, 40, new Color(0.25f, 0.9f, 0.5f), out _healthFill);
            _healthText = HudUi.Text("100 / 100", 22, Color.white, TextAnchor.MiddleCenter);
            _healthText.style.position = Position.Absolute;
            _healthText.style.left = 0; _healthText.style.right = 0; _healthText.style.top = 0; _healthText.style.bottom = 0;
            hpBar.Add(_healthText);
            vitals.Add(cdBar);
            vitals.Add(hpBar);
            root.Add(vitals);

            // Threat (top-right).
            _threatText = HudUi.Text("HUSKS  0", 30, new Color(1f, 0.62f, 0.4f), TextAnchor.UpperRight);
            _threatText.style.position = Position.Absolute;
            _threatText.style.right = 40; _threatText.style.top = 28; _threatText.style.width = 380;
            root.Add(_threatText);

            // Macro stack (top-center).
            var macro = HudUi.Group(Align.Center);
            macro.style.position = Position.Absolute;
            macro.style.top = 22; macro.style.left = 0; macro.style.right = 0;
            _phaseText = HudUi.Text("", 30, new Color(0.55f, 0.9f, 1f), TextAnchor.MiddleCenter);
            _resourceText = HudUi.Text("", 22, new Color(0.7f, 0.95f, 0.8f), TextAnchor.MiddleCenter);
            _resourceText.style.marginTop = 4;
            _locationText = HudUi.Text("", 18, new Color(0.6f, 0.85f, 1f), TextAnchor.MiddleCenter);
            _locationText.style.marginTop = 4;
            var goalBar = HudUi.Bar(360, 16, new Color(0.8f, 0.6f, 1f), out _goalFill);
            goalBar.style.marginTop = 8;
            _goalText = HudUi.Text("GOAL  0 / 10", 13, Color.white, TextAnchor.MiddleCenter);
            _goalText.style.position = Position.Absolute;
            _goalText.style.left = 0; _goalText.style.right = 0; _goalText.style.top = 0; _goalText.style.bottom = 0;
            goalBar.Add(_goalText);
            macro.Add(_phaseText);
            macro.Add(_resourceText);
            macro.Add(_locationText);
            macro.Add(goalBar);
            root.Add(macro);

            // Build palette row (bottom-center). The row passes clicks through; its buttons pick.
            _paletteRow = new VisualElement();
            _paletteRow.style.position = Position.Absolute;
            _paletteRow.style.bottom = 24; _paletteRow.style.left = 0; _paletteRow.style.right = 0;
            _paletteRow.style.flexDirection = FlexDirection.Row;
            _paletteRow.style.justifyContent = Justify.Center;
            _paletteRow.pickingMode = PickingMode.Ignore;
            root.Add(_paletteRow);

            // Downed overlay.
            _downed = new VisualElement();
            _downed.style.position = Position.Absolute;
            _downed.style.left = 0; _downed.style.right = 0; _downed.style.top = 0; _downed.style.bottom = 0;
            _downed.style.backgroundColor = new Color(0.35f, 0f, 0f, 0.35f);
            _downed.style.alignItems = Align.Center;
            _downed.style.justifyContent = Justify.Center;
            _downed.pickingMode = PickingMode.Ignore;
            _downed.Add(HudUi.Text("DOWNED - RESPAWNING", 52, new Color(1f, 0.45f, 0.4f), TextAnchor.MiddleCenter));
            _downed.style.display = DisplayStyle.None;
            root.Add(_downed);
        }

        static Color PhaseColor(byte phase)
        {
            switch (phase)
            {
                case CyclePhase.Calm: return new Color(0.45f, 0.9f, 0.7f);
                case CyclePhase.Siege: return new Color(1f, 0.45f, 0.3f);
                default: return Color.white;
            }
        }

        static string PhaseLabel(byte phase)
        {
            switch (phase)
            {
                case CyclePhase.Calm: return "AT BASE";
                case CyclePhase.Siege: return "UNDER SIEGE";
                default: return "";
            }
        }

        static string StructureName(byte type)
        {
            switch (type)
            {
                case StructureType.Turret: return "Turret";
                case StructureType.Wall: return "Wall";
                case StructureType.Pylon: return "Pylon";
                case StructureType.Harvester: return "Harvester";
                case StructureType.Fabricator: return "Fabricator";
                case StructureType.Conveyor: return "Conveyor";
                default: return "?";
            }
        }
    }
}