using System.Collections.Generic;
using System.Linq;
using Godot;
using Theriapolis.Core;
using Theriapolis.Core.Data;
using Theriapolis.Core.Entities;
using Theriapolis.Core.Rules.Combat;
using Theriapolis.Core.Tactical;
using Theriapolis.Core.Time;
using Theriapolis.Core.Util;
using Theriapolis.Core.World;
using Theriapolis.Core.World.Generation;
using Theriapolis.Core.World.Settlements;
using Theriapolis.GodotHost.Input;
using Theriapolis.GodotHost.Platform;
using Theriapolis.GodotHost.Rendering;
using Theriapolis.GodotHost.UI;

namespace Theriapolis.GodotHost.Scenes;

/// <summary>
/// M7.2 — the play screen. Wraps <see cref="WorldRenderNode"/> with the
/// game-state layer: player actor, world clock, chunk streamer, NPC
/// markers, player controller, and a top-left HUD overlay. Click on the
/// world map to travel; WASD to step at tactical zoom.
///
/// Per the M7 plan §6: PlayScreen owns the chunk streamer (so M7.3 save
/// can serialise its delta store) and the actor manager (so M7.5 can
/// drive interact prompts). The world-map view and the tactical view
/// are the same scene at different zoom levels — there is no separate
/// WorldMapScreen, by design.
///
/// M7.2 omissions (deferred to later sub-milestones):
///   - Save / load round-trip (M7.3)
///   - Pause menu (M7.4)
///   - Interact prompt + dialogue push (M7.5)
///   - Encounter detection stub + autosave toast (M7.6)
/// </summary>
public partial class PlayScreen : Control
{
    private const float ClickSlopPixels = 4f;

    // Composed Core systems
    private WorldGenContext _ctx = null!;
    private ContentResolver _content = null!;
    private InMemoryChunkDeltaStore _deltas = null!;
    private ChunkStreamer _streamer = null!;
    private ActorManager _actors = null!;
    private WorldClock _clock = null!;
    private PlayerController _controller = null!;
    private AnchorRegistry _anchorRegistry = null!;

    // Godot tree
    private WorldRenderNode _render = null!;
    private PlayerMarker _playerMarker = null!;
    private readonly Dictionary<int, NpcMarker> _npcMarkers = new();
    private Label _hudLabel = null!;
    private PanelContainer _hudPanel = null!;

    // Click-vs-drag state (left-click only; PanZoomCamera handles
    // middle/right-drag pan independently).
    private Vector2 _mouseDownPos;
    private int _mouseDownTileX, _mouseDownTileY;
    private bool _mouseDownTracked;

    public override void _Ready()
    {
        var session = GameSession.From(this);
        if (session.Ctx is null)
        {
            GD.PushError("[play] No WorldGenContext on session — falling back to title.");
            BackToTitle();
            return;
        }
        _ctx = session.Ctx;

        Theme = CodexTheme.Build();
        SetAnchorsAndOffsetsPreset(LayoutPreset.FullRect);

        // World render layer — biome + polylines + settlements + camera.
        _render = new WorldRenderNode();
        AddChild(_render);
        _render.Initialize(_ctx.World);

        // Core systems.
        _content = new ContentResolver(
            new Theriapolis.Core.Data.ContentLoader(ContentPaths.DataDir));
        _deltas = new InMemoryChunkDeltaStore();
        _streamer = new ChunkStreamer(
            _ctx.World.WorldSeed, _ctx.World, _deltas, _content.Settlements);
        _streamer.OnChunkLoaded   += _render.AddChunkNode;
        _streamer.OnChunkEvicting += _render.RemoveChunkNode;
        _streamer.OnChunkLoaded   += HandleChunkLoaded;
        _streamer.OnChunkEvicting += HandleChunkEvicting;

        _clock = new WorldClock();
        _actors = new ActorManager();
        _anchorRegistry = new AnchorRegistry();
        _anchorRegistry.RegisterAllAnchors(_ctx.World);

        // Spawn player at the Tier-1 anchor (Millhaven), or the centre of
        // the world if no inhabited settlement exists.
        var spawn = ChooseSpawn(_ctx.World);
        if (session.PendingCharacter is not null)
        {
            var p = _actors.SpawnPlayer(spawn, session.PendingCharacter);
            if (!string.IsNullOrWhiteSpace(session.PendingName))
                p.Name = session.PendingName;
        }
        else
        {
            _actors.SpawnPlayer(spawn);
        }

        _controller = new PlayerController(_actors.Player!, _ctx.World, _clock);
        _controller.TacticalIsWalkable = (tx, ty) => _streamer.SampleTile(tx, ty).IsWalkable;

        // Player marker.
        _playerMarker = new PlayerMarker
        {
            Position = new Vector2(_actors.Player!.Position.X, _actors.Player.Position.Y),
            FacingAngleRad = _actors.Player.FacingAngleRad,
        };
        AddChild(_playerMarker);

        _render.Camera.Position = _playerMarker.Position;
        SetInitialZoom();
        BuildHud();

        // Clear pending so a quit-to-title doesn't see stale data.
        session.PendingCharacter = null;
        session.PendingName = "Wanderer";
        session.PendingRestore = null;
        session.PendingHeader = null;
    }

    public override void _Process(double delta)
    {
        if (_actors?.Player is null || _render is null) return;
        float dt = (float)delta;

        bool tactical = _render.Camera.Zoom.X >= WorldRenderNode.TacticalRenderZoomMin;

        // Tactical WASD direction (world-map mode ignores keys — middle-drag
        // pans, click-to-travel sets the destination).
        float dx = 0f, dy = 0f;
        if (tactical)
        {
            if (Godot.Input.IsKeyPressed(Key.W) || Godot.Input.IsKeyPressed(Key.Up))    dy -= 1f;
            if (Godot.Input.IsKeyPressed(Key.S) || Godot.Input.IsKeyPressed(Key.Down))  dy += 1f;
            if (Godot.Input.IsKeyPressed(Key.A) || Godot.Input.IsKeyPressed(Key.Left))  dx -= 1f;
            if (Godot.Input.IsKeyPressed(Key.D) || Godot.Input.IsKeyPressed(Key.Right)) dx += 1f;
        }

        _controller.Update(dt, dx, dy, tactical, isFocused: true);

        // Sync the player marker from Core state.
        var p = _actors.Player;
        _playerMarker.Position = new Vector2(p.Position.X, p.Position.Y);
        _playerMarker.FacingAngleRad = p.FacingAngleRad;

        // Camera follow when traveling or in tactical (matches MonoGame).
        if (_controller.IsTraveling || tactical)
            _render.Camera.Position = _playerMarker.Position;

        // Stream tactical chunks around the player when at tactical zoom.
        if (tactical)
            _streamer.EnsureLoadedAround(p.Position, C.TACTICAL_WINDOW_WORLD_TILES);

        // Counter-scale markers so on-screen size stays constant.
        float zoom = _render.Camera.Zoom.X;
        if (zoom > 0f)
        {
            float inv = 1f / zoom;
            _playerMarker.Scale = new Vector2(inv, inv);
            _playerMarker.ShowFacingTick = tactical;
            foreach (var marker in _npcMarkers.Values)
                marker.Scale = new Vector2(inv, inv);
        }

        UpdateHud(tactical);
    }

    public override void _UnhandledInput(InputEvent @event)
    {
        if (@event is not InputEventMouseButton mb || mb.ButtonIndex != MouseButton.Left)
            return;

        if (mb.Pressed)
        {
            _mouseDownPos = mb.Position;
            var worldPos = ScreenToWorld(mb.Position);
            _mouseDownTileX = (int)Mathf.Floor(worldPos.X / C.WORLD_TILE_PIXELS);
            _mouseDownTileY = (int)Mathf.Floor(worldPos.Y / C.WORLD_TILE_PIXELS);
            _mouseDownTracked = true;
            return;
        }

        // Release.
        if (!_mouseDownTracked) return;
        _mouseDownTracked = false;
        bool wasClick = mb.Position.DistanceTo(_mouseDownPos) <= ClickSlopPixels;
        if (!wasClick) return;

        bool tactical = _render.Camera.Zoom.X >= WorldRenderNode.TacticalRenderZoomMin;
        if (!tactical && InBounds(_mouseDownTileX, _mouseDownTileY))
        {
            _controller.RequestTravelTo(_mouseDownTileX, _mouseDownTileY);
            GetViewport().SetInputAsHandled();
        }
    }

    private Vector2 ScreenToWorld(Vector2 screenPos)
        => _render.Camera.GetCanvasTransform().AffineInverse() * screenPos;

    private static bool InBounds(int x, int y)
        => (uint)x < C.WORLD_WIDTH_TILES && (uint)y < C.WORLD_HEIGHT_TILES;

    // ──────────────────────────────────────────────────────────────────────
    // Chunk → NPC lifecycle (Phase 5 M5)

    private void HandleChunkLoaded(TacticalChunk chunk)
    {
        if (_content is null) return;
        for (int i = 0; i < chunk.Spawns.Count; i++)
        {
            var spawn = chunk.Spawns[i];
            if (_actors.FindNpcBySource(chunk.Coord, i) is not null) continue;

            if (spawn.Kind == SpawnKind.Resident)
            {
                var resident = ResidentInstantiator.Spawn(
                    _ctx.World.WorldSeed, chunk, i, spawn,
                    _ctx.World, _content, _actors, _anchorRegistry);
                if (resident is not null) MountNpcMarker(resident);
                continue;
            }

            var template = NpcInstantiator.PickTemplate(spawn.Kind, chunk.DangerZone, _content.Npcs);
            if (template is null) continue;

            int tx = chunk.OriginX + spawn.LocalX;
            int ty = chunk.OriginY + spawn.LocalY;
            var npc = _actors.SpawnNpc(template, new Vec2(tx, ty), chunk.Coord, i);
            MountNpcMarker(npc);
        }
    }

    private void HandleChunkEvicting(TacticalChunk chunk)
    {
        var toRemove = new List<int>();
        foreach (var npc in _actors.Npcs)
        {
            if (npc.SourceChunk is { } src && src.Equals(chunk.Coord))
            {
                toRemove.Add(npc.Id);
                if (!string.IsNullOrEmpty(npc.RoleTag))
                    _anchorRegistry.UnregisterRole(npc.RoleTag);
            }
        }
        foreach (int id in toRemove)
        {
            _actors.RemoveActor(id);
            if (_npcMarkers.Remove(id, out var marker))
                marker.QueueFree();
        }
    }

    private void MountNpcMarker(NpcActor npc)
    {
        var marker = new NpcMarker
        {
            Position = new Vector2(npc.Position.X, npc.Position.Y),
            Allegiance = npc.Allegiance,
        };
        AddChild(marker);
        _npcMarkers[npc.Id] = marker;
    }

    // ──────────────────────────────────────────────────────────────────────
    // Spawn + initial-zoom helpers

    private static Vec2 ChooseSpawn(WorldState w)
    {
        var tier1 = w.Settlements.FirstOrDefault(s => s.Tier == 1 && !s.IsPoi);
        if (tier1 is not null) return new Vec2(tier1.WorldPixelX, tier1.WorldPixelY);
        var anyInhabited = w.Settlements.FirstOrDefault(s => !s.IsPoi);
        if (anyInhabited is not null) return new Vec2(anyInhabited.WorldPixelX, anyInhabited.WorldPixelY);
        return new Vec2(
            C.WORLD_WIDTH_TILES * C.WORLD_TILE_PIXELS * 0.5f,
            C.WORLD_HEIGHT_TILES * C.WORLD_TILE_PIXELS * 0.5f);
    }

    private void SetInitialZoom()
    {
        // Frame ~24 tiles across the screen — comfortable overland zoom.
        Vector2 viewport = GetViewport().GetVisibleRect().Size;
        float targetZoom = viewport.X / (24f * C.WORLD_TILE_PIXELS);
        targetZoom = Mathf.Clamp(targetZoom,
            _render.Camera.MinZoom,
            WorldRenderNode.TacticalRenderZoomMin * 0.95f);
        _render.Camera.Zoom = new Vector2(targetZoom, targetZoom);
    }

    // ──────────────────────────────────────────────────────────────────────
    // HUD overlay (top-left panel, codex-styled)

    private void BuildHud()
    {
        var hudLayer = new CanvasLayer { Layer = 50, Name = "Hud" };
        AddChild(hudLayer);

        _hudPanel = new PanelContainer
        {
            ThemeTypeVariation = "Card",
            MouseFilter = MouseFilterEnum.Ignore,
            OffsetLeft = 12, OffsetTop = 12,
            OffsetRight = 420, OffsetBottom = 220,
        };
        hudLayer.AddChild(_hudPanel);

        var margin = new MarginContainer { MouseFilter = MouseFilterEnum.Ignore };
        margin.AddThemeConstantOverride("margin_left", 12);
        margin.AddThemeConstantOverride("margin_top", 8);
        margin.AddThemeConstantOverride("margin_right", 12);
        margin.AddThemeConstantOverride("margin_bottom", 8);
        _hudPanel.AddChild(margin);

        _hudLabel = new Label
        {
            Text = "…",
            ThemeTypeVariation = "CardBody",
            AutowrapMode = TextServer.AutowrapMode.WordSmart,
            MouseFilter = MouseFilterEnum.Ignore,
        };
        margin.AddChild(_hudLabel);
    }

    private void UpdateHud(bool tactical)
    {
        var p = _actors.Player!;
        int ptx = (int)Mathf.Floor(p.Position.X / C.WORLD_TILE_PIXELS);
        int pty = (int)Mathf.Floor(p.Position.Y / C.WORLD_TILE_PIXELS);
        int cx = Mathf.Clamp(ptx, 0, C.WORLD_WIDTH_TILES - 1);
        int cy = Mathf.Clamp(pty, 0, C.WORLD_HEIGHT_TILES - 1);
        ref var t = ref _ctx.World.TileAt(cx, cy);

        string charBlock = "";
        if (p.Character is { } pc)
        {
            int ac = Theriapolis.Core.Rules.Stats.DerivedStats.ArmorClass(pc);
            charBlock = $"{p.Name}  HP {pc.CurrentHp}/{pc.MaxHp}  AC {ac}\n";
        }

        string viewBlock = tactical
            ? "View: Tactical   (WASD to step)"
            : "View: World Map  (click a tile to travel)";

        string status = _controller.IsTraveling
            ? "Traveling…"
            : tactical
                ? "Mouse-wheel out to leave tactical."
                : "Mouse-wheel in for tactical.";

        _hudLabel.Text =
            charBlock +
            $"Seed: 0x{_ctx.World.WorldSeed:X}\n" +
            $"Player: ({ptx}, {pty})  {t.Biome}\n" +
            $"{viewBlock}\n" +
            $"Time: Day {_clock.Day}, {_clock.Hour:D2}:{_clock.Minute:D2}\n" +
            $"{status}\n" +
            "M7.3 brings save/load. ESC pause arrives M7.4.";
    }

    // ──────────────────────────────────────────────────────────────────────
    // Quit path (M7.4 will wire ESC → pause; for now Esc returns to title)

    public override void _Input(InputEvent @event)
    {
        if (@event is InputEventKey { Pressed: true, Keycode: Key.Escape })
        {
            GetViewport().SetInputAsHandled();
            BackToTitle();
        }
    }

    private void BackToTitle()
    {
        var session = GameSession.From(this);
        session.ClearPending();
        session.Ctx = null;

        var parent = GetParent();
        if (parent is null) return;
        foreach (Node sibling in parent.GetChildren())
            if (sibling != this) sibling.QueueFree();
        parent.AddChild(new TitleScreen());
        QueueFree();
    }
}