using System.Collections.Generic;
using Godot;

namespace WorldSim;

/// <summary>
/// Main loop and time system (SPEC §9).
/// 1 tick = 1 in-game minute; 1440 ticks = 1 day.
/// Day/night drives activity bias: gather/build by day, rest/socialize by night.
/// </summary>
public partial class GameManager : Node2D
{
    public static GameManager? Instance { get; private set; }

    [Export] public int Seed = 12345;

    // --- Settlements ------------------------------------------------------
    // Expansion phase: multiple towns, each a soul culture with its own
    // centroid, buildings, and granary. NPCs affiliate with a home town
    // but roam freely — the space between towns is where cultures meet.

    [Export] public int SouthPopulation = 12;    // nature souls
    [Export(PropertyHint.Range, "0,15,1")]
    public int SelfishCount = 3;                 // east souls living in the South
    [Export] public int NorthPopulation = 10;    // generational souls

    public record TownDef(string Name, Vector2 Center, SoulType Soul);

    public IReadOnlyList<TownDef> Towns => _towns;
    private readonly List<TownDef> _towns = new()
    {
        new("South", new Vector2(128f, 190f), SoulType.Nature),
        new("North", new Vector2(128f, 62f),  SoulType.Generational),
    };

    [Export(PropertyHint.Range, "1,2000,1")]
    public float TicksPerRealSecond = 20f;   // sim speed; ~1500 ≈ one day/sec for soaks

    /// <summary>Auto-quit after this many days (0 = run forever). Set for
    /// headless soaks so runs self-terminate cleanly — no external kill, no
    /// orphaned process racing the next run's CSV writes.</summary>
    [Export] public int StopAfterDays = 0;

    public World World { get; private set; } = null!;
    public List<Npc> Npcs { get; } = new();
    public List<Building> Buildings { get; } = new();

    public long TotalTicks { get; private set; }
    public int Day => (int)(TotalTicks / 1440);
    public int MinuteOfDay => (int)(TotalTicks % 1440);
    public bool IsNight => MinuteOfDay < 6 * 60 || MinuteOfDay >= 22 * 60;

    // --- Seasons: the pressure that makes community structure matter ------

    [Export] public int DaysPerSeason = 30;

    public int SeasonIndex => (Day / DaysPerSeason) % 4;

    public string SeasonName => SeasonIndex switch
    {
        0 => "spring", 1 => "summer", 2 => "autumn", _ => "winter",
    };

    /// <summary>Food regen multiplier — winter gives almost nothing.</summary>
    public float SeasonFoodMult => SeasonIndex switch
    {
        0 => 1.5f, 1 => 1.0f, 2 => 0.8f, _ => 0.05f,
    };

    /// <summary>Wood regen multiplier — growth slows in the cold.</summary>
    public float SeasonWoodMult => SeasonIndex switch
    {
        0 => 1.2f, 1 => 1.0f, 2 => 1.0f, _ => 0.4f,
    };

    private double _tickAccumulator;

    public override void _Ready()
    {
        Instance = this;
        TotalTicks = 8 * 60;   // start at 08:00 — day one begins mid-morning, not asleep
        World = new World(Seed);
        World.Generate();
        SpawnNpcs();
        StatsLogger.Init();
        GD.Print($"[WorldSim] World generated (seed {Seed}), {Npcs.Count} NPCs dropped in.");
    }

    private void SpawnNpcs()
    {
        // Dropped near their town's seed point with scatter — no scripted
        // layout. Where each community actually forms is the experiment.
        var rng = new System.Random(Seed);

        void Spawn(string town, Vector2 center, SoulProfile soul, int count, string prefix)
        {
            for (int i = 0; i < count; i++)
            {
                var npc = new Npc
                {
                    Name = $"{prefix}_{(char)('A' + Npcs.Count % 26)}{(Npcs.Count >= 26 ? Npcs.Count.ToString() : "")}",
                    HomeTown = town,
                    Soul = soul,
                    PersonalityModifier = (float)(rng.NextDouble() * 0.4 - 0.2),
                    Position = center + new Vector2(rng.Next(-12, 13), rng.Next(-12, 13)),
                    // Staggered ages so the founding generation doesn't die
                    // in one terrible week.
                    AgeDays = rng.Next(0, 100),
                    LifeExpectancyDays = 150 + rng.Next(0, 80),
                };
                npc.Know.Capacity = 1.0f + (float)rng.NextDouble();
                Npcs.Add(npc);
            }
        }

        foreach (var town in _towns)
        {
            if (town.Name == "South")
            {
                Spawn(town.Name, town.Center, SoulProfile.NatureSoul(), SouthPopulation, "South");
                for (int i = 0; i < SelfishCount; i++)
                    Spawn(town.Name, town.Center, SoulProfile.SelfishSoul(), 1, "South");
            }
            else if (town.Name == "North")
            {
                Spawn(town.Name, town.Center, SoulProfile.GenerationalSoul(), NorthPopulation, "North");
            }
        }
    }

    /// <summary>How many villagers (other than <paramref name="except"/>)
    /// are currently sleeping at this shelter.</summary>
    public int RestingOccupancy(Building b, Npc? except = null)
    {
        int count = 0;
        foreach (var npc in Npcs)
            if (npc != except && npc.State == NpcState.Resting &&
                npc.Position.DistanceTo(b.Site) <= 2.5f)
                count++;
        return count;
    }

    public int TownPopulation(string town)
    {
        int count = 0;
        foreach (var npc in Npcs)
            if (npc.HomeTown == town) count++;
        return count;
    }

    public Vector2 TownCentroid(string town)
    {
        Vector2 sum = Vector2.Zero;
        int count = 0;
        foreach (var npc in Npcs)
        {
            if (npc.HomeTown != town) continue;
            sum += npc.Position;
            count++;
        }
        if (count == 0)
        {
            foreach (var t in _towns)
                if (t.Name == town) return t.Center;
            return new Vector2(World.GridSize / 2f, World.GridSize / 2f);
        }
        return sum / count;
    }

    public override void _Process(double delta)
    {
        _tickAccumulator += delta * TicksPerRealSecond;
        while (_tickAccumulator >= 1.0)
        {
            _tickAccumulator -= 1.0;
            Tick();
        }
    }

    /// <summary>
    /// Soul-to-soul atmospheric pressure (ported from the Unity POC's
    /// SoulFieldSystem): souls in proximity press on each other's
    /// atmospheres. An encased soul darkens the room; a clear soul makes
    /// it slightly easier for everyone near them to radiate. Both
    /// directions apply; the net effect depends on relative debris.
    /// </summary>
    private void ApplySoulPressure()
    {
        const float radius = 8f;
        const float strength = 0.00004f;

        for (int i = 0; i < Npcs.Count; i++)
        {
            for (int j = i + 1; j < Npcs.Count; j++)
            {
                var a = Npcs[i];
                var b = Npcs[j];
                float dist = a.Position.DistanceTo(b.Position);
                if (dist > radius) continue;

                float falloff = 1f - dist / radius;

                float fromA = Mathf.Lerp(-strength, strength, a.Imprint.Total) * falloff;
                b.Imprint.ExternalPerception = Mathf.Clamp(b.Imprint.ExternalPerception + fromA, 0f, 1f);

                float fromB = Mathf.Lerp(-strength, strength, b.Imprint.Total) * falloff;
                a.Imprint.ExternalPerception = Mathf.Clamp(a.Imprint.ExternalPerception + fromB, 0f, 1f);
            }
        }
    }

    // --- Mortality: generations end, and what wasn't passed on ends too --

    public int DeathsToday { get; set; }
    private int _bornCount;

    private void TickMortality()
    {
        var dying = new List<Npc>();
        foreach (var npc in Npcs)
        {
            npc.AgeDays += 1f;
            if (npc.AgeDays >= npc.LifeExpectancyDays)
                dying.Add(npc);
        }

        var rng = new System.Random(Seed + (int)TotalTicks);
        foreach (var dead in Npcs.ToArray())
        {
            if (!dying.Contains(dead)) continue;
            Npcs.Remove(dead);
            DeathsToday++;

            // Everything unshared dies with them: skills, memories, echoes.
            // What survives is what they taught, built, and stored.
            foreach (var other in Npcs)
                other.ForgetPerson(dead);

            // A youth comes of age in the same town, same culture, knowing
            // almost nothing — but raised among the living, not in a void.
            // They spawn beside the town's wisest elder, so the young begin
            // life within reach of what the community still remembers. The
            // town's knowledge is only what its living carry — but the young
            // start where that knowledge is.
            _bornCount++;
            Npc? elder = null;
            float bestKnow = -1f;
            foreach (var other in Npcs)
                if (other.HomeTown == dead.HomeTown && other.Know.Total > bestKnow)
                    { bestKnow = other.Know.Total; elder = other; }
            Vector2 cradle = elder?.Position ?? TownCentroid(dead.HomeTown);

            var youth = new Npc
            {
                Name = $"{dead.HomeTown}_{(char)('A' + _bornCount % 26)}{_bornCount + 25}",
                HomeTown = dead.HomeTown,
                Soul = dead.Soul,     // raised in the culture that raised them
                PersonalityModifier = (float)(rng.NextDouble() * 0.4 - 0.2),
                Position = cradle + new Vector2(rng.Next(-4, 5), rng.Next(-4, 5)),
                AgeDays = 0f,
                LifeExpectancyDays = 150 + rng.Next(0, 80),
            };
            youth.Know.Capacity = 1.0f + (float)rng.NextDouble();
            Npcs.Add(youth);

            GD.Print($"[Passing] day {Day}: {dead.Name} dies at {dead.AgeDays:0} days " +
                     $"(knowledge {dead.Know.Total:0.00} lost); {youth.Name} comes of age.");
        }
    }

    /// <summary>Where the community's feet actually are — new communal
    /// buildings are founded here, not at a scripted town center.</summary>
    public Vector2 CommunityCentroid()
    {
        if (Npcs.Count == 0) return new Vector2(World.GridSize / 2f, World.GridSize / 2f);
        Vector2 sum = Vector2.Zero;
        foreach (var npc in Npcs) sum += npc.Position;
        return sum / Npcs.Count;
    }

    private void Tick()
    {
        TotalTicks++;

        foreach (var npc in Npcs)
            npc.Tick(World, this);

        ApplySoulPressure();

        if (TotalTicks % 1440 == 0)
        {
            World.RegenerateDaily(SeasonFoodMult, SeasonWoodMult);
            foreach (var building in Buildings)
                building.DailyUpkeep();
            foreach (var npc in Npcs)
                npc.FadeEchoes(0.005f);
            TickMortality();
            StatsLogger.LogDay(this);
            if (Day % 10 == 0)
                GD.Print($"[WorldSim] Day {Day} complete.");

            if (StopAfterDays > 0 && Day >= StopAfterDays)
            {
                GD.Print($"[WorldSim] Reached day {Day} — stopping.");
                GetTree().Quit();
            }
        }
    }
}