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 TownPopulationEach = 16;   // per settlement (~64 total, room to grow)

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

    // Four towns at the compass points of the world, each its own culture
    // (per DESIGN.md): North reveres lineage, South lives with the land,
    // West performs material wealth, East schemes for self.
    public IReadOnlyList<TownDef> Towns => _towns;
    private readonly List<TownDef> _towns = new()
    {
        new("North", new Vector2(384f, 130f), SoulType.Generational),
        new("South", new Vector2(384f, 638f), SoulType.Nature),
        new("West",  new Vector2(130f, 384f), SoulType.Materialist),
        new("East",  new Vector2(638f, 384f), SoulType.Selfish),
    };

    private static SoulProfile ProfileFor(SoulType t) => t switch
    {
        SoulType.Generational => SoulProfile.GenerationalSoul(),
        SoulType.Nature       => SoulProfile.NatureSoul(),
        SoulType.Materialist  => SoulProfile.MaterialistSoul(),
        _                     => SoulProfile.SelfishSoul(),
    };

    [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();

    /// <summary>Rebuilt each tick; proximity queries go through it so the
    /// hot loops stay near-linear as population grows.</summary>
    public SpatialGrid Grid { get; } = new(cellSize: 12f);

    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)
            Spawn(town.Name, town.Center, ProfileFor(town.Soul), TownPopulationEach, town.Name);
    }

    /// <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;
    }

    /// <summary>A town's fixed cardinal seed — its permanent home on the
    /// map, unaffected by where its people happen to wander.</summary>
    public Vector2 TownAnchor(string town)
    {
        foreach (var t in _towns)
            if (t.Name == town) return t.Center;
        return new Vector2(World.GridSize / 2f, World.GridSize / 2f);
    }

    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) return TownAnchor(town);

        // Anchor-weighted: the settlement's build-center stays near its
        // cardinal seed even as villagers roam outward to distant resources.
        // Towns keep their place on the compass instead of drifting to the
        // middle of the map where everyone's foraging paths overlap.
        return (sum / count).Lerp(TownAnchor(town), 0.7f);
    }

    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;

        // Spatial grid: each soul presses only on the few within reach,
        // not on everyone. Directed pass (a→b for every nearby b) so each
        // ordered pair is handled once from the source's side.
        foreach (var a in Npcs)
        {
            Grid.ForEachNear(a.Position, radius, b =>
            {
                if (b == a) return;
                float dist = a.Position.DistanceTo(b.Position);
                if (dist > radius) return;
                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);
            });
        }
    }

    // --- Mortality & birth: generations end, and new ones are born --------
    // Death no longer auto-spawns a replacement. People die and are simply
    // gone; children come from bonded pairs (TickReproduction). Population
    // is now births vs deaths — a town can grow, shrink, or die out.

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

    private void TickMortality()
    {
        var rng = new System.Random(Seed + (int)TotalTicks);

        foreach (var dead in Npcs.ToArray())
        {
            dead.AgeDays += 1f;
            if (dead.AgeDays < dead.LifeExpectancyDays) continue;

            Npcs.Remove(dead);
            DeathsToday++;

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

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

    /// <summary>
    /// Children come from bonds (Phase B). A bonded pair — both grown adults,
    /// both fed, with a roof in town — may conceive once per season. The
    /// child spawns beside its parents, inherits their town and culture, and
    /// begins knowing almost nothing but growing up among those who do. This
    /// is how a town persists: not by respawn-on-death, but by families.
    /// </summary>
    /// <summary>Rough carrying capacity per town — beds plus a margin the
    /// land can feed. Births taper toward zero as a town fills it.</summary>
    private const int TownCarryingCapacity = 28;

    private void TickReproduction()
    {
        var rng = new System.Random(Seed * 7 + (int)TotalTicks);
        var newborns = new List<Npc>();

        // Town populations, to damp births near carrying capacity.
        var pop = new Dictionary<string, int>();
        foreach (var npc in Npcs)
            pop[npc.HomeTown] = pop.GetValueOrDefault(npc.HomeTown) + 1;

        foreach (var a in Npcs)
        {
            var b = a.Partner;
            if (b == null) continue;
            if (a.GetHashCode() >= b.GetHashCode()) continue;   // count each pair once
            if (!a.IsAdult || !b.IsAdult) continue;
            if (a.Nourishment < 0.5f || b.Nourishment < 0.5f) continue;    // both fed
            // Fertile from adulthood through most of life — a wide window so
            // generations overlap and a town isn't one bad cohort from ruin.
            if (a.AgeDays > a.LifeExpectancyDays * 0.85f) continue;

            // Logistic damping: a full town barely breeds; an emptied one
            // (after a plague) breeds back toward capacity. This is what
            // keeps population in a band instead of exploding or dying out.
            float townPop = pop.GetValueOrDefault(a.HomeTown);
            float roomFactor = Mathf.Clamp(1f - townPop / TownCarryingCapacity, 0f, 1f);
            if (roomFactor <= 0f) continue;

            // High enough to outrun the founding cohort's die-off and keep
            // generations overlapping; logistic damping caps the ceiling so
            // it can't explode. Deliberately generous — a shrinking town is
            // a worse failure than a full one.
            double dailyChance = 0.12 * roomFactor;
            if (rng.NextDouble() > dailyChance) continue;

            _bornCount++;
            var child = new Npc
            {
                Name = $"{a.HomeTown}_{(char)('a' + _bornCount % 26)}{_bornCount + 25}",
                HomeTown = a.HomeTown,
                Soul = a.Soul,   // raised in the culture that bore them
                PersonalityModifier = (float)(rng.NextDouble() * 0.4 - 0.2),
                Position = a.Position + new Vector2(rng.Next(-3, 4), rng.Next(-3, 4)),
                AgeDays = 0f,
                LifeExpectancyDays = 150 + rng.Next(0, 80),
            };
            child.Know.Capacity = 1.0f + (float)rng.NextDouble();
            newborns.Add(child);
            BirthsToday++;
            pop[a.HomeTown] = (int)townPop + 1;   // count the newborn toward capacity
            GD.Print($"[Birth] day {Day}: {a.Name} & {b.Name} ({a.HomeTown}) → {child.Name}.");
        }

        Npcs.AddRange(newborns);
    }

    /// <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()
    {
        Grid.Rebuild(Npcs);

        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();
            TickReproduction();
            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();
            }
        }
    }
}