using SpaceGame.Simulation.Api.Contracts;

namespace SpaceGame.Simulation.Api.Simulation;

public sealed class SimulationEngine
{
  public void Tick(SimulationWorld world, float deltaSeconds)
  {
    UpdateStations(world, deltaSeconds);

    foreach (var ship in world.Ships)
    {
      RefreshControlLayers(ship);
      PlanControllerTask(ship, world);
      var controllerEvent = UpdateControllerTask(ship, world, deltaSeconds);
      AdvanceControlState(ship, controllerEvent);
      TrackHistory(ship);
    }

    world.GeneratedAtUtc = DateTimeOffset.UtcNow;
  }

  public WorldSnapshot BuildSnapshot(SimulationWorld world)
  {
    return new WorldSnapshot(
      world.Label,
      world.Seed,
      world.GeneratedAtUtc,
      world.Systems.Select((system) => new SystemSnapshot(
        system.Definition.Id,
        system.Definition.Label,
        ToDto(system.Position),
        system.Definition.StarColor,
        system.Definition.StarSize,
        system.Definition.Planets.Select((planet) => new PlanetSnapshot(
          planet.Label,
          planet.OrbitRadius,
          planet.Size,
          planet.Color,
          planet.HasRing)).ToList())).ToList(),
      world.Nodes.Select((node) => new ResourceNodeSnapshot(
        node.Id,
        node.SystemId,
        ToDto(node.Position),
        node.OreRemaining,
        node.MaxOre,
        node.ItemId)).ToList(),
      world.Stations.Select((station) => new StationSnapshot(
        station.Id,
        station.Definition.Label,
        station.Definition.Category,
        station.SystemId,
        ToDto(station.Position),
        station.Definition.Color,
        station.DockedShipIds.Count,
        station.OreStored,
        station.RefinedStock,
        station.FactionId)).ToList(),
      world.Ships.Select((ship) => new ShipSnapshot(
        ship.Id,
        ship.Definition.Label,
        ship.Definition.Role,
        ship.Definition.ShipClass,
        ship.SystemId,
        ToDto(ship.Position),
        ship.State,
        ship.Order?.Kind,
        ship.DefaultBehavior.Kind,
        ship.ControllerTask.Kind,
        ship.Cargo,
        ship.Definition.CargoCapacity,
        ship.Definition.CargoItemId,
        ship.FactionId,
        ship.Health,
        ship.History.ToList())).ToList(),
      world.Factions.Select((faction) => new FactionSnapshot(
        faction.Id,
        faction.Label,
        faction.Color,
        faction.Credits,
        faction.OreMined,
        faction.GoodsProduced,
        faction.ShipsBuilt,
        faction.ShipsLost)).ToList());
  }

  private void UpdateStations(SimulationWorld world, float deltaSeconds)
  {
    foreach (var station in world.Stations)
    {
      if (station.Definition.Category != "refining" || station.OreStored < 60f)
      {
        continue;
      }

      station.ProcessTimer += deltaSeconds;
      if (station.ProcessTimer < 8f)
      {
        continue;
      }

      station.ProcessTimer = 0f;
      station.OreStored -= 60f;
      station.RefinedStock += 60f;
      var faction = world.Factions.FirstOrDefault((candidate) => candidate.Id == station.FactionId);
      if (faction is not null)
      {
        faction.GoodsProduced += 60f;
        faction.Credits += 18f;
      }
    }
  }

  private void RefreshControlLayers(ShipRuntime ship)
  {
    if (ship.Order is not null && ship.Order.Status == "queued")
    {
      ship.Order.Status = "accepted";
    }
  }

  private void PlanControllerTask(ShipRuntime ship, SimulationWorld world)
  {
    if (ship.Order is not null)
    {
      ship.ControllerTask = new ControllerTaskRuntime
      {
        Kind = "travel",
        TargetEntityId = null,
        TargetSystemId = ship.Order.DestinationSystemId,
        TargetPosition = ship.Order.DestinationPosition,
        Threshold = world.Balance.ArrivalThreshold,
      };
      return;
    }

    if (ship.DefaultBehavior.Kind == "auto-mine")
    {
      PlanAutoMine(ship, world);
      return;
    }

    if (ship.DefaultBehavior.Kind == "patrol" && ship.DefaultBehavior.PatrolPoints.Count > 0)
    {
      ship.ControllerTask = new ControllerTaskRuntime
      {
        Kind = "travel",
        TargetPosition = ship.DefaultBehavior.PatrolPoints[ship.DefaultBehavior.PatrolIndex],
        TargetSystemId = ship.SystemId,
        Threshold = 18f,
      };
      return;
    }

    ship.ControllerTask = new ControllerTaskRuntime
    {
      Kind = "idle",
      Threshold = world.Balance.ArrivalThreshold,
    };
  }

  private void PlanAutoMine(ShipRuntime ship, SimulationWorld world)
  {
    var behavior = ship.DefaultBehavior;
    var refinery = world.Stations.FirstOrDefault((station) => station.Id == behavior.RefineryId);
    var node = behavior.NodeId is null
      ? world.Nodes
        .Where((candidate) => candidate.SystemId == behavior.AreaSystemId)
        .OrderByDescending((candidate) => candidate.OreRemaining)
        .FirstOrDefault()
      : world.Nodes.FirstOrDefault((candidate) => candidate.Id == behavior.NodeId);

    if (refinery is null || node is null)
    {
      behavior.Kind = "idle";
      ship.ControllerTask = new ControllerTaskRuntime { Kind = "idle", Threshold = world.Balance.ArrivalThreshold };
      return;
    }

    behavior.NodeId ??= node.Id;
    switch (behavior.Phase)
    {
      case "extract":
        ship.ControllerTask = new ControllerTaskRuntime
        {
          Kind = "extract",
          TargetEntityId = node.Id,
          TargetSystemId = node.SystemId,
          TargetPosition = node.Position,
          Threshold = 14f,
        };
        break;
      case "travel-to-station":
        ship.ControllerTask = new ControllerTaskRuntime
        {
          Kind = "travel",
          TargetEntityId = refinery.Id,
          TargetSystemId = refinery.SystemId,
          TargetPosition = refinery.Position,
          Threshold = refinery.Definition.Radius + 8f,
        };
        break;
      case "dock":
        ship.ControllerTask = new ControllerTaskRuntime
        {
          Kind = "dock",
          TargetEntityId = refinery.Id,
          TargetSystemId = refinery.SystemId,
          TargetPosition = refinery.Position,
          Threshold = refinery.Definition.Radius + 4f,
        };
        break;
      case "unload":
        ship.ControllerTask = new ControllerTaskRuntime
        {
          Kind = "unload",
          TargetEntityId = refinery.Id,
          TargetSystemId = refinery.SystemId,
          TargetPosition = refinery.Position,
          Threshold = 0f,
        };
        break;
      case "undock":
        ship.ControllerTask = new ControllerTaskRuntime
        {
          Kind = "undock",
          TargetEntityId = refinery.Id,
          TargetSystemId = refinery.SystemId,
          TargetPosition = new Vector3(refinery.Position.X + world.Balance.UndockDistance, refinery.Position.Y, refinery.Position.Z),
          Threshold = 8f,
        };
        break;
      default:
        ship.ControllerTask = new ControllerTaskRuntime
        {
          Kind = "travel",
          TargetEntityId = node.Id,
          TargetSystemId = node.SystemId,
          TargetPosition = node.Position,
          Threshold = 18f,
        };
        behavior.Phase = "travel-to-node";
        break;
    }
  }

  private string UpdateControllerTask(ShipRuntime ship, SimulationWorld world, float deltaSeconds)
  {
    var task = ship.ControllerTask;
    switch (task.Kind)
    {
      case "idle":
        ship.State = "idle";
        return "none";
      case "travel":
        return UpdateTravel(ship, world, deltaSeconds);
      case "extract":
        return UpdateExtract(ship, world, deltaSeconds);
      case "dock":
        return UpdateDock(ship, world, deltaSeconds);
      case "unload":
        return UpdateUnload(ship, world, deltaSeconds);
      case "undock":
        return UpdateUndock(ship, world, deltaSeconds);
      default:
        ship.State = "idle";
        return "none";
    }
  }

  private string UpdateTravel(ShipRuntime ship, SimulationWorld world, float deltaSeconds)
  {
    var task = ship.ControllerTask;
    if (task.TargetPosition is null || task.TargetSystemId is null)
    {
      ship.State = "idle";
      return "none";
    }

    var distance = ship.Position.DistanceTo(task.TargetPosition.Value);
    if (distance <= task.Threshold)
    {
      ship.Position = task.TargetPosition.Value;
      ship.TargetPosition = ship.Position;
      ship.SystemId = task.TargetSystemId;
      ship.State = "arriving";
      return "arrived";
    }

    var speed = ship.Definition.Speed;
    if (ship.SystemId != task.TargetSystemId)
    {
      ship.State = distance > 800f ? "ftl" : "spooling-ftl";
      speed = ship.Definition.FtlSpeed;
    }
    else if (distance > 200f)
    {
      ship.State = distance > 500f ? "warping" : "spooling-warp";
      speed = ship.Definition.Speed * 4.5f;
    }
    else
    {
      ship.State = "approaching";
      speed = ship.Definition.Speed;
    }

    ship.Position = ship.Position.MoveToward(task.TargetPosition.Value, speed * deltaSeconds);
    ship.TargetPosition = task.TargetPosition.Value;
    return "none";
  }

  private string UpdateExtract(ShipRuntime ship, SimulationWorld world, float deltaSeconds)
  {
    var task = ship.ControllerTask;
    var node = world.Nodes.FirstOrDefault((candidate) => candidate.Id == task.TargetEntityId);
    if (node is null || task.TargetPosition is null)
    {
      ship.State = "idle";
      return "none";
    }

    var distance = ship.Position.DistanceTo(task.TargetPosition.Value);
    if (distance > task.Threshold)
    {
      ship.State = "mining-approach";
      ship.Position = ship.Position.MoveToward(task.TargetPosition.Value, ship.Definition.Speed * deltaSeconds);
      return "none";
    }

    ship.State = "mining";
    ship.ActionTimer += deltaSeconds;
    if (ship.ActionTimer < 1f)
    {
      return "none";
    }

    ship.ActionTimer = 0f;
    var mined = MathF.Min(world.Balance.MiningRate, ship.Definition.CargoCapacity - ship.Cargo);
    mined = MathF.Min(mined, node.OreRemaining);
    ship.Cargo += mined;
    node.OreRemaining -= mined;
    if (node.OreRemaining <= 0f)
    {
      node.OreRemaining = node.MaxOre;
    }

    return ship.Cargo >= ship.Definition.CargoCapacity ? "cargo-full" : "none";
  }

  private string UpdateDock(ShipRuntime ship, SimulationWorld world, float deltaSeconds)
  {
    var task = ship.ControllerTask;
    var station = world.Stations.FirstOrDefault((candidate) => candidate.Id == task.TargetEntityId);
    if (station is null || task.TargetPosition is null)
    {
      ship.State = "idle";
      return "none";
    }

    var distance = ship.Position.DistanceTo(task.TargetPosition.Value);
    if (distance > task.Threshold)
    {
      ship.State = "docking-approach";
      ship.Position = ship.Position.MoveToward(task.TargetPosition.Value, ship.Definition.Speed * deltaSeconds);
      return "none";
    }

    ship.State = "docking";
    ship.ActionTimer += deltaSeconds;
    if (ship.ActionTimer < world.Balance.DockingDuration)
    {
      return "none";
    }

    ship.ActionTimer = 0f;
    ship.State = "docked";
    ship.DockedStationId = station.Id;
    station.DockedShipIds.Add(ship.Id);
    ship.Position = station.Position;
    return "docked";
  }

  private string UpdateUnload(ShipRuntime ship, SimulationWorld world, float deltaSeconds)
  {
    if (ship.DockedStationId is null)
    {
      ship.State = "idle";
      return "none";
    }

    var station = world.Stations.FirstOrDefault((candidate) => candidate.Id == ship.DockedStationId);
    if (station is null)
    {
      ship.DockedStationId = null;
      ship.State = "idle";
      return "none";
    }

    ship.State = "transferring";
    var moved = MathF.Min(ship.Cargo, world.Balance.TransferRate * deltaSeconds);
    ship.Cargo -= moved;
    station.OreStored += moved;
    var faction = world.Factions.FirstOrDefault((candidate) => candidate.Id == ship.FactionId);
    if (faction is not null)
    {
      faction.OreMined += moved;
      faction.Credits += moved * 0.4f;
    }

    return ship.Cargo <= 0.01f ? "unloaded" : "none";
  }

  private string UpdateUndock(ShipRuntime ship, SimulationWorld world, float deltaSeconds)
  {
    var task = ship.ControllerTask;
    if (ship.DockedStationId is null || task.TargetPosition is null)
    {
      ship.State = "idle";
      return "none";
    }

    var station = world.Stations.FirstOrDefault((candidate) => candidate.Id == ship.DockedStationId);
    station?.DockedShipIds.Remove(ship.Id);
    ship.DockedStationId = null;
    ship.State = "undocking";
    ship.Position = ship.Position.MoveToward(task.TargetPosition.Value, ship.Definition.Speed * deltaSeconds);
    return ship.Position.DistanceTo(task.TargetPosition.Value) <= task.Threshold ? "undocked" : "none";
  }

  private void AdvanceControlState(ShipRuntime ship, string controllerEvent)
  {
    if (ship.Order is not null && controllerEvent == "arrived")
    {
      ship.Order = null;
      ship.ControllerTask.Kind = "idle";
      return;
    }

    if (ship.DefaultBehavior.Kind == "auto-mine")
    {
      switch (ship.DefaultBehavior.Phase, controllerEvent)
      {
        case ("travel-to-node", "arrived"):
          ship.DefaultBehavior.Phase = ship.Cargo >= ship.Definition.CargoCapacity ? "travel-to-station" : "extract";
          break;
        case ("extract", "cargo-full"):
          ship.DefaultBehavior.Phase = "travel-to-station";
          break;
        case ("travel-to-station", "arrived"):
          ship.DefaultBehavior.Phase = "dock";
          break;
        case ("dock", "docked"):
          ship.DefaultBehavior.Phase = "unload";
          break;
        case ("unload", "unloaded"):
          ship.DefaultBehavior.Phase = "undock";
          break;
        case ("undock", "undocked"):
          ship.DefaultBehavior.Phase = "travel-to-node";
          ship.DefaultBehavior.NodeId = null;
          break;
      }
    }

    if (ship.DefaultBehavior.Kind == "patrol" && controllerEvent == "arrived" && ship.DefaultBehavior.PatrolPoints.Count > 0)
    {
      ship.DefaultBehavior.PatrolIndex = (ship.DefaultBehavior.PatrolIndex + 1) % ship.DefaultBehavior.PatrolPoints.Count;
    }
  }

  private static void TrackHistory(ShipRuntime ship)
  {
    var signature = $"{ship.State}|{ship.DefaultBehavior.Kind}|{ship.ControllerTask.Kind}|{ship.Cargo:0.0}";
    if (signature == ship.LastSignature)
    {
      return;
    }

    ship.LastSignature = signature;
    ship.History.Add($"{DateTimeOffset.UtcNow:HH:mm:ss}  state={ship.State} behavior={ship.DefaultBehavior.Kind} task={ship.ControllerTask.Kind} cargo={ship.Cargo:0.#}");
    if (ship.History.Count > 18)
    {
      ship.History.RemoveAt(0);
    }
  }

  private static Vector3Dto ToDto(Vector3 value) => new(value.X, value.Y, value.Z);
}