using static SpaceGame.Api.Shared.Runtime.SimulationRuntimeSupport;
using static SpaceGame.Api.Shared.Runtime.ShipBehaviorKinds;

namespace SpaceGame.Api.Ships.AI;

public sealed partial class ShipAiService
{
    private const float WarpEngageDistanceKilometers = 250_000f;
    private const float FrigateDps = 7f;
    private const float DestroyerDps = 12f;
    private const float CruiserDps = 18f;
    private const float CapitalDps = 26f;

    private readonly IBalanceService balance;

    public ShipAiService(IBalanceService balance)
    {
        this.balance = balance;
    }

    internal void UpdateShip(SimulationWorld world, ShipRuntime ship, float deltaSeconds, ICollection<SimulationEventRecord> events)
    {
        if (ship.ReplanCooldownSeconds > 0f)
        {
            ship.ReplanCooldownSeconds = MathF.Max(0f, ship.ReplanCooldownSeconds - deltaSeconds);
        }

        var previousState = ship.State;
        var previousOrderId = ship.ActiveOrderId;
        var previousTaskId = GetCurrentSubTask(ship)?.Id;

        SyncEmergencyOrders(world, ship);
        SyncBehaviorOrders(world, ship);
        EnsureOrderExecution(world, ship, events);
        ExecuteOrder(world, ship, deltaSeconds, events);
        TrackHistory(ship);
        EmitStateEvents(ship, previousState, previousOrderId, previousTaskId, events);
    }

    private void EnsureOrderExecution(SimulationWorld world, ShipRuntime ship, ICollection<SimulationEventRecord> events)
    {
        var currentOrder = ship.OrderQueue.GetCurrentOrder();
        if (currentOrder is null)
        {
            ClearActiveOrder(ship);
            ApplyIdleOrBlockedState(world, ship);
            return;
        }

        if (currentOrder.Status == OrderStatus.Queued)
        {
            currentOrder.Status = OrderStatus.Active;
        }

        if (!ship.NeedsReplan
            && string.Equals(ship.ActiveOrderId, currentOrder.Id, StringComparison.Ordinal)
            && ship.ActiveSubTaskIndex < ship.ActiveSubTasks.Count)
        {
            return;
        }

        if (ship.ReplanCooldownSeconds > 0f && !string.Equals(ship.ActiveOrderId, currentOrder.Id, StringComparison.Ordinal))
        {
            return;
        }

        var subTasks = BuildOrderSubTasks(world, ship, currentOrder);
        if (subTasks is null || subTasks.Count == 0)
        {
            FailOrder(ship, currentOrder, currentOrder.FailureReason ?? "order-unavailable");
            ClearActiveOrder(ship);
            ship.NeedsReplan = true;
            ship.ReplanCooldownSeconds = 0.1f;
            ship.LastReplanReason = currentOrder.FailureReason ?? "order-unavailable";
            events.Add(new SimulationEventRecord("ship", ship.Id, "order-failed", $"{ship.Definition.Name} failed {currentOrder.Label ?? currentOrder.Kind}.", DateTimeOffset.UtcNow));
            ApplyIdleOrBlockedState(world, ship);
            return;
        }

        BeginOrderExecution(ship, currentOrder, subTasks);
        events.Add(new SimulationEventRecord("ship", ship.Id, "order-started", $"{ship.Definition.Name} started {currentOrder.Label ?? currentOrder.Kind}.", DateTimeOffset.UtcNow));
    }

    private void ExecuteOrder(SimulationWorld world, ShipRuntime ship, float deltaSeconds, ICollection<SimulationEventRecord> events)
    {
        var order = ship.ActiveOrderId is null ? null : ship.OrderQueue.FindById(ship.ActiveOrderId);
        if (order is null)
        {
            ClearActiveOrder(ship);
            ApplyIdleOrBlockedState(world, ship);
            return;
        }

        if (ship.ActiveSubTaskIndex >= ship.ActiveSubTasks.Count)
        {
            CompleteOrderExecution(ship, order, events);
            return;
        }

        var subTask = ship.ActiveSubTasks[ship.ActiveSubTaskIndex];
        if (subTask.Status == WorkStatus.Pending)
        {
            subTask.Status = WorkStatus.Active;
        }
        else if (subTask.Status == WorkStatus.Blocked)
        {
            ship.State = ShipState.Blocked;
            ship.TargetPosition = subTask.TargetPosition ?? ship.Position;
            return;
        }

        var outcome = UpdateSubTask(world, ship, subTask, deltaSeconds);
        switch (outcome)
        {
            case SubTaskOutcome.Active:
                return;
            case SubTaskOutcome.Completed:
                subTask.Status = WorkStatus.Completed;
                subTask.Progress = 1f;
                ship.ActiveSubTaskIndex += 1;
                if (ship.ActiveSubTaskIndex >= ship.ActiveSubTasks.Count)
                {
                    CompleteOrderExecution(ship, order, events);
                }

                return;
            case SubTaskOutcome.Failed:
                subTask.Status = WorkStatus.Failed;
                FailOrderExecution(ship, order, subTask.BlockingReason ?? "subtask-failed", events);
                return;
        }
    }

    private static void BeginOrderExecution(ShipRuntime ship, ShipOrderRuntime order, IReadOnlyList<ShipSubTaskRuntime> subTasks)
    {
        ship.ActiveOrderId = order.Id;
        ship.ActiveSubTaskIndex = 0;
        ship.ActiveSubTasks.Clear();
        ship.ActiveSubTasks.AddRange(subTasks);
        ship.NeedsReplan = false;
        ship.ReplanCooldownSeconds = 0f;
        ship.LastReplanReason = "order-execution-started";
        ship.LastDeltaSignature = string.Empty;
    }

    private static void ClearActiveOrder(ShipRuntime ship)
    {
        ship.ActiveOrderId = null;
        ship.ActiveSubTaskIndex = 0;
        ship.ActiveSubTasks.Clear();
    }

    private void CompleteOrderExecution(ShipRuntime ship, ShipOrderRuntime order, ICollection<SimulationEventRecord> events)
    {
        ship.OrderQueue.TryCompleteOrder(order.Id);
        if (order.SourceKind == ShipOrderSourceKind.Behavior
            && string.Equals(order.SourceId, RepeatOrders, StringComparison.Ordinal)
            && ship.DefaultBehavior.RepeatOrders.Count > 0)
        {
            ship.DefaultBehavior.RepeatIndex = (ship.DefaultBehavior.RepeatIndex + 1) % ship.DefaultBehavior.RepeatOrders.Count;
        }

        ClearActiveOrder(ship);
        ship.NeedsReplan = true;
        ship.ReplanCooldownSeconds = 0.25f;
        ship.LastReplanReason = "order-completed";
        ship.LastDeltaSignature = string.Empty;
        events.Add(new SimulationEventRecord("ship", ship.Id, "order-completed", $"{ship.Definition.Name} completed {order.Label ?? order.Kind}.", DateTimeOffset.UtcNow));
    }

    private void FailOrderExecution(ShipRuntime ship, ShipOrderRuntime order, string failureReason, ICollection<SimulationEventRecord> events)
    {
        FailOrder(ship, order, failureReason);
        ClearActiveOrder(ship);
        ship.NeedsReplan = true;
        ship.ReplanCooldownSeconds = 0.5f;
        ship.LastReplanReason = failureReason;
        ship.LastDeltaSignature = string.Empty;
        events.Add(new SimulationEventRecord("ship", ship.Id, "order-failed", $"{ship.Definition.Name} failed {order.Label ?? order.Kind}.", DateTimeOffset.UtcNow));
    }

    private static void FailOrder(ShipRuntime ship, ShipOrderRuntime order, string failureReason)
    {
        ship.OrderQueue.TryFailOrder(order.Id, failureReason);
        ship.LastDeltaSignature = string.Empty;
    }

    private static ShipSubTaskRuntime? GetCurrentSubTask(ShipRuntime ship) =>
      ship.ActiveSubTaskIndex >= ship.ActiveSubTasks.Count ? null : ship.ActiveSubTasks[ship.ActiveSubTaskIndex];

    private void ApplyIdleOrBlockedState(SimulationWorld world, ShipRuntime ship)
    {
        var (behaviorKind, _) = ResolveBehaviorSource(world, ship);
        if (IsBehaviorBlockingFailure(behaviorKind, ship.LastAccessFailureReason))
        {
            ship.State = ShipState.Blocked;
            ship.TargetPosition = ship.Position;
            return;
        }

        ship.State = ShipState.Idle;
        ship.TargetPosition = ship.Position;
    }

    private void SyncEmergencyOrders(SimulationWorld world, ShipRuntime ship)
    {
        var desiredOrder = BuildEmergencyOrder(world, ship);
        ship.OrderQueue.RemoveWhere(order =>
            order.SourceKind == ShipOrderSourceKind.Behavior
            && string.Equals(order.SourceId, ShipOrderKinds.Flee, StringComparison.Ordinal)
            && (desiredOrder is null || !string.Equals(order.Id, desiredOrder.Id, StringComparison.Ordinal)));

        if (desiredOrder is null)
        {
            return;
        }

        ship.OrderQueue.AddOrReplaceManagedOrderAtFront(desiredOrder);
    }
}