/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using UniRx;
using CultMath;
using static CultMath.math;
using float2 = CultMath.float2;

public class Agent
{
    private const float FORWARD_DELTA_THRESHOLD = 20;
    private const float THRUST_DELTA_THRESHOLD = 1;
    // The Strength of one Track paint in this ship's own IncomingPaints: a fire-control emitter tracking this
    // that hard (rulings lock-warning-strength, sensor-stat-set item 4, launcher-lock-solution-quality).
    private const float LockAlarm = .5f;
    protected BaseState _rootState;
    private BaseState _currentState;
    private VelocityLimit _velocityLimit;
    
    public AgentTask Task { get; set; }
    // What this pilot's side knows of other ships. A ship outside a flight is a side of one: a view over itself, until
    // Flight.Join sets the flight's.
    public PilotView View { get; internal set; }
    // Zone-scoped, from 1: the ordinal of this pilot's own dice, set by Zone.CreateAgent as it admits the pilot (0 for
    // an agent built outside a zone's admission).
    public uint Id { get; set; }
    public Ship Ship { get; }
    public ItemManager ItemManager { get; }
    public GameplaySettings Settings { get; }
    // How this pilot fights: its faction's doctrine for its role (Zone.CreateAgent resolves it).
    public RoleDoctrine Doctrine { get; }
    public float TopSpeed => _velocityLimit?.Limit ?? 100;

    public Agent(Ship ship, RoleDoctrine doctrine)
    {
        Ship = ship;
        View = new PilotView(ship);
        Doctrine = doctrine;
        ItemManager = Ship.ItemManager;
        Settings = Ship.ItemManager.GameplaySettings;

        _rootState = _currentState = new BaseState(this);
        _velocityLimit = Ship.GetBehavior<VelocityLimit>();
    }

    public void Transition(BaseState targetState, Action onTransition = null)
    {
        //ItemManager.Log($"{Ship.Name} changing state from {_currentState.GetType().Name} to {targetState.GetType().Name}");
        _currentState.OnExitState();
        _currentState = targetState;
        onTransition?.Invoke();
        _currentState.OnEnterState();
    }

    public void Update(float delta)
    {
        // The pilot tick commands Turn every tick, in every state: a state that pilots overwrites this zero with its
        // demand, and one that does not leaves the hull holding course instead of inheriting the last state's rate.
        Ship.Command.Turn = TurnCommand.OfRate(0);
        VentOnTrack();
        _currentState.Update(delta);
        foreach (var transition in _currentState.Transitions)
            if (transition.Condition())
            {
                Transition(transition.TargetState, transition.OnTransition);
                break;
            }
    }

    // The AI plays the player's rule on the player's information: vent when one Track paint on this ship passes half. It
    // reads only this ship's own IncomingPaints, so it runs in every state (ruling vent-in-any-state), and a ship
    // carrying no vent does nothing.
    private void VentOnTrack()
    {
        if (TrackAlarm) Use(b => b is VapourDumpData);
    }

    // One Track paint on this ship passes the alarm: the ship vents, and does not overdrive on the same tick.
    public bool TrackAlarm => Ship.IncomingPaints.Any(p => p.Mode == PaintMode.Track && p.Strength > LockAlarm);

    // Through TryActivateConsumable, one of a kind at a time: a Stackable design would otherwise be drained once per tick.
    public void Use(Predicate<BehaviorData> kind)
    {
        if (Ship.HasActiveConsumable(kind)) return;
        var consumable = Ship.FirstCarriedConsumable(kind);
        if (consumable != null) Ship.Command.Use(consumable);
    }

    public void Accelerate(float2 targetVelocity, bool noTurn = false)
    {
        var deltaV = targetVelocity - Ship.Velocity;
        var deltaVMag = length(deltaV);
        var deltaVDirection = normalize(deltaV);
        // If Delta V is above the threshold, direct the ship towards the delta and use only main thrusters
        if (!noTurn && deltaVMag > FORWARD_DELTA_THRESHOLD)
        {
            Ship.Command.Turn = TurnCommand.Toward(deltaVDirection);
            Ship.Command.Movement = float2(0, pow(dot(Ship.Direction, deltaVDirection), 2));
        }
        // If Delta V is low, use all thrusters and leave Turn to the caller (MoveTo already pointed it at the target)
        else if(deltaVMag > THRUST_DELTA_THRESHOLD)
        {
            var right = Ship.Direction.Rotate(ItemRotation.Clockwise);
            Ship.Command.Movement = float2(dot(right, deltaVDirection), dot(Ship.Direction, deltaVDirection));
        }
        else
        {
            Ship.Command.Movement = float2.zero;
        }
    }
}

public class StateTransition
{
    public StateTransition(BaseState targetState, Func<bool> condition, Action onTransition)
    {
        TargetState = targetState;
        Condition = condition;
        OnTransition = onTransition;
    }

    public BaseState TargetState { get; }
    public Func<bool> Condition { get; }
    public Action OnTransition { get; }
}