/*************************************************************************
 * ModernUO                                                              *
 * Copyright 2019-2026 - ModernUO Development Team                       *
 * Email: hi@modernuo.com                                                *
 * File: AITimer.cs                                                      *
 *                                                                       *
 * This program is free software: you can redistribute it and/or modify  *
 * it under the terms of the GNU General Public License as published by  *
 * the Free Software Foundation, either version 3 of the License, or     *
 * (at your option) any later version.                                   *
 *                                                                       *
 * You should have received a copy of the GNU General Public License     *
 * along with this program. If not, see <http://www.gnu.org/licenses/>.  *
 ************************************************************************/

using System;

namespace Server.Mobiles;

/// <summary>
/// Drives an AI on two clocks: decisions at <see cref="BaseCreature.CurrentSpeed"/>, plus
/// move-only wakes at <see cref="BaseAI.NextMove"/> while a pursuit is live. Each tick
/// schedules the earlier of the two deadlines.
/// </summary>
public sealed class AITimer : Timer
{
    private readonly BaseAI _owner;
    private long _nextThink;
    private long _nextWake; // when the pending wheel entry fires
    private bool _inTick;
    private int _detectHiddenMinDelay;
    private int _detectHiddenMaxDelay;

    // The initial delay is irrelevant: Activate is the only start path and sets its own.
    public AITimer(BaseAI owner) : base(TimeSpan.Zero, TimeSpan.FromSeconds(owner.Mobile.CurrentSpeed))
    {
        _owner = owner;
        _owner._nextDetectHidden = Core.TickCount;
        _nextThink = Core.TickCount;
    }

    public void Activate()
    {
        _nextThink = Core.TickCount;

        if (Running)
        {
            return;
        }

        // Short random spread: the creature responds within a think while a sector's
        // worth of timers avoids a same-tick burst; the idle think jitter keeps the
        // cohort apart from there.
        Delay = TimeSpan.FromMilliseconds(Utility.Random(256));
        Start();
        _nextWake = Core.TickCount + (long)Delay.TotalMilliseconds;
    }

    // Think now. A think grants no action: steps, swings, casts, and abilities keep their own gates.
    public void Prod()
    {
        _nextThink = Core.TickCount;

        if (Running)
        {
            Reschedule();
            return;
        }

        Delay = TimeSpan.Zero;
        Start();
        _nextWake = Core.TickCount + (long)Delay.TotalMilliseconds;
    }

    // A speed-up must not wait out a stale, longer think deadline.
    public void OnSpeedChanged()
    {
        var candidate = Core.TickCount + (long)(_owner.Mobile.CurrentSpeed * 1000);

        if (candidate - _nextThink < 0)
        {
            _nextThink = candidate;
            Reschedule();
        }
    }

    // Moves the pending wake earlier. Interval is only read after the next fire,
    // so this needs Stop, Delay = remaining, Start.
    private void Reschedule()
    {
        if (_inTick || !Running)
        {
            return; // ScheduleNext handles it at tick end
        }

        var now = Core.TickCount;
        var deadline = _nextThink;

        if (_owner.TryGetMoveWake(out var nextMove) && nextMove - now > 0 && nextMove - deadline < 0)
        {
            deadline = nextMove;
        }

        if (deadline - _nextWake >= 0)
        {
            return; // pending wake is already early enough
        }

        Stop();
        Delay = TimeSpan.FromMilliseconds(Math.Max(0, deadline - now));
        Start();
        _nextWake = now + (long)Delay.TotalMilliseconds;
    }

    protected override void OnTick()
    {
        _inTick = true;

        try
        {
            OnTickCore();
        }
        finally
        {
            _inTick = false;
        }
    }

    private void OnTickCore()
    {
        if (ShouldStop())
        {
            Stop();
            return;
        }

        if (Core.TickCount - _nextThink >= 0)
        {
            _owner.Mobile.OnThink();

            if (ShouldStop())
            {
                Stop();
                return;
            }

            HandleBardEffects();

            if (_owner.Mobile.Controlled ? _owner.Obey() : _owner.Think())
            {
                HandleDetectHidden();
            }

            // Cadence from the post-decision speed (decisions may flip active/passive).
            var period = (long)(_owner.Mobile.CurrentSpeed * 1000);
            _nextThink = Core.TickCount + period;

            // Idle cadence drifts: a zero-mean jitter random-walks think phases apart, so
            // creatures spawned or woken together cannot stay in lock-step (a one-shot
            // spread can collide and identical periods never separate). Engaged cadence
            // stays exact — pursuit timing anchors to real step times.
            if (_owner.Mobile.CurrentSpeed == _owner.Mobile.PassiveSpeed)
            {
                var jitter = (int)(period >> 3);
                _nextThink += Utility.RandomMinMax(-jitter, jitter);
            }
        }
        else
        {
            _owner.ContinueMove();
        }

        ScheduleNext();
    }

    private void ScheduleNext()
    {
        var now = Core.TickCount;
        var delay = _nextThink - now;

        if (_owner.TryGetMoveWake(out var nextMove))
        {
            var moveDelay = nextMove - now;

            // Only a future budget is a wake — a blocked creature must not spin the timer.
            if (moveDelay > 0 && moveDelay < delay)
            {
                delay = moveDelay;
            }
        }

        // The wheel rounds up to its 8ms resolution; a non-positive delay becomes one turn.
        Interval = TimeSpan.FromMilliseconds(delay);
        _nextWake = now + (long)Interval.TotalMilliseconds;
    }

    private bool ShouldStop()
    {
        if (_owner.Mobile.Deleted)
        {
            return true;
        }

        if (_owner.Mobile.Map == null || _owner.Mobile.Map == Map.Internal || _owner.Mobile.PlayerRangeSensitive &&
            !_owner.Mobile.Controlled && !_owner.Mobile.Map.GetSector(_owner.Mobile.Location).Active)
        {
            _owner.Deactivate();
            return true;
        }

        return false;
    }

    private void HandleBardEffects()
    {
        if (_owner.Mobile.BardPacified)
        {
            _owner.DoBardPacified();
        }
        else if (_owner.Mobile.BardProvoked)
        {
            _owner.DoBardProvoked();
        }
    }

    private void CacheDetectHiddenDelays()
    {
        var delay = Math.Min(30000 / _owner.Mobile.Int, 120);
        _detectHiddenMinDelay = delay * 900;  // 26s to 108s
        _detectHiddenMaxDelay = delay * 1100; // 32s to 132s
    }

    private void HandleDetectHidden()
    {
        if (!_owner.CanDetectHidden || Core.TickCount - _owner._nextDetectHidden < 0)
        {
            return;
        }

        _owner.DetectHidden();

        if (_detectHiddenMinDelay == 0 || _detectHiddenMaxDelay == 0)
        {
            CacheDetectHiddenDelays();
        }

        _owner._nextDetectHidden = Core.TickCount + Utility.RandomMinMax(_detectHiddenMinDelay, _detectHiddenMaxDelay);
    }
}