ex-col-02-bucket-chain/BucketChain/Person.cs

namespace BucketChain;

/// <summary>
///     Represents a person working together with others in a bucket chain to extinguish a fire.
/// </summary>
public sealed class Person
{
    private Bucket? _backwardBucket;
    private Bucket? _forwardBucket;

    /// <summary>
    ///     Creates a new person.
    ///     We are not interested in any specific details of the person,
    ///     only the position in the chain is relevant.
    /// </summary>
    public Person()
    {
        // TODO
    }

    /// <summary>
    ///     Gets if the person currently has at least one bucket (forward or backward).
    /// </summary>
    public bool HasBucket => _forwardBucket != null || _backwardBucket != null;

    /// <summary>
    ///     Gets the left neighbor of the person. Can be null.
    /// </summary>
    public Person? LeftNeighbor { get; private set; }

    /// <summary>
    ///     Gets the right neighbor of the person. Can be null.
    /// </summary>
    public Person? RightNeighbor { get; private set; }

    /// <summary>
    ///     Gets the number of the last step in which this person performed a bucket move action.
    ///     Each person can only move, at most, once per step.
    /// </summary>
    public int LastStepPerformed { get; private set; }

    /// <summary>
    ///     The person joins an existing bucket chain at a specific position.
    ///     This position is defined by the passed person and the information if this person will join
    ///     the chain on the left or right side of the passed person.
    ///     If the passed person already had a neighbor at this side this person joins between them.
    /// </summary>
    /// <param name="neighbor">The neighbor in the bucket chain</param>
    /// <param name="isLeftNeighbor">If true the passed person will become the left hand side
    ///     neighbor of this person; otherwise it will become the right hand side neighbor</param>
    public void JoinChain(Person neighbor, bool isLeftNeighbor)
    {
        var neighborOfNeighbor = isLeftNeighbor ? neighbor.RightNeighbor : neighbor.LeftNeighbor;
        if (neighborOfNeighbor != null)
        {
            if(isLeftNeighbor)
            {
                neighborOfNeighbor.LeftNeighbor = this;
                RightNeighbor = neighborOfNeighbor;
                LeftNeighbor = neighbor;
                neighbor.RightNeighbor = this;
            }
            else
            {
                neighborOfNeighbor.RightNeighbor = this;
                LeftNeighbor = neighborOfNeighbor;
                RightNeighbor = neighbor;
                neighbor.LeftNeighbor = this;
            }
        }
        else
        {
            if (isLeftNeighbor)
            {
                neighbor.RightNeighbor = this;
                LeftNeighbor = neighbor;
            }
            else
            {
                neighbor.LeftNeighbor = this;
                RightNeighbor = neighbor;
            }
        }
    }

    /// <summary>
    ///     Attempts to move the forward bucket along the chain towards the fire.
    ///     The person negotiates with the right hand side neighbor.
    ///     If that neighbor can accept a forward bucket it received it.
    ///     They also check if the right hand side neighbor has a backward (towards the well)
    ///     bucket. If this person is able to receive the backward bucket it receives it.
    ///     If at least one bucket is exchanged both involved people are done for the current step.
    /// </summary>
    /// <param name="currentStep">Number of the current (chain) operation step</param>
    /// <returns>True if the move attempt produced no errors - this does not mean
    ///     that a bucket was moved, only that no invalid state was detected; false otherwise</returns>
    public bool MoveBucket(int currentStep)
    {
        if (currentStep < 0 || currentStep == LastStepPerformed || RightNeighbor == null)
        {
            return false;
        }
        
        if ((RightNeighbor._forwardBucket == null || RightNeighbor._forwardBucket.IsEmpty) && _forwardBucket != null)
        {
            RightNeighbor._forwardBucket = _forwardBucket;
            _forwardBucket = null;
        }
        if (RightNeighbor._backwardBucket != null && _backwardBucket == null)
        {
            _backwardBucket = RightNeighbor._backwardBucket;
            RightNeighbor._backwardBucket = null;
        }
        
        LastStepPerformed = currentStep;
        RightNeighbor.LastStepPerformed = currentStep;
        return true;
    }

    /// <summary>
    ///     Fights the passed fire with water from the forward bucket. This empties the bucket.
    ///     After using it the now empty bucket is moved to the backward position.
    /// </summary>
    /// <param name="fire">The fire to throw water at</param>
    public void FightFire(Fire fire)
    {
        var amount = _forwardBucket?.Empty();
        fire.GetHitByWater(amount ?? 0);
        _backwardBucket = _forwardBucket;
        _forwardBucket = null;
    }

    /// <summary>
    ///     Uses the passed well to fill the bucket.
    ///     If this person currently has no empty bucket to fill but there are still unused buckets
    ///     available for the chain a new bucket will be introduced with this method.
    ///     If the person has no forward bucket but a backward bucket that one is filled.
    /// </summary>
    /// <param name="well">The well to use for filling the bucket</param>
    /// <param name="additionalBucket">A new bucket to use; can be null</param>
    public void UseWell(Well well, Bucket? additionalBucket)
    {
        // fill forward bucket if empty
        if (_forwardBucket is { IsEmpty: true }) // using here pattern, bc rider suggests it
        {
            well.FillBucket(_forwardBucket);
        }
        // else fill backward bucket if empty
        else if (_forwardBucket == null && _backwardBucket is { IsEmpty: true })
        {
            well.FillBucket(_backwardBucket);

            // if successful, swap buckets
            if (!_backwardBucket.IsEmpty)
            {
                _forwardBucket = _backwardBucket;
                _backwardBucket = null;
            }
        }
        // else add additional bucket
        else if (additionalBucket != null)
        {
            if (_forwardBucket == null)
            {
                _forwardBucket = additionalBucket;
                well.FillBucket(_forwardBucket);
            }
            else if (_backwardBucket == null)
            {
                _backwardBucket = additionalBucket;
                well.FillBucket(_backwardBucket);
            }
        }
    }

    /// <summary>
    ///     Creates a string representation of this person instance.
    ///     Shows if the person has none, an empty or full bucket.
    ///     If the person has both forward and backward buckets the forward bucket is displayed.
    /// </summary>
    /// <returns>String representation of the person</returns>
    public override string ToString()
    {
        if (_forwardBucket != null)
        {
            return _forwardBucket.IsEmpty ? "🔘" : "🔵";
        }
        if (_backwardBucket != null)
        {
            return _backwardBucket.IsEmpty ? "🔘" : "🔵";
        }
        return "🫲";
    }
}