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

namespace BucketChain;

/// <summary>
///     Represents a bucket chain which connects a well with a fire by cooperating people with buckets.
/// </summary>
public sealed class Chain
{
    private readonly Fire _fire;
    private readonly int _requiredPeople;
    private readonly Well _well;
    private readonly double _bucketSize;
    private Person _firstPerson;
    private int _availableBuckets;

    /// <summary>
    ///     Creates a new bucket chain based on the supplied parameters.
    /// </summary>
    /// <param name="requiredPeople">Min. amount of people required to reach the fire</param>
    /// <param name="availableBuckets">Max. amount of buckets that can be active in the chain</param>
    /// <param name="bucketSize">Size of the buckets used in the chain - all buckets have the same size</param>
    /// <param name="well">A reference to the well, used as water source</param>
    /// <param name="fire">A reference to the fire this chain attempts to extinguish</param>
    /// <param name="firstPerson">Reference to the first person in the chain</param>
    public Chain(int requiredPeople, int availableBuckets, double bucketSize, 
        Well well, Fire fire, Person firstPerson)
    {
        _requiredPeople = requiredPeople;
        _availableBuckets = availableBuckets;
        _bucketSize = bucketSize;
        _well = well;
        _fire = fire;
        _firstPerson = firstPerson;
    }

    /// <summary>
    ///     Operates the bucket chain. This includes multiple things:
    ///     1) Refill the well
    ///     2) Allow the fire to grow
    ///     3) If first person has a bucket, fill it at the well
    ///     4) Move the buckets along the chain of people
    ///     5) If the last person reaches the fire and has a full bucket, use it to fight the fire
    ///     People can join the chain at various positions, so the <see cref="Chain"/> always has to
    ///     determine the current first person before operating.
    /// </summary>
    /// <param name="currentStep">The current step</param>
    /// <param name="error">Set to true if an error occurred while operating, e.g. invalid state of the chain</param>
    /// <returns>True if the fire could be extinguished in this step; false otherwise</returns>
    public bool Operate(int currentStep, out bool error)
    {
        error = false;
        
        // step 1
        _well.Refill();
        
        // step 2
        _fire.BurnHigher();
        
        // step 3
        Bucket? bucket = null;
        if (GetBucketCount() < _availableBuckets)
        {
            bucket = new Bucket(_bucketSize);
        }
        _firstPerson.UseWell(_well, bucket);
        
        // step 4
        var currentPerson = _firstPerson;
        Person? lastPerson = null;
        int i;
        for (i = 0; i < _requiredPeople; i++)
        {
            if (currentPerson == null)
            {
                // chain is shorter than requiredPeople
                break;
            }

            lastPerson = currentPerson;
            bool movedSuccessfully = currentPerson.MoveBucket(currentStep);

            if (!movedSuccessfully)
            {
                // check if move failed because the step was already performed
                if (currentPerson.LastStepPerformed != currentStep &&
                    (currentPerson.RightNeighbor?.HasBucket ?? false))
                {
                    // move failed because of an invalid state (neighbor can't accept the bucket)
                    error = true;
                    return false;
                }
                // else, move wasn't successful because it was already performed
                // continue without error
            }

            currentPerson = currentPerson.RightNeighbor;
        }

        // Step 5
        if (i == _requiredPeople && lastPerson is { HasBucket: true })
        {
            lastPerson.FightFire(_fire);
        }
        
        return _fire.Extinguished;
    }
    
    private int GetBucketCount()
    {
        int count = 0;
        Person? currentPerson = _firstPerson;
        while (currentPerson != null)
        {
            if (currentPerson.HasBucket)
            {
                count++;
            }
            currentPerson = currentPerson.RightNeighbor;
        }

        return count;
    }

    /// <summary>
    ///     Represents this <see cref="Chain"/> with the referenced <see cref="Well"/>, <see cref="Fire"/>
    ///     and <see cref="Person"/> instances as string, ready to print to the terminal.
    /// </summary>
    /// <returns>String representation of the bucket chain</returns>
    public override string ToString()
    {
        string result = $"{_well} | ";
        Person? currentPerson = _firstPerson;
        for (int i = 0; i < _requiredPeople; i++)
        {
            result += $"{currentPerson?.ToString() ?? "\u2754"} | ";
            currentPerson = currentPerson?.RightNeighbor;
        }
        
        result += $"{_fire}";
        return result;
    }
}