namespace BucketChain;

/// <summary>
///     Represents a bucket used to transport water.
/// </summary>
public sealed class Bucket
{
    private readonly double _capacityLiters;
    private double _contentLiters;

    /// <summary>
    ///     Creates a new bucket with the given capacity.
    /// </summary>
    /// <param name="capacityLiters">Bucket capacity in liters</param>
    public Bucket(double capacityLiters)
    {
        _capacityLiters = capacityLiters;
        _contentLiters = 0D;
    }

    /// <summary>
    ///     Gets if this bucket is currently completely empty or not.
    /// </summary>
    public bool IsEmpty => _contentLiters <= 0D;

    /// <summary>
    ///     Fills the bucket to the brim if enough water is available.
    ///     If there is not enough water to fill the bucket completely it takes as much as possible.
    ///     If the bucket is already full no water is taken.
    /// </summary>
    /// <param name="maxAvailable">Max. available water, in liters</param>
    /// <returns>The amount taken for filling the bucket</returns>
    public double Fill(double maxAvailable)
    {
        if (_capacityLiters - _contentLiters <= 0D || maxAvailable <= 0D)
        {
            return 0D;
        }

        var amountTaken = _contentLiters;
        _contentLiters = _contentLiters + maxAvailable > _capacityLiters
            ? _capacityLiters
            : _contentLiters + maxAvailable;
        
        amountTaken -= _contentLiters;
        return Math.Abs(amountTaken);
    }

    /// <summary>
    ///     Empties the bucket. The amount stored within before emptying is returned.
    /// </summary>
    /// <returns>Amount emptied from the bucket, in liters</returns>
    public double Empty()
    {
        var content = _contentLiters;
        _contentLiters = 0D;
        return content;
    }
}