using System;
using System.Diagnostics;

namespace BotSharp.Algorithm.Bayesian
{
    /// <summary>
    /// Struct ConditionalProbability
    /// </summary>
    [DebuggerDisplay("P({Class}|{Token})={Probability}")]
    public struct ConditionalProbability : IEquatable<ConditionalProbability>
    {
        /// <summary>
        /// The class
        /// </summary>
        public readonly IClass Class;

        /// <summary>
        /// The token
        /// </summary>
        public readonly IToken Token;

        /// <summary>
        /// The conditional probability
        /// </summary>
        public readonly double Probability;

        /// <summary>
        /// The occurrence of the token during the training phase.
        /// </summary>
        public readonly long Occurrence;

        /// <summary>
        /// Initializes a new instance of the <see cref="ConditionalProbability" /> struct.
        /// </summary>
        /// <param name="class">The class.</param>
        /// <param name="token">The token.</param>
        /// <param name="probability">The probability.</param>
        /// <param name="occurrence">The occurrence.</param>
        /// <exception cref="System.ArgumentNullException">@class
        /// or
        /// token</exception>
        /// <exception cref="System.ArgumentOutOfRangeException">probability;Probability must greater than or equal to zero
        /// or
        /// probability;Probability must less than or equal to one</exception>
        public ConditionalProbability(IClass @class, IToken token, double probability, long occurrence)
        {
            if (ReferenceEquals(@class, null)) throw new ArgumentNullException("class");
            if (ReferenceEquals(token, null)) throw new ArgumentNullException("token");
            if (probability < 0) throw new ArgumentOutOfRangeException("probability", probability, "Probability must greater than or equal to zero");
            if (probability > 1) throw new ArgumentOutOfRangeException("probability", probability, "Probability must less than or equal to one");
            if (probability < 0) throw new ArgumentOutOfRangeException("occurrence", occurrence, "Occurrence must greater than or equal to zero");

            Class = @class;
            Token = token;
            Probability = probability;
            Occurrence = occurrence;
        }

        /// <summary>
        /// Determines whether the specified <see cref="System.Object" /> is equal to this instance.
        /// </summary>
        /// <param name="obj">Another object to compare to.</param>
        /// <returns><see langword="true" /> if the specified <see cref="System.Object" /> is equal to this instance; otherwise, <see langword="false" />.</returns>
        public override bool Equals(object obj)
        {
            if (ReferenceEquals(obj, null)) return false;
            return obj is ConditionalProbability && Equals((ConditionalProbability) obj);
        }

        /// <summary>
        /// Indicates whether the current object is equal to another object of the same type.
        /// </summary>
        /// <param name="other">An object to compare with this object.</param>
        /// <returns>true if the current object is equal to the <paramref name="other" /> parameter; otherwise, false.</returns>
        public bool Equals(ConditionalProbability other)
        {
            return Class.Equals(other.Class)
                   && Token.Equals(other.Token)
                   && Probability.Equals(other.Probability);
        }

        /// <summary>
        /// Returns a hash code for this instance.
        /// </summary>
        /// <returns>A hash code for this instance, suitable for use in hashing algorithms and data structures like a hash table.</returns>
        public override int GetHashCode()
        {
            var hash = 27;
            hash = (13 * hash) + Class.GetHashCode();
            hash = (13 * hash) + Token.GetHashCode();
            hash = (13 * hash) + Probability.GetHashCode();
            return hash;
        }

        /// <summary>
        /// Returns a <see cref="System.String" /> that represents this instance.
        /// </summary>
        /// <returns>A <see cref="System.String" /> that represents this instance.</returns>
        public override string ToString()
        {
            return String.Format("P({0}|{1})={2:P}", Class, Token, Probability);
        }
    }
}