using System.Diagnostics.CodeAnalysis;

namespace MultiversalDiplomacy.Model;

/// <summary>
/// A timeline of a game. Essentially a wrapper around <see cref="int"/> for tracking the multiversal dimension.
/// </summary>
public struct Timeline
{
    public readonly int number;

    /// <summary>
    /// Timeline designations for differentiating timelines. Shortenable to the first character.
    /// </summary>
    private static readonly string[] primaryDesignations = new string[]
    {
        "alfa",
        "bravo",
        "charlie",
        "delta",
        "echo",
        "foxtrot",
        "golf",
        "hotel",
        "india",
        "juliett",
        "kilo",
        "lima",
        "mike",
        "november",
        "oscar",
        "papa",
        "quebec",
        "romeo",
        "sierra",
        "tango",
        "uniform",
        "victor",
        "whiskey",
        "xray",
        "yankee",
        "zulu"
    };

    /// <summary>
    /// Disambiguators used once all primary timeline designations have been used.
    /// </summary>
    private static readonly string[] secondaryDesignations = new string[]
    {
        "",
        "-prime",
        "-second",
        "-third",
        "-fourth",
        "-fifth",
        "-sixth",
        "-seventh",
        "-eighth",
        "-ninth",
    };

    /// <summary>
    /// Short versions of the secondary timeline disambiguators.
    /// </summary>
    private static readonly string[] secondaryDesignationsShort = new string[]
    {
        "",
        "'",
        "\"",
        "\x2073",
        "\x2074",
        "\x2075",
        "\x2076",
        "\x2077",
        "\x2078",
        "\x2079",
    };

    public Timeline(int number)
    {
        if (number < FIRST_TIMELINE)
        {
            throw new ArgumentException($"Invalid timeline number: {number}", nameof(number));
        }
        if (number >= primaryDesignations.Length * secondaryDesignations.Length)
        {
            throw new ArgumentException($"Timeline number too high: {number}", nameof(number));
        }
        this.number = number;
    }

    /// <summary>
    /// The first timeline number.
    /// </summary>
    public const int FIRST_TIMELINE = 0;

    /// <summary>
    /// Which primary designation the timeline has.
    /// </summary>
    private int primaryIndex => number % primaryDesignations.Length;

    /// <summary>
    /// Which secondary designation the timeline has.
    /// </summary>
    private int secondaryIndex => number / primaryDesignations.Length;

    /// <summary>
    /// Returns the timeline's full string representation.
    /// </summary>
    /// <returns>The timeline designation as a string, such as "bravo" or "delta-prime".</returns>
    public override string ToString()
        => primaryDesignations[primaryIndex] + secondaryDesignations[secondaryIndex];

    /// <summary>
    /// Returns a shorter string representation of the timeline.
    /// </summary>
    /// <returns>The timeline's designation as a string, such as "b" or "d'".</returns>
    public string ToShort()
        => primaryDesignations[primaryIndex][0] + secondaryDesignationsShort[secondaryIndex];

    /// <summary>
    /// Returns a value indicating whether this instance is equal to a specified <see cref="Timeline"/> value.
    /// </summary>
    /// <returns>true if obj has the same value as this instance; otherwise, false.</returns>
    public override bool Equals([NotNullWhen(true)] object? obj)
        => obj is Timeline other
        ? number.Equals(other.number)
        : false;

    /// <summary>
    /// Returns the hash code for this instance.
    /// </summary>
    /// <returns>A 32-bit signed integer hash code.</returns>
    public override int GetHashCode()
        => number.GetHashCode();

    public static int operator -(Timeline first, Timeline second)
        => Math.Abs(first.number - second.number);
}