using System;
using System.Collections.Generic;
using System.Runtime.CompilerServices;

namespace ContentPatcher.Framework;

internal readonly struct IndexedString :
    IEquatable<IndexedString>,
    IEquatable<string>,
    IComparable<IndexedString>
{
    internal static IndexedString Empty => new(string.Empty);
    internal static readonly StringComparer Comparer = StringComparer.OrdinalIgnoreCase;
    internal const StringComparison Comparison = StringComparison.OrdinalIgnoreCase;

    internal readonly string Value => IndexedStringTable.GetString(this.Index);
    internal readonly int Index;

    internal readonly int Length => this.Value.Length;

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public IndexedString()
    {
        this.Index = IndexedString.Empty.Index;
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    internal IndexedString(string value)
    {
        (this.Index, _) = IndexedStringTable.GetIndex(value);
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    internal bool Contains(string value)
    {
        return this.Value.Contains(value, Comparison);
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    internal bool Contains(char value)
    {
        return this.Value.Contains(value);
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static explicit operator string(IndexedString indexedString) => indexedString.Value;

    public static bool operator ==(IndexedString left, IndexedString right) => left.Index == right.Index;
    public static bool operator !=(IndexedString left, IndexedString right) => left.Index != right.Index;

    public static bool operator ==(IndexedString left, string right) => left.Value == right;
    public static bool operator !=(IndexedString left, string right) => left.Value != right;

    public static bool operator ==(string left, IndexedString right) => left == right.Value;
    public static bool operator !=(string left, IndexedString right) => left != right.Value;

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public int CompareTo(IndexedString other)
    {
        return this.Index.CompareTo(other.Index);
    }


    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public override bool Equals(object? other)
    {
        return other switch
        {
            IndexedString indexedString => this.Index == indexedString.Index,
            string normalString => this.Equals(normalString),
            _ => false
        };
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public bool Equals(IndexedString other)
    {
        return this.Index == other.Index;
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public bool Equals(string? other)
    {
        return Comparer.Equals(this.Value, other);
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public override string ToString()
    {
        return this.Value;
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public override int GetHashCode()
    {
        return this.Index.GetHashCode();
    }
}

internal static class IndexedStringExt
{
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    internal static IndexedString AsIndexed(this string value) => value.Length == 0 ? IndexedString.Empty : new(value);

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    internal static IndexedString ToIndexedString<T>(this T obj) where T : notnull => obj.ToString()?.AsIndexed() ?? IndexedString.Empty;
}