using System.Diagnostics.Contracts;
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using StitchATon2.Infra.Buffers;

namespace StitchATon2.Domain;

public static class Utils
{
    [Pure]
    public static string GetSBSNotation(int row)
        => row <= 26
            ? new string([(char)(row + 'A' - 1)])
            : new string(['A', (char)(row + 'A' - 27)]);

    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
    private static int DivCeil(int a, int b)
    {
        return (a + b - 1) / b;
    }
    
    public static (int Column, int Row) GetSBSCoordinate(string coordinate)
    {
        var column = coordinate[^1] - '0';
        if(char.IsDigit(coordinate[^2]))
            column += 10 * (coordinate[^2] - '0');

        var row = char.IsLetter(coordinate[1])
            ? 26 + coordinate[1] - 'A' + 1
            : coordinate[0] - 'A' + 1;

        return (column, row);
    }
    
    
    public static IBuffer<int> BoundsMatrix(float scaleFactor, int length, int max, int offset)
    {
        var vectorSize = DivCeil(length, Vector<float>.Count);
        using var buffer = MemoryAllocator.Allocate<Vector<float>>(vectorSize);

        var span = buffer.Span;
        var vectorMin = Vector<int>.Zero;
        var vectorOffset = new Vector<int>(offset - 1);
        var vectorMax = new Vector<int>(max - 1);
        var vectorScale = new Vector<float>(scaleFactor);

        var vectorSequence = SequenceVector(0f, 1f);

        var seq = 0f;
        for (var i = 0; i < vectorSize; i++, seq += Vector<float>.Count)
        {
            var sequence = new Vector<float>(seq) + vectorSequence;
            span[i] = Vector.Multiply(sequence, vectorScale);
            span[i] = Vector.Add(span[i], vectorScale);
            span[i] = Vector.Ceiling(span[i]);
        }
        
        var result = MemoryAllocator.Allocate<int>(vectorSize * Vector<int>.Count);
        var resultSpan = MemoryMarshal.Cast<int, Vector<int>>(result.Span);
        for (var i = 0; i < vectorSize; i++)
        {
            resultSpan[i] = Vector.ConvertToInt32(span[i]);
            resultSpan[i] = Vector.Add(resultSpan[i], vectorOffset);
            resultSpan[i] = Vector.Min(resultSpan[i], vectorMax);
            resultSpan[i] = Vector.Max(resultSpan[i], vectorMin);
        }

        return result;
    }

    private static Vector<float> SequenceVector(float start, float step)
    {
        var vector = Vector<float>.Zero;
        ref var reference = ref Unsafe.As<Vector<float>, float>(ref vector);
        for (var i = 0; i < Vector<float>.Count; i++)
        {
            ref var current = ref Unsafe.Add(ref reference, i);
            current = start + step * i;
        }

        return vector;
    }
}