using System;
using xCommons.Extensions;

namespace xAiService.Helpers
{
    public static class VectorHelper
    {
        /// <summary>
        /// Normalize a Vector ...
        /// </summary>
        /// <param name="vector"></param>
        public static void Normalize(float[] vector)
        {
            //
            // Validate ...
            if (vector.IsNull() || !vector.HasChild())
            {
                return;
            }

            //
            float sum = 0f;
            foreach (var value in vector)
            {
                sum += value * value;
            }

            //
            float norm = MathF.Sqrt(sum);
            if (norm <= 1e-9f)
            {
                return;
            }

            //
            for (int i = 0; i < vector.Length; i++)
            {
                vector[i] /= norm;
            }
        }

        /// <summary>
        /// Similarity Check ...
        /// </summary>
        /// <param name="a"></param>
        /// <param name="b"></param>
        /// <returns></returns>
        public static float CosineSimilarity(float[] a, float[] b)
        {
            //
            if (a.IsNull() || b.IsNull())
            {
                return 0f;
            }

            //
            if (a.Length != b.Length)
            {
                return 0f;
            }

            //
            float dot = 0f;
            float normA = 0f;
            float normB = 0f;
            for (int i = 0; i < a.Length; i++)
            {
                //
                dot += a[i] * b[i];
                normA += a[i] * a[i];
                normB += b[i] * b[i];
            }

            //
            float denominator = MathF.Sqrt(normA) * MathF.Sqrt(normB);
            if (denominator <= 1e-9f)
            {
                return 0f;
            }

            //
            var result = dot / denominator;
            return result;
        }
    }
}