package mathutil

import "math"

// CosineSimilarity computes cosine similarity between two vectors.
func CosineSimilarity(a, b []float32) float64 {
	var dot, normA, normB float64
	for i := range a {
		dot += float64(a[i]) * float64(b[i])
		normA += float64(a[i]) * float64(a[i])
		normB += float64(b[i]) * float64(b[i])
	}
	norm := math.Sqrt(normA) * math.Sqrt(normB)
	if norm == 0 {
		return 0
	}
	return dot / norm
}

// Normalize normalizes a vector to unit length.
func Normalize(v []float32) []float32 {
	var norm float64
	for _, x := range v {
		norm += float64(x) * float64(x)
	}
	norm = math.Sqrt(norm)
	if norm == 0 {
		return make([]float32, len(v))
	}
	out := make([]float32, len(v))
	for i, x := range v {
		out[i] = float32(float64(x) / norm)
	}
	return out
}

// DotProduct computes the dot product of two vectors.
func DotProduct(a, b []float32) float64 {
	var sum float64
	for i := range a {
		sum += float64(a[i]) * float64(b[i])
	}
	return sum
}