package developmentembedding

import (
	"crypto/sha256"
	"fmt"
	"math"
	"strconv"
	"strings"
)

const Dimensions = 1536

// Vector is a deterministic local-development projection. It is not a
// production semantic embedding and exists only to exercise the storage,
// filtering and lifecycle contracts without an external model account.
func Vector(content string) []float64 {
	values := make([]float64, Dimensions)
	for block := 0; block < Dimensions/32; block++ {
		digest := sha256.Sum256([]byte(fmt.Sprintf("%d:%s", block, content)))
		for index, value := range digest {
			values[block*32+index] = (float64(value) - 127.5) / 127.5
		}
	}
	var squared float64
	for _, value := range values {
		squared += value * value
	}
	norm := math.Sqrt(squared)
	if norm != 0 {
		for index := range values {
			values[index] /= norm
		}
	}
	return values
}

func Literal(values []float64) string {
	var builder strings.Builder
	builder.Grow(len(values) * 12)
	builder.WriteByte('[')
	for index, value := range values {
		if index > 0 {
			builder.WriteByte(',')
		}
		builder.WriteString(strconv.FormatFloat(value, 'g', 8, 64))
	}
	builder.WriteByte(']')
	return builder.String()
}