package embedding

import (
	"context"
	"crypto/sha256"
	"encoding/binary"
	"math"
)

type FakeProvider struct {
	dims  int
	model string
}

func NewFakeProvider(dims int, model string) *FakeProvider {
	if dims <= 0 {
		dims = 1536
	}
	if model == "" {
		model = "fake"
	}
	return &FakeProvider{dims: dims, model: model}
}
func (p *FakeProvider) Dimensions() int      { return p.dims }
func (p *FakeProvider) Model() string        { return p.model }
func (p *FakeProvider) ProviderName() string { return "fake" }
func (p *FakeProvider) Embed(ctx context.Context, input []string) ([]Vector, error) {
	out := make([]Vector, 0, len(input))
	for _, text := range input {
		select {
		case <-ctx.Done():
			return nil, ctx.Err()
		default:
		}
		v := make(Vector, p.dims)
		seed := sha256.Sum256([]byte(text))
		var norm float64
		for i := 0; i < p.dims; i++ {
			b := sha256.Sum256(append(seed[:], byte(i), byte(i>>8)))
			n := binary.BigEndian.Uint32(b[:4])
			val := (float64(n%2000000)/1000000.0 - 1.0)
			v[i] = float32(val)
			norm += val * val
		}
		if norm > 0 {
			scale := float32(1 / math.Sqrt(norm))
			for i := range v {
				v[i] *= scale
			}
		}
		out = append(out, v)
	}
	return out, nil
}