package embeddings

import (
	"context"
	"errors"

	"github.com/missionworkforce/missionmatch/internal/platform/config"
	"github.com/missionworkforce/missionmatch/internal/platform/inference"
)

// megamindEmbedder is the Embedder backed by the stateless MEGAMIND inference plane. It is the
// production path for cleared CUI data: the embedding model runs out of process on the Apple Silicon
// cluster (Metal), and this adapter reaches it through the typed inference client (timeouts, retries,
// circuit breaker). It L2 normalizes the returned vectors so cosine distance over the pgvector column is
// meaningful, matching the contract every other provider here follows.
type megamindEmbedder struct {
	client *inference.Client
	dim    int
}

// newMegamind builds the MEGAMIND backed Embedder from the embeddings config.
func newMegamind(cfg config.Embeddings) (Embedder, error) {
	if cfg.MegamindURL == "" {
		return nil, errors.New("embeddings: MM_MEGAMIND_URL required for the megamind provider")
	}
	model := cfg.Model
	if model == "" {
		model = "all-minilm"
	}
	// THE BEARER IS PASSED THROUGH, and its absence was a single point of failure hiding in an omitted field.
	//
	// The gateway requires a bearer on every route except the health check. This constructor accepted an
	// APIKey on the config and never handed it to the client, so the megamind embedding provider could not
	// authenticate AT ALL. It appeared to work only because MM_MEGAMIND_URL points at port 8090, which is a
	// fifteen line node reverse proxy belonging to another project that injects the credential and forwards to
	// the real gateway. Every embedding in this platform therefore depended on that proxy process being alive,
	// and if it stopped there was no way to recover from inside this codebase, because no code path could
	// supply a token.
	//
	// Found by Gate A, and the failure shape is worth remembering: the unauthenticated call returned 401, the
	// error was swallowed upstream, and the test reported SIMILARITY 0. It read as "the embedder has no
	// semantics" when the real cause was "the request was refused". A transport failure wearing the costume of
	// a bad model score is the most misleading result in this whole build.
	c, err := inference.New(inference.Config{
		BaseURL:    cfg.MegamindURL,
		EmbedModel: model,
		Dimension:  cfg.Dimension,
		Token:      cfg.APIKey,
	})
	if err != nil {
		return nil, err
	}
	return &megamindEmbedder{client: c, dim: cfg.Dimension}, nil
}

func (m *megamindEmbedder) Dimension() int { return m.dim }

func (m *megamindEmbedder) Embed(ctx context.Context, text string) ([]float32, error) {
	out, err := m.EmbedBatch(ctx, []string{text})
	if err != nil {
		return nil, err
	}
	return out[0], nil
}

func (m *megamindEmbedder) EmbedBatch(ctx context.Context, texts []string) ([][]float32, error) {
	res, err := m.client.Embed(ctx, texts)
	if err != nil {
		return nil, err
	}
	for i := range res.Embeddings {
		normalize(res.Embeddings[i])
	}
	return res.Embeddings, nil
}