// Package embed produces dense vector embeddings for brain content.
//
// Wire format is Ollama's `/api/embed`, with the canonical request shape
// `{"model": "...", "input": "..."}` and a 2-D `embeddings` response.
// Default deployment runs `nomic-embed-text` on iguana, which returns
// 768-dim vectors compatible with the brain_embeddings table schema.
package embed

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"
)

// Client posts embedding requests to an Ollama-compatible endpoint.
type Client struct {
	URL   string
	Model string
	HTTP  *http.Client
}

// New constructs a Client. Returns nil when url is empty so callers can
// treat a missing BRAIN_EMBED_URL as "feature disabled" via a single nil
// check.
func New(url, model string) *Client {
	if url == "" {
		return nil
	}
	return &Client{
		URL:   strings.TrimRight(url, "/"),
		Model: model,
		HTTP:  &http.Client{Timeout: 30 * time.Second},
	}
}

// Embed returns the embedding vector for text. Empty text is rejected
// up-front to keep upstream errors from masking caller mistakes.
func (c *Client) Embed(ctx context.Context, text string) ([]float32, error) {
	if strings.TrimSpace(text) == "" {
		return nil, fmt.Errorf("embed: empty text")
	}
	reqBody, _ := json.Marshal(map[string]any{
		"model": c.Model,
		"input": text,
	})
	req, err := http.NewRequestWithContext(ctx, http.MethodPost,
		c.URL+"/api/embed", bytes.NewReader(reqBody))
	if err != nil {
		return nil, err
	}
	req.Header.Set("Content-Type", "application/json")
	resp, err := c.HTTP.Do(req)
	if err != nil {
		return nil, err
	}
	defer func() { _ = resp.Body.Close() }()
	if resp.StatusCode/100 != 2 {
		body, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("embed: status %d: %s", resp.StatusCode, string(body))
	}
	var out struct {
		Embeddings [][]float32 `json:"embeddings"`
	}
	if err := json.NewDecoder(resp.Body).Decode(&out); err != nil {
		return nil, fmt.Errorf("embed: decode: %w", err)
	}
	if len(out.Embeddings) == 0 || len(out.Embeddings[0]) == 0 {
		return nil, fmt.Errorf("embed: empty embeddings in response")
	}
	return out.Embeddings[0], nil
}