package embed

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

type EmbedClient struct {
	baseURL string
	client  *http.Client
	model   string
}

type EmbedRequest struct {
	Model string   `json:"model"`
	Input []string `json:"input"`
}

type EmbedResponse struct {
	Data []struct {
		Embedding []float32 `json:"embedding"`
	} `json:"data"`
}

func NewEmbedClient(baseURL string) *EmbedClient {
	return &EmbedClient{
		baseURL: baseURL,
		client:  &http.Client{Timeout: 30 * time.Second},
		model:   "intfloat/e5-small-v2",
	}
}

func (c *EmbedClient) Embed(ctx context.Context, texts []string) ([][]float32, error) {
	if len(texts) == 0 {
		return [][]float32{}, nil
	}
	if len(texts) > 100 {
		return nil, fmt.Errorf("batch too large: %d > 100", len(texts))
	}

	body := EmbedRequest{
		Model: c.model,
		Input: texts,
	}
	payload, err := json.Marshal(body)
	if err != nil {
		return nil, fmt.Errorf("marshal embed request: %w", err)
	}

	req, err := http.NewRequestWithContext(ctx, "POST", c.baseURL+"/v1/embeddings", bytes.NewReader(payload))
	if err != nil {
		return nil, fmt.Errorf("embed request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("embed call: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		bodyBytes, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("embed service returned %d: %s", resp.StatusCode, string(bodyBytes))
	}

	respBody, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("read embed response: %w", err)
	}

	var er EmbedResponse
	if err := json.Unmarshal(respBody, &er); err != nil {
		return nil, fmt.Errorf("parse embed response: %w", err)
	}
	if len(er.Data) != len(texts) {
		return nil, fmt.Errorf("embed mismatch: expected %d embeddings, got %d", len(texts), len(er.Data))
	}

	result := make([][]float32, len(er.Data))
	for i, d := range er.Data {
		result[i] = d.Embedding
	}
	return result, nil
}

// CosineSimilarity вычисляет косинусную близость между двумя векторами
func CosineSimilarity(a, b []float32) float32 {
	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])
	}
	if normA == 0 || normB == 0 {
		return 0
	}
	return float32(dot / (math.Sqrt(normA) * math.Sqrt(normB)))
}