package memory

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

type VectorService struct {
	APIKey    string
	BaseURL   string
	Model     string
	Dimension int
}

var (
	vectorSvc *VectorService
	vectorMu sync.RWMutex
)

type VectorOption func(*VectorService)

func WithAPIKey(key string) VectorOption {
	return func(v *VectorService) {
		v.APIKey = key
	}
}

func WithBaseURL(url string) VectorOption {
	return func(v *VectorService) {
		v.BaseURL = url
	}
}

func WithModel(model string) VectorOption {
	return func(v *VectorService) {
		v.Model = model
	}
}

func WithDimension(dim int) VectorOption {
	return func(v *VectorService) {
		v.Dimension = dim
	}
}

func InitVector(opts ...VectorOption) error {
	vectorSvc = &VectorService{
		APIKey:    "",
		BaseURL:   "https://api.siliconflow.cn/v1",
		Model:     "BAAI/bge-m3",
		Dimension: 1024,
	}
	for _, opt := range opts {
		opt(vectorSvc)
	}
	return nil
}

func GetVectorService() *VectorService {
	vectorMu.RLock()
	defer vectorMu.RUnlock()
	return vectorSvc
}

func (v *VectorService) Generate(text string) ([]byte, error) {
	if text == "" {
		return make([]byte, v.Dimension*4), nil
	}

	reqBody := map[string]interface{}{
		"input": text,
		"model": v.Model,
	}
	bodyBytes, err := json.Marshal(reqBody)
	if err != nil {
		return nil, fmt.Errorf("序列化请求失败: %w", err)
	}

	req, err := http.NewRequestWithContext(
		context.Background(),
		"POST",
		v.BaseURL+"/embeddings",
		bytes.NewReader(bodyBytes),
	)
	if err != nil {
		return nil, fmt.Errorf("创建请求失败: %w", err)
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", "Bearer "+v.APIKey)

	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("请求失败: %w", err)
	}
	defer resp.Body.Close()

	respBody, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("读取响应失败: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("API 返回错误: %d %s", resp.StatusCode, string(respBody))
	}

	var result struct {
		Data []struct {
			Embedding []float32 `json:"embedding"`
		} `json:"data"`
	}

	if err := json.Unmarshal(respBody, &result); err != nil {
		return nil, fmt.Errorf("解析响应失败: %w", err)
	}

	if len(result.Data) == 0 || len(result.Data[0].Embedding) == 0 {
		return nil, fmt.Errorf("未获取到向量")
	}

	embedding := result.Data[0].Embedding
	buf := new(bytes.Buffer)
	if err := binary.Write(buf, binary.LittleEndian, embedding); err != nil {
		return nil, fmt.Errorf("编码向量失败: %w", err)
	}

	return buf.Bytes(), nil
}

func (v *VectorService) GenerateBatch(texts []string) ([][]byte, error) {
	if len(texts) == 0 {
		return [][]byte{}, nil
	}

	reqBody := map[string]interface{}{
		"input": texts,
		"model": v.Model,
	}
	bodyBytes, err := json.Marshal(reqBody)
	if err != nil {
		return nil, fmt.Errorf("序列化请求失败: %w", err)
	}

	req, err := http.NewRequestWithContext(
		context.Background(),
		"POST",
		v.BaseURL+"/embeddings",
		bytes.NewReader(bodyBytes),
	)
	if err != nil {
		return nil, fmt.Errorf("创建请求失败: %w", err)
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", "Bearer "+v.APIKey)

	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("请求失败: %w", err)
	}
	defer resp.Body.Close()

	respBody, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("读取响应失败: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("API 返回错误: %d %s", resp.StatusCode, string(respBody))
	}

	var result struct {
		Data []struct {
			Embedding []float32 `json:"embedding"`
		} `json:"data"`
	}

	if err := json.Unmarshal(respBody, &result); err != nil {
		return nil, fmt.Errorf("解析响应失败: %w", err)
	}

	embeddings := make([][]byte, len(result.Data))
	for i, data := range result.Data {
		embedding := data.Embedding
		buf := new(bytes.Buffer)
		if err := binary.Write(buf, binary.LittleEndian, embedding); err != nil {
			continue
		}
		embeddings[i] = buf.Bytes()
	}

	return embeddings, nil
}

func (v *VectorService) CosineSimilarity(a, b []byte) float64 {
	if len(a) == 0 || len(b) == 0 {
		return 0
	}

	vecLen := len(a) / 4
	if len(b)/4 < vecLen {
		vecLen = len(b) / 4
	}

	var dotProduct float32
	var normA float32
	var normB float32

	for i := 0; i < vecLen; i++ {
		offset := i * 4
		fa := binary.LittleEndian.Uint32(a[offset : offset+4])
		fb := binary.LittleEndian.Uint32(b[offset : offset+4])
		f32a := math.Float32frombits(fa)
		f32b := math.Float32frombits(fb)
		dotProduct += f32a * f32b
		normA += f32a * f32a
		normB += f32b * f32b
	}

	if normA == 0 || normB == 0 {
		return 0
	}

	return float64(dotProduct / (normA * normB))
}