// Package matting 封装图片抠图服务调用，将衣物图片上传到 BiRefNet 抠图服务，
// 返回透明底 PNG 图片字节。
package matting

import (
	"bytes"
	"context"
	"fmt"
	"io"
	"mime/multipart"
	"net/http"
	"time"

	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/global"
)

const (
	mattingPath = "/matting"
	healthzPath = "/healthz"
)

// Client 抠图服务客户端。
type Client struct {
	baseURL    string
	httpClient *http.Client
}

// NewClient 从全局配置创建客户端。
func NewClient() *Client {
	return NewClientWithAddr(global.MattingModelSetting.Host, global.MattingModelSetting.Port)
}

// NewClientWithAddr 使用指定 Host/Port 创建客户端，便于测试与解耦。
func NewClientWithAddr(host string, port int) *Client {
	return &Client{
		baseURL: fmt.Sprintf("http://%s:%d", host, port),
		httpClient: &http.Client{
			Timeout: 120 * time.Second,
		},
	}
}

// Matting 调用抠图服务，将图片上传并返回透明底 PNG 字节。
func (c *Client) Matting(ctx context.Context, imageData []byte) ([]byte, error) {
	var body bytes.Buffer
	writer := multipart.NewWriter(&body)

	part, err := writer.CreateFormFile("file", "image.png")
	if err != nil {
		return nil, fmt.Errorf("matting create form file: %w", err)
	}
	if _, err := part.Write(imageData); err != nil {
		return nil, fmt.Errorf("matting write image: %w", err)
	}
	if err := writer.Close(); err != nil {
		return nil, fmt.Errorf("matting close multipart: %w", err)
	}

	request, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+mattingPath, &body)
	if err != nil {
		return nil, fmt.Errorf("matting create request: %w", err)
	}
	request.Header.Set("Content-Type", writer.FormDataContentType())

	response, err := c.httpClient.Do(request)
	if err != nil {
		return nil, fmt.Errorf("matting do request: %w", err)
	}
	defer response.Body.Close()

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

	if response.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("matting api error: status=%d, body=%s", response.StatusCode, summarize(data))
	}

	return data, nil
}

// HealthCheck 检查抠图服务是否就绪。
func (c *Client) HealthCheck(ctx context.Context) error {
	request, err := http.NewRequestWithContext(ctx, http.MethodGet, c.baseURL+healthzPath, nil)
	if err != nil {
		return fmt.Errorf("matting create healthz request: %w", err)
	}

	response, err := c.httpClient.Do(request)
	if err != nil {
		return fmt.Errorf("matting healthz request: %w", err)
	}
	defer response.Body.Close()

	if response.StatusCode != http.StatusOK {
		return fmt.Errorf("matting healthz status: %d", response.StatusCode)
	}
	return nil
}

// summarize 截断响应体摘要，避免错误信息打印大体积二进制。
func summarize(data []byte) string {
	const maxLen = 512
	if len(data) > maxLen {
		return string(data[:maxLen]) + "..."
	}
	return string(data)
}