package util

import (
	"fmt"
	"net/http"
	"os"
	"path/filepath"
	"strings"
)

// DetectFileType 根据返回的二进制内容推断 contentType + 扩展名（尽量稳定）
func DetectFileType(data []byte) (contentType string, ext string) {
	if len(data) == 0 {
		return "application/octet-stream", ""
	}
	ct := http.DetectContentType(data)
	// gateway.DetectContentType 可能带 charset 等参数：text/plain; charset=utf-8
	if idx := strings.Index(ct, ";"); idx > 0 {
		ct = strings.TrimSpace(ct[:idx])
	}
	switch ct {
	case "audio/mpeg":
		return ct, ".mp3"
	case "audio/wave", "audio/wav", "audio/x-wav":
		return ct, ".wav"
	case "video/mp4":
		return ct, ".mp4"
	case "image/png":
		return ct, ".png"
	case "image/jpeg":
		return ct, ".jpg"
	case "application/pdf":
		return ct, ".pdf"
	case "text/plain":
		return ct, ".txt"
	case "application/json":
		return ct, ".json"
	default:
		// 兜底：尝试从 ct 截取 subtype 作为后缀（例如 application/json）
		if parts := strings.Split(ct, "/"); len(parts) == 2 {
			sub := parts[1]
			// 避免出现 "plain; charset=utf-8" 之类的后缀
			if idx := strings.Index(sub, ";"); idx > 0 {
				sub = strings.TrimSpace(sub[:idx])
			}
			return ct, "." + sub
		}
		return ct, ""
	}
}

// SaveTmpResult 将模型输出写入临时文件，用于 OSS 上传失败后的“仅重试 OSS”。
func SaveTmpResult(taskID string, data []byte, ext string) (string, error) {
	dir := filepath.Join(os.TempDir(), "model-asynch")
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return "", err
	}
	if ext == "" {
		ext = ".bin"
	}
	if ext[0] != '.' {
		ext = "." + ext
	}
	path := filepath.Join(dir, fmt.Sprintf("%s%s", taskID, ext))
	if err := os.WriteFile(path, data, 0o644); err != nil {
		return "", err
	}
	return path, nil
}