package handler

import (
	"crypto/rand"
	"encoding/hex"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"time"
)

// saveUploadFile 保存上传文件（工艺图纸PDF / 巡检照片），返回生成的相对文件名（含日期子目录）
func saveUploadFile(r *http.Request, field, dir string) (string, error) {
	sub := time.Now().Format("2006-01-02")
	full := filepath.Join(dir, sub)
	if err := os.MkdirAll(full, 0o755); err != nil {
		return "", err
	}
	file, header, err := r.FormFile(field)
	if err != nil {
		return "", err
	}
	defer file.Close()

	ext := strings.ToLower(filepath.Ext(header.Filename))
	if ext == "" {
		ext = ".bin"
	}
	name := time.Now().Format("20060102150405") + "_" + randHex(6) + ext
	dst, err := os.Create(filepath.Join(full, name))
	if err != nil {
		return "", err
	}
	defer dst.Close()
	if _, err := io.Copy(dst, file); err != nil {
		return "", err
	}
	return filepath.ToSlash(filepath.Join(sub, name)), nil
}

func randHex(n int) string {
	b := make([]byte, n)
	_, _ = rand.Read(b)
	return hex.EncodeToString(b)[:n*2]
}

// serveUploadFile 下发上传目录中的文件（仅允许 单层日期子目录/文件名，防路径穿越）
func serveUploadFile(w http.ResponseWriter, r *http.Request, dir, name string) {
	name = strings.TrimSpace(name)
	clean := filepath.Clean(filepath.FromSlash(name))
	if clean == "." || clean == ".." ||
		strings.HasPrefix(clean, ".."+string(filepath.Separator)) ||
		filepath.IsAbs(clean) || strings.ContainsRune(name, '\x00') {
		http.Error(w, "非法文件名", http.StatusBadRequest)
		return
	}
	f, err := os.Open(filepath.Join(dir, clean))
	if err != nil {
		http.Error(w, "文件不存在", http.StatusNotFound)
		return
	}
	defer f.Close()
	ct := "application/octet-stream"
	base := strings.ToLower(clean)
	switch {
	case strings.HasSuffix(base, ".pdf"):
		ct = "application/pdf"
	case strings.HasSuffix(base, ".jpg"), strings.HasSuffix(base, ".jpeg"):
		ct = "image/jpeg"
	case strings.HasSuffix(base, ".png"):
		ct = "image/png"
	}
	w.Header().Set("Content-Type", ct)
	http.ServeContent(w, r, name, time.Time{}, f)
}